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This paper presents a generalised Newmark method (GNM) incorporating a displacement hardening mechanism for the prediction of permanent displacements accumulated by diaphragm walls during earthquakes. A key feature of the proposed approach is the adoption of an evolution law for the critical acceleration, which links its current value to the accumulated wall permanent displacements. This displacement hardening mechanism is based on a simplified relation between the average plastic shear deformations experienced by the passive zone of soil below dredge level and the mobilised soil friction angle. This relation is determined indirectly by the evolution of the passive earth-pressure coefficient with wall displacement/rotation, as obtained in quasi-static model wall experiments. The proposed approach has been validated by comparing its predictions with the experimental data obtained in centrifuge model tests of cantilevered and propped walls. In spite of the simplifying assumptions on which it is based, the GNM has demonstrated that it is capable of capturing the essential features of the retaining structures' kinematics and provides realistic predictions of permanent wall displacements. [ABSTRACT FROM AUTHOR]

Damage zones are common around faults, but their effects on earthquake mechanics are still incompletely understood. Here, we investigate how damage affects rupture patterns, source time functions (STF) and ground motions in 2D fully‐dynamic cycle models. We find that back‐propagating rupture fronts emerge in large faults and can be triggered by residual stresses left by previous ruptures or by damage‐induced pulse‐to‐crack transitions. Damage‐induced back‐propagating fronts are modulated by slip rate oscillations, amplify high‐frequency radiation, and sharpen the multiple peaks in STF even in the absence of frictional heterogeneity or fault segmentation. Near‐field ground motion is predominantly controlled by stress heterogeneity left by prior seismicity, and further amplified within the damage zone by trapped waves and outside it by secondary rupture fronts. This study refines our knowledge on damage zone effects on earthquake rupture and identifies their potentially observable signatures in the near and far field. Plain Language Summary: Faults are surrounded by layers of fractured rocks, known as damage zones, which can affect earthquakes and related hazards, but in ways that are still not well understood. Here, by running computer simulations, we investigate how damage zones influence earthquake ruptures and consequent ground motions. Our models fully account for seismic wave effects, produce multiple earthquake cycles, and span a large range of fault lengths and damage zone properties that are representative of natural faults. We identify characteristic patterns of earthquake rupture produced by damage zones: back‐propagating fronts that re‐rupture the fault, and oscillatory fault motions that affect ground shaking amplitude and frequency content. We identify which of these effects might be observable in seismograms recorded near and far from the fault. Overall, our computational study highlights significant effects of damage zones on earthquakes and on the shaking they produce. These results can guide us to better interpret earthquake source and ground motion observations, and to predict the potential characteristics of future events. Key Points: Reduction of nucleation size and pulse‐crack transitions are two distinct damage zone effects that induce back‐propagating rupture frontsDamage effects can enhance high‐frequency radiation and complexity of source time functions, potentially observable in the far fieldBack‐propagating fronts have potential signatures in near‐field seismograms and can affect peak ground motions [ABSTRACT FROM AUTHOR]

Rock strength has long been linked to lithospheric deformation and seismicity. However, independent constraints on the related elastic heterogeneity are missing, yet could provide key information for solid Earth dynamics. Using coseismic Global Navigation Satellite Systems (GNSS) data for the 2011 M9 Tohoku-oki earthquake in Japan, we apply an inverse method to infer elastic structure and fault slip simultaneously. We find compliant material beneath the volcanic arc and in the mantle wedge within the partial melt generation zone inferred to lie above ~100 km slab depth. We also identify low-rigidity material closer to the trench matching seismicity patterns, likely associated with accretionary wedge structure. Along with traditional seismic and electromagnetic methods, our approach opens up avenues for multiphysics inversions. Those have the potential to advance earthquake and volcano science, and in particular once expanded to InSAR type constraints, may lead to a better understanding of transient lithospheric deformation across scales. [ABSTRACT FROM AUTHOR]

We evaluate seismicity and tectonics along the San Andreas Fault (SAF) in southern California to elucidate ongoing near‐field crustal deformation processes. The principal slip surfaces (PSSs) or the fault core that accommodate major earthquakes, form the boundary between the tectonic plates. We analyze seismicity catalogs extending back to 1857, 1932, and 1981 with progressively improved magnitude of completeness and spatial resolution. The 1857 to present statewide catalog that is complete at M5.5+ documents minimal aftershock activity for the Mw7.9 1857 and 1906 Mw7.8 San Francisco earthquakes. The higher quality 1932 and 1981 catalogs show that the PSSs (the rupture zone) of the 1857 Mw7.9 Fort Tejon earthquake exhibits remarkable seismic quiescence both in the core and in the adjacent extended‐damage zone. Further south, the fault core is still aseismic but the shape of the SAF is more complex, and the rate of adjacent seismicity is much higher. This fault complexity and the seismicity rate are larger the more the strike of the SAF deviates from the Pacific plate velocity‐vector direction. The focal mechanisms of the SAF adjacent earthquakes are also heterogeneous and rarely have strikes and dips that are consistent with slip on the nearby PSSs. We infer that the southern SAF is locked, and a lack of seismicity at the core of the fault may be a standard feature of faults that almost exclusively accommodate high‐slip rates by producing major earthquakes. Correspondingly future aftershock sequences of major earthquakes on the southern SAF will likely have below average aftershock productivity. Plain Language Summary: The fast‐moving San Andreas Fault (SAF) that runs up the spine of California from the Salton Sea to Cape Mendocino, forms the plate boundary between the Pacific and North America plates. It has accommodated California's two largest earthquakes, the 1857 Mw7.9 Fort Tejon and the 1906 Mw7.8 San Francisco, which ruptured the fault for hundreds of kilometers. We focus on analyzing the seismicity of the southern SAF from 1857 to present. Almost no small earthquakes occur along the core of the southern SAF, from south of Parkfield to the Salton Sea. To the north, the 1857 Mw7.9 earthquake was followed by relatively few immediate aftershocks, and since 1932 this section of the fault has been very seismically quiescent. To the south of the 1857 rupture, the rate of extended‐damage zone seismicity inversely correlates with the SAF strike deviation from the Pacific plate vector relative to the SAF strike. In particular, the east‐west striking 28 km long Mill Creek segment may impede SAF slip, which results in abundant off‐fault seismicity and transfer of tectonic strain into the eastern California shear zone and the Peninsular Ranges. Key Points: The near‐field seismicity of the southern San Andreas Fault (SAF) is limited to the adjacent extended‐damage zone and mostly absent from the fault coreStep changes in the 95% depth and in the texture of seismicity depth distribution likely define the presence of the SAF fault coreSeismicity rate in the damage zone positively correlates with SAF deviation from Pacific plate vector except in the quiescent 1857 rupture [ABSTRACT FROM AUTHOR]

The reduction of effective normal stress during earthquake slip due to thermal pressurization of fault zone pore fluids is a significant fault weakening mechanism. Explicit incorporation of this process into frictional fault models involves solving the diffusion equations for fluid pressure and temperature outside the fault at each time step, which significantly increases the computational complexity. Here, we propose a proxy for thermal pressurization implemented through a modification of the rate-and-state friction law. This approach is designed to emulate the fault weakening and the relationship between breakdown energy and slip resulting from thermal pressurization and is appropriate for fully dynamic simulations of multiple earthquake cycles. It preserves the computational efficiency of conventional rate-and-state friction models, which in turn can enable systematic studies to advance our understanding of the effects of fault weakening on earthquake mechanics. In 2.5-D simulations of pulse-like ruptures on faults with finite seismogenic width, based on our thermal pressurization proxy, we find that the spatial distribution of slip velocity near the rupture front is consistent with the conventional square-root singularity, despite continued slip-weakening within the pulse, once the rupture has propagated a distance larger than the rupture width. An unconventional singularity appears only at shorter rupture distances. We further derive and verify numerically a theoretical estimate of the breakdown energy dissipated by our implementation of thermal pressurization. These results support the use of fracture mechanics theory to understand the propagation and arrest of very large earthquakes. [ABSTRACT FROM AUTHOR]

The slip style of continental midcrustal shear zones plays a crucial role in determining the seismogenic potential of faults, but it remains poorly understood because geological observations that can be directly tied to seismic behavior are scarce. We describe frictional-viscous shear zones in the Red River fault, China, which consists of two segments with distinct seismic behaviors and fluid availabilities. The northern segment hosts moderate to large earthquakes, and midcrustal fault slip is localized into mylonitized pseudotachylyte-bearing layers where dynamically recrystallized quartz records flow stresses exceeding 100 MPa and accelerated viscous creep. The southern segment is dominantly aseismic but active microseismically. Fault slip is accommodated in several mylonitized cataclasite layers, comprising interconnected biotite and intervening fractured clasts, with evidence for pervasive dissolution-precipitation creep. Microstructures, paleopiezometry, and microphysical modeling suggest transient aseismic slip in response to increased strain rates during viscous creep at <50 MPa. We interpret that along-strike variations in fluid environment control fault slip styles and seismic behaviors. The dry and strong northern segment is capable of nucleating large earthquakes, while greater fluid availability in the southern segment activates dissolution-precipitation creep at low driving stresses, which limits interseismic elastic strain accumulation at frictional-viscous transition depths. In this model, compaction-driven fluid pressurization and dilatant hardening are invoked to explain the aseismic slip transients in the southern segment. [ABSTRACT FROM AUTHOR]

The Haiyuan fault system plays a crucial role in accommodating the eastward expansion of the Tibetan Plateau (TP) and is currently slipping at a rate of several centimeters per year. However, limited seismic activities have been observed using geodetic techniques in this area, impeding the comprehensive investigation into regional tectonics. In this study, the geometric structure and source models of the 2022 Mw 6.7 and the 2016 Mw 5.9 Menyuan earthquakes were investigated using Sentinel-1A SAR images. By implementing an atmospheric error correction method, the signal-to-noise ratio of the 2016 interferometric synthetic aperture radar (InSAR) coseismic deformation field was significantly improved, enabling InSAR observations with higher accuracy. The results showed that the reliability of the source models for those events was improved following the reduction in observation errors. The Coulomb stress resulting from the 2016 event may have promoted the strike-slip movement of the western segment of the Lenglongling fault zone, potentially expediting the occurrence of the 2022 earthquake. The coseismic slip distribution and the spatial distribution of aftershocks of the 2022 event suggested that the seismogenic fault may connect the western segment of the Lenglongling fault (LLLF) and the eastern segment of the Tuolaishan fault (TLSF). Additionally, the western segment of the surface rupture zone of the northern branch may terminate in the secondary branch close to the Sunan-Qilian fault (SN-QL) strike direction, and the earthquake may have triggered deep aftershocks and accelerated stress release within the deep seismogenic fault. [ABSTRACT FROM AUTHOR]

Shear strength of damage zone, representing the stress threshold for rupture initiation, is a critical parameter in faulting mechanics. Despite its significance, the damage‐zone's shear strength has not been estimated in natural earthquake ruptures. Here we employed coseismic deformation and strain, kinematic slip model, and finite element modeling to determine the elastic properties and peak shear stress of coseismic damage zones along the 2021 Mw 7.4 Maduo earthquake. Through the analysis of the lowest shear stress resulting in surface ruptures and the highest stress without surface rupture, we constrained the strength within a range of 7–17 MPa. Our result is consistent with strength (5–16 MPa) of sandstone samples from laboratory tests, demonstrating the validity of this estimation. Although factors such as fault maturity and confining pressure influence strength variation, the strength can directly reflect the stress threshold required for macroscopic surface rupture formation in fault damage zones dominated by sandstone. Plain Language Summary: Shear strength of a fault damage zone inform us its ability to withstand shear stress before surface rupture occurs. This information often provides insights into the earthquakes rupture hazards near the Earth's surface. Natural earthquakes provide a perfect opportunity for us to address the question of "what is the shear strength of a fault damage zone." To this end, we require a set of comparative references: the utmost shear stress that a damage zone can withstand without surface rupture and the minimal one necessary for the zone to generate surface rupture. In this investigation, we studied the 2021 Maduo earthquake because it had multiple distinct surface rupture segments in some places but not in others. By comparing shear stress in these segments, we could figure out how strong the damage zones were. We used real observations and numerical simulations to estimate how much stress these damage zones can withstand. Our results indicate that, for damage zones embedded in intact sandstone with a Young's modulus of 15 GPa, its strength ranges from 7 to 17 MPa. Significantly, our study is the first to reveal the shear strength of damage zone from a nutural earthquake using geodetic data. Key Points: Shear modulus and shear stress for coseismic damage zone were determined using coseismic deformation and finite element modelEstimated shear strength from overlap range of coseismic stress between surface rupture and non‐rupture parts ranges from 7 to 17 MPaShear strength exhibits positive and negative correlations with confining pressure and fault maturity, respectively [ABSTRACT FROM AUTHOR]

Dilatant hardening is one proposed mechanism that causes slow earthquakes along faults. Previous experiments and models show that dilatant hardening can stabilize fault rupture and slip in several lithologies. However, few studies have systematically measured the mechanical behavior across the transition from dynamic to slow rupture or considered how the associated damage varies. To constrain the processes and scales of dilatant hardening, we conducted triaxial compression experiments on cores of Crab Orchard sandstone and structural analyses using micro‐computed tomography imaging and petrographic analysis. Experiments were conducted at an effective confining pressure of ∼10 MPa, while varying confining pressure (10–130 MPa) and pore fluid pressure (1–120 MPa). Above 15 MPa pore fluid pressure, dilatant hardening slows the rate of fault rupture and slip and deformation becomes more distributed amongst multiple faults as microfracturing increases. The resulting increase in fracture energy has the potential to control fault slip behavior. Plain Language Summary: When rocks are breaking, the pore spaces and developing fractures dilate, resulting in a decrease in pore fluid pressures. This decrease can strengthen the rock from ongoing deformation in a process known as dilatant hardening. We conducted experiments to better understand how this strengthening effect works, in particular looking at the ratio of pore fluid pressure to the external confining pressure (simulating rocks buried at depth), and also analyzed how the fractures that develop can vary from dilatant hardening. We found a threshold pressure at which the strengthening peaked, and increasing pore fluid pressure did not change how strong the rocks got from continuing deformation. We also observed a drastic increase in how damage was distributed due to this hardening effect at both a large (visible to the naked eye) and small scale (only visible in a high‐magnification microscope). These results indicate that dilatant hardening can increase how much energy must be expended to break the rock and to cause faults to slip when pore fluid pressures are high enough, and likely plays a role in stabilizing fault slip, causing earthquakes to slow down and be less dynamic. Key Points: We measured the transition between dynamic and stable rupture as a result of dilatant hardeningWe observed differences in microstructural development tied to the shift in rupture styleWe developed a model of fracture nucleation and propagation at different pore fluid pressures [ABSTRACT FROM AUTHOR]

Earthquake-triggered landslides (ETLs) feature large quantities, extensive distributions, and enormous losses to human lives and critical infrastructures. Near-real spatial prediction of ETLs can rapidly predict the locations of coseismic landslides just after a violent earthquake and is a vital technical support for emergency response. However, near-real prediction of ETLs has always been a great challenge with relatively low accuracy. This work proposes an ensemble prediction model of EnPr by integrating machine learning tree models and a deep learning convolutional neural network. EnPr exhibits relatively strong prediction and generalization performance and achieves relatively accurate prediction of ETLs. Six great seismic events occurring from 2008 to 2022 on the southeastern margin of the Tibetan Plateau are selected to conduct ETL prediction. In a chronological order, the 2008 Ms 8.0 Wenchuan, 2010 Ms 7.1 Yushu, 2013 Ms 7.0 Lushan, and 2014 Ms 6.5 Ludian earthquakes are employed for model training and learning. The 2017 Ms 7.0 Jiuzhaigou and 2022 Ms 6.1 Lushan earthquakes are adopted for ETL prediction. The prediction accuracy merits of ACC and AUC attain 91.28% and 0.85, respectively, for the Jiuzhaigou earthquake. The values of ACC and AUC achieve 93.78% and 0.88, respectively, for the Lushan earthquake. The proposed EnPr algorithm outperforms the algorithms of XGBoost, random forest (RF), extremely randomized trees (ET), convolutional neural network (CNN), and Transformer. Moreover, this work reveals that seismic intensity, high and steep relief, pre-seismic fault tectonics, and pre-earthquake road construction have played significant roles in coseismic landslide occurrence and distribution. The EnPr model uses globally accessible open datasets and can therefore be used worldwide for new large seismic events in the future. [ABSTRACT FROM AUTHOR]

Coseismic slip on the Patton Bay splay fault system during the 1964 Mw 9.2 Great Alaska Earthquake contributed to local tsunami generation and vertically uplifted shorelines as much as 11 m on Montague Island in Prince William Sound (PWS). Sudden uplift of 3.7–4.3 m caused coastal lagoons along the island's northwestern coast to gradually drain. The resulting change in depositional environment from marine lagoon to freshwater muskeg created a sharp, laterally continuous stratigraphic contact between silt and overlying peat. Here, we characterize the geomorphology, sedimentology, and diatom ecology across the 1964 earthquake contact and three similar prehistoric contacts within the stratigraphy of the Hidden Lagoons locality. We find that the contacts signal instances of abrupt coastal uplift that, within error, overlap the timing of independently constrained megathrust earthquakes in PWS—1964 Common Era, 760–870 yr BP, 2500–2700 yr BP, and 4120–4500 yr BP. Changes in fossil diatom assemblages across the inferred prehistoric earthquake contacts reflect ecological shifts consistent with repeated draining of a lagoon system caused by >3 m of coseismic uplift. Our observations provide evidence for four instances of combined megathrust‐splay fault ruptures that have occurred in the past ∼4,200 years in PWS. The possibility that 1964‐style combined megathrust‐splay fault ruptures may have repeated in the past warrants their consideration in future seismic and tsunami hazards assessments. Plain Language Summary: During the Mw 9.2 1964 Great Alaska Earthquake, both the subduction zone and the crustal faults connected to the subduction zone (called splay faults) slipped, lifting shorelines up to 11 m on Montague Island in Prince William Sound (PWS) and contributing to local tsunami generation. The sudden uplift cut off tidal connection to coastal lagoons on Montague Island's northwest coast, producing a change to a drier, freshwater environment. The sudden environmental change created a clear sedimentary change from pre‐earthquake lagoon silt to post‐earthquake rooted soil in the stratigraphy of a study site known as Hidden Lagoons. Using the stratigraphic evidence of the 1964 uplift as a guide, we investigated deeper into the subsurface of Hidden Lagoons to see if there were previous instances of subduction zone and splay fault activation. We discovered three previous stratigraphic boundaries marking times when earthquakes uplifted the land. Changes in the species of diatoms across these boundaries show that the marine lagoon system was repeatedly drained by earthquakes causing over 3 m of uplift. These uplift events match the timing of four of the eight known prehistoric subduction zone earthquakes in PWS, suggesting that splay faults have slipped with the subduction zone multiple times over the past ∼4,200 years. Key Points: We find widespread stratigraphic evidence for the 1964 M9.2 earthquake and three prehistoric earthquake contacts on Montague Island, AlaskaStratigraphic and diatom analyses suggest ruptures of splay faults may have occurred in conjunction with 4 of 8 documented Alaska‐Aleutian subduction zone earthquakesHazard assessments may want to consider the tsunami potential with possible future 1964‐style combined megathrust‐splay fault ruptures [ABSTRACT FROM AUTHOR]

The varied atomic arrangements in face-centered cubic (FCC) solid solutions introduce atomic-scale fluctuations to their energy landscapes that influence the operation of dislocation-mediated deformation mechanisms. These effects are particularly pronounced in concentrated systems, which are of considerable interest to the community. Here, we examine the effect of local fluctuations in planar fault energies on the evolution of deformation twinning microstructures in randomly arranged FCC solid solutions. Our approach leverages the kinetic Monte Carlo (kMC) method to provide kinetically weighted predictions for competition between two processes: deformation twin nucleation and deformation twin thickening. The kinetic barriers underpinning each process are drawn from the statistics of planar fault energies, which are locally sampled using molecular statics methods. kMC results show an increase in the fault number densities of solid solutions relative to a homogenized reference, which is found to be driven by the fluctuations in planar fault energies. Based on kMC relations, an effective barrier model is derived to predict the competition between deformation twinning nucleation and thickening processes under a fluctuating planar fault energy landscape. A key result from this model is a measurement of the length-scale over which the influence of local fluctuations in planar fault energies diminish and nucleation/thickening-dominated behaviors converge to bulk predictions. More broadly, the tools developed in this study enable examination of the influence of chemistry and length-scale on the evolution of deformation twinning mechanisms in FCC solid solutions. [ABSTRACT FROM AUTHOR]

Assessing the dynamic properties of rocks remains a foundational pursuit in the field of rock engineering, providing crucial insights into their mechanical behaviors across a spectrum of loading conditions, including static, cyclic, and dynamic scenarios. This paper expounds upon the utilization of the nonresonance (NR) torsional shear test and its implications for understanding rock responses, particularly in the context of low and medium loading rates. The NR method serves as a pivotal tool for investigating model rock materials subjected to loading conditions characterized by low frequencies and amplitudes. Renowned for its efficacy, this method allows the simultaneous determination of two critical dynamic parameters: shear modulus (G) and damping ratio (D), all at a specific loading frequency. It has been ascertained that the loading rate increased as the loading frequency and applied amplitude of loading increased. With increasing loading rate, the shear modulus consequently increased while the damping ratio decreased. It is observed that the dynamic responses of both ramp and sinusoidal loading waveforms increase concurrently with the amplitudes of the applied torque and loading frequencies. The sinusoidal waveform exhibits greater dynamicity than the ramp waveform at a certain loading rate. Furthermore, this study delves into the intricate analysis of the nonlinear viscoelastic dynamic response exhibited by rocks, utilizing the modified hyperbolic (MH) model and the Ramberg–Osgood (RO) model as analytical tools. The findings derived from curve fitting exercises unequivocally underscore the superior applicability of the Ramberg–Osgood model, particularly in characterizing modulus reduction behavior. Conversely, the modified hyperbolic model emerges as the preferred choice for comprehensive damping ratio analyses. This study enhances the comprehension of rock dynamics and responses under diverse loading conditions, contributing valuable understanding to rock engineering. Insights into loading and strain rate effects aid informed decisions and preventive measures for rock deformation and collapse risks. Practical Applications: This research suggests vital findings regarding the response of intact model materials to various dynamic loading conditions, providing significant insights for comprehending the mechanical response of rock structures exposed to cyclic loading conditions, which have the potential to create weaknesses in rocks resulting in untimely failures. The research can be utilized to assess the response of rocks in the context of seismic incidents, specifically those characterized by shear waves at particular frequencies. This study evaluates the response of rocks during earthquakes by establishing a correlation between the amplitude of torsional shear loading and the peak ground displacement linked to seismic events. In addition to its seismic implications, this research aids in advancing accurate predictive models and instruments that assess the stability and integrity of rock formations under different loading rates—a consequence of the symbiosis between frequency and amplitude. Professionals may ensure efficient risk mitigation, make well-informed decisions, and execute preventative measures concerning rock collapse and deformation by virtue of their comprehensive awareness of the delicate relationship between loading rate and dynamic rock properties. Incorporating the findings into engineering design standards and codes can bring about substantial improvements, augmenting the overall reliability and protection of rock structures. [ABSTRACT FROM AUTHOR]

The horizontal displacement of a reinforced-soil retaining wall is a common deformation mode of seismic damage. The horizontal displacement time history and accumulative deformation after earthquakes are important parameters for evaluating the seismic performance of a reinforced-soil retaining wall, but theoretical study on this issue is scarce at the moment. In this study, an analytical method is proposed to calculate the horizontal displacement time history of a block-faced reinforced soil retaining wall. The method is based on the pseudo-dynamic method and differential kinematics equations, and this method was used to calculate the reinforcement material's tensile displacement and overall displacement in the reinforced area under earthquake motion, while simultaneously taking into account the accumulative deformation. The rationality and accuracy of this method are verified through comparison with model experiments and existing theories. Besides, parameter analysis was carried out to further confirm the applicability of this method. The study shows the method takes into account the influence of the accumulated deformation, and can effectively calculate the horizontal displacement time history of the block-faced reinforced soil retaining wall under larger magnitudes. Although the calculated values are smaller than the actual deformation, they are still relatively close. • Based on pseudo dynamic method and differential kinematics equations, an analytical method is proposed to calculate the horizontal displacement time history of a block-faced reinforced soil retaining wall. [ABSTRACT FROM AUTHOR]

The standard Permanent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) technique, which is commonly used for surface motion analysis, assumes linear deformation velocities. While effective for monitoring urban subsidence over short periods, it falls short when dealing with non-linear, earthquake-related deformations over extended timeframes. To address this limitation, we use a non-linear PSInSAR technique, which is an enhancement of PSInSAR, to identify non-linear deformation patterns. We processed Sentinel-1A images from ascending and descending orbits in the Islamabad/Rawalpindi region from December 2015 to January 2023 using non-linear PSInSAR. By calculating the differences in deformation, we analyzed surface movements and assessed the impact of the 2017 earthquake on urban areas. Our findings reveal that the earthquake significantly increased the deformation in ascending and descending orbit tracks, with an average deformation of up to 70 mm/yr and a line-of-sight movement of up to 30 mm/yr. Our observations indicate that the deformation is directed towards the line of sight in the north and south of the deformed area, suggesting subsidence between the two uplifting faults, potentially linked to a concealed fault line along the deformation zone boundary. This contradicts previous arguments, suggesting that water extraction is the leading cause of deformation. Our analysis with non-linear PSInSAR demonstrates that tectonics play a significant role in deformation, providing valuable insights into tectonic-activity-induced deformations in urban areas over the long term. [ABSTRACT FROM AUTHOR]

The article focuses on synthesizing research on the seismotectonics of the San Andreas Fault System within the San Gorgonio Pass region of Southern California. It explores the complex fault geometry, slip distribution, and seismic hazard implications through multidisciplinary studies, including geology, geophysics, and modeling. It aims to enhance understanding of fault behavior and earthquake risk assessment, serving as a model for studying restraining bends in strike-slip faults globally.

Elevated pore fluid pressure is proposed to contribute to slow earthquakes along shallow subduction plate boundaries. However, the processes that create high fluid pressure, disequilibrium compaction and dehydration reactions, lead to different effective stress paths in fault rocks. These paths are predicted by granular mechanics frameworks to lead to different strengths and deformation modes, yet granular mechanics do not predict their effects on fault stability. To evaluate the role of fluid overpressure on shallow megathrust strength and slip behavior, we conducted triaxial shear experiments on chlorite and celadonite rich gouge layers. Experiments were conducted at constant temperature (130 and 100°C), confining pressure (130 and 140 MPa), and pore fluid pressures (between 10 and 120 MPa). Fluid overpressure due to disequilibrium compaction was simulated by increasing confining and pore fluid pressure synchronously without exceeding the target effective pressure, whereas overpressure due to dehydration reactions was simulated by first loading the sample to a target isotropic effective pressure and then increasing pore fluid pressure to reduce the effective pressure. We find that the effects of fluid pressure and stress path on the mechanical behavior of the chlorite and celadonite gouges can generally be described using the critical state soil mechanics (CSSM) framework. However, path effects are more pronounced and persist to greater displacements in chlorite because its microstructure is more influenced by stress path. Due to its effects on microstructure, the stress path also imparts greater control on the rate‐dependence of chlorite strength, which is not predicted by CSSM. Plain Language Summary: High pore fluid pressure has been linked to complex slip modes along subduction plate boundary faults, such as low frequency earthquakes and slow slip. However, the role that pressurized fluids play in controlling these slip modes remains unclear. Along shallow subduction faults (<10 km), the source of pore fluid overpressure transitions with increasing depth from disequilibrium compaction of sediments to fluid release due to dehydration reactions like the smectite to illite transition. Using deformation experiments, we studied how different stress paths simulating these two processes affect the mechanical, frictional, and microstructural properties of shallow subduction fault rock at high fluid pressure. Key Points: Effective stress path and rock composition control effects of high pore fluid pressure on fault constitutive behaviorStress path effects on frictional behavior are more pronounced in simulated chlorite gouge than celadonite gouge due to differences in microstructureChlorite‐rich faults stabilize with increasing displacement at high pore fluid pressure and slow slip speeds [ABSTRACT FROM AUTHOR]

Genuine non‐double‐couple (non‐DC) components of a seismic source, defined here as the non‐DC components that are not due to summation of pure double‐couple (DC) components, provide important insight into special physical processes in non‐earthquake sources such as explosion, volcano eruption and collapse etc. Yet they remain challenging to be resolved. To address the issue and explore the physical mechanism of those special events, we develop a waveform‐polarity‐based moment tensor (WPMT) inversion method and employ it to study physical process in the 2014–2015 Bárðarbunga volcano event sequence. The WPMT method incorporates P‐wave polarity data and seismic waveforms in the source inversion, designs a source simplicity test to check possible complex rupture in the seismic source, and employs a simulated annealing algorithm to search the best source solution. The simplicity test checks consistency of the source processes in the initiation stage of the event and the major energy release process of the event, thus ensuring that the inferred non‐DC components are genuine to the seismic source. Real event and synthetic tests indicate that the WPMT method can identify and resolve genuine non‐DC components in a seismic source. The WPMT inversions of the Bárðarbunga sequence yield many genuine non‐DC source components and reveal that the eruptions are accompanied by seismic activities in depths of 1–5 km with magma migrations out of chambers, collapses of conduits, failures of normal faults, and a magma recharge at a depth of 9 km accompanied by a failure on a nearby normal fault. Plain Language Summary: Special seismic events such as explosion, collapse and volcanic eruption possess source components that are different from fault solutions used to represent a typical tectonic earthquake of simple shear. The identification and quantification of the source components of those special seismic sources thus play an important role in deciphering the physical process during those events. Yet, it remains challenging to resolve the source components of special seismic events due to the ambiguity of distinguishing them from an apparent one due to complex earthquake rupture. We develop a waveform‐polarity‐based moment‐tensor inversion to resolve the source components of a special seismic source and employ the method to study the physical process in the 2014–2015 Bárðarbunga volcano event sequence in Iceland. Real event and synthetic tests confirm method's capability of identifying and constraining the source components of special non‐earthquake events. The study of the Bárðarbunga sequence reveals that the eruptions are accompanied by seismic activities in depths of 1–5 km with magma migrations out of chambers, collapses of conduits, failures of normal faults, and a magma recharge at a depth of 9 km accompanied by a failure on a nearby normal fault. Key Points: We propose a waveform‐polarity‐based moment tensor inversion method to extract non‐double‐couple components of moderate seismic eventsReal event and synthetic tests show the method is effective in distinguishing and resolving genuine non‐double‐couple componentsMethod application reveals magma activities, conduit collapses and induced earthquakes during the 2014–2015 Bárðarbunga eruptions [ABSTRACT FROM AUTHOR]

Large block‐bounding faults on the Tibetan plateau are significant geological structures that accommodate tectonic movements and accumulate stress, leading to large earthquakes. Quantifying the interseismic slip deficit rate helps to better assess the earthquake potential. We combine available InSAR (2015–2020) and interseismic GPS data to determine fault coupling along 14 major block‐bounding faults. Spatially dense InSAR measurements remarkably improve the resolution of the coupling model. Combined with a GPS‐constrained block model, we examine the performance of the inversion approach with the stress constraint and the common Laplacian smoothing based on both synthetic tests and real data. We suggest that, for continental strike‐slip faults, adding the stress constraint can mitigate unphysical coupling distributions due to unreasonable assumptions or modeling artifacts, reducing the model uncertainty and improving the accuracy of the coupling model. This is particularly useful for segments featured by a highly heterogeneous distribution of coupling along the transition zone from locking to creeping region, partially‐coupling segment, and junction zone between main and subsidiary faults. We present a large‐scale fault coupling map along the major block‐bounding faults on the northeastern and eastern Tibetan plateau, highlighting the distinct degrees of fault coupling and lateral variations. The collage of coupling maps along different faults demonstrates the kinematic features over a broad time scale during earthquake cycles ranging from early to late interseismic phases, such as the segments ruptured during the 2001 Kokoxili earthquake and the 1920 Haiyuan earthquake. Plain Language Summary: Large faults at the boundary of blocks accommodate a significant portion of the relative movement between adjacent blocks and accumulate tectonic stress during the interseismic period. Consequently, these faults have a high potential to generate large earthquakes. To evaluate the distribution of strain accumulation, we analyze InSAR (2015–2020) and interseismic GPS measurements to construct a coupling model, which tells us the extent to which two blocks are locked together and accumulate stress before the next earthquake. We focus on 14 major faults on the eastern and northeastern Tibetan plateau. The addition of the spatially dense InSAR data helps to resolve the coupling distribution in greater detail, where GPS observations are limited. We evaluate different approaches to determine fault coupling, including stress constraints and smoothing techniques. Our findings indicate that adding a stress constraint performs better than the smoothing operator and helps mitigate physically unrealistic coupling distributions in the inversion using the spatial smoothing method. The stress constraint improves the accuracy of the coupling model. Based on the stress‐constrained inversion, we present a comprehensive fault coupling map in the northeastern and eastern Tibetan plateau, highlighting the spatial variations of fault coupling, which can be used in earthquake hazard assessment. Key Points: Stress constraints can mitigate unphysical coupling distributions and reduce the uncertainty of the coupling model for continental faultsWe highlight the improvement when using stress constraints in the case of sharp coupling contrasts along the strike‐slip faultWe provide a new coupling model along 14 major block‐bounding faults on the eastern and northeastern Tibetan plateau [ABSTRACT FROM AUTHOR]

All instrumented basaltic caldera collapses have generated Mw > 5 very long period earthquakes. However, previous studies of source dynamics have been limited to lumped models treating the caldera block as rigid, leaving open questions related to how ruptures initiate and propagate around the ring fault, and the seismic expressions of those dynamics. We present the first 3D numerical model capturing the nucleation and propagation of ring fault rupture, the mechanical coupling to the underlying viscoelastic magma, and the associated seismic wavefield. We demonstrate that seismic radiation, neglected in previous models, acts as a damping mechanism reducing coseismic slip by up to half, with effects most pronounced for large magma chamber volume/ring fault radius or highly compliant crust/compressible magma. Viscosity of basaltic magma has negligible effect on collapse dynamics. In contrast, viscosity of silicic magma significantly reduces ring fault slip. We use the model to simulate the 2018 Kı̄lauea caldera collapse. Three stages of collapse, characterized by ring fault rupture initiation and propagation, deceleration of the downward‐moving caldera block and magma column, and post‐collapse resonant oscillations, in addition to chamber pressurization, are identified in simulated and observed (unfiltered) near‐field seismograms. A detailed comparison of simulated and observed displacement waveforms corresponding to collapse earthquakes with hypocenters at various azimuths of the ring fault reveals a complex nucleation phase for earthquakes initiated on the northwest. Our numerical simulation framework will enhance future efforts to reconcile seismic and geodetic observations of caldera collapse with conceptual models of ring fault and magma chamber dynamics. Plain Language Summary: Caldera collapse manifests as the rapid subsidence of a kilometer‐scale block of crust circumscribed by a near‐circular fault on top of a volcano. The subsidence of the caldera block is caused by the eruption‐induced withdrawal of magma and reduction in pressure in the underlying magma chamber. All scientifically instrumented caldera collapses at volcanoes with low‐viscosity magma are accompanied by earthquakes of magnitude 5 and above. How do magma viscosity and the seismic wave radiation influence the amount of slip per earthquake on the fault? What can we learn about the dynamics of these earthquakes from seismic records? We address these questions by performing computer simulations of caldera collapse earthquakes and compare the results to the seismic records from the Kı̄lauea caldera collapse of 2018. Key Points: Seismic wave radiation through ring fault and magma, as well as high magma viscosity, reduce fault slip by up to half during collapseRupture propagation, downward momentum transfer via magma pressure waves, and chamber pressurization are identified in unfiltered seismogramsComparison between simulated and observed near‐field seismograms from Kı̄lauea 2018 reveals complex nucleation phase on the ring fault [ABSTRACT FROM AUTHOR]

Two centrifuge shaking table tests were carried out to investigate the seismic response of a subway station structure in liquefiable interlayer site. For the centrifuge shaking table test of underground structures, there is no precedent for the model preparation of the liquefiable interlayer site for reference. In the paper, some model making techniques were proposed for the liquefiable interlayer site, including the preparation of liquefiable interlayer site (clay consolidation, sand saturation and assembly of interlayer site), structural waterproof treatment, releasing initial pore pressure in the sand layer during centrifugal loading. The model tests obtained ideal results, which achieved the experimental goal of studying the seismic response of subway station structure in liquefiable interlayer site. The research conclusions are as follows. The vertical inertia effect of the overlying soil could significantly increase the axial pressure on the columns of an underground frame structure and then, reduce its horizontal deformation capacity. The columns are the weak components of a subway station structure, which are easy to be damaged under earthquake. The ends of a column are the vulnerable parts and were prone to damage. The classification standard of the limits of relative displacement ratio for underground structure proposed by Du et al. (Du et al. in Earthq Eng Struct Dyn 50:655–672, 2021) is reliable and can provide a method for earthquake damage response evaluation of an underground structure. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of soil–structure interaction (SSI) on the inelastic displacement ratio of bridge structures subjected to near-fault pulse-like earthquake ground motions. SSI was modeled using a discrete-time recursive filter approach and frequency-dependent foundation–soil impedance functions. A total of 105 near-fault earthquake ground motion records were used for the analysis. The study also compared the soil–foundation–superstructure (SFS) system with a fixed-base system to explore the effects of spectral period normalization, strength reduction factor, earthquake magnitude, site-to-source distance, and peak ground velocity on the inelastic displacement ratio. The findings indicate that both the SFS and fixed-base systems have significant inelastic displacement demand under near-fault earthquakes, with values that can be 2–3 times higher than those predicted by ASCE-41-13, particularly in the short period range. Furthermore, as the structural period approaches the earthquake pulse period, the SFS system generally shows larger inelastic displacement ratios compared to the fixed-base system. The analytical results provide insight into the factors affecting the inelastic displacement ratio for near-fault pulse-like earthquakes. [ABSTRACT FROM AUTHOR]

Pore fluid is ubiquitous within the Earth's crust and severely impacts shear rupture propagation and the slip behaviors of faults. We conducted triaxial experiments on sandstone to investigate the effects of crack damage, confining pressure, and water on fault slip behaviors and rupture propagation. Two loading configurations, conventional loading and increasing-amplitude cyclic loading, were conducted to compare the inelastic behavior and failure modes of sandstone samples. In addition to a macroscopic deformation and mechanical properties analysis, a noncontact optical scanner and magnetic resonance imaging technique were used to analyze the microstructural evolution of the sandstone. The results show that a higher confining pressure results in a more homogeneous fault plane. Fault slip behaviors can be divided into the slip-strengthening and slip-weakening stages. In the brittle regime, pore water reduces the brittle strength of rocks but does not induce different fault slip behaviors. When the confinement is high enough, rocks fail in the brittle–ductile transition regime where dynamic faulting is prohibited. In the brittle–ductile transitional regime, pore water enhances stabilization, and the slip behaviors distinctively differ from those occurring without water. [ABSTRACT FROM AUTHOR]

The northeastern margin of the Tibetan Plateau (NE Tibetan Plateau) exhibits active geological structures and has experienced multiple strong earthquakes, with M ≥ 7, throughout history. Particularly noteworthy is the 1920 M81/2 earthquake in the Haiyuan region that occurred a century ago and is documented as one of the deadliest earthquakes. Consequently, analyzing seismic risks in the northeastern margin of the Tibetan Plateau holds significant importance. The b value, a crucial parameter for seismic activity, plays a pivotal role in seismic hazard analyses. This study calculates the spatial b values in this region based on earthquake catalogs since 1970. The study area encompasses several major active faults, and due to variations in b values across different fault types, traditional grid-search methods may introduce significant errors in calculating the spatial b value within complex fault systems. To address this, we employed the hierarchical space–time point–process (HIST-PPM) method proposed by Ogata. This method avoids partitioning earthquake samples, optimizes parameters using Akaike's Bayesian Information Criterion (ABIC) with entropy maximization, and theoretically allows for a higher spatial resolution and more accurate b value calculations. The results indicate a high spatial heterogeneity in b values within the study area. The northwestern and southeastern regions exhibit higher b values. Along the Haiyuan fault zone, the central rupture zone of the Haiyuan earthquake has relatively higher b values than other regions of this fault zone, which is possibly related to the sufficient release of stress during the main rupture of the Haiyuan earthquake. The b values vary from high in the west to low in the east along the Zhongwei fault. On the West Qinling fault zone, the epicenter of the recent Minxian–Zhangxian earthquake is associated with a low b value. In general, regions with low b values correspond well to areas with moderate–strong seismic events in the past 50 years. The spatial differences in b values may reflect variances in seismic hazards among fault zones and regions within the same fault zone. [ABSTRACT FROM AUTHOR]

Today's earthquakes are the most direct manifestation of the latest tectonic activity and are the most powerful tool to understand the characteristics of nonrigid deformation within a continent. Particularly, the newly formed faults that have been active since the Late Pleistocene are characterized to have low development maturity, poor connectivity in geometric structure, and obvious difference in strike/depth dip in different sections. Therefore, earthquakes can reveal their three-dimensional space changes, especially the characteristics of brittle-ductile transition depth. Earthquakes can also promote the understanding of the preparation and earthquake generation process of newly formed active faults. The newly formed strike-slip active faults in the Bohai Bay Basin have experienced many strong earthquakes, including the Tangshan MS7.8 and the three Ninghe MS≥ 6.2 earthquakes. The crustal brittle-ductile transition depth revealed by these earthquakes has an important practical significance to understanding the seismogenic mechanism and activity of the region. In this paper, the new fault in the Baodi Miaozhuang uplift in the Bohai Bay Basin is taken as the target fault. In addition, the 2012 Baodi MS4.0 and MS3.5 earthquakes in the Baodi uplift and the 1976 Ninghe MS6.2 and MS6.9 and the 1977 Ninghe MS6.2 earthquakes in the Miaozhuang uplift are taken as the research objects. Finally, the CAP method is used to study the source mechanism solution and the source depth of the Baodi MS4.0 and MS3.5 earthquakes based on the waveform data from the Capital Circle Digital Seismic Network. The double difference method is used to locate the source positions of two earthquake sequences by employing the Sp converted wave of near earthquakes to accurately determine the source depth. Moreover, combined with other data, the seismogenic mechanism of earthquakes in this area and the brittle-ductile transition depth of new fractures are discussed. The following results were found. (1) The source properties of the Baodi MS4.0 and MS3.5 earthquakes are not completely consistent with the known faults on the exposed surface of the Baodi Miaozhuang uplift. Combining the research results of the source parameters of the three Ninghe earthquakes having an MS ≥ 6.2, it is inferred that they all occurred in the Baodi-Ninghe deep fault. (2) Based on the models of electrical structure and rheological structure in the focal area, the five significant earthquakes in Baodi Miaozhuang uplift reveal that the brittle-ductile transition depth of the Baodi-Ninghe deep fault is about 15 km. (3) Based on the dynamic evolution process of the Bohai Bay Basin and relevant deep geophysical exploration data, it is hypothesized that the seismic activity in this area is mainly the result of the Baodi-Ninghe deep fault and deep fluid actions. [ABSTRACT FROM AUTHOR]

The significant Shillong earthquake of 1897 in the western part of the Shillong Massif profoundly impacted the entire Northeast India region, resulting in extensive devastation at both surface and subsurface levels. Numerous land fissures, sand veins, swampy areas, and land tilting and upliftment were formed during the earthquake in the western part of the Shillong plateau. This study adopts an integrated approach, combining seismic, geophysical, and fluvial geomorphology methods, to quantify the co-seismic subsurface rupture. Multichannel Surface Wave Analyzer (MASW) and resistivity surveys are conducted at fourteen locations along three profiles crossing the Krishnai and Chedrang Rivers in the Chedrang valley. In certain specified locations, significant surface rupture is observed, and the co-seismic surface uplift is measured to be 5 + 1 m on vertical planes at the western end of the rupture of the Oldham fault. The shear wave velocities along the profiles range from 184 to 466 m/s, indicating a platform for intense shallow seismicity triggered by fracture. The region experiences intense seismic activity, with the bottom of the seismogenic zone estimated to be 40 km, mainly dominated by thrust with strike-slip components. The local stress pattern in the Chedrang valley, oriented NE-SW, differs from the regional stress pattern, NNW-SSE, indicating the influence of geodynamic controls. Fluvial-morphometric measurements of the Krishnai and Chedrang Rivers for six different stretches in each case during 1964, 1991, and 2014 reveal a westward shifting of the Krishnai River ranging from 190 to 269 m, while the Chedrang River exhibits variable south-westward avulsion along these stretches, shifting approximately 132–312 m. Detailed fluvial morphological mapping highlights a key site where the stratigraphy of the fault scarp, reaching a height of 13ft, indicates the presence of modern channels, colluviums, gravel, and pebble beds with sand lenses, representing a portion of a mega thrust event. Simultaneously, high-resolution topographic profiles are analyzed using Total Station (GPS based) to observe co-seismic surface uplifts induced by the 1897 earthquake. The simplest deformation model suggests that a majority of the intra-seismic elastic loading east of the Krishnai and Chedrang rivers was uplifted during the 1897 earthquake due to co-seismic and post-seismic rupture, primarily in the western part of the Shillong plateau beneath the Chedrang valley. This energy transfer affected the north–south direction of the Krishnai valley, where the Krishnai river and the 'Mori' (dead) Krishnai river exist, as evidenced by subsurface deformation and subsequent avulsion of the Krishnai river. The parameters investigated in this study contribute to a better understanding of the geodynamics and seismic hazard assessment of the region, providing valuable insights into the consequences of the 1897 earthquake and its implications for future seismic events. [ABSTRACT FROM AUTHOR]

The potential for future earthquakes on faults is often inferred from inversions of geodetically derived surface velocities for locking on faults using kinematic models such as block models. This can be challenging in complex deforming zones with many closely spaced faults or where deformation is not readily described with block motions. Furthermore, surface strain rates are more directly related to coupling on faults than surface velocities. We present a methodology for estimating slip deficit rate directly from strain rate and apply it to New Zealand for the purpose of incorporating geodetic data in the 2022 revision of the New Zealand National Seismic Hazard Model. The strain rate inversions imply slightly higher slip deficit rates than the preferred geologic slip rates on sections of the major strike‐slip systems including the Alpine Fault, the Marlborough Fault System and the northern part of the North Island Fault System. Slip deficit rates are significantly lower than even the lowest geologic estimates on some strike‐slip faults in the southern North Island Fault System near Wellington. Over the entire plate boundary, geodetic slip deficit rates are systematically higher than geologic slip rates for faults slipping less than one mm/yr but lower on average for faults with slip rates between about 5 and 25 mm/yr. We show that 70%–80% of the total strain rate field can be attributed to elastic strain due to fault coupling. The remaining 20%–30% shows systematic spatial patterns of strain rate style that is often consistent with local geologic style of faulting. Plain Language Summary: The potential for future earthquakes on faults is often inferred from velocities of the ground surface derived from satellite geodesy, but this approach can be challenging in complex deforming zones with many closely spaced faults. We present a new methodology for estimating the rate at which energy is accumulating on faults using measurements of surface strain rates. The method is applied to New Zealand for the purpose of incorporating geodetic data in the 2022 revision of the New Zealand National Seismic Hazard Model. We show that 70%–80% of the total deformation field can be attributed to energy accumulation on known active faults while the source of the remaining 20%–30% remains unknown. Along some of the major faults in New Zealand we find some important differences in rates of energy accumulation from what is expected from geologic data. Estimated rates are significantly lower than even the lowest geologic estimates on some faults in the fault system near highly‐populated Wellington. Key Points: We develop a method to invert geodetically derived strain rates for slip deficit rates on faultsWe find small but systematic differences between slip deficit rates and geologic slip ratesAbout 70%–80% of the surface strain can be attributed to elastic strain due to coupling on faults [ABSTRACT FROM AUTHOR]

On 15 January 2023, a shallow, moderate earthquake with a magnitude (Mw) of 4.7 and a depth of one kilometer struck the northern part of Leyte Island in the central Philippines. Originating along the northern Leyte segment of the Philippine Fault, a well-established creeping fault, the earthquake caused significant geologic, structural, and socio-economic impacts despite its low magnitude. Probable surface rupture and landslides were reported, leading to a comprehensive field investigation. Our investigation revealed an ~8 km discontinuous surface rupture along the northern Leyte segment of the Philippine Fault, with a maximum left-lateral displacement of 2 cm. This was the first documented occurrence of such a phenomenon associated with an earthquake of a magnitude less than 6, particularly along a creeping fault segment. The maximum ground shaking felt was reported on the PHIVOLCS Earthquake Intensity Scale (PEIS) to be VI (very strong), equivalent to a Modified Mercalli Intensity (MMI) of VI along the fault strike. However, strong motion accelerographs recorded a peak ground acceleration (PGA) of 0.407 g, equivalent to PEIS VIII (very destructive), attributed to local site amplification influenced by subsurface geology. In the area where the local site amplification occurred, limited liquefaction was observed on marshlands with recent and alluvial deposits. Two landslides were observed in the mountainous area west of the fault. Structural damages were noted in areas with PEIS VI intensity and areas transected by the surface rupture. Despite the earthquake's low magnitude, the event documented significant impacts, including surface ruptures, liquefaction, landslides, and severe structural damage. The peculiarities of this event are attributed to the shallowness of the earthquake source, and local site conditions, including geology, geomorphology, and soil properties, contributed to the severity of the impacts. Moderate in size, this earthquake emphasizes the importance of documenting moderate-sized earthquakes as a tool and guide for medium- and long-term earthquake risk assessment and resiliency. [ABSTRACT FROM AUTHOR]

Ruptures of pipelines can result in dangerous fluids spreading toward populated areas. It is critical for designers to have tools that can accurately predict whether populated areas might be within a plume rupture zone. Numerical simulations using computational fluid dynamics (CFD) are compared here with experimental and real-world carbon dioxide ruptures. The experimental data were used to validate the computer model; subsequently, the algorithm was used for a real-world rupture from 2020 that occurred in the USA. From experiments, CFD predictions were superior to diffusion model results based on measurements made downstream of the release (within 1% concentration). Results from the real-world simulation confirm that a nearby town was in a plume pathway. Citizens in the town sought medical attention consistent with the calculated plume concentrations. CFD predictions of the airborne concentration of carbon dioxide in the town approximately 1 mile (1.5 km) downstream of the rupture reveal time-averaged concentrations of ~5%. One person was unconscious for ~45 min at a distance of 0.6 miles from the rupture site; other unconscious persons were in the center of the town (~1 mile from the rupture site) and ~1.2 miles from the rupture. These reports are in excellent agreement with the calculated plume concentrations in the region. [ABSTRACT FROM AUTHOR]

Recent seismic events have unequivocally highlighted the susceptibility of fault-crossing bridges to the synergistic effects of ground surface vibrations on either side of the fault plane and the tectonic dislocations arising from fault-induced surface ruptures. This study delineates both seismic and parametric response analyses of fault-crossing suspension bridges, employing a straightforward yet efficacious method for simulating desired ground motions near fault-rupture zones. Herein, we introduce a user-friendly method to incorporate predicted fault-induced displacements, accounting for both fling-step and directivity effects, into processed ground motion chronologies, enabling the generation of dip-slip fault ground motions. The accuracy and efficacy of the proposed method are affirmed by juxtaposing the generated ground motions with the observed ones (MGM). An exhaustive parametric analysis, addressing factors like fault-crossing location, fault-crossing angle, and frequency components of fault-crossing ground motions, of a suspension bridge over a rupture fault, is executed using the fashionable ANSYS software. This study provides clear and specific guidelines for the seismic design of suspension bridges traversing rupture faults. [ABSTRACT FROM AUTHOR]

On September 17th and 18th, 2022, shallow earthquakes with magnitudes of 6.6 (ML) and 6.8 (ML) occurred in the eastern Taiwan Longitudinal Valley, which marks the collision zone between the Philippine Sea plate and the Eurasian plate, and led to noticeable surface deformation and ruptures within 70 km. This study primarily focuses on the southernmost section of the rupture zone—the Pingting Terrace. Surface rupture locations and behaviors correspond to changes in topography, providing mutual confirmation that the deformation behavior of Pingting Terrace is complex. Based on the distribution of surface ruptures and topography changes, this study roughly divides the Pingting Terrace into northern and southern segments, using the central concave feature as a boundary. The Riedel shear model analysis results show that the principal shear directions in the northern and southern segments are N–S trending and azimuth 20°, respectively. The maximum principal stress orientations are around 135° for the northern and 155° for the southern segments. These findings align with the fault mechanical investigation of the Lichi Mélange in the northern Muken River area of the Pingting Terrace. This suggests spatial changes in shear zone orientations within the Lichi Mélange, which contribute to developing pressure ridges due to transpressional forces. As a result, the Pingting Terrace experiences rapid uplift, causing the Luliao River to migrate southward into the Beinan River, while the eastern Beinan River turns to the eastward edge of the Pingting Terrace. Key points: Co-seismic surface rupture analysis using Riedel shear model. Flower structure of the Pingting Terrace. Relationship between the River channel change and the tectonic activity. [ABSTRACT FROM AUTHOR]

The neotectonic processes are crucial for identification of active faults in a seismic unstable area. The Aїn Smara active fault runs along the Middle Rhumel Valley located in Constantine area of Algerian Eastern Tell Atlas mountain chain and it emerges in the south‒western part of the epicentral zone of the earthquake occurred on October 27, 1985 (Mw = 5.8) within a corridor displaying morphological features and deformed Pliocene‒Quaternary layers, which are the consequence of transpressive tectonic regime. In our study the morpho-tectonic and structural research supported by the fieldwork, was performed. The thick fault gouge indicating simple shear deformation, fault breccias and minor faults affecting the Pliocene limestone and Quaternary alluvial terraces, were found. The active fault splits into northern and southern segments. The northern segment corresponds to the El Aria Fault that ruptured during the earthquake in 1985 and the southern segment with the studied Aĭn Smara Fault. Our research showed the significant extent of the active fault and including its parameters for improved seismic hazard assessment of the Constantine area. [ABSTRACT FROM AUTHOR]

The seismogenesis of rocks is mainly affected by their mineral composition and in situ conditions (temperature and state of stress). Diverse laboratory experiments have explored the frictional behaviour of the rocks and rock-forming minerals most common in the crust and uppermost mantle. However, it is debated how to "upscale" these results to the lithosphere. In particular, most earthquakes in the crust nucleate down to the crustal seismogenic depth (CSD), which is a proxy for the maximum depth of crustal earthquake ruptures in seismic hazard assessments. In this study we propose a workflow to upscale and validate those laboratory experiments to natural geological conditions relevant for crustal and upper-mantle rocks. We used the southern Caribbean and northwestern South America as a case study to explore the three-dimensional spatial variation of the CSD (mapped as D90, the 90 % percentile of hypocentral depths) and the temperatures at which crustal earthquakes likely occur. A 3D steady-state thermal field was computed for the region with a finite-element scheme using the software GOLEM, considering the uppermost 75 km of a previously published 3D data-integrative lithospheric configuration, lithology-constrained thermal parameters, and appropriate upper and lower boundary conditions. The model was validated using additional, independent measurements of downhole temperatures and heat flow. We found that the majority of crustal earthquakes nucleate at temperatures less than 350 ∘ C, in agreement with frictional experiments of typical crustal rocks. A few outliers with larger hypocentral temperatures evidence nucleation conditions consistent with the seismogenic window of olivine-rich rocks, and can be due to either uncertainties in the Moho depths and/or in the earthquake hypocentres or the presence of ultramafic rocks within different crustal blocks and allochthonous terranes accreted to this complex margin. Moreover, the spatial distribution of crustal seismicity in the region correlates with the geothermal gradient, with no crustal earthquakes occurring in domains with low thermal gradient. Finally, we find that the largest earthquake recorded in the region (Mw=7.1 , Murindó sequence, in 1992) nucleated close to the CSD, highlighting the importance of considering this lower-stability transition for seismogenesis when characterizing the depth of seismogenic sources in hazard assessments. The approach presented in this study goes beyond a statistical approach in that the local heterogeneity of physical properties is considered in our simulations and additionally validated by the observed depth distribution of earthquakes. The coherence of the calculated hypocentral temperatures with those expected from laboratory measurements provides additional support to our modelling workflow. This approach can be applied to other tectonic settings worldwide, and it could be further refined as new, high-quality hypocentral locations and heat flow and temperature observations become available. [ABSTRACT FROM AUTHOR]

Displacement and seismic activities are critical elements in understanding the geodynamic behaviour of regions. Particularly in Banten, a region with significant irrigation infrastructure, these factors have implications for land use and infrastructure stability. From 2017–2020, Banten experienced varying displacement dynamics and seismic events, and DInSAR processing proved instrumental in achieving high-precision vertical displacement measurements. The challenge was to discern the pattern of these displacements in relation to significant earthquakes and the implications for specific high-density irrigation zones. Our study reveals a notable differentiation in displacement dynamics across different periods, especially in regions proximal to earthquake epicentres. For instance, the 2019 earthquake of magnitude 5 MW corresponded with uplift activities in certain irrigation areas, contrary to the subsidence observed in the preceding period. These findings emphasise the intricate relationship between seismic activities, vertical displacements, and their potential impact on key infrastructural elements in Banten. Moreover, understanding this interplay is not only crucial for regional planning but also offers insights into how such dynamics can influence areas with similar geophysical properties globally. Broadly, our results underscore the importance of consistent monitoring and analytical methodologies, like DInSAR, in regions susceptible to seismic shifts. Such knowledge can inform infrastructure development, resource allocation, and disaster preparedness strategies, ensuring the safety and sustainability of both natural and man-made environments. [ABSTRACT FROM AUTHOR]

Significant amounts of gases are emitted from the earth's crust into the atmosphere before, during, and after major earthquakes. To understand the relationship between gas emissions, earthquakes, and tectonics, we conducted a thorough investigation using satellite data from AQUA AIRS. We focused on three major earthquakes: the 12 May 2008 Wenchuan MW 7.9 earthquake in China's intra-continental plate, the 26 December 2004 Sumatra-Andaman MW 9.1 earthquake in Indonesia Island, and the 4 April 2010 Baja California MW 7.2 earthquake in Mexico's active plate margin. Anomalies in the total column (TotCO) and multiple layers (CO VMR) of carbon monoxide were observed along fault zones, with peak values at the epicenter areas. Furthermore, temporal anomalies of TotCO and CO VMR appeared in the month of the Wenchuan earthquake in the intra-continent, three months prior to the Sumatra-Andaman earthquake and one month before the Baja California earthquake in the active plate margins, respectively. Notably, the duration of CO anomalies before earthquakes in active plate margins was longer than that in the intra-continental region, and the intensity of the CO anomaly in active plate margins was higher than that in the intra-continental region. The results show a profound correlation with both seismic and tectonic activities, which was particularly evident in the earthquake's magnitude, rupture length, and the tectonic settings surrounding the epicenter. Furthermore, the type of the fault at which the earthquake occurred also played an important role in these CO anomaly variations. These findings support the identification of earthquake precursors and may help improve our understanding of earthquake forecasting and tectonics. [ABSTRACT FROM AUTHOR]

The potential of faults to show earthquake‐generating slip instabilities depends not only on the intrinsic frictional properties of the fault zone, but also on the elasticity of the surrounding material. A velocity‐weakening fault is expected to show increasingly unstable frictional behavior with decreasing local elastic stiffness around the fault zone. Fault zone roughness can cause slip in the shear direction to be accompanied by fault‐normal movement, modulated by fault‐normal elastic properties, however these effects are poorly understood. Here, we systematically vary the stiffness surrounding the fault in both the shear‐parallel and fault‐normal directions, to investigate the origin of slip instabilities and changes in friction constitutive properties. We confirm the transition from stable sliding through slow slip to stick‐slip due to reduced fault‐parallel stiffness, and that the occurrence of different types of slip events can be explained by the ratio between shear and critical stiffness. In contrast, reducing the fault‐normal stiffness produces stick‐slip instabilities under conditions where the conventional critical stiffness criterion predicts stable sliding, and does not produce transitional slow slip events. Our data suggest that: (a) the stability criterion for frictional slip should be modified to incorporate fault‐normal stiffness, and (b) the unexpected slip instabilities may represent wrinkle‐like slip pulses, possibly due to a stiffness asymmetry introduced by lowering the fault normal stiffness on one side of the fault. This implies that earthquakes may occur when the fault‐normal stiffness, or bulk modulus for natural faults, is decreased and/or asymmetric across the fault zone, both of which may be common in nature. Plain Language Summary: Earthquakes occur on fault planes, but whether a fault will show stable sliding or host earthquakes, or their lab equivalent called "stick‐slip", depends only partly on the fault properties but also on how the fault and the surrounding rock respond to stress changes (the stiffness). Previous studies have shown that the transition between stick‐slip instabilities and stable sliding along a fault, can be triggered by changing the stiffness in the direction along the fault plane. However, faults commonly also have movement perpendicular to the fault plane, for example, if the fault surface is very rough, and therefore we study the effect of stiffness changes both perpendicular and parallel to the fault plane. We confirm previous observations when changing the stiffness parallel to the fault plane, but also observe unexpected stick‐slip instabilities when we decrease the stiffness perpendicular to the fault plane. This means that: (a) we have to adjust the stiffness criterion where stick‐slip instabilities are expected to include the fault‐normal stiffness, and (b) the unexpected stick‐slip instabilities at low fault perpendicular stiffness may be a different type of slip instability, called wrinkle‐like slip pulses, that may occur when one side of the fault is stiffer than the other. Key Points: Reduced fault‐normal stiffness alone can cause stick‐slip instabilities, but not slow slip in quartz gougeSystematically reducing both fault‐normal and shear‐parallel stiffness shows highly irregular slip eventsAdapting the critical stiffness criterion for fault‐normal stiffness shows slip instabilities are more likely [ABSTRACT FROM AUTHOR]

We successfully detected widely distributed ground displacements for the 2023 Kahramanmaraş, Turkey, earthquakes by conducting interferometric synthetic aperture radar (InSAR) analyses using a ScanSAR observation mode. Major deformation extended approximately 350 and 150 km along the southern and northern strands bifurcating in the west of the East Anatolian Fault, produced by the main shock and the largest aftershock. The deformation map reveals that the ruptures propagated on the Erkenek, Pazarcık and Amanos segments on the southern strand and the Çardak segment on the northern strand. The fault plane of the northern strand bends approximately 45° at both edges with Z-shaped crank geometry. The bending fault at the western edge runs just along the Çardak segment but does not reach the Savrun segment, while at the eastern edge it deviates from known active faults such as Sürgü, Malatya faults and Doğansehır fault zone. A 3-D displacement map demonstrates that almost pure left-lateral fault motions were distributed along the two strands, with little vertical deformation. The moment magnitudes estimated from the slip distribution model were 7.82 and 7.66 for the southern and northern strands, respectively, with the Erkenek and Çardak segments having the largest released seismic moments on each strand, corresponding to approximately 31 and 57 per cent of the total, respectively. The Coulomb Failure Function change values indicate that the main shock can promote the largest aftershock with a standard value of the effective friction coefficient. Additionally, the unclamping effect controlled by the frictional property of the rock was a key factor in pulling the trigger of the seismic event on the northern strand. The historically accumulated and released seismic energies were imbalanced for the Pazarcık and Erkenek segments, suggesting that the 2023 event does not support a simple characteristic earthquake model; rather, it may be consistent with a supercycle model, in which the slip remnants from the characteristic earthquakes have been historically accumulated as coupling on a fault and released as huge earthquakes at longer intervals. [ABSTRACT FROM AUTHOR]

Atlantic Canada encompasses geological evidence of the orogenic and rifting episodes that inspired the development of the theory of plate tectonics and the fundamental concept of the Wilson cycle. To provide a regional crustal-scale view that can complement surface mapping studies and sparse seismological investigations, an onshore–offshore 3-D constrained gravity inversion methodology is proposed involving incorporation of topography and an inversion mesh that is laterally variable in terms of its maximum depth extent. A 3-D density anomaly model for the entirety of Atlantic Canada and its environs is generated, with the inverted density distribution structure and extracted isodensity surfaces showing excellent correspondence with independent and co-located controlled source and passive seismic constraints. The full density model and crustal thicknesses from this work are made freely available so that they may be used for further study, for instance as inputs for deformable plate reconstruction modelling. [ABSTRACT FROM AUTHOR]

Pore fluids are ubiquitous throughout the lithosphere and are commonly invoked as the cause of induced seismicity and slow earthquakes. We perform lab experiments to address these questions for drained fault conditions and low pore pressure. We shear simulated faults at effective normal stress σn′ $\left({\sigma }_{n}^{\prime }\right)$ of 20 MPa and pore pressures Pp from 1 to 4 MPa. We document the full range of lab earthquake behaviors from slow slip to elasto‐dynamic rupture and show that slow slip can be explained by the slip rate dependence of the critical rheologic stiffness without dilatancy hardening or other fluid effects. Our fault permeabilities ranges from 10−18 to 10−17 m2 with an initial porosity of 0.1 and estimated fluid diffusion time ≈1 s. Slow slip and quasi‐dynamic fault motion may arise from high Pp at higher pressures but dilatancy strengthening is not a general requirement. Plain Language Summary: Earthquakes begin and propagate within the fluid‐saturated rocks of Earth's crust. Many investigators have suggested that high pore fluid pressure (Pp) is essential for slow earthquakes and tremor. These studies rely on the idea that changes in Pp can impact rupture propagation speed by dilatant volume increase during faulting with concurrent increases in fault effective normal stress. Thus, understanding the processes that produce slow‐slip versus dynamically propagating rupture is integral to seismic hazard forecasting. Here, we describe experiments on granular faults that produce the full spectrum of slip observed in nature. We measure the mechanical and hydraulic behavior of the faults and determine that frictional and fluid‐driven processes occur in conjunction. Importantly, we demonstrate that frictional processes are sufficient to explain slow‐slip when fluid migration is not inhibited. We demonstrate that for low pore fluid pressures, the full transition from slow slip to dynamic rupture events can be explained as a frictional effect via the critical rheologic stiffness. Key Points: The frictional stability transition does not require dilatant hardening for granular fault zones sheared at low pore pressuresSlow earthquakes and quasi‐dynamic fault slip can be explained by the strain‐rate dependence of the critical fault stiffness (Kc)For the effective normal stresses studied, pore pressure has a negligible impact on frictional stability and the mode of fault slip [ABSTRACT FROM AUTHOR]

The Mj6.5 (Mw6.2) event that occurred on 5 May 2023 near the northern shoreline of the northeastern tip of the Noto Peninsula, central Japan, is the largest event to date in a long‐lasting, intense earthquake swarm. Here we have created a more precise aftershock catalog associated with the 2023 Mj6.5 and the second‐largest 2022 Mj5.4 sequence to understand the rupture process of this largest earthquake. Most of the aftershocks are aligned along a ∼45° SE‐dipping plane. The mainshock initially ruptured the same deep section of the fault zone that had been ruptured by the 2022 Mj5.4 event, before propagating rapidly to shallow depths and to offshore along the ruptured fault plane. The aftershock front migrated at a speed of ∼20 km/hr. This rapid upward migration of the immediate aftershocks might be driven by upwelling of crustal fluids along the intensely fractured and permeable fault zone via mainshock dynamic rupture. Plain Language Summary: Near the northeastern tip of the Noto Peninsula, central Japan, a long‐lasting, intense earthquake swarm has continued since November 2020. On 5 May 2023, the largest Mj6.5 (Mw6.2) event to date occurred. We precisely located the aftershock distribution following the 2023 Mj6.5 and the second‐largest 2022 Mj5.4 sequence and enhanced the catalog by searching events based on waveform similarity to understand the rupture process of this largest earthquake. The 2023 Mj6.5 event initially ruptured the same deep section of the fault that had been ruptured by the 2022 Mj5.4 event, before propagating rapidly to shallow depths and to offshore along the ruptured fault. We can see that the aftershock front moved at a speed of ∼20 km/hr, which is a rare case that constrains the rapid movement of aftershocks. The rapid upward movement of the aftershocks may have been caused by the upwelling of crustal fluids along the permeable fault zone created by the dynamic rupture of the mainshock. Key Points: We constructed a more precise aftershock catalog associated with the two major ruptures during a long‐lasting intense seismic swarmWe identify a rapid migration of early aftershocks following the largest 2023 Mj6.5 earthquake to date during the seismic swarmUpwelling of crustal fluids along the fractured permeable fault zone could drive the rapid migration of early aftershocks [ABSTRACT FROM AUTHOR]

On 6 February 2023, the MW 7.8 Pazarcik and the MW 7.5 Elbistan earthquakes occurred in southeastern Turkey, close to the Syrian border, causing many deaths and a great deal of property destruction. The Pazarcik earthquake mainly damaged the East Anatolian Fault Zone (EAFZ). The Elbistan earthquake mainly damaged the Cardak fault (CF) and the Doğanşehir fault (DF). In this study, Sentinel-1A ascending (ASC) and descending (DES) orbit image data and pixel offset tracking (POT) were used to derive surface deformation fields in the range and azimuth directions induced by the Pazarcik and Elbistan earthquakes (hereinafter referred to as the Turkey double earthquakes). Utilizing GPS coordinate sequence data, we computed the three-dimensional surface deformation resulting from the Turkey double earthquakes. The surface deformation InSAR and GPS results were combined to invert the coseismic slip distribution of the EAFZ, CF, and DF using a layered earth model. The results show that the coseismic ruptures of the Turkey double earthquakes were dominated by left-lateral strike-slips. The maximum slip was 7.76 m on the EAFZ and about 8.2 m on the CF. Both the earthquakes ruptured the surface. The Coulomb failure stress (CFS) was computed based on the fault slip distribution and the geometric parameters of all the active faults within 300 km of the MW 7.8 Pazarcik earthquake's epicenter. The CFS change resulting from the Pazarcik earthquake suggests that the subsequent Elbistan earthquake was triggered by the Pazarcik earthquake. The Antakya fault experienced an increase in CFS of 8.4 bars during this double-earthquake event. Therefore, the MW 6.3 Uzunbağ earthquake on 20 February 2023 was jointly influenced by the Turkey double earthquakes. Through stress analysis of all the active faults within 300 km of the MW 7.8 Pazarcik earthquake's epicenter, the Ecemis segment, Camliyayla fault, Aadag fault, Ayvali fault, and Pula segment were all found to be under stress loading. Particularly, the Ayvali fault and Pula segment exhibited conspicuous stress loading, signaling a higher risk of future seismic activity. [ABSTRACT FROM AUTHOR]

The fortification system of the tunnel structure spanning the active fault, such as the failure mechanism and fault-resistant design (measures), has not been thoroughly established. In this study, the self-developed cross-fault large-scale bedrock dislocation loading device platform is utilized to carry out the model test of the tunnel structure and soil site of sand and cohesive soil when the low-angle reverse fault dislocation occurs, based on the earthquake damage. The results demonstrate that: (1) When the fault is staggered, the segmented flexible joint tunnel segment is more favorable in the cohesive soil site. (2) When compared to the cohesive soil tunnel structure site, the strain change of the tunnel structure in the sandy soil site is greater, with the vault increasing by roughly two times and the arch bottom increasing by nearly six times. After the tunnel is buried, the uplift range of the sand cover layer grows, revealing uneven deformation, and the rupture zone migrates to the footwall; hence, the sand site plays a "add seismic" role in the cross-fault tunnel structure. (3) Knowing the location and shape of the rupture range of the overburden soil caused by bedrock dislocation under different inclination angles and soil properties is required in the design in order to place the buried depth and segment length of the tunnel reasonably and take fault-resistant measures. [ABSTRACT FROM AUTHOR]

The developmental phase of the fault deformation zone denotes the zone of weak deformation (with strong concealment) that evolves within the sedimentary cover of the basin. Recent studies have unveiled the objectively existing tectonic phenomenon of weakly deformed tectonic belts within the sedimentary basin cover, closely intertwined with oil and gas accumulation. To elucidate the deformation intensity and hydrocarbon accumulation scale within the cap cover deformation zone, a pivotal concern in oil and gas geology, this study focuses on the Dongying Sag. The structural physical simulation experiment method, incorporating variable caprock thickness and variable shear strength, is employed to scrutinize the impact of basement fault strike-slip activity on the development of faults in the sedimentary caprock of the basin and dyed oil is charged. In conjunction with sag examples, Early R shear single-channel migration-isolated aggregation, Early and mid-term R shear main channel migration-geese and beaded aggregation, P shear main channel migration-intermittent zonal aggregation, Full channel migration-continuous belt aggregation accumulation models of basement faults are established. It is emphasized that the R shear pressurized deformation section and the R and P shear intersection section in the deformation zone are favorable target areas for oil and gas exploration. [ABSTRACT FROM AUTHOR]

Evidence from recent earthquakes has shown destructive consequences of fault-induced permanent ground movement on structures. Such observations have increased the demand for improvements in the design of structures that are dramatically vulnerable to surface fault ruptures. In this study a novel connection between the raft and the piles is proposed to mitigate the hazards associated with a normal fault on pile-raft systems by means of 3D finite element (FE) modeling. Before embarking on the parametric study, the strain-softening constitutive law used for numerical modeling of the sand has been validated against centrifuge test results. The exact location of the fix-head and unconnected pile-raft systems relative to the outcropping fault rupture in the free-field is parametrically investigated, revealing different failure mechanisms. The performance of the proposed connection for protecting the pile-raft system against normal fault-induced deformations is assessed by comparing the geotechnical and structural responses of both types of foundation. The results indicate that the pocket connection can relatively reduce the cap rotation and horizontal and vertical displacements of the raft in most scenarios. The proposed connection decreases the bending moment response of the piles to their bending moment capacity, verging on a fault offset of 0.6 m at bedrock. [ABSTRACT FROM AUTHOR]

On February 6, 2023, two destructive earthquakes of 7.7 MW and 7.6 MW occurred in Pazarcık (Kahramanmaraş) and Elbistan (Kahramanmaraş) at 04:17 and 13:24 hours, respectively. These earthquakes caused a surface rupture with a total length of 450 km in the region with an average displacement of 3 m between the Arabian and Anatolian plates. This study was conducted to investigate the physical deformation of the aquifer system and the current water quality characteristics in the affected region utilizing field observations and on-site analysis of water sources and tap water. The study revealed significant physical changes in the karstic springs and groundwater wells, including turbidity discharges from all karstic springs due to the limestone-covered terra rosa soils in the region, destruction of groundwater wells near the coastal alluvial aquifer due to liquification, significant intrusion of sea water due to settlements caused by liquefaction in the alluvial aquifer, presence of microbiological pathogens carried by particles creating turbidity in the water sources, and presence of microbiological pathogens in some tap waters due to contamination by pollutants resulting from damage to the water and sewerage networks. These preliminary findings suggest that the earthquake-induced shaking and physical deformation impacted the quality of groundwater sources and tap water in the region. [ABSTRACT FROM AUTHOR]

We conducted a study on the Aceh Fault, an active right-lateral strike-slip fault in northern Sumatra, Indonesia. Despite its seismic hazard potential, the slip characteristics of this fault are not well-understood. Using a combination of remote sensing and field methods, we mapped the distribution of displacement recorded by offset channels along the fault. Our goal is to identify evidence of past surface rupture, characterize their tectonic geomorphology setting, and assess their potentials as slip-rate and paleoseismic sites. The documented right-lateral displacements of channels and ridges from 35 observation points are mostly in the order of magnitude of hundreds of meters, with only a few sites exhibiting meter-scale measurable offsets. Our results provide important first-order data that can be used to locate sites suitable for paleoseismic trenching or offset investigations. This information will support the development of a maximum magnitude and earthquake recurrence model of the fault, which are crucial for seismic hazard analysis in the region. [ABSTRACT FROM AUTHOR]

This work examines the sub-shear and super-shear steady-state growth of mode III fractures in flexoelectric materials, nonetheless, exhibiting Mach type shock wave patterns that resemble reported lattice dynamics results and three-dimensional calculations and experiments. Our mathematical models provide weak discontinuous solutions of the steady-state dynamic equations. In flexoelectric solids, super-shear rupture is possible with Mach lines appearing at sub-shear as well as super-shear crack rupture velocities. This is contrary to classical singular elastodynamics, where the notions of super-shear growth and hyperbolicity coincide. The results show that the deformation near the crack-tip agrees with studies based on lattice dynamics. In the first part of this work, a novel finite element approach has been developed where the problem is decomposed into two prestressed plates that are interconnected, resulting into the predicted radiation patterns and Mach lines. The polarization field is obtained from the calculated displacement field and is used in turn to calculate the magnetic and the electric fields. The analysis offers an analogy to the co-seismic magnetic fields encountered during mode III dominated earthquake rupture events. [ABSTRACT FROM AUTHOR]