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Background: Faulting induced by earthquakes and its analysis are of great importance for areas with high probability of earthquakes. However, there has been no particularly effective methods to evaluate the damage and applicable solutions for recovery. In this paper, the damage from Türkiye earthquakes is investigated by authors, which has important theoretical significance and practical value. On 6 February, 2023, two successive earthquakes with magnitudes (Mw) of 7.8 (called Pazarcık earthquake) and 7.6 (Ekinözü earthquake) occurred in the south-eastern part of Türkiye. The total length of the surface ruptures was more than 500 km long and resulted in striations reflecting the sinistral faulting and extensive ground deformations. In this study, the authors present the outcomes of the investigations on the surface ruptures, their characteristics, stress field associated with both earthquakes, shear strength property of fault segments and the damaging effects on various structures and made some recommendations with the purpose of how to build structures in active fault zones and decrease the negative effects of faulting on structures. Results: Besides summarizing the main characteristics of the world-shaking Kahramanmaraş earthquake doublet in southeast Türkiye in 2023, this study described the main features of the surface ruptures, their relation to the inferred crustal stresses in Türkiye, and the damaging effects on the major engineering structures. The observations and inferences are of great significance for understanding the causes of earthquakes and future seismic risk assessment. Various laboratory experiments were performed on the samples of fault gouge gathered from the sites of surface ruptures and these experimental results provided very valuable quantitative information on the constitutive models of the fault zones. The observations clearly showed that it is almost impossible to prevent damage on structures due to surface ruptures, if certain engineering principles such as increasing higher ductility, lowering gravitational center and/or the implementations of raft foundations are followed. Conclusions: The stress state inferences obtained from the striation of the fault surface ruptures as well as from the focal plane solutions are expected to be useful to evaluate the regional stress state of the earthquake region. Assessments indicated that the stress states in Arabian plate and Anadolu platelet are different from each other. However, in-situ direct stress measurement techniques would be quite useful to validate the stress state inferred in this study. The laboratory experiments on samples gathered from the fault outcrops of the earthquakes using direct shear tests, stick-slip tests as well as conventional tensile, compressive and triaxial tests provided the quantitative values for the parameters of constitutive laws for fault zones, which can be utilized in the numerical simulation of earthquakes. If a fault break happens to be just passing underneath the structures, it is almost impossible for mankind to prevent the damage to structures. However, the authors made some recommendations to reduce the negative effects of fault ruptures on structures. These recommendations are such that the structures should be built as ductile and redundant structures with lower center of gravity and raft foundations. Dam construction should be on active faults should be avoided. If they are to be built for whatever reason, they should be of rock-fill type. As tubular structures and tunnels would be generally subjected forced displacement field, it is recommended to utilize flexible joints, segmented and enlargement to deal such displacement fields. [ABSTRACT FROM AUTHOR]

On 18 August 2020, Masbate Island was struck by a magnitude (MW) 6.6 earthquake. This seismic event represents the second occurrence of a strong earthquake (M > 6) in 17 years, emphasizing the necessity for further investigation into the characteristics of this event. In this study, we employ Interferometric Synthetic Aperture Radar, seismicity analysis, and field investigations to comprehensively characterize the coseismic and postseismic slip associated with the event. Our findings reveal a 50‐km‐long fault rupture along the Masbate segment of the Philippine Fault, with ∼23 km surface rupture mapped onshore, despite the occurrence of interseismic creep. The slip distribution demonstrates decreasing displacements northwestward toward the creeping section, with a maximum left‐lateral displacement of 0.97 m near the epicenter. Toward the southeast offshore, the rupture terminates at a left stepover of a fault. While the surface rupture appears relatively straight and narrowly concentrated, the secondary ruptures and mapped offshore faults reveal a more complex transtensional fault structure in the southeastern part of Masbate Island. This fault complexity represents an asperity that facilitates high‐stress accumulation and rupture initiation. Postseismic slip persists for several months along the onshore creeping segment. Based on comprehensive measurements of both cumulative and coseismic slip along the Masbate fault segment, we calculate a slip rate ranging between 2.8 and 3.8 cm/year and a recurrence interval of 16–41 years for earthquakes similar to the 2020 earthquake. Our study highlights how heterogeneity in fault properties, including geometry and coupling state, influences the distribution of slip and magnitude of earthquakes. The 2020 Masbate earthquake provides valuable insights into the rupture dynamics and fault behavior of the Philippine Fault in the Masbate region. Plain Language Summary: The 2020 earthquake on Masbate Island, Philippines, provided an opportunity to study how faults behave during earthquakes. We used different methods to understand the movement of the ground during and after the earthquake. We found that the fault ruptured for about 23 km on land, despite its slow movement before the earthquake. The rupture continued along the fault's offshore extension. The fault structure becomes more complex in the southeastern part of Masbate Island. After the earthquake, the ground continued to move for several months along the fault. Our research helps us understand how different factors affect earthquakes, which is important for predicting and preparing for future earthquakes in the region. Key Points: The 2020 Masbate earthquake nucleated offshore along the Philippine Fault, rupturing 23 km onshore accompanied by postseismic slipThe Masbate segment of the Philippine Fault is characterized by both aseismic and seismic slip which account for the total slip budgetThe earthquake demonstrated how creeping behavior and fault geometry complexities control rupture extent [ABSTRACT FROM AUTHOR]

Between August and November 2016, three major earthquake events occurred in Central Italy. The first event, with M6.1, took place on 24 August 2016, the second (M5.9) on 26 October, and the third (M6.5) on 30 October 2016. As part of the Italy-US GEER team investigation, we recorded the amplitude and character of offset on the Mount Vettore Fault Zone (MVFZ) using traditional manual field recording and mapping techniques and advanced state-of-the-art geomatics methods of LIDAR and Structure From Motion.Extensive field surveys by INGV geologists and the GEER team were performed on the flanks of Mt Vettore after the 24 August and 30 October events, and a limited survey was done between the two October events by INGV. These surveys indicated normal offset on several strands of the MVFZ, along the upper flanks of Mount Vettore and on the Piano Grande basin floor. The primary trace of the fault had measurable offset up to 215 cm in the northern section of the fault (42.810N-42.818N), and lesser offsets in the southern and central portion of the fault (42.796N-42.810N). In tandem with the traditional field recording of offset, we collected TLS-LIDAR at several locations and flew approximately 5 km of the fault with unmanned aerial systems (UAS) to image the offsets. Lidar and Structure-from-Motion point cloud models were merged to construct a virtual topographic model of the fault. Comparison between the virtual offsets in the point cloud data and the field measurements at the same location found close agreement within 20% of the measured field values. The results indicate that LIDAR and UAS-based methods for collecting and analyzing topographic fault offsets are accurate and potentially greatly improve the magnitude of fault offset data sets from events with measurable surface rupture.

Abstract Background Faulting induced by earthquakes and its analysis are of great importance for areas with high probability of earthquakes. However, there has been no particularly effective methods to evaluate the damage and applicable solutions for recovery. In this paper, the damage from Türkiye earthquakes is investigated by authors, which has important theoretical significance and practical value. On 6 February, 2023, two successive earthquakes with magnitudes (Mw) of 7.8 (called Pazarcık earthquake) and 7.6 (Ekinözü earthquake) occurred in the south-eastern part of Türkiye. The total length of the surface ruptures was more than 500 km long and resulted in striations reflecting the sinistral faulting and extensive ground deformations. In this study, the authors present the outcomes of the investigations on the surface ruptures, their characteristics, stress field associated with both earthquakes, shear strength property of fault segments and the damaging effects on various structures and made some recommendations with the purpose of how to build structures in active fault zones and decrease the negative effects of faulting on structures. Results Besides summarizing the main characteristics of the world-shaking Kahramanmaraş earthquake doublet in southeast Türkiye in 2023, this study described the main features of the surface ruptures, their relation to the inferred crustal stresses in Türkiye, and the damaging effects on the major engineering structures. The observations and inferences are of great significance for understanding the causes of earthquakes and future seismic risk assessment. Various laboratory experiments were performed on the samples of fault gouge gathered from the sites of surface ruptures and these experimental results provided very valuable quantitative information on the constitutive models of the fault zones. The observations clearly showed that it is almost impossible to prevent damage on structures due to surface ruptures, if certain engineering principles such as increasing higher ductility, lowering gravitational center and/or the implementations of raft foundations are followed. Conclusions The stress state inferences obtained from the striation of the fault surface ruptures as well as from the focal plane solutions are expected to be useful to evaluate the regional stress state of the earthquake region. Assessments indicated that the stress states in Arabian plate and Anadolu platelet are different from each other. However, in-situ direct stress measurement techniques would be quite useful to validate the stress state inferred in this study. The laboratory experiments on samples gathered from the fault outcrops of the earthquakes using direct shear tests, stick-slip tests as well as conventional tensile, compressive and triaxial tests provided the quantitative values for the parameters of constitutive laws for fault zones, which can be utilized in the numerical simulation of earthquakes. If a fault break happens to be just passing underneath the structures, it is almost impossible for mankind to prevent the damage to structures. However, the authors made some recommendations to reduce the negative effects of fault ruptures on structures. These recommendations are such that the structures should be built as ductile and redundant structures with lower center of gravity and raft foundations. Dam construction should be on active faults should be avoided. If they are to be built for whatever reason, they should be of rock-fill type. As tubular structures and tunnels would be generally subjected forced displacement field, it is recommended to utilize flexible joints, segmented and enlargement to deal such displacement fields.

The 2022 Paktika earthquake (moment magnitude: 6.2) occurred on June 22, 2022, near the border between the Khost and Paktika Provinces of Afghanistan, causing heavy damage and casualties in Paktika Province. This study evaluated the crustal deformation and associated strong motions induced by the Paktika earthquake. Crustal deformations were determined using the Differential Interferometric Synthetic Aperture Radar (DInSAR) technique and three-dimensional finite element method (3D-FEM) and the results were compared. The permanent ground displacements obtained from the DInSAR and 3D-FEM analyses were similar in terms of amplitude and areal distribution. Strong motions were estimated using the 3D-FEM with and without considering regional topography. The estimations of maximum ground acceleration, velocity, and permanent ground deformations were compared among each other as well as with those inferred from failures of some simple structures in the Spera and Gayan districts. The inferred maximum ground acceleration and velocity from the failed adobe structures were more than 300 Gal and 50 cm/s, respectively, nearly consistent with the estimates obtained using empirical methods. The empirical method yielded a maximum ground acceleration of 347 Gal, whereas the maximum ground velocity was approximately 50 cm/s. In light of these findings, some surface expressions of crustal deformations and strong ground motions, such as failures of soil and rock slopes and rockfalls, have been presented. The rock slope failures in the epicentral area were consistent with those observed during various earthquakes in Afghanistan and worldwide.

The 2022 Paktika earthquake (moment magnitude: 6.2) occurred on June 22, 2022, near the border between the Khost and Paktika Provinces of Afghanistan, causing heavy damage and casualties in Paktika Province. This study evaluated the crustal deformation and associated strong motions induced by the Paktika earthquake. Crustal deformations were determined using the Differential Interferometric Synthetic Aperture Radar (DInSAR) technique and three-dimensional finite element method (3DFEM) and the results were compared. The permanent ground displacements obtained from the DInSAR and 3D-FEM analyses were similar in terms of amplitude and areal distribution. Strong motions were estimated using the 3D-FEM with and without considering regional topography. The estimations of maximum ground acceleration, velocity, and permanent ground deformations were compared among each other as well as with those inferred from failures of some simple structures in the Spera and Gayan districts. The inferred maximum ground acceleration and velocity from the failed adobe structures were more than 300 Gal and 50 cm/s, respectively, nearly consistent with the estimates obtained using empirical methods. The empirical method yielded a maximum ground acceleration of 347 Gal, whereas the maximum ground velocity was approximately 50 cm/s. In light of these findings, some surface expressions of crustal deformations and strong ground motions, such as failures of soil and rock slopes and rockfalls, have been presented. The rock slope failures in the epicentral area were consistent with those observed during various earthquakes in Afghanistan and worldwide. [ABSTRACT FROM AUTHOR]

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With the continuous development of railway construction in China, mountain railway tunnels will inevitably pass through active fault areas, and the dislocation of active fault will have a significant impact on the safety of tunnel structure. Therefore, it is of great practical significance to carry out relevant research on anti-fault design of tunnel across fault. Articulated design has a significant effect on anti-fault resistance of tunnel lining across active fault area. In order to explore the influence of articulated parameters on anti-fault effect of tunnel lining across active fault area, a three-dimensional elastic-plastic finite element model was established based on concrete plastic damage constitutive model of a tunnel in a strike-slip active fault area of Sichuan - Tibet Railway. The damage distribution characteristics and shear strain of secondary lining with different length of segment and width of hinged joint were analyzed. The results show that under the maximum error distance of 30 cm in one hundred years, the second lining of tunnel without anti-fault measures has a serious tensile damage at the side wall near the fault surface, and has a tendency of transfixion, while the tunnel vault and invert have a serious compressive damage, and the compressive damage factors have a tendency of transfixion at both sides of the side wall. The articulated design has a good control effect on the transverse deformation of the tunnel, which can significantly improve the anti-fault performance of the tunnel. The shorter the length of the second lining segment, the better the anti-fault effect of the tunnel. In the articulated design of tunnel lining, the segment length should not exceed 12 m. The damage of the second lining of the tunnel is basically the same under different hinged joint widths. The change of the width of the hinged joint has no obvious influence on the anti-fault effect of the tunnel. The width of the hinged front in the hinged design should not be greater than 0. 3 m when the requirements are met. [ABSTRACT FROM AUTHOR]

Fault rupture propagation is more complex in the overlying soil with intercalation than in homogeneous soil, and it is challenging to simulate this phenomenon accurately using the finite element method. To address this issue, an improved nonlocal model that incorporates softening modulus modification is proposed. The methodology has the advantage that the solutions are independent of both mesh sizes and characteristic lengths, while maintaining objective softening rates of materials. Using the proposed methodology, a series of numerical simulations are conducted to investigate the effects of different mechanical parameters, such as elastic modulus, friction angle and dilation angle of the soil within the intercalation, as well as the impact of geometries, such as the depth and thickness of the intercalation, on the fault rupture progress. This study not only provides significant insights into the mechanisms of fault rupture propagation, specifically in relation to intercalations, but also shows a great value in promoting the current research on fault rupture.

The Samos Island (Aegean Sea) Earthquake occurred on 30 October 2020. It produced a tsunami that impacted coastal communities, ground shaking that was locally amplified in some areas and that led to collapse of structures with 118 fatalities in both Greece and Turkey, and wide-ranging geotechnical effects including rockfalls, landsliding, and liquefaction. As a result of the global COVID-19 pandemic, the reconnaissance of this event did not involve the deployment of international teams, as would be typical for an event of this size. Instead, following initial deployments of separate Greek and Turkish teams, the reconnaissance and documentation efforts were managed in a coordinated manner with the assistance of international partners. This coordination ultimately produced a multi-agency joint report published on the 2-month anniversary of the earthquake, and this special issue. This paper provides an overview of the reconnaissance activities undertaken to document the effects of this important event and summarizes key lessons spanning topic areas from seismology to emergency response.

Between August and November 2016, three major earthquake events occurred in Central Italy. The first event, with M6.1, took place on 24 August 2016, the second (M5.9) on 26 October, and the third (M6.5) on 30 October 2016. As part of the Italy-US GEER team investigation, we recorded the amplitude and character of offset on the Mount Vettore Fault Zone (MVFZ) using traditional manual field recording and mapping techniques and advanced state-of-the-art geomatics methods of LIDAR and Structure From Motion.Extensive field surveys by INGV geologists and the GEER team were performed on the flanks of Mt Vettore after the 24 August and 30 October events, and a limited survey was done between the two October events by INGV. These surveys indicated normal offset on several strands of the MVFZ, along the upper flanks of Mount Vettore and on the Piano Grande basin floor. The primary trace of the fault had measurable offset up to 215 cm in the northern section of the fault (42.810N-42.818N), and lesser offsets in the southern and central portion of the fault (42.796N-42.810N). In tandem with the traditional field recording of offset, we collected TLS-LIDAR at several locations and flew approximately 5 km of the fault with unmanned aerial systems (UAS) to image the offsets. Lidar and Structure-from-Motion point cloud models were merged to construct a virtual topographic model of the fault. Comparison between the virtual offsets in the point cloud data and the field measurements at the same location found close agreement within 20% of the measured field values. The results indicate that LIDAR and UAS-based methods for collecting and analyzing topographic fault offsets are accurate and potentially greatly improve the magnitude of fault offset data sets from events with measurable surface rupture.

Surface fault rupture can lead to significant harm to engineered structures and facilities due to differential displacement in the ground. With the growing demand for land use, it might become essential to implement strategies to protect structures against hazards arising from fault rupture propagation. This study examines a novel mitigation approach utilizing an underpinning technique. To lessen foundation rotation during a fault rupture, a pile similar to the underpinning technique is employed beneath the foundation. This pile is not used to reinforce the main foundation; rather, it serves as a structural element to reduce hazards during a fault rupture with the removed support between the foundation and the pile. The effectiveness of this pile in the soil under the structure is evaluated through a series of numerical models. The findings suggest that while this pile is effective in mitigating the dangers of surface fault rupture, such as building rotation, its application should be guided by comprehensive geotechnical investigation given the complex nature of fault-foundation interaction issues. [ABSTRACT FROM AUTHOR]

A large‐scale physics‐based simulation is conducted to investigate ground motion distribution in the Mw 7.0 2016 Kumamoto earthquake, Japan. The model simulates the earthquake scenario from fault rupture to wave propagation, and localized site response with consideration of the combined effect of soil nonlinearity and topographic amplification. The simulation domain is 51 km × 43 km × 25 km, and the obtained ground motion time histories are compared satisfactorily with recordings from KiK‐net and K‐NET. Ground motion distribution considering nonlinear soil response and topographic amplification is presented. A 3D equivalent linear model is developed to mimic the soil nonlinearity, and it is demonstrated that neglecting soil nonlinearity could over‐predict peak ground acceleration (PGA) and underestimate peak ground velocity (PGV) near the fault. The topographic amplification factors (TAFs) of PGA and PGV are found between 0.5 and 2.0, with a correlation coefficient of 0.7 between them. Predictive equations are proposed to correlate TAFs of PGA and PGV with topographic features, which are represented by relative heights obtained at different length scales. Finally, major earthquake damages are summarized with reference to the obtained ground motion intensity map. [ABSTRACT FROM AUTHOR]

Featured Application: As described in the examined case studies, the developed GIS-based computational tool can be efficiently applied for the selection of the optimal routing of energy and telecommunication cables by considering various design criteria and potential geohazards. Submarine lifelines (pipelines and cables) often cross areas characterized by earthquake-related geohazards (tectonic faulting, landslides and seabed liquefaction). Avoiding geologically hazardous areas increases the length (i.e., cost), whereas a potential crossing may detrimentally affect the structural performance of the infrastructure, requiring more sophisticated design approaches and/or more costly and probably impractical deep sea condition-mitigation measures. Under such adverse conditions, a cost-effective and resilient lifeline route is deemed necessary. The current paper presents a smart decision-support tool for the optimal route selection of submarine cables, assessing whether the proposed routing could effectively cross a (seismically) geologically hazardous area. The GIS-based tool is based on an efficient methodology that combines a least-cost path analysis with a multi-criteria decision method. Accordingly, several routes can be derived for user-defined scenarios, by assigning different weight factors in the adopted design criteria and hazards. When crossing fault zones, the problem of fault-cable intersection is quantitatively assessed in a realistic manner via advanced numerical models. The optimal route can be selected by considering the potential cable distress (i.e., exceedance of allowable cable strains). This tool can be efficiently implemented for deriving the optimal route of energy and telecommunication offshore cables, as it is described in the examined real case studies. [ABSTRACT FROM AUTHOR]

Despite its critical role in the study of earthquake processes, numerical simulation of the entire stages of fault rupture remains a formidable task. The main challenges in simulating a fault rupture process include the complex evolution of fault geometry, frictional contact, and off‐fault damage over a wide range of spatial and temporal scales. Here, we develop a phase‐field model for quasi‐dynamic fault nucleation, growth, and propagation, which features two standout advantages: (i) it does not require any sophisticated algorithms to represent fault geometry and its evolution; and (ii) it allows for modeling fault nucleation, propagation, and off‐fault damage processes with a single formulation. Built on a recently developed phase‐field framework for shear fractures with frictional contact, the proposed formulation incorporates rate‐ and state‐dependent friction, radiation damping, and their impacts on fault mechanics and off‐fault damage. We show that the numerical results of the phase‐field model are consistent with those obtained from well‐verified approaches that model the fault as a surface of discontinuity, without suffering from the mesh convergence issue in the existing continuous approaches to fault rupture (e.g., the stress glut method). Further, through numerical examples of fault propagation in various settings, we demonstrate that the phase‐field approach may open new opportunities for investigating complex earthquake processes that have remained overly challenging for the existing numerical methods. [ABSTRACT FROM AUTHOR]

The application of fault-slip seismic sources is critical to the success of ground motion dynamic response analysis. Previous research established a finite seismic source to analyze stability in underground engineering. In this paper, a sophisticated numerical method based on the distinct element method (3DEC) is proposed to simulate the fault-slip seismic sources of an underground research laboratory (URL) exploration tunnel. Two indices, i.e., the peak ground velocity (PGV) and the strain energy density (SED), are used to analyze the sensitivity of the seismic source types, the seismic source radius, and the rupture velocities of the rock mass dynamic response. The simulation results indicate that a circular seismic source can be used so that the boundary produces a small singularity, with the seismic source having a remarkable influence on the PGV and SED. In addition, we consider that the rupture velocity is more suitable for engineering practices. A simulation method has been developed that allows the rock mass stability of a URL to be further explored. [ABSTRACT FROM AUTHOR]

This study delves into the profound repercussions of geohazards on water supply systems, specifically in the aftermath of the Kahramanmaras earthquakes. The influence of these geohazards was far-reaching, impacting a vast geographical expanse affected by the seismic events. The primary focus of this investigation centers on the provinces of Adiyaman, Gaziantep, and Hatay, providing representative damage examples from the earthquake-affected areas. The study illustrates various types of pipe failures induced by geohazards such as fault displacements, landslides, and liquefaction. The analysis encompasses diverse cases of damage, starting from the water resources, progressing through issues at transmission lines, and extending to challenges faced by pumping and treatment facilities. Key aspects of damages and geohazards are presented, shedding light on the intricate dynamics of these interactions. It is crucial to note the scarcity of real cases in the existing literature, emphasizing the need for extensive site investigations and dedicated research endeavors to construct a comprehensive database of case histories in this domain. This study addresses this gap, contributing valuable insights into the tangible impacts of geohazards on water supply systems. By comprehending and effectively addressing the risks associated with geohazards, water supply organizations can fortify the safety and resilience of their infrastructure. The findings presented herein offer a foundation for informed decision-making and strategic planning, fostering a proactive approach to mitigate potential damages and enhance the overall robustness of water supply systems in regions prone to seismic events and associated geohazards. • Analyzes geohazard impacts on water systems after the 2023 Kahramanmaras earthquakes in Adiyaman, Gaziantep, and Hatay. • Documents pipeline failures like tensile, buckling, and joint issues, emphasizing the need for resilient infrastructure. • Fault ruptures, landslides, and liquefaction caused severe water infrastructure damage, complicating recovery efforts. • Increased turbidity from seismic activity affected water quality, requiring intensive treatment and careful monitoring. • Stresses operational resilience and pre-event planning to maintain water service continuity during seismic events. [ABSTRACT FROM AUTHOR]

The current paper evaluates the response of a tunnel subjected to strike-slip fault rupture with experimental and numerical approaches. Some state-of-art techniques were adopted in the analysis. A new formula containing sodium silicate was used for the similar material. Endoscope technique was used in the model test to log the crack propagating inside the tunnel. And hybrid discrete–continuous modeling was introduced to perform a sophisticated numerical investigation. Two small-scale model tests were carried out, in which the interaction of the tunnel with the fault rupture, the deformation pattern, and the strain evolution and crack propagation in the tunnel liner were observed. The model tests indicate that the failure of the tunnel mainly resulted by the faulting-induced circular cracks concentrated in the vicinity of the shear zone and longitudinal cracks at the passive side portion. Then, the hybrid DEM-FDM model was constructed and calibrated based on the experimental data, with which the response and mechanism of the tunnel subjected to strike-slip fault rupture were numerically investigated to identify the influences of some important factors. The longitudinal and transverse deformation profiles of the tunnel were found to be dominated by the rock mass condition and the buried depth of the tunnel. And the tunnel's design factors have significant effects on the stress and failure mode of the liner. For a soft or thin tunnel liner, the failure zones were more concentrated. The tunnel would fail in a 'shear' mode. In contrast, for a hard or thick liner, the magnitude of the tensile strain is less, yet the tension failure area is larger. The tunnel would fail in a 'squeeze' mode. Based on the obtained results, suggestions on the design of tunnel liner against the strike-slip fault rupture were proposed. Highlights: A discrete-continuous hybrid numerical model was constructed to analyze a tunnel subjected to strike-slip fault rupture. The hybrid discrete-continuous numerical model was calibrated based on especially designed model tests. In model tests, the progressive crack propagating inside the tunnel liner was logged with an endoscope technique. A detailed parametric study was performed for a tunnel subjected to a strike-slip fault rupture. [ABSTRACT FROM AUTHOR]

In the light of current concerns related to induced seismicity associated with geological carbon sequestration (GCS), this paper summarizes lessons learned from recent modeling studies on fault activation, induced seismicity, and potential for leakage associated with deep underground carbon dioxide (CO2) injection. Model simulations demonstrate that seismic events large enough to be felt by humans require brittle fault properties and continuous fault permeability allowing pressure to be distributed over a large fault patch to be ruptured at once. Heterogeneous fault properties, which are commonly encountered in faults intersecting multilayered shale/sandstone sequences, effectively reduce the likelihood of inducing felt seismicity and also effectively impede upward CO2 leakage. A number of simulations show that even a sizable seismic event that could be felt may not be capable of opening a new flow path across the entire thickness of an overlying caprock and it is very unlikely to cross a system of multiple overlying caprock units. Site-specific model simulations of the In Salah CO2 storage demonstration site showed that deep fractured zone responses and associated microseismicity occurred in the brittle fractured sandstone reservoir, but at a very substantial reservoir overpressure close to the magnitude of the least principal stress. We conclude by emphasizing the importance of site investigation to characterize rock properties and if at all possible to avoid brittle rock such as proximity of crystalline basement or sites in hard and brittle sedimentary sequences that are more prone to injection-induced seismicity and permanent damage.

In seismic events, rupture resulted from the earthquake causes two types of ground deformation, namely, the permanent pseudo-static deviations on fault and transient dynamic fluctuations away from fault. Fault rupture extends in soil through bedrock and makes various concerns for structures made by human. On this basis, we examined reverse fault effect on ground-level buildings using numerical analysis and ABAQUS finite-element software. In this regard, some types of buildings were placed on ground near to fault and fault route angle was examined in the presence and absence of building in two layers of soil with different densities. Finally, vertical deformation of ground, horizontal strain of ground, lateral displacement of building, and bending moment of structure were examined beneath fault effect. Results reveal that fault route angle depends on soil layer material, and horizontal strain resulted from fault effect on ground increases by placing building. However, vertical displacement of ground will decrease by placing overhead (building) and the highest part of fault effect will be on columns of first floor.

Submarine lifelines (pipelines and cables) often cross areas characterized by earthquake-related geohazards (tectonic faulting, landslides and seabed liquefaction). Avoiding geologically hazardous areas increases the length (i.e., cost), whereas a potential crossing may detrimentally affect the structural performance of the infrastructure, requiring more sophisticated design approaches and/or more costly and probably impractical deep sea condition-mitigation measures. Under such adverse conditions, a cost-effective and resilient lifeline route is deemed necessary. The current paper presents a smart decision-support tool for the optimal route selection of submarine cables, assessing whether the proposed routing could effectively cross a (seismically) geologically hazardous area. The GIS-based tool is based on an efficient methodology that combines a least-cost path analysis with a multi-criteria decision method. Accordingly, several routes can be derived for user-defined scenarios, by assigning different weight factors in the adopted design criteria and hazards. When crossing fault zones, the problem of fault-cable intersection is quantitatively assessed in a realistic manner via advanced numerical models. The optimal route can be selected by considering the potential cable distress (i.e., exceedance of allowable cable strains). This tool can be efficiently implemented for deriving the optimal route of energy and telecommunication offshore cables, as it is described in the examined real case studies.

Earthquake early warning (EEW) not only improves resilience against the risk of earthquake disasters, but also provides new insights into seismological processes. The Finite-Fault Rupture Detector (FinDer) is an efficient algorithm to retrieve line-source models of an ongoing earthquake from seismic real-time data. In this study, we test the performance of FinDer in the Sichuan-Yunnan region (98.5oE–106.0oE, 22.0oN–34.0oN) of China for two datasets: the first consists of seismic broadband and strong-motion records of 58 earthquakes with 5.0 ≤ MS ≤ 8.0; the second comprises additional waveform simulations at sites where new stations will be deployed in the near future. We utilize observed waveforms to optimize the simulation approach to generate ground-motion time series. For both datasets the resulting FinDer line-source models agree well with the reported epicenters, focal mechanisms, and finite-source models, while they are computed faster compared to what traditional methods can achieve. Based on these outputs, we determine a theoretical relation that can predict for which magnitudes and station densities FinDer is expected to trigger, assuming that at least three neighboring stations must have recorded accelerations of 4.6 cm/s2 or more. We find that FinDer likely triggers and sends out a report, if the average distance between the epicenter and the three closest stations, Depi, is equal or smaller than log10 (Ma + b) + c, where a = 1.91, b = 5.93, and c = 2.34 for M = MW ≥ 4.8, and c = 2.49 for M = MS ≥ 5.0, respectively. If the data used in this study had been available in real-time, 40–70% of sites experiencing seismic intensities of V-VIII (on both Chinese and MMI scales) and 20% experiencing IX-X could have been issued a warning 5–10 s before the S-wave arrives. Our offline tests provide a useful reference for the planned installation of FinDer in the nationwide EEW system of Chinese mainland.

In the present study, the interaction mechanism of a 10-story moment-resisting building frame sitting on the conventional piled raft foundation with a strike-slip fault rupture with a dip angle of 90̊ is studied via three-dimensional finite element numerical simulation using ABAQUS. In addition, an alternative composite foundation system with geosynthetics reinforced interposed layer between piles and raft is proposed to improve the safety and performance of foundation under strike-slip fault ruptures. The interposed layer is reinforced with two high tensile strength of the geotextile layer. The inelastic behaviour of piles under large ground deformations is simulated using moment-curvature relationships of the real reinforced concrete section of piles and ductility concepts. The performance of both composite and conventional piled raft foundations are evaluated in terms of the geotechnical and structural responses of foundations including rotational and translational displacements and shear forces of the raft, as well as shear forces and ductility capacity of piles. The obtained results show the superior performance of composite foundation with geotextile reinforced interposed layer in terms of a significant reduction in shear forces in the raft and piles, as well as ductility demand in the piles. • A composite foundation, where piles were disconnected from the raft, was proposed to mitigate fault rupture effects. • Interaction mechanism of a building sitting on the proposed composite foundation with strike-slip fault rupture was assessed. • The proposed composite foundation exhibited a superior performance by reducing shear forces and ductility demand in piles. [ABSTRACT FROM AUTHOR]

In this paper, we present model simulations of ground motions caused by CO2-injection-induced fault reactivation and analyze the results in terms of the potential for damage to ground surface structures and nuisance to the local human population. It is an integrated analysis from cause to consequence, including the whole chain of processes starting from earthquake inception in the subsurface, wave propagation toward the ground surface, and assessment of the consequences of ground vibration. For a small magnitude (Mw=3) event at a hypocenter depth of about 1000m, we first used the simulated ground-motion wave train in an inverse analysis to estimate source parameters (moment magnitude, rupture dimensions and stress drop), achieving good agreement and thereby verifying the modeling of the chain of processes from earthquake inception to ground vibration. We then analyzed the ground vibration results in terms of peak ground acceleration (PGA), peak ground velocity (PGV) and frequency content, with comparison to U.S. Geological Survey's instrumental intensity scales for earthquakes and the U.S. Bureau of Mines' vibration criteria for cosmetic damage to buildings, as well as human-perception vibration limits. Our results confirm the appropriateness of using PGV (rather than PGA) and frequency for the evaluation of potential ground-vibration effects on structures and humans from shallow injection-induced seismic events. For the considered synthetic Mw=3 event, our analysis showed that the short duration, high frequency ground motion may not cause any significant damage to surface structures, but would certainly be felt by the local population. © 2014.

In this paper, we present model simulations of ground motions caused by CO2-injection-induced fault reactivation and analyze the results in terms of the potential for damage to ground surface structures and nuisance to the local human population. It is an integrated analysis from cause to consequence, including the whole chain of processes starting from earthquake inception in the subsurface, wave propagation toward the ground surface, and assessment of the consequences of ground vibration. For a small magnitude (Mw=3) event at a hypocenter depth of about 1000m, we first used the simulated ground-motion wave train in an inverse analysis to estimate source parameters (moment magnitude, rupture dimensions and stress drop), achieving good agreement and thereby verifying the modeling of the chain of processes from earthquake inception to ground vibration. We then analyzed the ground vibration results in terms of peak ground acceleration (PGA), peak ground velocity (PGV) and frequency content, with comparison to U.S. Geological Survey's instrumental intensity scales for earthquakes and the U.S. Bureau of Mines' vibration criteria for cosmetic damage to buildings, as well as human-perception vibration limits. Our results confirm the appropriateness of using PGV (rather than PGA) and frequency for the evaluation of potential ground-vibration effects on structures and humans from shallow injection-induced seismic events. For the considered synthetic Mw=3 event, our analysis showed that the short duration, high frequency ground motion may not cause any significant damage to surface structures, but would certainly be felt by the local population. © 2014.

This research introduces a new effective approach, including a weak vertical wall (WVW) and a strong inclined wall (SIW) under a shallow foundation, to reduce the rotations caused by a fault rupture. A series of centrifuge tests, followed by numerical modeling and verified by the test results, were conducted to explore the most suitable characteristics of an inclined wall. It is shown that a WVW is, in some cases, ineffective when it is not in the fault rupture path. Furthermore, uncertainties related to determining the exact location of the fault outcrop make it essential to construct a SIW beneath a foundation to protect the foundation that has already been improved by the WVW. The results proved that the application of the proposed approach could reduce the damage potential to the surface and embedded foundations located at various positions relative to reverse faults with various dip angles. [ABSTRACT FROM AUTHOR]

Fluid pressure changes affect fault stability and can promote the initiation of earthquakes and aseismic slip. However, the relationship between seismic and aseismic fault slip during fluid injection remains poorly understood. Here, we investigate, through 3‐D hydromechanical modeling, the spatiotemporal evolution of seismicity and aseismic slip on a permeable, slip‐weakening fault subjected to a local injection of fluid, under different prestress conditions. The model results in an expanding aseismic slip region, which concentrates shear stress at its edge and triggers seismicity. The aseismic slip dominates the slip budget, whatever the initial fault stress. We find that the seismicity is collocated with the aseismic rupture front rather than with the fluid pressure diffusion front. On faults initially far from failure, the aseismic rupture front is located behind or at the pressure front. On faults initially closer to failure, the model predicts that both the rupture front and the seismicity outpace the pressurized zone, resulting in a sharp increase of the migration velocity and released moment of the seismicity. Insights gained from this modeling study exhibit various features that are observed in sequences of induced earthquakes in both field experiments and natural reservoir systems and can help guide the interpretation of past and future observations of induced seismicity. Plain Language Summary: The injection of fluids deep below ground can induce earthquakes, but it can also trigger slow deformations. Studying the relationship between fluid perturbation and seismic and aseismic deformations is fundamental to understand the mechanisms of injection‐induced seismicity in order to mitigate seismic risk. Here, we present results of computer models of the response of a fault to fluid injection. We show that, in the presence of induced aseismic slip, the seismicity is not directly induced by the elevated fluid pressure but by the stresses generated by the expansion of the aseismic slip region. The seismicity initiates and diffuses along the edge of the stress‐increase zone, rather than along the edge of the zone of elevated fluid pressure. We find two different behaviors depending on how stressed the fault is before injection. For a fault initially far from failure, the aseismic slip and the seismicity are confined in the pressurized zone. On the contrary, if a fault is initially close to failure, both the aseismic slip front and the seismicity front accelerate and outpace the fluid pressure front. Thus, the transient stress‐increase associated with the aseismic slip and the initial stress conditions are key factors that control the triggering of seismicity. Key Points: 3‐D hydromechanical models show that injection‐induced seismicity along a permeable fault is not limited to the pressurized volumeSeismicity follows the migration of the shear stress concentration near the aseismic slip front rather than the fluid pressure frontOnce the shear stress front outpaces the pressure front, the seismicity migration accelerates and cannot be explained by fluid diffusion [ABSTRACT FROM AUTHOR]

The strong ground motions, large crustal deformation, and tsunami generated by the 2011 Tohoku-oki earthquake (Mw 9.1) reveal that a large coseismic slip likely propagated to shallow depth in the Japan Trench. Although data acquired by onshore networks cannot resolve the slip behavior of the updip fault rupture, marine geophysical and geological studies provide direct evidence of coseismic slip to the trench. Differential bathymetry data show ∼50 m of coseismic seafloor displacement extending to the central Japan Trench (38–39.2°N). Seismic data show that coseismic slip ruptured the seafloor within the trench. Pelagic clays may have promoted slip propagation to shallow depths, whereas disturbed/metamorphosed clays may have restricted slip to the main rupture zone. Those observations imply that a smooth, broadly distributed, weak, clay-rich sediment in a shallow part of a subduction zone is a characteristic factor that can foster a large coseismic slip to the trench and, consequently, the generation of a large tsunami. ▪ During the 2011 Tohoku-oki earthquake (Mw 9.1), more than ∼50 m of slip occurred on a fault that ruptured the seafloor in the central Japan Trench. ▪ The fault rupture reaching the seafloor caused a large tsunami. ▪ Marine geophysical explorations revealed that a clay-rich sediment in the subduction zone was one factor fostering the large fault slip. ▪ Understanding of slip behavior in the shallow portion of a subduction zone will help us prepare for future large tsunamis along the Japan-Kuril Trench. [ABSTRACT FROM AUTHOR]

The uncertainties in ground motions may result from several factors, e.g., (i) the fault rupture process, (ii) the wave propagation, (iii) the site amplification from the earthquake bedrock to the ground surface. The uncertainty in the fault rupture slip is taken as a main factor of uncertainties in the present paper and the critical fault rupture slip distribution causing the maximum structural response is found by using the stochastic Green's function method as a generator of ground motions. Then, a multi-degree-of-freedom (MDOF) building structure is introduced as a model structure and an optimal damper placement problem is discussed for the critical ground motion. The main topic in this paper is the simultaneous determination of the critical fault rupture slip distribution and the optimal damper placement. The sequential quadratic programming method is used in the problem of critical fault rupture slip distribution and a sensitivity-based method is introduced in the optimal damper placement problem. Furthermore, the robustness for the maximum interstory drift in MDOF building structures under the uncertainty in fault rupture slip distributions is presented for resilient building design by using the robustness function. Since the critical case leads to the most unfavorable structural response, the proposed method can provide structural designers with a promising tool for resilient building design.

It is known that, while the stochastic Green's function method is suitable for generating ground motions with short periods, the three-dimensional finite difference method (FDM) is appropriate for ground motions with rather long periods. In the previous research, the stochastic Green's function method was used for finding the critical earthquake ground motion for variable fault rupture slip (slip distribution and rupture front). However, it cannot be used for ground with irregularities and for wave component with rather long periods. In responding to this request, the FDM is used in this paper for finding the critical ground motion for structures with rather long natural period. Since the FDM is time-consuming, it seems unfavorable to use it in a simple sensitivity algorithm where an independent response sensitivity is calculated for many design parameters. To overcome this difficulty, the bi-cubic spline interpolation of uncertain parameter distributions (seismic moment distribution in this paper) and the response surface method for predicting the response surface from some sampling points are used effectively in this paper. The uncertainty parameter is the fault rupture slip distribution described in terms of seismic moments. It is found that the critical ground motion for structures with rather long natural period can be found effectively by the proposed method.

Contemporary analysis–design methods against faulting can significantly improve life-safety, but the problem of permanent deformation persists. This paper proposes a novel mitigation technique, addressing post-seismic serviceability. A "smart" barrier is employed to divert the fault rupture, introducing a minimum energy path. The "smart" barrier consists of two sheet-pile walls, connected with rows of sacrificial members. The latter are steel rings, whose performance is a function of geometry. The proposed system can be produced in the form of prefabricated panels, and its performance is largely insensitive to site conditions or workmanship. The barrier is compressed, absorbing tectonic deformation with minimum disturbance to the protected structure. The problem is analyzed employing the FE-method, using a thoroughly validated soil constitutive model with strain softening, confirming the efficiency of the mitigation concept. Further analyses demonstrate the use of sacrificial rings to protect continuous bridge decks, being installed between the deck and the bearings. • A "smart" barrier is proposed to protect critical infrastructure by diverting the fault rupture. • It consists of two sheet-pile walls, connected to each other with rows of sacrificial members. • The sacrificial members are steel rings, the ultimate capacity of which is a function of geometry. • The proposed "smart" barrier can be produced in the form of prefabricated panels. • The sacrificial rings can also be used to protect continuous bridge decks. [ABSTRACT FROM AUTHOR]

• Effect of tunnel existence on the reverse fault shallow foundation interaction. • Effects of foundation position, tunnel depth, diameter and relative location. • The tunnel changes fault rapture path and may increase the foundation rotation. • Investigating the effect of fault rupture on the internal forces of tunnel. • Absorbing fault rupture path, Trenching an EPS wall can reduce foundation rotation. Permanent ground deformations induced by fault movements can be damaging to engineering structures built on or near active faults. Most experimental and numerical studies have so far confirmed the fact that the presence of a tunnel in the vicinity of an active fault can change the zone of large deformations on the ground surface. This paper investigates the effect of tunnel existence on the interaction between a reverse fault and a shallow foundation using the finite element method. This paper also analyzes the manner in which a foundation in faulting zones responds to various parameters such as foundation position, tunnel depth and diameter, and the position of the tunnel relative to the rupture path in free-field condition. The mechanical response of the tunnel lining is also examined. The results show that the existence of a tunnel, in some cases, can increase the foundation rotation. Varying the tunnel diameter did not cause any significant changes in the general pattern of failure and the location of shear planes near the tunnel. However, a tunnel with a larger diameter causes the rupture to deviate and propagate in a wider area of the soil layer. It was found that increasing the tunnel depth extends a branch of the rupture path towards the footwall and expands the shear zone on a wider area. In the end, this paper examines the effectiveness of expanded polystyrene sheet (EPS) walls in mitigating the surface fault rupture and reducing the foundation rotation. [ABSTRACT FROM AUTHOR]

A comprehensive study is presented to illustrate the effect of an expanded polystyrene sheet (EPS) wall for absorbing fault rupture and its effects on shallow embedded foundations. Numerical modeling has been thoroughly validated through centrifuge test results. Various embedment depths and fault dip angles were considered to specify the critical foundation position on the soil surface. Furthermore, the impact of vertical trenching of an EPS wall, next to a rigid foundation, was investigated to mitigate surface foundation deformation. Results indicated that, due to high compressibility and low shear resistance that is not time dependent, an EPS wall panel protects the foundation by absorbing fault induced shear strains in the soil stratum. The effectiveness of such walls depends mainly on the geometry, location and mechanical characteristics of the walls, foundation location, bedrock fault offset, and fault dip angle. [ABSTRACT FROM AUTHOR]

This study utilizes large-scale shake table test to investigate the seismic performance of an isolated bridge with lead rubber bearings crossing an active fault. Two transverse restraining systems with and without shear keys are tested by applying spatially varying ground motions. It is shown that the near-fault span exhibits larger bearing displacement than the crossing-fault span. Bridge piers away from the fault rupture are more vulnerable than those adjacent to the fault rupture by attracting more seismic demand. It is also verified that the shear keys are effective in restraining the bearing displacement on the near-fault span, particularly under the large permanent ground displacement. [ABSTRACT FROM AUTHOR]

Abstract Recent earthquake events have shown that besides the earthquake forces, interaction between the fault rupture and structure could cause a lot of damage to the surface and underground structures. Field observations have revealed a need to design structures for fault induced loading in regions with active faults. In this present study, three-dimensional numerical modelling using ABAQUS finite element software is used to study the interactive mechanism of normal fault rupture with a 20-story moment-resisting building frame sitting on a raft, connected piled raft, and cushioned piled raft foundations. The performance of a foundation-structure system is examined by considering geotechnical and structural performance objectives such as structural inter-story drift, raft displacement, and the bending moment and shear forces within the raft and piles. In order to improve the geotechnical and structural performance of foundations and buildings, a new foundation system with cushioned piles below the raft is proposed because of its superior performance with regards to raft rocking and permanent structural inter-story drifts under normal fault rupture. This proposed foundation system also curtailed the bending moments induced in the piles. [ABSTRACT FROM AUTHOR]

It is well known that coseismic landslides are likely to occur under stronger shaking at shorter epicentral distance under the effects of topography and amplification of shaking together with such local geology as rock and soil types. However, this paper addresses a different issue that is the role of faults played in the triggering of landslides, both coseismic and non-seismic, and the long-term slope instability that lasts for decades or centuries after devastating earthquakes. Experiences during and after gigantic landslides are important to understand what happens in and around faults. Noteworthy is that there are cases in which slope instability starts after earthquakes and lasts for some time along surface manifestation of faults, whether or not they are the causative fault. Another important issue is the recovery of stability in shallow parts of slopes. Experiences in Japan, Taiwan and China suggest that a few decades is needed for this re-stabilization. Discussion is further made of geologically generated ground water pressure that is another causative mechanism of landslides. Thus, further field study is encouraged to promote slope hazard assessment. • Long-term slope instability after major earthquakes was studied by introducing examples in the past. • Compound effects of earthquake and rainfall on slope instability are presented. • Continuous slope instability along major tectonic lines is discussed. • Landslides triggered by abnormal ground water pressure are touched upon. • The concepts of process zone and geopressure should be investigated in more details. • The studied cases suggest the importance of more geological/geomorphological studies for understanding the landslide hazards in tectonically active regions of the world. [ABSTRACT FROM AUTHOR]

The process of theoretical ground motion generation consists of (i) the fault rupture process, (ii) the wave propagation from the fault to the earthquake bedrock, (iii) the site amplification. The uncertainty in the site amplification was taken into account in the previous research (Makita et al., 2018). On the other hand, the uncertainty in the fault rupture slip (slip distribution and rupture front) is dealt with in the present paper. The wave propagation from the fault to the earthquake bedrock is expressed here by the stochastic Green's function method in which the Fourier amplitude of the ground motion at the earthquake bedrock from a fault element is represented by the Boore's model and the phase angle is modeled by the phase difference method. The validity of the proposed method is investigated through the comparison with the existing simulation result by other methods. By using the proposed method for ground motion generation and for optimization under uncertainty in the fault rupture slip, a methodology is presented for deriving the critical ground motion imposing the maximum response of an elastic SDOF model at the earthquake bedrock or at the free ground surface. It is shown that the critical response exhibits the SDOF response several times larger than that due to the average fault rupture slip model. Furthermore, the robustness evaluation with respect to the uncertain fault rupture slip and the uncertain fault rupture front is presented for resilient building design. Since the critical ground motion produces the most detrimental building response among possible scenarios, the proposed method can be a reliable tool for resilient building design.

Pseudotachylytes are generated by the cooling and solidification of frictional melt produced along a fault surface during seismic slip. Pseudotachylytes can, therefore, provide important constraints on thermal histories of faults during coseismic slip: survivor clast mineralogies and quenched crystallite morphologies have previously been used to constrain the peak temperatures during slip. Here we show that silicon‐diffusion gradients are preserved around quartz survivor clasts and that these can be used to constrain the immediate cooling histories of pseudotachylytes after the cessation of slip. The variation of diffusion length with position in pseudotachylyte veins can be well reproduced by combining simple thermal history models with Arrhenius parameters for diffusion of appropriate magma compositions. Plain Language Summary: During earthquakes the slip on fault surfaces can be large and rapid enough to cause melting of the fault rocks. We present a new method to estimate the thermal history of the faulting process by measuring chemical diffusion profiles in quenched glass which defines some ancient exhumed fault surface. Key Points: Diffusion profiles are preserved around quartz survivor clasts in pseudotachylitesThere is systematic variation of diffusion length scale from edges of pseudotachylite veins to their centersThermal histories can be extracted from the diffusion data [ABSTRACT FROM AUTHOR]