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In intracratnoic basins, the effect of strike‐slip faults on sedimentary microfacies is generally underestimated due to their small scale. Based on the integration of core, well logs, and three‐dimensional seismic data, this study presents a comprehensive analysis of the Permian carbonate platform and strike‐slip faults in the southwestern Kaijiang‐Liangping trough of the Sichuan Basin. The relationship between strike‐slip faults and Permian carbonate microfacies is investigated. The results reveals the existence of a NW‐trending strike‐slip fault zone along the platform margin, exhibiting clear segmentation. The western side of the study area exhibits a rimmed platform margin characterized by type I reefs, which corresponds to the presence of a large‐scale strike‐slip fault zone. In contrast, the eastern side is characterized by a no‐rimmed and weak rimmed platform margin, accompanied by type II reefs, which align with smaller strike‐slip fault zones. It was found that the strike‐slip fault had some effects on the platform and reef‐shoal complex of the Permain Changxing Formation. First, the platform was divided by strike‐slip fault into three segments to show rimmed, week rimmed and no‐rimmed platform. Second, reef‐shoal complex devolped along the faulted high position in the strike‐slip fault zone, and separated by faulted depression. Third, strike‐slip faults can offset or migrated the reef‐shoal complex and platform margin. Additionally, the thickness of the platform margin varies across strike‐slip fault zone, which is related to the activity of strike‐slip faults. The strike‐slip faults affect the microfacies by controlling the pre‐depositional paleotopography. This case suggests that the strike‐slip faults play a crucial role in the diversity and distribution of carbonate microfacies in the intracratonic basin. [ABSTRACT FROM AUTHOR]

The X-type strike-slip fault system and weathering crust karst fracture-cave and channel reservoirs were developed in the Halahatang area of the northern Tarim Basin. However, the relationship between the reservoir and the strike-slip fault remains controversial. Based on the core data, and taking an NE-striking strike-slip fault as an example, this paper dissects the karst reservoir from wells along the strike-slip fault damage zone and analyzes the control of scales, properties, and segmentation styles of strike-slip faults on karst reservoirs. The results show that (1) the scale of the strike-slip fault controls the distribution of the reservoir—the wider the fault damage zone, the wider the fracture-cave reservoirs; (2) the transtensional segments of the strike-slip fault are more likely to produce karstification, and the buried-hill area and the interbedded area are controlled by different hydrodynamic conditions to form different types of karst reservoirs; (3) six different parts of the strike-slip fault are conducive to the formation scale of fault fracture zones. This research provides new insight into recognizing karst reservoirs within strike-slip fault damage zones, which can be further applied to predict karst reservoirs controlled by strike-slip faults. [ABSTRACT FROM AUTHOR]

The internal fault architecture is crucial in assessing the significance of faults in fluid migration. The development of overlapping zones between segments and subsidiary structures is characteristic of a strike–slip faults. However, their internal architectures and roles in fluid migration are still poorly understood. The Tarim Basin's recently identified strike–slip faults imply that the petroleum resource is hosted in caves that were formed by subsequent dissolution after the formation of the fault zones in carbonate rocks, indicating that the internal fault architecture may be closely linked to the accumulation of petroleum. We investigated the architecture of the strike–slip fault zone using field, geochemical, seismic and well‐logging data. The results revealed that the strike–slip faults contain flower‐like structures in their vertical profiles and an en échelon and 'X' conjugate pattern in their horizontal slices. The fault core may become more complex because of the flower structure as fault breccia, slip surfaces, hydrothermal veins, dissolved pores and caves develop, and the damage zone contains multiple stages of fractures with high dip angles. Compared with 'X' pattern conjugate faults, NE‐trending strike–slip faults have a more developed and connected fault zone. The fault core acts as a fast conduit for fluid transport and experiences significant elemental losses, and the elemental variations in the damage zone may relate in long‐term and relatively lower‐level fluid–rock interactions. Three fault zone architecture models were created, namely, a releasing bend, a restraining bend and a single segment, and their controlling impacts on fluid migration were addressed accordingly. Our findings imply that fluid migration and accumulation are more favourable at the releasing bend than at the restraining bend and single segment. [ABSTRACT FROM AUTHOR]

Inversions of interseismic geodetic surface velocities often cannot uniquely resolve the three‐dimensional slip‐rate distribution along closely spaced faults. Microseismic focal mechanisms reveal stress information at depth and may provide additional constraints for inversions that estimate slip rates. Here, we present a new inverse approach that utilizes both surface velocities and subsurface stressing‐rate tensors to constrain interseismic slip rates and activity of closely spaced faults. We assess the ability of the inverse approach to recover slip rate distributions from stressing‐rate tensors and surface velocities generated by two forward models: (a) a single strike‐slip fault model and (b) a complex southern San Andreas fault system (SAFS) model. The single fault model inversions reveal that a sparse array of regularly spaced stressing‐rate tensors can recover the forward model slip distribution better than surface velocity inversions alone. Because focal mechanism inversions currently provide normalized deviatoric stress tensors, we perform inversions for slip rate using full, deviatoric or normalized deviatoric forward‐model‐generated stressing‐rate tensors to assess the impact of removing stress magnitude from the constraining data. All the inversions, except for those that use normalized deviatoric stressing‐rate tensors, recover the forward model slip‐rate distribution well, even for the SAFS model. Jointly inverting stressing rate and velocity data best recovers the forward model slip‐rate distribution and may improve estimates of interseismic deep slip rates in regions of complex faulting, such as the southern SAFS; however, successful inversions of crustal data will require methods to estimate stressing‐rate magnitudes. Key Points: Joint inversions of velocity and stressing‐rate data can better estimate slip rates along complex faults than individual inversionsInverting data at multiple depths can better estimate fault locking depth than inverting data at a single depthApplication of the new method requires estimates of crustal deviatoric stressing‐rate tensors with magnitude [ABSTRACT FROM AUTHOR]

Since ~ 25 Ma ago the plate margin between the Australian plate and the Philippine Sea and Pacific-Caroline plates in northwestern New Guinea has been undergoing oblique convergence and resulted in various uplifts and compressional deformation in the Bird's Head Peninsula. These reflect partitioning into north-northeast compression and east-west sinistral strike-slip faulting analogous to that in the Sumatran active margin. We present new data on the provenance of the upper Miocene to lower Pliocene succession in the northeastern Bird's Head Peninsula and its structure that has enabled a new tectonic synthesis. Initiation of oblique convergence resulted in development of the sinistral strike-slip Sorong Fault and docking of the Oligocene Arfak Volcanics from the southern Philippine Sea Plate. At ~ 15–12 Ma the compressional component initiated 40 km of dextral offset of the Sorong Fault along the northwest-trending Ransiki Fault. Subsequently, sinistral movement along the Sorong Fault was impeded by formation of a restraining bend at the Ransiki Fault, with uplift shown by the provenance of the local upper Miocene to lower Pliocene conglomerates. Further compressional deformation in the late Pliocene to Pleistocene caused widespread uplift and folding in the adjacent upper Miocene to lower Pliocene succession. [ABSTRACT FROM AUTHOR]

The Fagradalsfjall eruption commenced on 19 March 2021 on a ~180-m-long eruptive fissure, following a 23-day dike intrusion. New eruptive fissures opened northeast of the initial eruption site on 5, 6–7, 10, and 13 April 2021. The northernmost eruption occurred on 5 April, approximately 1 km northeast of the initial fissure, with the other fissure openings between this and the initial eruptive vents. Still images from web cameras and time-lapse cameras are available for five of the fissure openings. These data show that the eruptions were preceded by steam emitted from cracks in the exact locations where the eruptions started. The time between the first steam observations and the visual appearance of glowing lava ranged between 15 s and 1.5 min during night observations and from 9 to 23 min during daytime observations. The difference in observation time is likely explained by the different lighting conditions. The eruptive vents are located where the north-easterly oriented dike intersected pre-existing north-south-oriented fractures, inferred to be strike-slip faults. These fractures could be identified on a high-resolution ICEYE interferogram as well as on pre-existing aerial photographs and digital elevation models. This interferogram spanned the first day of the eruption (19–20 March 2021). It not only displays deformation related to the pre-eruptive dike intrusion but also shows lineations in locations where eruptive vent openings occurred later in April 2021. These findings demonstrate how Interferometric Synthetic Aperture Radar Analysis (InSAR) can be used to forecast likely locations of subsequent eruptive vent openings, which is of great importance for hazard assessment and defining exclusion zones during fissure eruptions. [ABSTRACT FROM AUTHOR]

The Mw 7.8 Kaikōura earthquake of November 14th, 2016 provided rare opportunities to evaluate ground deformation during a large strike-slip earthquake. Following the earthquake, both halves of a displaced paleoseismic trench were re-excavated and extended to test, refine, and extend the known late Holocene chronology of surface rupturing earthquakes on the Kekerengu Fault. 28 organic-bearing samples were collected during these excavations. Of these, six samples provided new 14C ages that could be superimposed on the preferred age model of (Little VDR, Kearse J, Norton K, Benson A, Wang N. 2018. Kekerengu fault, New Zealand: Timing and size of Late Holocene surface ruptures. Bulletin of the Seismological Society of America. 108(3B):1556–1572) to derive an expanded, updated age model of earthquake events on the fault that is now based on 16 dated samples. Including the 2016 earthquake, we recognise six surface rupturing earthquakes on the Kekerengu Fault since ∼2000 cal. B.P. Based on the last five events, our analysis yields an updated estimate of the mean recurrence interval for surface rupturing on the fault of 375 ± 32 yrs (1σ) since ∼1650 cal. B.P. An older, sixth event (E5) was not included in the preferred age model due to uncertainties in interpretation; however, incorporating this event into an alternative, six-event age model would adjust the recurrence interval estimate to 433 ± 22 yrs (1σ) since ∼2000 cal. B.P. [ABSTRACT FROM AUTHOR]

During the Kaikōura earthquake, a paleoseismic trench was dextrally displaced ∼9 m and shortened by 1.3 ± 0.4 m – the largest globally recorded displacement of a trench. Analysis showed that two processes accommodated subequal amounts of slip at the surface: (1) discrete dextral-slip on two steeply-dipping faults bounding a <3.5 m wide central deformation zone; and (2) coseismic clockwise rotation of turf rafts and pervasive sediment deformation in that zone. The second (successive) process resulted in upward (<1 m) and outward (<2 m) bulging along low-angle thrusts, creating horizontal fault-perpendicular shortening that exceeds the heave (∼1.3 m). This discrepancy results from coseismic rotation of rafts, that shorten upon approaching perpendicularity with the fault – creating extra apparent shortening (in fault-orthogonal view). Comparison of pre- and post-earthquake trench logs indicates that strike-slip ruptures at the same site can be expressed differently over time; fault strands carrying major displacement in 2016 were not the locus of deformation in the previous earthquake(s), suggesting temporal unpredictability is important in defining fault zones. The last several paleoearthquakes at the trench produced cm-dm scale normal-sense dip separations across faults; however, the 2016 earthquake created compressive structures including up-bulging and low-angle reverse faulting, as well as fissuring. This contrast in deformation style likely resulted from an >8° clockwise rotation of the local slip vector in 2016 (becoming transpressive), highlighting that small changes in slip kinematics may affect rupture zone structures. [ABSTRACT FROM AUTHOR]

The present work is based on the multidisciplinary geo-structural analysis of the hydrothermal zone of Aïn Ouarka. Located in the Western Saharan Atlas of Algeria, this region presents a very good example where geothermal sources are largely controlled by tectonics events. Employing 114 fracture segments (faults, open fractures, joints) were identified especially in the Mesozoic formations. These faults lineaments are analyzed in terms of frequency, geometry and kinematics. Our results show that the structural patterns consist of two conjugate strike-slip fractures: (i) the dextral component on the WE and NW faults and (ii) the sinistral component on the NS faults. Statistical analysis shows that these fractures correspond to the Riedel shear style where the transformation zone is WE oriented and it compartmentalizes blocks. Under the effect of NW‒SE compressive, the stress collapsed zone appears as a pull-apart graben. This zone is affected by deep fractures, which are accompanied by an uplift of Triassic material. The transtension lead the formation of shearing, these fractures become as active over times. Riedel fractures, synthetic (Y, P and R) oriented 90° N, 70° N and 120° N but also the anthetic fractures (R') oriented respectively 160° N show that there were reactivated during later tectonic episodes. Correlation with surface geothermal manifestations, aeomagnetism, and tectonic fracturing reveals that fractures are distributed along three main directions NNW/SSE and WNW/ESE and the atlasic direction oriented 70° N. For the faults depth, we relied on the processing of aeromagnetic data. Our results show that the depths of the tectonic structures argue in favor of a collapsed zone along the WE fault of Aïn Ouarka where the depths increase from 0.5 km to more than 2 km approaching the central zone. In this zone an emergence of sources of hot water is noted. The results obtained show that the distribution of the basement depth on the two flanks of the WE fault reaches almost 100 m thus revealing the vertical throw of the WE fault. The hydrodynamic model elaborated shows that under the regional tectonic regime probably recent, a collapsed zone has been highlighted. This cataclysm engendered uplift of plutonic reservoir at shallow depth. Rainwater infiltrates through permeable Mesozoic formations, flows towards the cataclysm zone. Subjected to high temperatures of plutonism, these waters warm up and rise under the effect of the low density to reach the surface in the form of hydrothermal springs. [ABSTRACT FROM AUTHOR]

The Ordovician strike-slip faults system in the Tahe area of the Tarim Basin provides an important opportunity for using 3D seismic data to document the structural characteristics, formation, and evolution of strike-slip faults and their relationship with oil and gas. With high-resolution 3D seismic data, the strike-slip faults are interpreted, classified, and described using the seismic coherence technique. The geometric characteristics, active periods, formation, and evolution process of strike-slip faults are analyzed, and the relationship between strike-slip faults and hydrocarbon accumulation and charging is discussed in this research project. On the map, the primary strike-slip faults on the east and west sides of the Tahe area are relatively sheared to each other, showing an "X" type conjugate fault, and the secondary strike-slip faults are scattered. In the cross-section, the primary strike-slip faults are inserted downward into the Cambrian basement and up to Devonian, and "Single line", "Y", "Flower", and "Parallel lines" structures are observed. Bounded by the top of Ordovician, the deep and shallow parts are vertically segmented, with different structure styles. The switch of the structural style of strike-slip faults is attributed to principal stress. A deep "positive flower" shape of faults was developed in the mid-Ordovician period under the effect of compressive stress. Meanwhile, a shallow "negative flower" shape of faults was developed from the late Ordovician to the mid-Devonian period under tensile stress. The "Compound Flower" shape of deep "positive flower" shape and shallow "negative flower" shape formed by compressive and tensile activities has a wider fracture range, which leads to deep fluid migration and shallow karstification. There are two combinations of deep Ordovician strike-slip faults in the section: "Lower single branch-upper flower type" and "lower single branch-upper single branch type". The primary faults of the former insertion into the Cambrian basement are associated with homologous secondary faults, while the latter has no derived secondary faults. It has an important impact on reservoir reconstruction and distribution, and the reservoir is controlled by faults. Strike-slip faults not only control the channel of oil and gas migration, but also the horizontal and vertical distribution of oil and gas. The closer the carbonate reservoir is to the primary fault, the more likely it is to form a high yield area. There are four types of oil and gas charging models controlled by strike-slip faults. In the area where the structure is high and the strike-slip faults are sheared relatively to each other, the larger the scale of faults, the more conducive it would be to oil and gas migration and accumulation. Among them, the charging model related to the primary fault has higher oil and gas migration efficiency. This research contributes to analyzing the relationship between strike-slip faults and oil and gas as well as playing a significant role in applications of oil and gas exploration in practical works. [ABSTRACT FROM AUTHOR]

The active tectonics of Anatolia is mostly characterized by its westward motion with respect to Eurasia between the Hellenic subduction in the west and Arabia-Eurasia continental collision in the east. Although most of the deformation is suggested to be confined along Anatolia's boundary elements, viz. the North and East Anatolian shear zones, recent studies indicate a higher magnitude of internal strain accumulation, especially along the parallel/subparallel strike-slip faults of its central province. We present the first morphochronology-based slip rate estimate for one of these strike-slip structures, the Ovacık Fault, by using cosmogenic 36Cl dating of offset fluvial deposits. At the Köseler Site (39.3643°N, 39.1688°E), two faulted risers, bounding the alluvial fan with its subplanar surface (NF1/NF1') and the inset terrace tread (NF1/T2), are offset 19-24 and 15-22 m, respectively. The scattered surface ages and variability of 36Cl concentrations in depth profiles suggest strong evidence for inheritance in alluvial fan and terrace deposits; thus, we used modelled depth-profile ages for both surfaces. The modelled ages 8-10 ka for NF1 and 6-8 ka for T2 yield slip-rate estimates 2.4 +0.5/-0.4 mm/a and 2.8 +0.7/-0.7 mm/a, respectively, for the upper-tread reconstruction of the NF1/NF1'and the lower-tread reconstruction of the NF1/T2. Our results together with previous slip-rate estimates for other structures show a significant internal deformation for Anatolia, especially along its subparallel strike-slip faults. These secondary faults slice Anatolia into several pieces giving rise to the formation of the Malatya-Erzincan, Cappadocian, and Central Anatolian slices, where the geometry is strongly controlled by the distribution of the Tethyan accretionary complexes. [ABSTRACT FROM AUTHOR]

The Iranian plateau is at the early stage of plateau development and intracontinental deformation in response to the Arabia‐Eurasia collision. Its compressive deformation is concentrated in the northern plateau but skips the central counterpart, challenging the common views envisaging the progressive uplift from the collisional front to the hinterland. Based on three‐dimensional, crustal‐scale numerical models, we present how the rheological heterogeneities common in continents control the deformation of the young Iranian plateau. The weak northern plateau ensures itself a preferential zone in accommodating continental collision. The N‐S strike‐slip faults within the non‐rigid central plateau, formed along the boundaries between the tectonic units with rheological contrast, suppress the shortening of the central plateau while further accentuating the compressive deformation of the northern plateau. Our results suggest a non‐progressive intracontinental deformation pattern where rheological boundaries and mechanically weak zones, not necessarily those close to collisional fronts, preferentially accommodate continental convergence. Plain Language Summary: Continental collisions can produce extensive intracontinental deformation and uplift, forming orogenic plateaus. Common views predict progressive plateau uplift from the collisional front to the hinterland. In the young Iranian plateau, however, uplift mainly occurs in its northern and southern (collisional front) boundary zones while its central part shows relatively low elevation. Here, we perform numerical modeling experiments to investigate the deformation and uplift mechanisms of the Iranian plateau, which can promote our understanding of plateau evolution. The models show that only when the northern plateau is weaker than the central counterpart, uplift will preferentially occur in the north. The central plateau, which displays minor compressive deformation and uplift, is not necessarily rigid. The large‐scale N‐S strike‐slip faults in this region that developed along the boundaries between tectonic blocks with strength contrast can facilitate compressive deformation to concentrate on the northern plateau, making the central plateau less uplift. The results suggest that rheological boundaries and mechanically weak zones, not necessarily those close to collisional fronts, deform preferentially to accommodate continental convergence. Therefore, we suggest a non‐progressive intracontinental deformation pattern, since orogenic plateaus are usually composed of multiple tectonic blocks with different properties. Key Points: 3D crustal‐scale models investigate the strain partitioning and non‐progressive uplift of the young Iranian plateauRheological heterogeneities and large‐scale strike‐slip faults jointly dominate the intracontinental deformationRheological boundaries and mechanically weak zones preferentially accommodate continental convergence [ABSTRACT FROM AUTHOR]

Simple mechanical arguments suggest that slip along interlocked, rough faults, damages surrounding rocks. The same arguments require that the scale of secondary damage is proportional to the size of geometric irregularities along the main fault. This relationship could apply at all scales, but has, so far, been difficult to observe at the 10s to 100 s of km scales of large, natural faults, often because large-scale deformation is distributed across wide, complex plate-boundary fault systems, like the San Andreas Fault. The geometry and geology of another large-scale plate-boundary strike slip fault—the Queen Charlotte Fault (QCF)—is, in contrast, especially simple. Here, we show that observations of secondary deformation are well-aligned with predictions of stress variations caused by geometric irregularities along the QCF, suggesting a geometric relationship between primary fault geometry and secondary deformation. The analytic stress solution reveals that the highest stresses and highest likelihood of failure are confined to a zone of influence (ZOI) with a width quantified by ZOI = λ / 2 π , where λ is the wavelength of geometric variations along the main fault. This simple model is consistent with ∼100-km-scale observations along the QCF and can theoretically be used to predict the width of secondary deformation at all scales. • Fault geometry controls width of stress perturbations and zone of influence (ZOI). • ZOI scales linearly with wavelength of fault geometry. • Secondary deformation along Queen Charlotte Fault within predicted ZOI. [ABSTRACT FROM AUTHOR]

• A comprehensive method integrating chronological, geochemical and seismic-geological analysis was applied to constrain multi-stage strike-slip fault system. • Faults/fractures were reactivated in northern Tarim Basin in Middle Ordovician, Early Permian, and Cenozoic. • Fault activities in Middle Ordovician and Early Permian were precisely dated by U-Pb dating and fluid inclusion. Dating the activity of complex faults and fracture systems is crucial for creating reliable geological models for various tectonics and subsurface engineering applications. This study presents a comprehensive study integrating U–Pb fracture cement dating, trace elements, and fluid inclusion temperature analysis with seismic analysis of faults, fault diagenesis, and burial history studies to better constrain faulting and fracture activities in an intra-cratonic strike-slip fault system in the northern Tarim Basin. Seismic profiles indicate at least three distinct phases of fault activity corresponding to the Middle Ordovician, Permian, and Paleogene periods. Fracture cementation and crosscutting relationships corroborate the identification of three fracturing stages. U–Pb dating of fractured cement has widely detected Middle Ordovician and Early Permian age intervals. Fluid inclusion homogenization temperatures from the fractured cements, ranging across < 50 °C, 70–130 °C, and 150–180 °C, correspond to three episodes of rapid subsidence during the Ordovician, Permian, and Neogene, respectively. These results suggest three phases of fault/fracture reactivation in the Middle Ordovician (prior to 470 Ma), Early Permian (prior to 295 Ma), and Cenozoic. The fault/fracture reactivation in the Ordovician is closely related to the regional tectonic transition from extension to compression, while fault and fracture reactivation in the Early Permian may be related to hydrothermal activity associated with large-scale igneous province and oil emplacement. Fault/fracture activity in the Cenozoic may be related to a reduction in subsidence, gradual reduction of geothermal gradients, and massive oil emplacement. This research underscores the significance of integrating geochemical and subsurface datasets for accurately determining the timing of faulting and fracturing in sedimentary basins. [ABSTRACT FROM AUTHOR]

Gravity and seismic tomography models of the tectonosphere, which allow greater detailing and refining of the structure of the crust and subcrustal mantle in the region are considered. In the East China Sea, the crust is considerably deconsolidated; this deconsolidation has been found to be continued within the subcrustal mantle down to a depth of 40–45 km. A wide NW-trending transform-fault-related pull-apart zone has been identified at the western boundary of the Pacific Plate. In the eastern East China Sea areas, the lower layer of the Philippine oceanic lithosphere is underthrust beneath the Ryukyu Arc with further underthrusting under a viscous subcrustal layer of the continental shelf. In the central sea areas, the oceanic lithosphere is upthrust on the continental marginal lithosphere. Evidence of a central-type structure, which is likely of plume origin, has been detected in the subasthenospheric mantle layer at the western boundary of the Philippine Sea plate, which is the middle fragment of the Ryukyu Arc. [ABSTRACT FROM AUTHOR]

We present a study of the brittle tectonics of Tunas Alkaline Complex focusing on the kinematic and geometric analysis of faults and brittle shear zones deforming the complex. The data acquired and respective interpretations sought to contribute to the post-Cretaceous tectonic structural models of southern Brazil. The ~83 Ma-old alkaline complex is made up of syenites, alkali syenites, plutonic and volcanic breccias, as well as trachyte, microsyenite, and bostonite dykes. Morphostructural analysis using remote sensing combined with right dihedral kinematic analysis of fault-slip data and relations of intersections among structures allowed us to characterize four Cenozoic paleostress fields and their respective tectonic pulses: (I) Eocene-Oligocene NW-SE extension responsible for normal oblique-slip faults striking N60-70E; (II) Oligocene-Miocene NE-SW compression associated with tectonic accommodation of the South American Plate at circa 27-26 Ma, and responsible for WNW-ESE-trending sinistral and NE-SW-trending dextral strike-slip faults; (III) Plio-Pleistocene N-S to NNW-SSE compression related to dextral reactivation of NW-SE-striking faults, sinistral reactivation of NE-SW-trending faults, and generation of NNWSSE-trending strike-slip faults; and (IV) Pleistocene-Holocene NW-SE to WNW-ESE compression that caused dextral reactivation of ENEWSW- trending faults and sinistral strike-slip reactivation of NNW-SSE-trending faults. [ABSTRACT FROM AUTHOR]

Pliocene–Quaternary faults are relevant structures with which to constrain the seismotectonic context and contribute to the evaluation of the seismic hazard of a region. Many of these faults, however, do not show clear surface evidence even when releasing earthquakes. For these reasons they can be extremely dangerous as they receive relatively little attention and can be difficult to identify. From among the various surface geology studies and/or palaeoseismological investigations, we focus our attention on the integration of different datasets such as seismic reflection profiles, surface kinematic data and the relocation of seismological data, which make it possible to identify and characterize active faults whose dimension and earthquake potential would otherwise not be large enough to make them identifiable. We take as an example the Montespertoli NE-trending fault in southern Tuscany (central Italy) with which we associate the 2016 M=3.9 Castelfiorentino earthquake. This structure is part of a wider (in the order of 15–20 km) crustal-scale shear zone, which may be responsible for strong historical earthquakes in the area. [ABSTRACT FROM AUTHOR]

The NW Moroccan Margin has a complex geological evolution, being located close to the transition zone between the Azores – Gibraltar Fracture Zone and the western front of the Betic–Rif collisional orogen. The interaction between tectonic, halokinetic and fluid flow processes with bottom-current activity shapes the seafloor and influences the distribution of seafloor biological communities (such as the cold-water coral mounds) and deep-water sedimentation. The aims of this work are to study the interaction of the paleo-oceanographic and morpho-tectonic processes that generated the various seafloor features of the NW Moroccan Margin. To achieve this, high-resolution multibeam bathymetry and parasound data acquired in the "ALBOCA II" cruise have been used, complemented by high-resolution 2D seismic reflection data and the EMODnet bathymetric compilation. Several morphological features were identified in the margin, which are related to different processes of sedimentary (contourites and sediment waves), structural (faults and diapirs), gravitational (slide scars, mass transport deposits), fluid migration (mud volcanoes and pockmarks) and biogenic (exposed and buried coral mounds) nature. The structural features (e.g., strike-slip faults) have a major control on the seafloor morphology and, consequently, on the development and evolution of the sedimentary systems in the study area. The evolution of the NW Moroccan Margin during the late Quaternary has been controlled by climatic variations and tectonic activity. The action of these factors has been dominant in distinct parts of the study area where: i) contourite terraces developed when climatic and oceanographic changes were the prevalent factor, ii) mounded and confined contourite drifts and local mass transport deposits formed when the major control was tectonic activity. • Integration of geomorphological, seismostratigraphic and oceanographic results at NW Moroccan Margin. • Structural features and recent tectonic activity have been a major influence on the seafloor morphology evolution. • Newly discovered contourite terraces, plastered sheeted, mounded, and confined drifts. • Bottom-water circulation and climatic variations have controlled the sedimentary processes shaping the margin. • Water-mass changes and interfaces shaped contourite terraces, sediment waves, and cold-water coral distribution. [ABSTRACT FROM AUTHOR]

The characterization of salt tectonics and its gravity-driven deformation processes are the key to a better understanding of the structural evolution of salt-bearing rifted margins. Unlike most salt basins that have experienced long-lasting deformation, the Messinian evaporites in the Levant Basin have been moderately deformed, offering the opportunity to study the early stage of salt tectonic deformation. Despite the availability of seismic reflection, borehole and bathymetrical data, some uncertainties still exist about the mechanisms responsible for the deformation and structural features observed in the deep-water Levant Basin. Our study includes physical experiments based on published seismic and structural interpretations conducted in the Levant Basin. Our physical experiments take into consideration the main driving parameters that controlled the development of the deep-water Levant Basin, testing the interplay and impact of gravity gliding and spreading from the Levant Margin, gravity spreading from the Nile Deep Sea Fan, and the influence of the passive buttress of the Eratosthenes Seamount. Deformation was imposed by depositing successive sand lobes and/or by tilting the experimental table. The physical models included a thick viscous silicone layer, analogue of the Messinian evaporitic sequence, overlain by a granular overburden, simulating the brittle clastic post-Messinian succession. Results show that the prominent gravity-driven force affecting the deformation pattern of the deep-water Levant Basin is the gravity spreading from the Nile Deep Sea Fan, whereas gravity spreading and gliding from the Levant Margin affect only the proximal to the margin areas. Additionally, the buttressing effect of the Eratosthenes Seamount and the location of the salt basin pinch-out played an important role in the final deformation pattern of this region of the Eastern Mediterranean. • Physical models of salt-related deformation in the Levant Basin are presented. • Effect of a delta lobe, margins, and a distal buttress have been tested. • The setup includes the effect of gravity gliding and spreading in the Levant Basin. • Gravity spreading from the Nile Deep Sea Fan deforms mostly the deep-basin. • Minor contribution of the Egypt and Levant margins. [ABSTRACT FROM AUTHOR]

The Andaman Sea Basin, a well-known back-arc spreading centre and a mature petroliferous basin, presents a unique and complex scenario for understanding the interplay of sedimentary processes and fault tectonics on seafloor geomorphology evolution, particularly in the eastern shelf region. This study, using high-resolution 3D seismic data and published exploratory well-seismic interpretation results, aims to establish a comprehensive stratigraphic framework for the Tanintharyi region, spanning the Lower Miocene, Middle Miocene, Upper Miocene, Pliocene, and Quaternary. A submarine canyon system was identified and investigated along the Tanintharyi continental slope within the East Andaman Basin, comprising thirteen slope-confined canyons arranged predominantly in an east-west vertical slope orientation. By analysing seismic reflection features, five distinct seismic facies have been identified, including basal lag (BL), slump and debris-flow deposits (SDFDs), canyon confined sheets (CCSs), laterally inclined packages (LIPs), and channel-levees (CLs). The evolution of this canyon system, a vital focus of this study, can be categorised into three phases based on the morphology and sedimentary structures observed: canyon initiation, canyon extension, and erosion-sedimentation. The findings of this study highlight the critical controlling role of faults in canyon evolution, with the intensity of fault activity displaying a negative correlation with canyon size, indicating the direct impact of faults on geomorphological changes. In addition, the geomorphological changes induced by fault activity have resulted in changes in sediment supply, dispersal, and sedimentation rates, thus significantly impacting the spatial distribution and dimensions of slope-confined canyons within the East Andaman Basin, with far-reaching implications. [Display omitted] • A matured canyon system exists in the Tanintharyi region of the East Andaman Basin. • Thirteen slope-confined canyons show nearly an east-west vertical slope alignment. • The sedimentary characteristics of these canyons display three stages of evolution. • Geomorphological changes induced by fault activity impacted the canyon's evolution. • Intensity of fault activities displays a negative correlation with canyon extent. [ABSTRACT FROM AUTHOR]

Intersecting orthogonal strike‐slip faults with opposite senses of slip pose the question of what allows rupture to propagate through the junction and through both faults versus confining rupture to a single fault. I conduct dynamic rupture simulations on simplified orthogonal strike‐slip fault systems, to determine which conditions produce rupture on both component faults. In models with uniform initial tractions on both faults, slip on the first fault must reduce normal stress on the second fault for it to rupture. If the first fault ends at the cross fault, a stopping phase causes the cross fault to rupture. In models where I resolve a uniform regional stress field on the faults, only a narrow range of stress orientations allow multifault ruptures. These results will be helpful for evaluating hazard near orthogonal strike‐slip faults. Plain Language Summary: There are many examples around the world where two strike‐slip earthquake faults cross each other at nearly 90° angles. This is not remarkable when only one of the faults in a pair causes an earthquake, but it becomes notable when two or more crossing faults move at the same time. This raises the question of what causes the second fault to get involved, or not. To address this question, I use computer simulations of the physics of the earthquake process to test dozens of different fault configurations and earthquake starting points. I find that the location where the earthquake starts on the first fault controls whether the second fault is made stronger versus weaker, and therefore whether both faults can move together in one earthquake. These results can help us understand earthquake hazard around crossing faults. Key Points: Nucleation location effectively controls whether multifault rupture occurs on orthogonal strike‐slip fault systemsA stopping phase from rupture reaching the end of one fault is often required to initiate rupture on the cross faultOnly a narrow range of regional stress orientations allows both cross‐faults to rupture [ABSTRACT FROM AUTHOR]

In this study, we probe the formation mechanisms of the 23 January 2018 Mw7.9 Kodiak earthquake in the Gulf of Alaska region from detailed structural analysis, combined with the regional crustal stress status evaluation via seismology methods measured by the b‐value imaging. The large earthquake not only aroused heated debate due to its intraplate deformation and complex rupture system approaching to the Aleutian subduction zone, but also the complex rupture system. Aftershocks of this event propagated along the ENE‐striking and NNW‐striking fractures in planar view, whereas it shows double‐layer seismicity zones at depth. The b‐value image indicates the highly fractured crustal stress status above 12 km and above 25 km, respectively, while the faulting was locked at a depth between 12 and 20 km. We suggest that mantle peridotite serpentinization induced the aseismic zone gap. Besides, the bathymetric map, the multichannel profiles, and the sub‐bottom seismic evidence across the study area have shown the sinistral seismogenic strike‐slip faults may have been reactivated from the deep‐seated oceanic fracture zones involving the subduction front. In addition, all these faults conjunction has formed the topographic uplift or fault blocks and contribute to the complex earthquake ruptures. [ABSTRACT FROM AUTHOR]

Ordovician carbonate rocks on the northern slope of the Tazhong Uplift in the Tarim Basin are modified to varying degrees by hydrothermal fluids related to multiple tectonic‐thermal events, but the nature, origin and circulation mechanisms of such hydrothermal fluids remain debated. In this article, in situ rare‐earth elements and yttrium (REE + Y) concentrations, previously published geochemical datasets and petrographic investigations are integrated to develop a thermo‐tectonic evolution model to improve understanding of silicification and dolomitisation occurring in the interior of the craton basin. δ30Si values, REE + Y ratios and fluid mixing models using modern black smoker fluid and seawater indicate that magma‐sourced hydrothermal fluids, rather than basinal brine heated by magmatism, are responsible for the precipitation of cherts. Petrological and geochemical evidence suggests that deep‐seated, ultramafic‐derived hydrothermal fluids and/or magmatic fluids associated with Permian volcanism may have been involved in the formation of hydrothermal dolomites in the study area. Accompanying formation and reactivation of the strike‐slip faults on the northern slope of the Tazhong Uplift, small volumes of hydrothermal fluids might have been triggered by seismic pumping. The early formed strike‐slip fault systems may also have served as conduits for the subsequent large‐scale transport of deep‐seated, ultramafic‐derived thermal fluids and/or Permian magmatic fluids, along which fluids were transported upwards at high flow rates. Carbonation of ultramafic rocks through interaction with deep‐seated hydrothermal fluids rich in CO2 may have served as a magnesium and silica source for dolomitisation and silicification. Trans‐tensional troughs on NNE‐trending strike‐slip faults with positive flower structure are favourable locations for dolomitisation and silicification. [ABSTRACT FROM AUTHOR]

[Display omitted] • Paleozoic deformation of the fault system in the Tazhong Uplift mainly occurred in the Middle Cambrian, Late Ordovician, and Middle Silurian to Middle Devonian. • NE-trending weak zones developed at the connective positions and bends of the deep thrust faults as accommodation faults in the Middle Cambrian. • The strike–slip faults were generated along the NE-trending weak zones in the Late Ordovician and reactivated in the Middle Silurian to Middle Devonian. • Early-stage Cambrian deformation occurred in the strike–slip faults holding high-productivity hydrocarbon wells. The Tazhong Uplift is an important petroliferous secondary structure unit in the Tarim Basin and has undergone multiple structural deformation. In the current study, we use 3D and 2D seismic data to investigate the nature of the fault system in the Tazhong Uplift. The deformation of the Cambrian sedimentary rocks in the Tazhong Uplift is generally neglected but noted in this study. We found that the Lower–Middle Cambrian rocks are involved in thrust faults. NE-trending weak zones acted as accommodation faults formed at the connective positions and bends of the deep thrust faults. The Middle Cambrian compressional stress stemmed from the northeastern margin of the Tarim Block, pointed SW, and caused the uprising of the Tabei Uplift. The second deformation occurred in the Late Ordovician. In this instance, the compressional stress stemmed from the SW direction of the Tazhong Uplift, which originated from the amalgamation of the Western Kunlun Terrane and Tarim Block. The main strike–slip fault surfaces and subordinate faults developed along the weak zones generated in the Middle Cambrian. The collision that occurred in the southeast part of the Tarim Block in the Middle Silurian to Middle Devonian resulted in the third deformation. The representative structures that occurred during this compressive deformation were the intensive NEE-trending thrust faults in the southeast of the Tazhong Uplift. The three stages of deformation played different and important roles in hydrocarbon accumulation. These strike–slip faults holding the high-productivity hydrocarbon wells generally experienced early-stage Cambrian deformation, had wide fracture damage zones in the Ordovician carbonate rock strata, and had weak en echelon faults in the Silurian to Middle Devonian clastic rocks. [ABSTRACT FROM AUTHOR]

[Display omitted] • The distribution of high production wells is related to the strike-slip fault zones. • Strike-slip faults provided a place for the development and alteration of reservoirs. • Four enrichment models were established through strike-slip faults and production characteristics. • Fault size, tension segment and structural highs affected the reservoirs. Uplifiting of the central Tarim Basin has attracted great interests since the discovery of a major condensed natural gas field in Ordovician carbonate successions at a depth of > 6000 m. The formation of the large-scale hydrocarbon reservoirs in reef shoals is typically thought to be influenced by paragenetic accumulation in the karstified reservoirs. However, because of the rapid decline of natural gas/petroleum production and the complex fluid distribution in limestone reservoirs, it is difficult to clarify the controlling factors of hydrocarbon enrichment. We integrate core, seismic, well logging and production data to illustrate the relationship hydrocarbon enrichment and fault system in this paper. First, productive wells are closely associated with major strike-slip fault zones. Second, most productive blocks are distributed in a banded or block-like manner within strike-slip fault sections. Third, strike-slip fault systems do not closely control reservoir quality; however, the enrichment of natural gas is linked to the development of strike-slip fault systems. Finally, all high-productivity wells are distributed around structural highs in major strike-slip fault zones. These lines of evidence suggest that the accumulation and enrichment of hydrocarbons were closely related to strike-slip fault zones rather than kastified reservoirs. Based on this, four models for the accumulation of hydrocarbons were proposed: fault uplift, graben periphery, fault intersection and fault–karst coupling. Large-scale strike-slip fault zones, transtensional segments and local structural highs were the main factors found to be controlling hydrocarbon enrichment and high productivity. Therefore, these three conditions improved the reservoir and provided paths and places for hydrocarbon migration and accumulation. These proposed hydrocarbon accumulation models contribute to a better understanding of these fault systems and further petroleum exploration. [ABSTRACT FROM AUTHOR]

Tsunami generation from earthquake-induced seafloor deformations has long been recognized as a major hazard to coastal areas. Strike-slip faulting has generally been considered insufficient for triggering large tsunamis, except through the generation of submarine landslides. Herein, we demonstrate that ground motions due to strike-slip earthquakes can contribute to the generation of large tsunamis (>1 m), under rather generic conditions. To this end, we developed a computational framework that integrates models for earthquake rupture dynamics with models of tsunami generation and propagation. The three-dimensional time-dependent vertical and horizontal ground motions from spontaneous dynamic rupture models are used to drive boundary motions in the tsunami model. Our results suggest that supershear ruptures propagating along strike-slip faults, traversing narrow and shallow bays, are prime candidates for tsunami generation. We show that dynamic focusing and the large horizontal displacements, characteristic of strike-slip earthquakes on long faults, are critical drivers for the tsunami hazard. These findings point to intrinsic mechanisms for sizable tsunami generation by strike-slip faulting, which do not require complex seismic sources, landslides, or complicated bathymetry. Furthermore, our model identifies three distinct phases in the tsunamic motion, an instantaneous dynamic phase, a lagging coseismic phase, and a postseismic phase, each of which may affect coastal areas differently. We conclude that near-source tsunami hazards and risk from strike-slip faulting need to be re-evaluated. [ABSTRACT FROM AUTHOR]

The paper presents the results of the study of objects spatially related to extremely high hydrocarbon (HC) emissions identified in the North Caspian Sea. The analysis of variable geological–geophysical parameters in these objects showed (i) a high correlation with large destruction zones of the crust, (ii) the occurrence in negative forms of the top of the consolidated crust, (iii) elevated Moho top in areas of their occurrence, and (iv) their coincidence with near-shear depressions in the sedimentary sequence. These objects are revealed on the basis of surface reflection. The study of their spatial location allowed them to be correlated with the main clusters of petroleum formation, which can be identified from geological prospecting data. In the South Caspian Sea, petroleum clusters are studied by both seismic survey and drilling up to 7 km. The results of these comprehensive studies substantiate the conclusion on the formation of excitation sources under certain conditions at a deep horizon of the crust favorable for HC generation. The summarized materials from the North and South Caspian Sea suggest that significant areas of higher HC emissions are caused by large-volume fluidizites that formed in the petroleum clusters. These objects occur in the southern areas of the North Caspian region under dominant shear geodynamic regime. The position of the negative structures of the platform cover near the zones of transregional strike-slip faults causes their near-shear type. The association of HC fluidizites with near-shear depressions is caused by their location in the extension areas of the crust favorable for the formation of pull-apart structures. The correlation of fluidizites with various structural-tectonic and sedimentation factors indicates the key role of the deep geodynamic regime in the formation of similar objects. [ABSTRACT FROM AUTHOR]

Localized geodetic deformation of arctan shape around locked strike‐slip faults is widely reported, but there are also important exceptions showing distributed deformation. Understanding the controlling mechanism is important to hazard assessment and geodynamic analysis. Here we use simple finite element viscoelastic earthquake cycle models to investigate the basic mechanics of this process. Our models feature a vertical strike‐slip fault in an elastic layer overlying a viscoelastic substrate of Maxwell or Burgers rheology, with or without a low‐viscosity shear zone representing deeper extension of the fault. We demonstrate that the primary control on the localization of interseismic deformation is the recurrence interval of past earthquakes. Given viscosity, shorter recurrence leads to greater localization, regardless of the rheological model used. The presence of a low‐viscosity deep fault does not change this conclusion, although it tends to lessen localization by promoting faster postseismic stress relaxation. Distributed deformation, although less reported, is a natural consequence of very long recurrence and in theory should be as common as localized deformation. We think that the apparent propensity of the latter is likely associated with the much greater quantity and better quality of geodetic observations from higher‐rate and shorter‐recurrence faults. Our results also show the important role of nearby earthquakes along the same fault. For faults of relatively short recurrence, frequent ruptures of nearby segments, modeled using a migrating rupture sequence, further enhance localization. For faults of very long recurrence, faster near‐fault deformation induced by a recent earthquake may give a false impression of localized interseismic deformation. Key Points: Shorter earthquake recurrence intervals lead to more localized interseismic deformation; long recurrence leads to distributed deformationRecent rupture of currently locked segment, or of other nearby segments of the same fault, enhances localized deformationApparent universality of localized deformation may owe to abundance of data from shorter‐recurrence faults with recent earthquakes [ABSTRACT FROM AUTHOR]

We present an updated GPS velocity field for Alaska and western Canada and use it to develop the first regionally comprehensive tectonic block model for the area based on modern geodetic data. The greatest tectonic influences along the southern margin are the translation, collision, and flat slab subduction of the Yakutat block and subduction of the Pacific plate. Northward directed velocities surrounding the Yakutat collisional front are consistent with indenter‐related deformation while southcentral Alaska is undergoing a counterclockwise rotation. Westerly velocities in western Alaska and along the Aleutian forearc suggest that crustal material is escaping into the Bering Sea region. The majority of relative plate motion is taken up along major boundary faults, but right‐lateral strike‐slip faults in interior and western Alaska accommodate part of the motion. Escape tectonics in western Alaska extends as far north as the Kaltag fault. We observe significant motion relative to North America in every part of Alaska, including the North Slope. Evidence of localized right‐lateral shear between the Totschunda and Fairweather faults suggests that strain transfer into interior Alaska has moved away from the eastern Denali‐Chatham Strait system to a more direct corridor. Observed deformation in southcentral Alaska indicates that locked portions of the Yakutat flat slab extend further east and north than previously estimated. Key Points: The first regionally comprehensive tectonic block model for Alaska and western Canada constrained by GPS data is presentedSignificant motion relative to North America is observed in every part of Alaska, including the North SlopeLocked portions of the Yakutat flat slab subduction interface extend further east and north than previously estimated [ABSTRACT FROM AUTHOR]

The detailed characteristics of the Paleozoic strike‐slip fault zones developed in the northern slope of Tazhong uplift are closely related to hydrocarbon explorations. In this study, five major strike‐slip fault zones that cut through the Cambrian‐Middle Devonian units are identified, by using 3D seismic data. Each of the strike‐slip fault zones is characterized by two styles of deformation, namely deeper strike‐slip faults and shallower en‐echelon faults. By counting the reverse separation of the horizon along the deeper faults, activity intensity on the deeper strike‐slip faults in the south is stronger than that on the northern ones. The angle between the strike of the shallower en‐echelon normal faults and the principal displacement zone (PDZ) below them is likely to have a tendency to decrease slightly from the south to the north, which may indicate that activity intensity on the shallower southern en‐echelon faults is stronger than that on the northern ones. Comparing the reverse separation along the deeper faults and the fault throw of the shallower faults, activity intensity of the Fault zone S1 is similar across different layers, while the activity intensity of the southern faults is larger than that of the northern ones. It is obvious that both the activity intensity of the same layer in different fault zones and different layers in the same fault zone have a macro characteristic in that the southern faults show stronger activity intensity than the northern ones. The Late Ordovician décollement layer developed in the Tazhong area and the peripheral tectonic events of the Tarim Basin have been considered two main factors in the differential deformation characteristics of the strike‐slip fault zones in the northern slope of Tazhong uplift. They controlled the differences in the multi‐level and multi‐stage deformations of the strike‐slip faults, respectively. In particular, peripheral tectonic events of the Tarim Basin were the dynamic source of the formatting and evolution of the strike‐slip fault zones, and good candidates to accommodate the differential activity intensity of these faults. [ABSTRACT FROM AUTHOR]

3D thermo-mechanical models have been constructed to explore the influence of pre-existing faults on the temporal-spatial distribution of high-grade amphibolite-granulite facies metamorphic rocks during extension. The different dip amounts of three pre-existing faults (refer to the Bole-Nangodi shear zones, the Jirapa shear zone and the Bulenga shear zone in the study area) are studied in models. The results show the lower crust exhumes occur at a relatively low rate prior to attaining a Stretching Factor = 4.2%. The partially molten lower crustal rocks tend to move (up to 20 km) towards the center of the model and focus exhumation in regions where pre-existing faults intersect. The high-strain corridors in models are used to understand the loci of exhumation in the Bole-Bulenga domain of NW Ghana. Accordingly, in the eastern and western parts of the high-grade rock corridors in NW Ghana, partially molten rocks exhumed from the lower into middle-upper crustal levels are interpreted to have been dominantly facilitated by the km-scale high-strain corridors. In the central part of the Bole-Bulenga domain, the high-grade rocks are interpreted to have been exhumed because of a coupling between two mechanisms: (1) The exhumation of partially molten rocks between the Jirapa and Bole-Nangodi faults increases in spatially due to the reduction in space from north to south. (2) The exhumation of lower partially molten rocks in the central part, as a result of inherited orthogonal (E-W) structures. [ABSTRACT FROM AUTHOR]

Large and shallow strike-slip earthquakes produce striking ground ruptures, damaging roads and infrastructure but providing great opportunities for examining the fault's structure. After the 2022 Mw 6.7 Menyuan earthquake, we observed abundant surface fractures by a combination of optical remote sensing, radar offset and unmanned aerial vehicle measurements. These fractures reveal a complex fault structure including apparent bending geometries and bifurcating branches, which are essential to understanding the mechanisms of faulting. In this paper, we used triangular dislocations to construct the fault geometry that reflected the distribution of measured strike changes but avoided unexcepted discontinuities and overlaps where the fault bent. The modeled fault geometry revealed an extensional releasing bend which was responsible for the southward branching of the fault rupture at its western edge. Our results also demonstrated the potential to explain the occurrence of aftershock clusters and to infer their fault geometries through the correlation analysis of the aftershock distribution and the slip induced stress field. The triangular dislocation model also enabled the calculation of the fault plane roughness and its spatial variation which directly controlled the fault slip magnitude and rupture termination. These analyses reveal an unprecedented level of detail of the fault structure and slip mechanics and, to some extent, offer insights into the physical processes and structural properties of crustal faults in the Earth's shallow crust. • Curved and branched surface ruptures were observed by multi-sourced geodetic data. • The fault structure was related to the distribution and clustering of aftershocks. • The fault rupture forked southward at its western end because of a releasing bend. • The fault plane roughness controlled the slip propagation and termination. [ABSTRACT FROM AUTHOR]

New gravimetric data are improving our understanding of the Palomares Fault Zone (PFZ) that accommodates the Águilas Arc tectonic indentation (eastern Betic Cordillera, SE Iberia) in the context of the Eurasia-Africa convergence. The PFZ limits the sedimentary infill geometry of the Vera and Pulpí Basins, and the western Guadalentín Corridor, which are located along the western boundary of the arc. Gravity anomaly models are in agreement with previous tectonic interpretations that suggest that the PFZ fragments and bends the depocenters of those basins, as it has been proposed for the antiforms (ranges) that are located eastwards. Furthermore, the gravity anomaly models show that the PFZ extends from the Cabrera Range to the Almagrera Range and ends in the north at the Pulpí Basin, where the basin infill is only deformed by a gentle symmetrical synform. As a consequence, the PFZ is (i) confined to the southern zone, where the deformation is most intense due to the displacement of the tectonic indenter, and (ii) disconnected from the front of the Águilas Arc and the Alhama de Murcia Fault (part of the Eastern Betic Shear Zone, EBSZ). The new extend of the PFZ we have documented supposes the structural segmentation of the EBSZ and reduces both seismotectonic and structural significances of the PFZ. The study of the PFZ shows that the boundaries of the indenter are the locus for diffused deformation accommodated by local-scale faulting along with structural rotations and deflections, rather than localized strike-slip faulting along the whole indenter margin. • New gravity data characterize the geometry of the basins next to the Palomares fault. • Palomares fault does not extend to the Pulpí basin that has a shape of gentle synform. • Models point to a migration of the deformation NW-wards of the Águilas Arc. • Shearing along the indenter boundary rotated folds instead of forming a large fault. • The length of the Palomares fault is constrained by folds rotation and deformation. [ABSTRACT FROM AUTHOR]

Since the Pliocene, rift basins have developed in the North Evia region at the south-western extension of the North Anatolian Fault. North Evia, therefore, is a key area for investigating Plio-Quaternary deformation within the diffuse Anatolian-Aegean–Eurasian plate boundary. In this study, we present a detailed map of offshore faults in the North Evia region based on three seismic reflection surveys: an airgun (2004) and two very high-resolution Sparker (2017 and 2021) single-channel surveys. Careful and systematic interpretation of these datasets revealed i) the identification of a new basin (Skiathos Basin) located at the western extension of the North Anatolian Fault and ii) two main fault sets striking oblique to the active N–S-directed extension. The seismicity analysis of the study area reveals pure strike-slip displacements along faults previously identified as normal. The NW–SE-striking faults bordering the North Evia Gulf rift are characterised by left-lateral displacements, and the NE–SW faults present dextral focal mechanisms, following the kinematic character of the North Anatolian Fault. We show that dextral strike-slip deformation recently occurred (in the late Quaternary) in the south-western extension of the North Anatolian Fault, suggesting the significant role of this fault system in the complex structural development of the North Evia region. • New seismic profiles in the western extension of North Anatolian Fault. • Mapping offshore fault networks in the North Evia region, Central Greece. • Evidence for a new basin between Sporades Islands and North Evia: Skiathos Basin. • Active strike-slip displacements along NW-SE and NE-SW striking faults. [ABSTRACT FROM AUTHOR]

Joint analysis of high-penetration multi-channel and high-resolution single-channel seismic reflection profiles, calibrated by deep well boreholes, allowed a detailed reconstruction of the Late Miocene to Recent tectonic history of the Capo Granitola and Sciacca fault systems offshore southwestern Sicily. These two fault arrays are part of a regional system of transcurrent faults that dissect the foreland block in front of the Neogene Sicilian fold and thrust belt. The Capo Granitola and Sciacca faults are thought to reactivate inherited Mesozoic to Miocene normal faults developed on the northern continental margin of Africa. During Latest Miocene-Pliocene, the two ~NNE-SSW striking faults were active in left transpression, which inverted Late Miocene extensional half-grabens and created push-up ridges along both systems. Tectonic activity decreased during the Pleistocene, but transpressional folds deform Middle-Late Pleistocene sediments as well, suggesting that the two fault systems are active. The ~40 km long longitudinal amplitude profile of 1st order folds (Capo Granitola and Sciacca anticlines) shows ~15–20 km bell-shaped undulations that represents 2nd order folds. The length of these undulations together with the map pattern of faults allowed to divide the CGFS and SFS into two segments, northern and southern, respectively. Total uplift of the Sciacca Anticline is twice than the uplift of the Capo Granitola Anticline. Incremental fold growth rates decreased during time from 0.22 mm/yr (Capo Granitola Anticline) and 0.44 mm/yr (Sciacca Anticline) in the Pliocene, to 0.07 and 0.22 mm/yr, respectively, during the last ~1.8 Ma. • Seismic reflection profiles evidence tectonic inversion and active strike-slip faults offshore SW Sicily foreland • Pliocene-Quaternary transpressional inversion of Late Miocene extensional basins • Transpressional fold growth rates were high in Latest Miocene-Pliocene and decreased during Quaternary [ABSTRACT FROM AUTHOR]

High-grade (amphibolite–granulite facies) tectono-metamorphic domains in the Sefwi terrane of Ghana are separated from adjacent lower-grade (greenschist facies) greenstone belts by two main shear zones. The high-grade rocks presumably exhumed along the sinistral shear zones during the D2 ENE-WSW transtension (~2073 Ma). To better understand the role boundary conditions and the spatial relationship of faults play in the exhumation of partially molten lower crust in the Sefwi terrane, ten 3D thermomechanical models have been constructed. The results show that the normal component of velocity boundary conditions mainly controls the exhumation (8–10 km) of the lower crust along pre-existing faults, while the exhumation in the relay zones between faults is controlled by the obliquity between the applied extensional velocity vector and the vertical wall on which it is applied. The strike of the exhumation belt made of partially molten lower crust rocks in the relay zone is sub-orthogonal to the horizontal maximum stretching axis. The isostatic compensation from low-density upper mantle to overlying crust (thinning) is higher under transtension than under extension. The lower crust exhumation influenced by inherited shear zones (ductile) can be used to better understand the loci of the high-grade rocks in the Sefwi terrane. We suggest that the Kukuom-Juaboso domain composed of amphibolite–migmatite facies rocks probably resulted from the concentration of partially molten rocks in the relay zone between the Ketesso and Kenyase shear zones during the D2 ENE-WSW transtension. The two shear zones probably underwent two main stages for growth and maturation from the D1 to D2 phases. The regional exhumation of the high-grade rocks in the Sefwi terrane probably occurred within < 5 Ma. [ABSTRACT FROM AUTHOR]

Abstract The Island Belt Fault Zone (IBZ) and Wagad-upland that are associated with past and recent earthquakes, have been investigated to ascertain the role of tectonics in landform evolution. Towards this, we used data from fill and strath terraces employing conventional geomorphology, sedimentology and optical chronology. The study suggests episodic accelerated crustal deformation along the NE-SW and NW-SE trending transverse strike-slip faults that are genetically related to the regional N-S directed compression. The deformation events are optically dated to ~61 ka, 47 ka, 38 ka, 29 ka, 15 ka and 2 ka. Uplift rate has been estimated from the height and age of the strath terraces along the river valleys of IBZ and Wagad upland. The study observed a significantly lower uplift rate (0.2–0.06 mm/year) compared to the Kachchh mainland (~1 mm). This is ascribed to the strain partitioning caused due to the presence of the KMF and KHF located in the south of the IBZ. Further, it is hypothesized that the restraining and releasing bends along the strike-slip faults could act as barriers to earthquake propagation and might act as nucleation sites for major earthquakes in the intraplate setting. Thus, the study calls for the identification of such locations in order to assess the severity of the future earthquakes in the region. Highlights • NE-SW and NW-SE trending transverse strike-slip faults are genetically related to the regional N-S directed compression. • Six major phases of enhanced uplift (crustal deformation) are dated to 61 ka, 47 ka, 38 ka, 29 ka, 15 ka and 2 ka. • Lower uplift rate of Island Belt Fault Zone w.r.t. the Kachchh mainland signifies the strain partitioning • In intraplate settings, restraining and releasing bends of strike-slip faults could be barriers to earthquake propagation • The restraining and releasing bends of strike-slip faults could act as nucleation sites for major earthquakes. [ABSTRACT FROM AUTHOR]

Abstract This article discusses the structural control of the Precambrian Al Ji'lani basic intrusion, which is one of numerous oval igneous intrusions scattered within different terranes of the Arabian-Nubian Shield. The area in the Ad Dawadimi vicinity exposes 75 km long northwest-trending sinistral en echelon fault systems. During East African Orogen, the master fault segments propagate as sinistral system creating a rhomboidal shape releasing stepover area, defined in this work as Al Ji'lani pull-apart structure. The fault kinematic analysis shows significant variation in stress tensors between data measured outside and inside Al Ji'lani pull-apart structure. The stress tensor, computed from fault population inside the pull-apart, typify a NW-SE to NNW-SSE pure tectonic extension. Outside the pull-apart structure, the stress tensor illustrates a pure strike slip stress regime with a minimum stress axis that varies from NW-SE to NNW-SSE, and maximum stress axis that varies from ENE-WSW to NE-SW. The pull-apart northwestern corner develops, at the end stage, a circular to elliptic basic intrusion known as the Al Ji'lani layered gabbro intrusion. The intrusion is located in the releasing stepover's corner and characterized by inward dipping layers, suggesting an evolution genetically related to the pull-apart growth. Field data and faults kinematic analysis reveal that the Al Ji'lani structure is an ancient Ediacaran–Cryogenian gabbro intrusion developed in pull-apart corner, widely recognized as preferential crustal weakness zone in recent systems of fault-related-volcanism. The results support a predominant relationship between brittle tectonic and volcanism rather than shearing as it was previously accepted. Highlights • During the Neoproterozoic East African Orogen, a NW-trending fault systems are formed in the Ad Dawadimi Terrane. • The overlapped pulled apart zone, produces a central rhomboidal shaped area defined as Al Ji'lani pull-apart structure. • The Al Ji'lani layered gabbro intruded the pull-apart corners: recognized as zone of preferential crustal weakness. [ABSTRACT FROM AUTHOR]

Why are strike slip faults not perfectly linear but made of successive segments? Are they reminiscences of the fracture of an initially sound crust by the bottom-up propagation of a crack subjected to mode III loading? The plausibility of this newly proposed scenario will be investigated here through model experiments and some theoretical explanations in the framework of brittle fracture. [ABSTRACT FROM AUTHOR]

Abstract Strike-slip fault zones are an important type of structure formed during continental orogenic events. Exploring the influence of strike-slip faults on the distribution of natural gas by using the 3D finite element method (FEM) is a frontier in the field of geoscience. In this paper, the effects of strike-slip faults on the heterogeneity of in situ stress and reservoir quality were systematically studied in a shallow commercial coalbed methane reservoir in the Shanxi Formation in the southern Qinshui Basin. Systematic 3D FEM modeling and in situ stress evaluation of a highly developed strike-slip fault zone were conducted. The results indicate that the simulated in situ stress distributions of σ H , σ h and σ v in the target layer present ranges of 10–55 MPa, 3–23 MPa and 5–30 MPa, respectively, which are consistent with acoustic emission and hydraulic fracturing measurements. Along the strike-slip faults, the distribution of horizontal in situ stress is mainly affected by the fault length and vertical throw. The stress magnitude differs greatly between the two sides of a given strike-slip fault, affecting the compaction degree and petrophysical properties of the gas-bearing reservoir on both sides of the fault. Along the strike of a given strike-slip fault, the minimum horizontal in situ stress exhibits distinct segmentation characteristics, which affect the distribution of wells with a higher and lower yields. For the 2 s-order faults (the Sitou and Houchengyao faults), wells with a higher gas production capacity are typically located on the northwestern side of the faults. In the middle and southern sections of the Sitou-Houchengyao strike-slip fault zone, both highly concentrated faults and large-scale opening faults (basement and surface faults) produce greater stress concentrations, and the gas production capacity of the gas wells in these areas is poor. When the main strike direction of the faults is consistent with the loading direction of the boundary stress, the stress concentration is relatively low; whereas, the stress concentration increases as the angle between the main fault strike and the loading direction increases. The shear stress of the target layer is characterized by clockwise rotation, which is an important control on the stress heterogeneity of the strike-slip faults in the study area. Highlights • 3D FEM modeling of a highly developed strike-slip fault zone. • Effects of strike-slip faults on stress heterogeneity. • Influence of strike-slip faults on the distribution of natural gas. [ABSTRACT FROM AUTHOR]

Why are strike slip faults not perfectly linear but made of successive segments? Are they reminiscences of the fracture of an initially sound crust by the bottom-up propagation of a crack subjected to mode III loading? The plausibility of this newly proposed scenario will be investigated here through model experiments and some theoretical explanations in the framework of brittle fracture. [ABSTRACT FROM AUTHOR]

In recent years, China has made significant progress in exploring oil and gas in sandstone and carbonate rocks with burial depths of more than 6000 m in the Tarim, Sichuan, and Junggar Basins. These ultra-deep reservoirs have widely developed natural fractures that are important storage spaces and primary flow pathways influencing hydrocarbon enrichment and production. For ultra-deep tight sandstone, fractures caused by tectonic, diagenetic, tectonic-diagenetic, and overpressure processes are widespread. In the foreland thrust belt, which is divided into five fracture domains, fault-related folds affect fracture distribution in ultra-deep sandstones. For ultra-deep carbonate rocks, strike-slip faults control scale, structural style, and linkage evolution of fractures. Fractures formed over multiple periods. Many fractures in Cretaceous sandstones formed recently whereas some of those in carbonate rocks formed in the Paleozoic when strata were buried less than 5000 m. With the increase in burial depth, fracture porosity (and, probably) connectivity is reduced by mineral deposits. Fracture-forming processes include overpressure, present in situ burial and tectonic loading. Other variables modifying fractures include when fractures formed (timing), regional and local structural position, and scale and fluid flow leading to heterogeneity in whether fractures are mineral filled, open, or enhanced by dissolution. Our review provides insights into the origins, characteristics, evolution, and effectiveness of fractures in ultra-deep sandstone and carbonate rocks. • Ultra-deep reservoirs develop natural fractures of tectonic, diagenetic, tectonic-diagenetic, and overpressure origins. • Fault-related folds and strike-slip faults are the foundational factors for controlling ultra-deep fracture development. • Natural fractures in ultra-deep reservoirs are mainly formed when their strata depth is less than 5000m. • Structural diagenesis, overpressure, and present in-situ stress affect the fracture effectiveness in ultra-deep reservoirs. [ABSTRACT FROM AUTHOR]

Based on the map of the gravitational-field anomalies with respect to the existing structural data, a single structural scheme of the Sanjiang-Middle Amur sedimentary basin is constructed. It reflects the Paleogene rift-related stage of the basin's evolution, when numerous grabens oriented mostly to the northeast formed under the action of NW-SE tension forces. The regularities in the location of the grabens indicate that the basin formed under conditions of interaction of right-lateral northeastern and left-lateral sublatitudinal and west-northwestern strike-slip faults. The ancient northeastern faults activated in the Paleogene formed marginal Western and Eastern zones of right-lateral strike-slip faults. En-echelon series of grabens in the central part mark the position of the rudimentary zones of the left-lateral strike-slip faults. The internal structure of the grabens is analyzed using the materials of the previous and new seismic and well data. The common and individual features of their structures are revealed. The structure of the grabens of the western and eastern marginal zones is demonstrated. It is noted that some grabens are prospective for raw hydrocarbons. An analysis of the deep structure of the territory of East Asia, including the basin, assumes the presence of an upwelling zone by the results of geophysical studies of recent years, primarily seismotomography. [ABSTRACT FROM AUTHOR]

The gold concentration areas in the northwestern Jiaodong Peninsula constituted an important gold metallogenetic region in Eastern China during the Mesozoic. The deep geological bodies' texture characteristic is important for exploring the resources thoroughly and understanding the metallogenic process. The detailed textures were revealed using high‐resolution seismic profiles through the three major ore‐controlling structures‐Sanshandao fault zone, Jiaojia fault zone and Zhaoping fault zone. This study aims to establish a deep structural framework of this area. Based on their formation mechanism, the fault structures developed in the area can be divided into regional and local fault structures. The structural styles are characterised by superimposing their compressional, strike‐slip and extensional multi‐stage activities. The crust is cut by vertical structures corresponding to a left‐lateral strike‐slip fault system on the surface. Nearby these structures are the arc‐shape structures formed by multi‐stage magma intrusions into the upper crust. Bounded by the Tancheng–Lujiang and Muping–Jimo fault zones, the current Jiaodong block, developed a series of NE‐trending strike‐slip fault systems, was probably formed by the assemblage of several obliquely aligned blocks. The intensive magmatism and hydrothermal activity between the blocks induced large‐scale mineralisation. It provides a new angle of view for understanding the cratonic destruction and large ore‐concentration formed during the Mesozoic. [ABSTRACT FROM AUTHOR]

Complex multifault earthquake ruptures involving secondary faults emphasize the necessity to characterize their seismogenic potential better and study their relationship with major faults to improve the seismic hazard assessment of a region. High-resolution geophysical data were interpreted to make a detailed characterization of the Averroes Fault and the North Averroes Faults, which are poorly known secondary right-lateral strike-slip faults located in the central part of the Alboran Sea (western Mediterranean). These faults appear to have evolved since the Pliocene as part of a distributed dextral strike-slip shear zone in response to local strain engendered by the diverging movement of the Carboneras Fault to the north, and the Yusuf and Alboran Ridge faults to the south. In addition, the architecture of these faults suggests that the Averroes Fault may eventually link with the Yusuf fault, thus leading to a higher seismogenic potential. Therefore, these secondary faults represent a hitherto unrecognized seismogenic hazard since they could produce earthquakes up to moment magnitude (M w ) 7.6. Our results highlight the importance of the role played by secondary faults in a specific kinematic framework. Their reciprocal linkage and their mechanical relationship with the main faults could lead to future complex fault ruptures. This information could improve fault source and earthquake models used in seismic and tsunami hazard assessment in this and similar regions. [ABSTRACT FROM AUTHOR]

Abstract: To characterize the along‐strike structural variations of the Juan de Fuca (JdF) Plate as it enters the Cascadia subduction zone, we present prestack time migrated multichannel seismic reflection images of the JdF Plate along a 400‐km‐long trench‐parallel transect extending from 44.3°N to 47.8°N. Beneath the 1.8–3.0‐km‐thick sediment cover, our data reveal basement topographic anomalies associated with a 1.2‐km‐high seamount and in the vicinity of propagator wakes (390–540‐m relief). Weak Moho reflections are imaged beneath the propagator wakes and coincide with reduced Vp in the lower crust and/or uppermost mantle. The inferred locations of propagator wakes in the downgoing plate collocate with some of the boundaries of episodic tremor and slip events. We propose that the structural and hydration heterogeneities associated with these features could lead to anomalous plate interface properties and contribute to episodic tremor and slip segmentation. Intracrustal reflections with apparent dips (20°–30°) consistent with subduction bending normal faults change near 45.8°N, from northward dipping reflections confined to the middle crust in the north to antithetic reflections through the crust in the south, coinciding with a Vp reduction in the lower crust. These observations indicate more extensive faulting deformation and associated hydration of the JdF Plate south of 45.8°N, which likely results from variations of slab dip and resistance to subduction across 46°N. Basement offsets and abrupt depth/amplitude changes in Moho reflections are imaged beneath the four major WNW trending strike‐slip faults that cross the Cascadia deformation front, providing strong evidence of a lower plate origin for these faults. [ABSTRACT FROM AUTHOR]

The northern slope of Tazhong uplift is one of the key areas in the Tarim Basin with great exploration potentials. Previous exploration experiences suggest that strike-slip faults distributed therein play an important role in reservoir formation and hydrocarbon accumulation. In this study, based on the interpretations of the 3D seismic data, six strike-slip fault zones cutting through the Cambrian-Middle Devonian units are identified and characterized. On the seismic cross sections, these faults show a complex geometric feature that consists of a lower positive flower structure in the Cambrian-Upper Ordovician and an upper negative flower structure in the Upper Ordovician-Middle Devonian. On the seismic coherence slices, the lower faults show a linear geometry orienting NNE and only developed within the principal displacement zone. The upper faults are NW trending and display right-stepping en-echelon arrangements. By analyzing the change in the reverse separation of the interface and counting the fault growth index, we suggest that the lower and upper faults developed sequentially in different geological times and formed as a result of two-stage evolution. The lower strike-slip faults may have been formed no early than the Late Ordovician. The upper en-echelon normal faults were developed during the Middle Silurian-Middle Devonian due to the reactivation of the lower strike-slip faults. The horizontal displacement determined from the time slices of faults S1, Sn1 and Sn4 are 743 (±150) m, 1545 (±150) m and 1780 (±150) m, respectively. Such a variation indicates that the amount of horizontal strike-slip displacement is likely to have a tendency to decrease from the south to the north, which agrees well with the regional geodynamics that the compressive stress was transmitted from the south to the north when the strike-slip faults developed during Late Ordovician and Middle Devonian. [ABSTRACT FROM AUTHOR]

Cenozoic strike-slip faults in Indochina were initially interpreted as related to SE expulsion of rigid blocks of continental crust between narrow, high-displacement strike-slip faults away from the Himalayan Orogen. Revision of this view indicates four main stages of development are present. The main 'rigid' block of Indochina actually underwent extensive, widespread Paleogene transpressional deformation during stage 1, involving pervasive strike-slip faulting, folding, structural inversion, sub-horizontal mid-lower crustal shearing, and widespread exhumation of several kilometres. This stage is associated with ∼ E -W oriented maximum horizontal stress (SHmax) (modern orientation). The three subsequent stages are: 2) 30–27 Ma transition, with retreat of transpressional deformation to the SE Tibetan Plateau, 3) 27–17 Ma onset of major sinistral displacement on ASRRSZ, 4) <17 Ma-present, diachronous reversal of motion on many faults, and cessation of extension in Thailand rifts. SHmax orientations evolved dominantly to between NE-SW and NW-SE orientations. Stage 4 is strongly linked with growth of the Tibetan Plateau, the modern GPS field, stress state, and geophysically-defined orientations of crustal and mantle flow. Five different strike-slip provinces have been identified for the post 30 Ma period, based on variations in structural style and kinematics caused by interacting factors including: 1) distance from the East Himalayan Syntaxis, 2) strength variations within SE Asian lithosphere, 3) pre-existing crustal fabrics 4) proximity to key regions contributing to the stress-state of SE Asia, 5) crustal and/or mantle flow. Whether the strike-slip faults are a product of a top- or bottom- driven system remains uncertain. Probably, the system is a hybrid. • A major Paleogene transpressional belt developed in Indochina. • Rigid block extrusion does not fit the Paleogene setting. • Five distinct Oligo-Neogene strike-slip provinces are described. • Cenozoic Strike-slip deformation developed in four key stages. • Ambiguous role of crustal and mantle flow as driving mechanisms. [ABSTRACT FROM AUTHOR]

The northeastern extremity of the East-Asian Rift Belt is designated as the Priokhotsky Rift, comprising the broadly north-south Torom (750 × 100 km) and Nizhneamursky (450 × 100 km) open faults formed by a system of northeast striking grabens associated with the closure of the Tan-Lu shear system and north-south striking grabens formed in a setting of oblique extension. Infilling of the grabens corresponding to the rift stage proper is the Eocene−Miocene coal-bearing molasse; the fields of the Miocene basalts are also related to it. The grabens of the rift belt are overlain by the Pliocene-Neopleistocene associations of rift basins in the forming plate cover of the Alpine platform. [ABSTRACT FROM AUTHOR]

A two-dimensional elastoplastic analytical model of stress-strain analysis of the pipeline under strike-slip faults was established based on the plastic flow theory and elastoplastic-beam theory, considering the effects of service loads and the nonlinearities of the pipeline and the pipe-soil interaction. According to the plastic flow theory, the axial, radial, and hoop plastic strains were derived, and the stress-strain relation was established under the plane stress state. The axial stress and strain of the pipeline induced by fault displacements were analyzed based on the elastoplastic beam theory. Additionally, the axial stresses, hoop stresses, and strains induced by the service loads (i.e., the internal pressure and the temperature variation) were also considered. The proposed model was verified by comparing the analytical results and the finite-element results. The results show that the proposed model can predict accurately the mechanical response of the pipeline subjected to strike-slip fault displacements, with minor deviations of within 10%. [ABSTRACT FROM AUTHOR]