Activity Of Strike-slip Faults Research Articles

Regional tectonic dynamics in Central Iran: Unveiling the interplay of fault systems through morphotectonic and seismological analyses in the Shotori mountains

Iran, located at the convergence of the Eurasian and Arabian tectonic plates, is a region of significant geologic and tectonic interest. This setting gives rise to complex tectonic dynamics that are crucial for understanding the seismicity and geological evolution of the area. This study provides novel insights into the tectonic dynamics of Central Iran, with a particular focus on the Shotori Mountains. Employing a combination of satellite imagery, earthquake catalog analysis, and field observations, we have studied the complex interactions among active fault systems in this part of Iran. Our investigation highlights the significant interactivity of these faults, especially at the convergence point of the Nayband strike-slip fault with the Esfandiar and Shotori thrust faults. This area is characterized by a high frequency of reverse mechanism earthquakes, primarily occurring in shallower crustal layers. A notable aspect of our findings is the identification of a distinct pattern of seismic activity linked to the interaction between different fault types. The Nayband shear zone, for instance, is critically responsible for right-lateral, oblique reverse faulting, and strike-slip events. This study also reveals a novel aspect of tectonic behavior in Central Iran: the correlation between strike-slip fault systems and their thrust terminations, influenced by the rotational dynamics of these faults. Our analysis suggests that the activation of strike-slip faults can precipitate the activation of their thrust terminations, a phenomenon particularly evident at their intersection points. This insight is crucial for understanding regional tectonic processes and could significantly impact seismic hazard assessments in Central Iran. Furthermore, the interaction between the Nayband strike-slip fault and its thrust terminations, such as the Shotori and Esfandiar faults, highlights areas of heightened tectonic activity. This study not only advances our understanding of the seismic and tectonic landscape of Central Iran but also has broader implications for regional tectonic studies and seismic risk management.

Continental depositional record of climate and tectonic evolution around the Eocene-Oligocene transition in southeast France: perpectives from the Vistrenque Basin (Camargue)

Based on detailed sedimentological analyses of cores, interpretation of well logs and a set of geochemical measurements performed on lacustrine sedimentary rocks, the palaeoenvironmental evolution and the sedimentary architecture of the Paleogene continental Vistrenque Basin (SE France) have been reconstructed. The analysis of sedimentary archives revealed three main stages of basin infill evolution: (1) a deep-lake basin (Priabonian-earliest Rupelian) whose sedimentation was dominated by terrigenous gravity-driven deposits during a period of high subsidence rate and strike-slip fault activity and under a prevailing humid climate; (2) an evaporative deep lake (early Rupelian) characterized by a drastic reduction in lake volume (forced-regression), terrigenous supplies and deposition of evaporites in disconnected sub-basins; (3) an overall long-term normal regressive stage (middle Rupelian to earliest Chattian) of lake infill characterized by an increase in terrigenous supplies and a vertical upward transition from deep-lake gravity-driven deposits to marginal lake and floodplain sedimentation. The onset of lake volume reduction and forced regression during the early Rupelian is associated with (1) the reworking of marginal lake carbonates into the deep lake areas, (2) the deposition of organic-rich sediments (TOC > 10%) coupled with sulphate-reduction processes in the deepest areas of the lake, (3) an important decrease in terrigenous supplies and (4) a long-term increase in δ18O of matrix-supported carbonates. This early Rupelian forced regression of the Vistrenque lacustrine system is interpreted to result from a regional decrease in precipitation in response to global cooling during the Eocene-Oligocene Transition (EOT). The final infill of the Vistrenque lake system (late Rupelian-early Chattian) and the onset of a floodplain occurred in more humid conditions during a stage of decreased activity of the Nîmes Fault, prior to or during an early stage of the Liguro-Provençal rifting.

Stability Analysis and Deformation Control of Tunnel with Extremely Weak Surrounding Rocks Caused by Strike-Slip Fault Activity

Stability Analysis and Deformation Control of Tunnel with Extremely Weak Surrounding Rocks Caused by Strike-Slip Fault Activity

The Strike-Slip Fault Effects on Tight Ordovician Reef-Shoal Reservoirs in the Central Tarim Basin (NW China)

The largest carbonate condensate field in China has been found in the central Tarim Basin. Ordovician carbonate reservoirs are generally attributed to reef-shoal microfacies along a platform margin. However, recent production success has been achieved along the NE-trending strike-slip fault zones that intersect at the platform margin. For this contribution, we analyzed the strike-slip fault effects on the reef-shoal reservoirs by using new geological, geophysical, and production data. Seismic data shows that some NE-trending strike-slip faults intersected the NW-trending platform margin in multiple segments. The research indicated that the development of strike-slip faults has affected prepositional landforms and the subsequent segmentation of varied microfacies along the platform margin. In addition, the strike-slip fault compartmentalized the reef-shoal reservoirs into multiple segments along the extent of the platform margin. We show that fractured reef-shoal complexes are favorable for the development of dissolution porosity along strike-slip fault damage zones. In the tight matrix reservoirs (porosity < 6%, permeability < 0.5 mD), the porosity and permeability could be increased by more than 2–5 times and to 1–2 orders of magnitude in the fault damage zone, respectively. This suggests that high production wells are correlated with “sweet spots” of fractured reservoirs along the strike-slip fault damage zones, and that the fractured reservoirs in the proximity of strike-slip fault activity might be a major target for commercial exploitation of the deep Ordovician tight carbonates.

Drainage divide migration in response to strike-slip faulting: An example from northern Longmen Shan, eastern Tibet

Drainage divides can become unstable due to tectonic disturbances and therefore can be used to constrain past tectonic activity. However, many studies have focused mainly on the influence of vertical motion with less attention on the drainage divide response to strike-slip faulting. How the drainage divide response to strike-slip faulting is still uninvestigated. Here we analyze the drainage divide stability along the Beichuan-Yingxiu Fault, an active dextral strike-slip fault with a reverse component in the Longmen Shan, on the eastern margin of the Tibetan Plateau. Based on activity of the Beichuan-Yingxiu Fault and response of the local landscape, we have identified a site in the Guixi area where a river capture event may occur in the near future, and a site in the Leigu area where a river capture event may have occurred. We used the χ-plot and Gilbert metrics methods to measure drainage divide stability at these two sites. The results show that (1) drainage divides near active strike-slip faults will be unstable before and after a capture event in response to strike-slip faulting and (2) before a capture event, the drainage divide on opposing sides of the strike-slip fault will migrate in opposite directions. This study systematically reveals the drainage divide migration generated in response to strike-slip faulting. We suggest that the drainage divide stability has the potential to be used to identify strike-slip fault activity and slip sense.

Sedimentary filling characteristics and controlling factors of lacustrine microbial carbonates sequence in the Santos Basin, Brazil

Based on comprehensive analysis of seismic, logging, core, thin section data, and stable isotopic compositions of carbon and oxygen, the sedimentary filling characteristics of the Lower Cretaceous Barra Velha Formation sequence in H oil field, Santos Basin, are studied, and the high-frequency sequence stratigraphic framework is established, and the spatial distribution of reef-shoal bodies are predicted and the controlling factors are discussed. During the depositional period of the Barra Velha Formation, the study area is a slope-isolated platform-slope sedimentary pattern from southwest to northeast and the change of climate background from rift to depression periods has resulted in the variation of sedimentary characteristics from the lower third-order sequence SQ1 (BVE 300 Member) of low-energy deep water to the upper third-order sequence SQ2 (BVE 200 and 100 members) of high-energy shallow water in the Barra Velha Formation. The activities of extensional faults and strike-slip faults in rift period and the sedimentary differentiation from platform margin to intra-platform in depression period made the sedimentary paleogeomorphology in these two periods show features of “three ridges and two depressions”. The reef-shoal bodies mainly developed in the SQ2-LHST period, with vertical development positions restricted by the periodic oscillation of the lake level, and developed on the top of each high-frequency sequence stratigraphic unit in SQ2-LHST in the platform. The strike-slip fault activity controlled the distribution of the reef-shoal bodies on the plane by changing the sedimentary paleogeomorphology. The positive flower-shaped strike-slip faults made the formation of local highlands at the margins of and inside the shallow water platforms and which became high-energy sedimentary zones, creating conditions for the development of reef-shoal bodies.

Seismic Hazard Potential in Yogyakarta Based on HVSR Curve Estimation

In 2006, the Special Region of Yogyakarta was shaken by a destructive earthquake. The United States Geological Survey (USGS) recorded that the earthquake had a magnitude of 6.3 Mw at a depth of 12.5 km below the surface that was triggered by strike slip fault activity. The severe damage occurred in Bantul district and Klaten district, where the Klaten area location were far from the earthquake epicenter. This proves that the magnitude and the earthquake source distance are not the only parameters for seismic hazard potential, but rather the presence of local site effects and building conditions. The present study aims to determine the characteristics of the soil and estimate the seismic hazard potential by using HVSR method. Horizontal to Vertical Spectral Ratio (HVSR) is one method that can be used to obtain the subsurface information from single station measurements. Furthermore, the inversion of Rayleigh wave ellipticity curve is used to obtain 1-D of shear wave velocity (Vs). The parameters from HVSR calculation and Rayleigh wave inversion were mapped to understand the subsurface structure beneath the Yogyakarta area. Based on the soil classification to Vs, Yogyakarta area is categorized to SD (Stiff soil/soft soil) and SC (Very dense soil and soft rock). The results of the mapping analysis indicated that Bantul district is an area with the highest potential of seismic hazard.

Exhumation and preservation conditions of Suyunhe porphyry molybdenum deposit in the West Junggar, Xinjiang (NW China): Constraints from the fission track and (U-Th)/He thermochronology

斑岩型矿床多形成于汇聚型板块边界。由于其较浅的就位深度，大部分古老的斑岩型矿床很容易受到后期的剥蚀而消失殆尽。研究斑岩型矿床成矿后的埋藏和去顶过程对于深入理解矿床的保存条件和区域找矿前景至关重要。新疆西准噶尔西部的苏云河斑岩型钼矿床形成于晚石炭世，是一处保存良好的斑岩型矿床，为我们研究前中生代斑岩成矿系统的保存条件提供了天然的实验室。本文首次针对该矿床开展了锆石和磷灰石裂变径迹与锆石（U-Th）/He低温热年代学分析，结合热历史反演模拟以及前人的年代学数据显示，苏云河斑岩钼矿的蚀变过程至少持续了55Myr。在早二叠世到中三叠世，矿区接受5.2~8.1km厚的沉积物覆盖。中三叠世至早白垩世（240~120Ma），矿床经历了快速剥露作用，剥露速率为49.0~56.7m/Myr，去顶量为7.4~9.2km。早白垩世（120Ma）至今为缓慢剥露阶段，剥露速率为6.7~21.7m/Myr，去顶量为0.8~2.6km。中三叠世至早白垩世的快速冷却事件可能并不是特定构造事件（比如：南部羌塘和昆仑-柴达木碰撞或者羌塘和拉萨碰撞）远程效应的产物，而与区域内走滑断层的活化密切相关。而矿床早期沉积的巨厚盖层以及早白垩世以来干旱气候和缓慢剥露，为石炭-二叠纪斑岩型钼矿得以保存提供了条件。;Porphyry deposit is a kind of epithermal deposit, which is mostly formed in the convergent plate boundary. However, ancient porphyry deposit was often destroyed and disappeared due to later tectonic or exhumation. Therefore, it is vital to reveal the exhumation and uplift process after mineralization for further understanding the preservation conditions and regional prospecting prospects of the deposits. Suyunhe porphyry molybdenum deposit in the west part of the West Junggar, Xinjiang was formed in Late Carboniferous. It is a well-preserved porphyry deposit, which provides a natural laboratory for us to study the preservation conditions of ancient porphyry metallogenic system. In this paper, we present new zircon and apatite fission track (ZFT and AFT) and zircon (U-Th)/He (ZHe) data for the Suyunhe porphyry molybdenum deposit. Combined with thermal modeling inversion, we suggest that the hydrothermal alteration process of the Suyunhe porphyry molybdenum deposit lasted at least 55Myr. It underwent a thick burial (5.2~8.1km) sediments from Early Permian to Middle Triassic. The deposit experienced a rapid exhumation stage from Middle Triassic to Early Cretaceous (240~120Ma). The exhumation rate was 49.0~56.7m/Myr, and the corresponding denudation amount was 7.4~9.2km. After the Cretaceous (120Ma), it entered a slow exhumation stage with an exhumation rate of 6.7~21.7m/Myr and exhumation amount of 0.8~2.6km. Among them, the Middle Triassic to Early Cretaceous rapid exhumation was not the product of far-field effects (e.g., the collision between Qiangtang and Kunlun-Qaidam or the collision between Qiangtang and Lhasa), but related to the activation of strike slip faults in the region. Therefore, early thick burial and later dry climate and slow exhumation provided key conditions for the preservation of the Carboniferous Suyunhe porphyry molybdenum deposit.

Understanding partitioning of deformation in highly arcuate orogenic systems: Inferences from the evolution of the Serbian Carpathians

Highly curved orogens often demonstrate a complex poly-phase tectonic evolution and significant strain partitioning. While the oroclinal bending towards the outer arc is understood to be often driven by rapid slab roll-back, processes driving such bending towards the back-arc domain are less understood. The Serbian segment of the larger, highly bended Carpathians–Balkanides Mountains is one key example where we studied the kinematics of nappe stacking and the mechanics of oroclinal bending by the means of a field kinematic study correlated with available information in adjacent orogenic segments. Although not apparent in the large-scale structure of the Serbian Carpathians, our results demonstrate a poly-phase evolution, where the late Early Cretaceous nappe stacking was followed by Oligocene–middle Miocene ~40° of clockwise rotations. The superposition of Dinarides extension with the oroclinal bending in the Carpathians created overlapping stages of orogen-perpendicular extension and dextral strike-slip coupled with orogen-parallel extension, driven by the 100 km cumulated offset of the Cerna and Timok Faults. Extension was associated with the formation of Oligocene–Miocene basins, providing critical timing constraints for our kinematic study. These deformations were followed by the late Miocene E-ward thrusting of the Upper Getic sub-unit, which was driven by a transfer of deformation in the orocline and around the Moesian Platform during the last stages of Carpathians collision. These results show that the mechanics of oroclinal bending is associated with the activation of strike-slip faults and strain partitioning by bi-modal extension, enhanced by the overlap between different geodynamic processes.

Morphotectonics of the northern Bogd fault and implications for Middle Pleistocene to modern uplift rates in southern Mongolia

Assessing the activity of strike-slip faults is often facilitated by cumulative offsets of morphological features. The December 4th 1957 Mongolia earthquake, generally referred to as the “Gobi Altai” or “Bogd” earthquake, had MW 8.1 and created long and complex surface ruptures of c. 350 km length along the Bogd fault that cuts across the foothills of the Gurvan Bogd mountains. Several left-laterally and vertically displaced Quaternary alluvial fans and morphogenic markers show cumulative offsets, allowing for an assessment of the effect of repeated earthquakes and active tectonics on landscape evolution. We propose to expand the active tectonic record along this fault up to a Middle Pleistocene time scale that spans regional climatic fluctuations, i.e. repeated glacial-interglacial cycles, and hence varying erosional and depositional rates.Five main drainage areas crosscutting the North Ikh Bogd segment of the Bogd fault were analysed and compared in terms of hypsometry, drainage steepness and alluvial fan slope inclination. Along the mountain front, deposits from all drainages form multiple alluvial fan levels that reflect recurring deposition-incision cycles. Previously published ages, as well as the spatial distribution of these fan levels, suggest that their incision and abandonment is induced by regionally dominant climate fluctuations. However, the increase of fan slope angles over time and the increased intensity of sub-surface folding observed in ground-penetrating radar profiles, suggests that cumulative tectonic uplift also has a strong impact on alluvial fan morphology. Estimates of the increase of fan slope angles as a result of cumulative tectonic uplift imply that Middle Pleistocene to modern vertical slip rates along the North Ikh Bogd segment of the Bogd fault are in the order of 0.9–1 mm/yr. However, much slower vertical slip rates along individual fault segments, ranging between 0.06 ± 0.01 mm/yr and 0.28 ± 0.07 mm/yr, indicate that uplift of the Ikh Bogd plateau occurs as a result of distributed deformation across multiple parallel fault strands within bedrock as well as alluvial fans. Our results emphasise the importance of regional studies along active faults that take into account the complexity of surface ruptures as well as the occurrence of related structures that can accommodate deformation.

Fluid pathways within shallow-generated damage zones of strike-slip faults – evidence of map-scale faulting in a continental environment, SW Permo-Mesozoic cover of the Late Palaeozoic Holy Cross Mountains Fold Belt, Poland

The damage zones of exhumed strike-slip faults dissecting Jurassic carbonates in the south-western part of the Late Palaeozoic Holy Cross Mountains Fold Belt reveal second-order faults and fractures infilled with syntectonic calcite. The subsequent development of a structural pattern of microscopic fault-related structures and calcite infillings reflects the activity of strike-slip faults that began in the Late Cretaceous (Late Maastrichtian) and lasted until the early Miocene (Langhian). The fabric of the syntectonic veins provides insights into the evolution of the permeable fault-related structures that were the main pathways for fluid flow during fault activity. Microstructural study of calcite veins coupled with stable isotope and fluid inclusion data indicates that calcite precipitated primarily in a rock-buffered system related to strike-slip fault movement, and secondarily in a partly open system related to the local activity of the releasing Chmielnik stepover or the uplift of the area. The presence of meteoric fluids descending from the surface into damage zones suggest that the strike-slip faulting might have taken place in a nonmarine, continental environment.

Identification Fault Characteristic in Southern Sulawesi by Focal Mechanism

Sulawesi has complex tectonic, signed by fault like Palu-Koro Fault, Walennae Fault, Matano Fault, Batui Fault and others. Mostly fault located on Southern Sulawesi and it caused earthquake in Southern Sulawesi. The aim at this study is to learn fault characteristic by focal mechanisms in Southern Sulawesi. Focal mechanism is method to analyze movement mechanism based on first polarity of earthquake P-wave to determine fault caused by earthquake fault which caused earthquake. In this study is located on Southern Sulawesi with 2°26’ - 6°50’ S and 118° -123°50’ E during 1976 – 2016 from Global-CMT. The hypocenter plotted to identify location of the earthquake. The fault parameter, such as strike, dip and slip plotted to interpret focal mechanism of fault caused earthquake. The data plotted by GMT to get distribution focal mechanism on Southern Sulawesi which shown 46 beach-balls. For interpretation, it divided into 3 regions; region I show oblique-reverse fault related to Makassar Thrust. Region II show left-strike-slip fault related to Matano Fault activity. Region I shows Paternoster fault and earthquake by sea spreading at Bone Gulf; Walennae Fault with strike-slip fault activity. Region III the most complex region show normal fault related to Tolo Fault activity. Region III shows Kolaka fault with strike-slip fault activity and earthquake by interaction between micro-continent observed as oblique-reverse fault activity.. The focal mechanism in this study effectively to observe the fault activity which can be used as guided for earthquake mitigation.

Tectonic constraints for hydrocarbon targets in the Dezful Embayment, Zagros Fold and Thrust Belt, SW Iran

Understanding of reservoir architecture is one of the most important steps in the petroleum exploration programs. New 2D/3D seismic data provided important insights into the tectonic evolution of the Dalpari prospect within the Dezful Embayment of the Zagros Fold and Thrust Belt, SW Iran. This hydrocarbon target has formed as a result of a transpressive dextral strike-slip fault activity mechanically interacting with reverse faults, out of the syncline thrusts and four orders of folds. In the northern part of the target, the existence of growth strata within the competent units of Gachsaran and Agha Jari Formations (i.e. Upper Miocene and Pliocene) helped to determine the time of the structural evolution of the hydrocarbon target. Finally, the existence of the incompetent strata (e.g. Gachsaran Formation and the Kalhur member of Asmari Formation) mechanically controlled the formation history of the Dalpari prospect. In a regional context, this architecture denotes local Zagros partitioning of the oblique convergence between the Afro-Arabian and Central-Iranian plates a problem that has been addressed by many other researchers in the past using.

Magnetic fabric of Plio-Pleistocene sediments from the Crotone fore-arc basin: Insights on the recent tectonic evolution of the Calabrian Arc (Italy)

Low-field anisotropy of magnetic susceptibility (AMS) analyses were performed on 532 samples collected in 36 (mostly lower Pliocene to lower Pleistocene) marine clay sites from the Crotone basin, a fore-arc basin located on top of the external Calabrian accretionary wedge. The Crotone basin formed since mid-late Miocene under a predominant extensional tectonic regime, but it was influenced thereafter by complex interactions with NW–SE left-lateral strike-faults bounding the basin, which also yielded post-1.2Ma ∼30° counterclockwise block rotations. The basin is filled by continental to marine sediments yielding one of the thickest and best-exposed Neogene succession available worldwide. The deep-marine facies – represented by blue-grey marly clays gave the best results, as they both preserved a clear magnetic fabric, and provided accurate chronology based on previously published magnetostratigraphy and calcareous plankton (i.e. foraminifers and nannofossils) biostratigraphy. Magnetic susceptibility range and rock magnetic analyses both indicate that AMS reflects paramagnetic clay matrix crystal arrangement. The fabric is predominantly oblate to triaxial, the anisotropy degree low (<1.06), and the magnetic foliation mostly subparallel to bedding. Magnetic lineation is defined in 30 out of 36 sites (where the e12 angle is <35°). By also considering local structural analysis data, we find that magnetic fabric was generally acquired during the first tectonic phases occurring after sediment deposition, thus validating its use as temporally dependent strain proxy. Although most of the magnetic lineations trend NW–SE and are orthogonal to normal faults (as observed elsewhere in Calabria), few NE–SW compressive lineations show that the Neogene extensional regime of the Crotone basin was punctuated by compressive episodes. Finally, compressive lineations (prolate magnetic fabric) documented along the strike-slip fault bounding the basin to the south support the significance of Pleistocene strike-slip tectonics. Thus the Crotone basin shows a markedly different tectonics with respect to other internal and western basins of Calabria, as it yields a magnetic fabric still dominated by extensional tectonics but also revealing arc-normal shortening episodes and recent strike-slip fault activity. The tectonics documented in the Crotone basin is compatible with a continuous upper crustal structural reorganization occurring during the SE-migration of the Calabria terrane above the Ionian subduction system.

Internal crustal deformation in the northern part of Shan-Thai Block: New evidence from paleomagnetic results of Cretaceous and Paleogene redbeds

In order to describe the internal deformation of the northeast part of the Shan-Thai Block resulting from the penetration of the Indian plate into Asia, a paleomagnetic study was carried out on the Cretaceous and Paleogene strata in the southern part of the Simao Terrane. High-temperature magnetic components with unblocking temperatures around 680 °C were isolated and positive fold test shows its primary nature of magnetization. The tilt corrected site-mean directions of the Lower Cretaceous and Upper Cretaceous from the Menglun area are Ds = 46.2°, Is = 45.9°, k = 11.0, α95 = 10.6° and Ds = 33.2°, Is = 30.9°, k = 68.4, α95 = 8.2°, respectively. The site-mean directions of the Upper Cretaceous and Lower Paleogene for the Mengban area are Ds = 50.5°, Is = 31.0°, k = 207.6, α95 = 6.4° and Ds = 43.5°, Is = 23.0°, k = 26.1, a95 = 13.4°, respectively. The results of the Lower Cretaceous and Upper Paleogene from the Mengla area are Ds = 46.9°, Is = 42.2°, k = 27.3, α95 = 7.7° and Ds = 41.8°, Is = 23.8°, k = 38.9°, a95 = 5.8°, respectively. In comparison with previous paleomagnetic data of the Simao Terrane, the rotational deformation can be divided into four stages. The Cretaceous and Paleocene sediments of the Simao Terrane experienced intensive folding before the early Oligocene. During the early Oligocene to early Miocene, the Shan-Thai and Indochina Blocks experienced southeastward extrusion with ~ 20° clockwise rotation relative to the South China Block. During the middle to late Miocene, the Shan-Thai Blocks experienced more 15° clockwise rotation. Since the late Miocene, the activity of strike-slip faults surrounding the Simao Terrane enhanced the internal differential rotations of the Terrane. These deformation processes finally resulted in a complex internal deformation of the Simao Terrane.

The tectonic and structural setting of the 4 September 2010 Darfield (Canterbury) earthquake sequence, New Zealand

Plate boundary deformation creates a south-easterly advancing, repetitive structural pattern in Canterbury dominated by the propagation of northeast-striking thrust assemblages. This pattern is regularly segmented by east-striking faults inherited from reactivated Cretaceous normal faults. The more evolved and deeply exposed structures in the foothills of north Canterbury provide insights into the tectonic processes of the blind structures now emerging from under the northern and eastern Canterbury Plains, where thrust and strike-slip fault activity are closely linked. The east-striking faults separate relative motion between thrust segments and accommodate oblique transpressive shear. Early stages of thrust emergence are dominated by anticlinal growth and blind, or partially buried, thrusts and backthrusts. The east-striking transecting faults therefore record timing of coseismic episodes of uplift and shortening with variable horizontal to vertical ratios and displacement rates on the hidden adjacent thrusts. The Greendale and blind Port Hills faults, with their associated aftershock patterns, are compatible with this style.

Controlling Factors of Overpressure Formation in the Yinggehai Basin

There are many previous studies on the formation mechanism of overpressure in sedimentary basins. The Yinggehai Basin is a typical strike-slip extensional basin with obvious overpressure phenomenon. Yinggehai Formation begins to appear overpressure in Central Diapir Zone with the depth of less than 2000 m. Undercompacted, hydrocarbon generation are the two main mechanisms for the formation of overpressure in Yinggehai Basin. Controlled by tectonic movements, Yinggehai Basin develops four kinds of structure-sedimentary patterns, and has a large deposition/subsidence rate formed thick mudstone layers. The thick mudstone layers not only form the undercompacted sedimentary background, also are good source rocks. Affected by Cenozoic lithospheric thinning, the Red River strike-slip fault activity and magmatic activity of local areas, Yinggehai Basin has high geo-temperature and high heat flow values which are conducive to hydrocarbon generation. This paper's study shows that tectonic movements control sedimentary facies types and distribution, deposition/subsidence rate, and geothermal field. Both of the two main mechanisms (undercompaction, hydrocarbon generation) of overpressure in Yinggehai Basin are all controlled by the tectonic movements. Therefore, the tectonic movements are the main controlling factor of overpressure formation in Yinggehai Basin.

Structural-dynamic relationships between the East Sikhote Alin volcano-plutonic belt and its folded basement

The East Sikhote Alin volcanoplutonic belt (ESAVB) extending along the coasts of the Sea of Japan and Tatar Strait is over 1000 km long and 35‐40 km wide on average. Similar to other elements of the East Asian volcanic belt, the latter represents a structure with the continuous development mode being superimposed or crossing protostructures of the eastern margin of the Asian continent regardless of their types and ages. The study of structural‐dynamic relationships between the basement that existed during synchronous dislocations and superimposed volcanic complexes reveals the geodynamic formation conditions of volcanic belts. The East Sikhote Alin volcano-plutonic belt was formed in the Late Cretaceous‐Paleogene. It is composed of sedimentary‐volcanogenic and volcano-plutonic rocks resting unconformably upon the folded basement represented largely by Lower Cretaceous terrigenous strata deformed into a system of open and isoclinal folds with a dominant northeastern strike (azimuth 40 ° ‐60 ° ) and complicated by imbricate updip‐ thrusts. In contrast to the basement, no dominant regional folded and dislocated systems were defined in volcanics during mapping. They demonstrate only fragments of folded‐bedded structures with variable strikes and dip angles as well as numerous fractures also oriented differently (largely, normal faults), the formation of which is thought to be related to local stresses during volcanoplutonic magmatism. Most researchers share the opinion that volcanics represents a superposed complex with its own dislocation type independent from tectonics of the Early Cretaceous folded basement. The discovery of a system of NNE-trending sinistral strikeslip faults with displacements amplitudes in the Late Cretaceous amounting to a few tens of kilometers made it possible to infer that the East Sikhote Alin volcanoplutonic belt was formed in response to Late Cretaceous activation of strike-slip faults [2‐4]. Such geodynamic conditions should result in the formation of ensembles of regularly oriented both folded structures and fractures characteristic of rocks overlying active strike-slip faults. This makes it crucial to study structures that developed in Late Cretaceous volcanics presumably in response to displacements along strike-slip faults.

Hydrothermal fluids assisted crustal-scale strike-slip on the Argentat fault zone

The role of hydrothermal fluids in assisting the activity of strike-slip faults is investigated using a range of new geological, geophysical, and geochemical data obtained on the Argentat fault, Massif Central, France. This fault zone, 180-km-long and 6 to 8 km-width, has experienced coeval intense channeling of hydrothermal fluids and brittle deformation during a short time span (300–295 Ma). According to seismic data, the fault core is a 4-km-wide, vertical zone of high fracture density that rooted in the middle crust (~13 km) and that involved fluids in its deeper parts (9–13 km depth). If stress analyses in the fault core and strain analyses in the damage zone both support a left-lateral movement along the fault zone, it is inferred that hydrothermal fluids have strongly influenced fault development, and the resulting fault has influenced fluid flow. Fluid pressure made easier fracturing and faulting in zones of competent rocks units and along rheological boundaries. Repeated cycles of increase of fault-fracture permeability then overpressure of hydrothermal fluids at fault extremity favored strong and fast development of the crustal-scale strike-slip fault. The high permeability obtained along the fault zone permitted a decrease of coupling across the weak fault core. Connections between shallower and lower crustal fluids reservoirs precipitate the decrease of fault activity by quartz precipitation and sulfides deposition. The zones of intense hydrothermal alteration at shallows crustal levels and the zones of fluid overpressure at the base of the upper crust both controlled the final geometry of the crustal-scale fault zone.

Late Devonian–Carboniferous tectonic evolution within the Firth of Forth, Midland Valley; as revealed from 2D seismic reflection data

Synopsis Results of integrated seismic mapping, within the Firth of Forth in the offshore Midland Valley of Scotland, are presented and illustrate aspects of the subsurface structure and tectonic evolution of the Upper Devonian to Carboniferous succession. Evidence for three main phases of tectonic activity has been recognized: (1) Late Devonian to Dinantian fault-controlled subsidence; (2) basin-wide Silesian subsidence, localized inversion and growth folding; (3) Late Silesian dextral transtensional and transpressional strike-slip faulting. During the first phase of tectonic activity, the NNE-trending Mid Forth Fault is interpreted to represent a Late Devonian to Dinantian extensional fault, with a small, mainly Dinantian depocentre developed in the hangingwall block that has subsequently been inverted during Silesian times. A major Late Devonian to Dinantian depocentre also occurs in the hangingwall block of the NE-trending offshore continuation of the Crossgatehall Fault, although it remains unclear whether this mainly Dinantian depocentre was developed during pull-apart as a result of extension or transtensional strike-slip fault movement. The NNE-trending Leven Syncline and Mid Forth Anticline within the hangingwall block of the Mid Forth Fault are interpreted as Silesian synsedimentary growth folds that formed during the second phase of tectonic activity. The peak of this activity occurred during intra-Westphalian B to Westphalian C times. In the third phase, the ENE-trending Inchkeith Fault Zone is interpreted as a Late Silesian transtensional–transpressional strike-slip fault that dextrally offsets the axial trace of the Leven Syncline. Evidence from the Firth of Forth could provide support for regional tectonic models involving mainly dextral strike-slip fault activity during Devonian–Carboniferous times, or mainly sinistral strike-slip during Devonian to Early Carboniferous followed by dextral strike-slip during Late Carboniferous times, for the development of the Upper Devonian and Carboniferous succession. However, the latter model is preferred as it provides the more convincing explanation for our interpretation that the NNE-trending Mid Forth Fault represents a Late Devonian to Dinantian extensional or transtensional fault that was inverted during Silesian times. This inversion may therefore reflect a major change in the regional stress field.