Sinistral Strike-slip Research Articles

Mineralogy and Geochemistry of Upper Miocene Igneous Rocks, Kos Island, Greece: Extension during Strike-Slip Faulting and Subduction Rollback

Upper Miocene volcanic and plutonic rocks on Kos island preserve a record of magmatic and tectonic events in the transition zone between the Aegean and Anatolian microplates. Their field setting, syn-intrusion deformation, mineralogy, and geochemistry were investigated. Volcanic rocks, including trachyandesite flows and trachyandesite to rhyolite domes, were extruded on a central E–W horst and directly overlie Alpine basement. Thick successions of trachytic flow tuffs are interbedded with fluvial and lacustrine basinal sediments to the south of this horst. Volcanism was synchronous with the emplacement of the Dikeos monzonite pluton, which is geochemically similar to some lithic clasts in the thick flow tuffs and is cut by mafic dykes including lamprophyres. Two main types of mafic magma were present: a K-rich lamprophyric magma that evolved to trachyandesite and more calc-alkaline magma similar to mafic enclaves in the monzonite. Syn-intrusion structures in the monzonite indicate emplacement during E–W sinistral strike-slip faulting that created local transtensional deformation, providing accommodation for a Dikeos magma reservoir. A change in the style of deformation in the Late Miocene led to NW-striking extension in the footwall, occupied by mafic dykes and mineralized veins, and extensional detachment of the hanging wall, resulting in unroofing of the monzonite.

Fault imaging using earthquake sequences: a revised seismotectonic model for the Albstadt Shear Zone, Southwest Germany

In Germany, the highest seismic hazard is associated with the Albstadt Shear Zone (ASZ) in the western Swabian Jura, a low mountain range in southwest Germany. The region is affected by continuous micro-seismic activity with the potential for damaging earthquakes (nine events with ML≥\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\ge $$\\end{document} 5 in the 20th\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{th}$$\\end{document} century). Within the AlpArray and StressTransfer projects nine temporary seismic stations have been installed in the region of the ASZ to densify the permanent seismic monitoring. In October 2018 and September 2019, the state seismological survey (LED) detected two low-magnitude earthquake sequences with hundreds of events in the area. The temporarily densified local network allows us to systematically analyze these sequences and to search for other sequences by applying a template-matching routine on data from 2018 to 2020. In total, six earthquake sequences could be identified with at least 10 events. The four largest sequences (> 50 events) consist of two fore- and aftershock sequence and two earthquake swarms. Earthquake swarms were so far not observed around the ASZ. Precise relative hypocenter relocations and the determination of fault-plane solutions allow us to propose a seismotectonic model based on the three imaged fault types: (a) The well-known NNE-SSW striking sinistral strike-slip ASZ at depths of 5-10 km, (b) a NW-SE striking dextral strike-slip fault zone at depths of 11-15 km beneath the Hohenzollerngraben (HZG), a shallow, apparently aseismic NW-SE striking graben structure; this NW-SE fault zone possibly is an inherited zone of weakness in the basement and facilitated the development of the HZG and (c) at the intersection of the ASZ with the NW-SE fault zone, complex faulting in form of NNW-SSE striking sinistral strike-slip and normal faulting possibly to accommodate local stresses.

Tectonic setting and Pan-African structural evolution of the western Saldania Belt, South Africa

Abstract The western Saldania Belt records the closure of the Adamastor Ocean and amalgamation of southwest Gondwana in the latest Neoproterozoic and early Phanerozoic, but the geodynamic setting and evolution of the belt remains controversial. Regional mapping and the integration of structural data presented in this paper document the juxtaposition of domains with distinct fabric development and kinematics. Structures record Pan-African strains and a strike-slip dominated sinistral transpression during southeast-directed subduction and convergence at low angles to the continental margin. Two main, structurally overlying domains – an upper and a lower domain – can be distinguished. Rocks of the upper domain record the partitioning of the transpressional strain into (1) broad regions of more or less upright, north to northwesterly-trending folds (F2) that record horizontal, mainly coaxial, east-northeast to west-southwest directed shortening at high angles to the continental margin, and (2) the northwesterly-trending, sinistral strike-slip Colenso Fault Zone that accommodates the margin-parallel, non-coaxial component of deformation between ca. 555 and 520 Ma. The strike-slip partitioning was promoted by strain localisation into synkinematic plutons of the Cape Granite Suite. In contrast, rocks in the pervasively transposed, mélange-like lower domain in the central Swartland region record episodes of vertical, coaxial shortening alternating with non-coaxial top-to-the-west and -northwest thrusting. The coaxial shortening strains relate to the thickening and gravitational loading of the succession in response to thrusting and tectonic underplating. Non-coaxial strains denote episodes of seismic slip during underthrusting. The different fabric domains are interpreted to represent a section through a fore-arc region, from the deeper level accretionary prism (lower domain) to the overlying, folded fore-arc basin succession (upper domain). Regional-scale klippen structures indicate the transfer of lower-domain phyllites into the overlying fore-arc sequence. The proposed fore-arc setting of the Saldania Belt suggests the subduction of the Adamastor Ocean below the leading edge of the Kalahari Craton. This challenges stratigraphic and structural correlations between the Saldania Belt and the Gariep Belt to the immediate north.

Newly Discovered NE-Striking Dextral Strike-Slip Holocene Active Caimashui Fault in the Central Part of the Sichuan-Yunnan Block and Its Tectonic Significance

The Sichuan-Yunnan block is a tectonically active region in China, with frequent large earthquakes occurring in and around it. Despite most earthquakes being concentrated along boundary faults, intraplate faults also have the potential to generate damaging earthquakes. Remote sensing makes it possible to identify these potential earthquake source faults. During an active fault investigation in the Liangshan area, a distinct lithological boundary named Caimashui fault was found. The geometric distribution and kinematic parameter of the fault is crucial for assessing seismic hazards and understanding the deformation pattern within the Sichuan-Yunnan block. The Caimashui fault is mapped with remote sensing interpretation, a field survey, and UAV measurement. Through trenching and Quaternary dating, the Late Quaternary active characteristics of the fault are studied. The fault is a Holocene active dextral strike-slip fault with a reverse component, exhibiting a dextral strike-slip rate of ~0.70 ± 0.11 mm/a. Paleoseismic investigation shows that the last surface rupture event of the Caimashui fault occurred later than 4150 ± 30a BP, with a magnitude of M ≥ 7.0. The fault may act as a secondary splitting fault, absorbing the deformation caused by various sinistral strike-slip rates of the boundary faults and the potential energy from the counterclockwise rotation of the Central Yunnan micro-block.

Conjugate extrusion with dextral oblique-slip faulting in SE Tibet: new insights into Oligo-Miocene deformation

SE Tibet experienced significant deformation during the Late Cenozoic, characterized by clockwise rotation of blocks separated by left-lateral strike-slip faults. Through field surveys, structural analyses and microstructural observations, we identified an early phase of ductile shear zones along three major faults: the Anninghe, Jinhe–Jinghe and Jinpingshan faults. New geochronological and thermochronological data collected from these fault zones and from carbonatites associated with a tear fault between two right-lateral oblique faults provide evidence that this slip occurred before c. 30 Ma. These findings lead to a new conceptual model suggesting that these north–south-trending right-lateral oblique-slip faults, together with the NW-trending left-lateral strike-slip faults in SE Tibet, form a network of large conjugate fractures. The conjugate fracture system, as a result of north- to NE-trending contraction, had a crucial role in controlling the overall tectonic framework of SE Tibet during the Oligocene. By integrating previous research and combining this with our latest findings, we propose a two-phases evolution model of Cenozoic tectonics in the region of SE Tibet, in which a drastic change in kinematics took place from an early phase (before ∼30 Ma) oblique dextral shearing to a late phase sinistral strike-slip faulting since the Miocene.

How great is the Great Glen Fault?

A popular conceptual tectonic model envisages the Great Glen Fault to be part of a sinistral strike-slip system active during the mid-Silurian through early Devonian with c. 700 km of displacement. Here we use sedimentological, geochemical and detrital zircon age data to show that restoring 250–300 km of displacement suffices to fulfil key geological constraints and reveal three new pre-strike-slip relationships: (i) Paleoproterozoic Makkovik-Ketilidian crust becomes placed proximal to numerous immature sandstone units in the Grampian and Northern Highlands of Scotland and County Mayo, Ireland, that are marked by single-mode peaks of 1.8–1.6 Ga detrital zircons sourced from that crust; (ii) the two most concentrated occurrences of appinite and metadolerite/gabbro in the Scottish-Irish Caledonides become matched; and (iii) the Donegal and Argyll granite suites can be paired. That amount of displacement provides, at least in part, the separation required between the Northern and Grampian Highlands to account for Scandian-age (Silurian) deformation in the former and its absence in the latter.

Satellite land surface temperature for mapping the structurally controlled geothermal anomalies in the Cretaceous rift, South Egypt

ABSTRACT Exploration of new geothermal systems often requires regional-scale investigation. Satellite Land Surface Temperature (LST) products are essential in geothermal anomaly identification and mapping. In this study, seven thermal anomalies covering Egypt were observed using the Sentinel-3 LST images acquired in 2019 and confirmed using the 2020 LST images. In addition, the LST analysis reveals three new anomalies covering the southern part of Egypt (Kalabsha, Natash, and Wadi Allaqi), which are structurally controlled. Nuqra-Kharit-Natash is a good site for geothermal energy owing to the following reasons: 1) the high geothermal gradient beneath the Wadi Natash region (heat flow ~100 mW/m2); 2) the presence of many geothermal anomalies retrieved from the analyses of the Landsat-8 acquired in August 2018; 3) existence of surface geothermal manifestation at the western boundary of the basin includes warm springs and the tufa deposits. Intricate structural patterns, including NW-oriented normal faults, ENE-to-WNW-oriented right-lateral faults, and NNE-oriented sinistral strike-slip faults, characterise Wadi Natash. Wadi Natash LST anomaly shows a solid relation to fault trends. High values of LST are arranged along NW and NNE faults and recorded the peak at the intersection of two fault trends. Recent seismic activity along the NNE fault system enhances the permeability along this trend and its intersection with the NW-oriented fault.

Spatial Variations of Late Quaternary Slip Rates along the Ganzi–Xianshuihe Fault Zone in the Eastern Tibet

The Ganzi–Xianshuihe Fault Zone is a large-scale sinistral strike-slip fault zone on the eastern Tibet. As the boundary fault zone of the Bayankala Block and the Chuandian Block, it controls the clockwise rotation of the southeastern Tibet. However, there is still controversy regarding the activity changes between fault zones. Therefore, accurately determining the slip rates of faults in the area is crucial for characterizing regional plate motions and assessing associated seismic hazards. We focused on studying four fault segments near the Ganzi–Xianshuihe Fault Zone, including the Manigango, Ganzi, Luhuo, and Daofu segments. In each segment, we selected typical sinistral piercing points and carried out Unmanned Aerial Vehicle (UAV) photogrammetry to obtain high-resolution terrain data. We utilized LaDiCaoz_V2.2 and GlobalMapper software (LaDiCaoz_V2.2 and Global Mapper v17.0) to measure the offsets, together with optically stimulated luminescence (OSL) dating, to constrain the timing of fault activity. The estimated slip rates for the Manigango, Ganzi, Luhuo, and Daofu segments are as follows: 9.2 ± 0.75 mm/yr, 9.59 ± 1.7 mm/yr, 4.23 ± 0.66 mm/yr, and 7.69 ± 0.76 mm/yr, respectively. Integrating previous results with slip rates estimated in this study, our analysis suggests the slip rate of the Ganzi–Xianshuihe Fault Zone is around 8–10 mm/year, exhibiting a consistent slip rate from northwest to southeast. This reflects the overall coordination of the movement on the eastern Tibet, with the strike-slip fault zone only controlling the direction of movement.

Imaging the Fault Plane Structure of Palu-Koro Fault from Earthquake Data Using Python

Abstract Palu-Koro Fault is one of the active faults located in Sulawesi and positioned in the middle of the Island, dividing the west and east-southeast arms. Its long history of earthquakes provides sufficient focal mechanisms data to be analyzed. This research used seven focal mechanism data of shallow magnitude earthquakes surrounding the pull-apart basin area of the Palu-Koro Fault. The focal mechanism data used is secondary data obtained containing the information needed. This research aims to create a 3D model of the pull-apart basin displaying the geometries of the fault planes and providing a closer look at the fault system surrounding the bounding fault zones. Python script was made to classify the mechanism of each earthquake based on its correlation to the trend of the Palu-Koro Fault. Nodal planes are categorized as whether it is presumed to be the fault plane or the auxiliary plane of the focal mechanism. The result found that not all earthquake data was classified through the assumed parameter set. Only five of seven earthquake data managed to be classified, while the rest showed a different focal mechanism. It is found from the python script created revealed the presence of three fault types: normal fault, normal left lateral oblique fault, and left lateral strike-slip. The 3D fault plane interpolation showed two distinct dipping directions, suggesting their association with the basin’s bounding fault, either the west or the east side. From the gathered information, previous research, and geological interpretation, the earthquake data can be concluded into three fault associations to the bounding fault: synthetic extension fault, antithetic extension fault, and sinistral strike-slip fault.

Geological structure of the Strelnica Massif (Muráň Plateau, Central Slovakia) based on new biostratigraphical data and geological mapping

The Strelnica massif is a part of the Muráň Plateau near Tisovec town. The massif is of prolonged triangular shape and is sharply defined by faults from all sides: the Muráň fault (line) on the SE side, the Mýto-Tisovec fault system from the SW side and a thrust/fault line with unclear character in the Martinová valley on the N side. The massif was supposed to be built by Lower to Middle Triassic carbonate complexes, however our new biostratigraphic data had proven that in fact most of these light grey carbonates belong mostly to Upper Triassic, which makes necessary the reinterpretation of the structure of the whole massif. Despite of new and more complicated structural interpretation, our new age data are in better agreement with earlier works from the Tisovec quarry as it was in earlier geological maps. Our mapping works also confirmed, that the Strelnica massif itself is built by two facially very different blocks: a deep-water type of succession with Reifling and Raming type limestones and a strongly tectonically reduced succesion from probably lower Carnian up to Liassic age. These two blocks are in tectonic contact along a fault line and both are lying on the Lower Triassic shaley complex which forms the basal horizon of the Muráň nappe. The Muráň fault (line) is covered by Quaternary deposits in the aera, but in addition we suppose also at least two newer fault systems: a NNW-SSE normal fault system, parallel with the Mýto-Tisovec fault system in the Rimava valley and a roughly WNW-ESE system with probable sinistral strike-slip kinematics. Both systems were locally known from the Tisovec quarry, or the structural measurements from the Dielik cave in the NE part of the massif, however not mapped in the whole massif.

Cenozoic deformation of the Weihe Graben in central China: Insights from Analogue modeling

The Weihe Graben is located in the composite area of the Tethys-Himalayan tectonic and circum-pacific tectonic domains and is an essential structural feature related to Cenozoic intracontinental deformation. However, two different hypotheses, sinistral strike-slip, and extensional mechanism, are proposed for the origin of this graben. In this study, we designed crust-scale analog models based on fault kinematics to better understand the deformation and dynamic mechanisms of the Weihe Graben. Fault kinematics shows early sinistral strike-slip and NW-SE extensional deformation and late NE-SW, S-N, and NW-SE extensional deformation. Our experimental results reveal that Model C1 (sinistral strike-slip + NW-SE extension) is the most similar to the geological structure of the Weihe Graben in the Paleogene. Furthermore, the NE-SW extension results in two larger subsidence areas in the northeast and southwest of the basin, similar to the formation of the two depressions during the Miocene. The S-N extension causes the basin to expand southward and northward, consistent with the sedimentary characteristics of Weihe Graben in the Pliocene. The NW-SE extension leads to relatively strong fault activity in the northwest and southeast of the basin, resembling the active fault characteristics since the Quaternary. Therefore, we propose that the Weihe Graben formed by a strike-slip and extensional combined mechanism in the Eocene-Oligocene, influenced by the far-field effects of the Indian-Asian collision and crust-mantle processes triggered by the stagnant paleo-Pacific plate. Subsequently, during the Neogene-Quaternary, the graben’s development shifted towards an extensional regime under the influence of the eastward extrusion of the Tibetan Plateau.

STRUCTURAL FEATURES OF THE PSHEKHA-ADLER FAULT ZONE OF THE GREATER CAUCASUS ACCORDING TO STRUCTURAL STUDIES

The study of minor faults carried out in the valley of the Belaya River made it possible to establish the tectodynamic conditions for the formation of the Pshekha-Adler fault zone of the Greater Caucasus. In this zone, the presence of strike-slip displacements of different scales and the predominance of the situation of horizontal displacement are shown. Using the method of cataclastic analysis, differences in the parameters of the stress-and-strain state in different tectonic complexes and structures of the region have been established. The revealed structural pattern of meridional and northeastern compression determine the regional dextral strike-slip fault and extensional fault nature of the meridional Pshekha-Adler fault zone with the development of sinistral strike-slip faults and extensional faults of the northeastern strike inside the deformation zone.

Three-dimensional displacement and slip distribution of the 2021 Mw 7.4 Maduo (Tibetan Plateau) earthquake determined by GNSS and InSAR

On May 22, 2021, an Mw 7.4 earthquake occurred on the Maduo-Jiangcuo fault, located in Maduo County, Qinghai Province (China). According to the co-seismic deformation and the three-dimensional displacement reached from the interferometric synthetic aperture radar (InSAR) and the global navigation satellite system (GNSS), the rupture trace in the NWW direction was mapped, spanning a length of approximately 160 km and the earthquake happened on a typical sinistral strike-slip fault. In three-dimensional displacement, the displacement in E-W was bigger than that in N-S and vertical, with the RMSE 3.01 mm, 15.28 mm, and 5.16 mm respectively. Moreover, the slip distribution inverted with the homogeneous half-space model and layered half-space model, indicated that the corresponding magnitude was 7.3 Mw and 7.4 Mw, and the corresponding peak slip was 5.53 m and 5.96 m. The correlation coefficients of observed and predicted both exceeded 0.791, meeting the need for slip inversion. What is more, the peak inversion depth was no more than 15 km with strike angle and dip angle of 269° and 82.9° in the homogeneous half-space model and 265° and 83.7° in the layered half-space model, respectively. In addition, the Coulomb stress changes decreased on the Maduo-Jiangcuo fault and accumulated on the East Kunlun fault, which might cause aftershocks and future earthquakes were still possible. In short, the 2021 Mw7.4 Maduo earthquake made it possible to unravel seismic behavior in the Tibet plateau, which is of great significance for seismic hazard research.

Kinematics of the Clarke River Shear Zone (northeastern Australia) and implications for the tectonic evolution of the Tasmanides

The Clarke River Shear Zone marks the boundary between the Thomson and Mossman orogens in the northeastern Tasmanides. To better understand the kinematic history of this east-northeast-trending shear zone, and its role during the tectonic history of eastern Gondwana, we investigated rock deformation along a segment of the Clarke River Shear Zone. Based on field observations, interpretation of aeromagnetic data and microstructural analysis, we show that the Clarke River Shear Zone experienced at least three phases of reactivation. Gently plunging stretching lineation and kinematic indicators, such as steeply plunging asymmetric folds and asymmetric porphyroclasts, correspond to an early phase of sinistral strike-slip ductile shearing. Subsequent general dextral shear deformation is suggested based on the presence of S-tectonites, symmetric porphyroclasts and kinematic indicators with dominant dextral and subordinate sinistral shear senses. This phase, which occurred under amphibolite-facies metamorphic conditions, was contemporaneous with the emplacement of the Craigie Tonalite, for which we obtained a new zircon U–Pb crystallisation age of 410.3 ± 1 Ma. A later reactivation phase along the Clarke River Shear Zone, under brittle conditions, is indicated by the presence of cataclasite zones and chlorite–epidote alteration. Based on our findings, and regional information on the tectono-magmatic evolution of northeastern Queensland, we suggest that the Clarke River Shear Zone was possibly a sinistral transform fault during the Silurian. During the Devonian, it is possible that deformation along the Clarke River Shear Zone was related to the transition between the non-retreating subduction zone in the north, and the highly mobile (retreating) plate boundary farther south. However, the dextral kinematic component associated with this deformation is not fully explained. Brittle deformation, likely associated with dextral transpression during the Carboniferous, marked the last stage of activity along the Clarke River Shear Zone.

Multi-scale hydrostructural approach for karst environment. Application to the Arcier hydrosystem (eastern France)

Based on a multi-scale and hydrostructural approach, this study presents the most relevant methodology to be applied to a karst hydrosystem in order to get a full understanding of underground water flow. It implies a complete structural analysis, from the hydrosystem scale to the outcrop scale, including the intermediate scale of the major geological structures. We illustrate the method in the Arcier hydrosystem, in the northwestern border of the Jura fold-and-thrust belt (Eastern France).Field mapping and structural analysis allow to update the geological vision of the hydrosystem with two kink-type fault propagation folds, including a trishear kinematic model, on either side of a plateau presenting a hollow-and-dome configuration. Fracturing analysis reveals a fault-fracture network that we infer governs the entire hydrosystem. A Riedel pattern is highlighted, characterized by a N–S-striking (N355° ± 5), sinistral strike-slip, regional shear zone. Then, two 3D geological models, at different scales, constructed with MOVE and Visual Karsys softwares are combined with water levels and artificial tracer tests. It reveals a multilayer aquifer and a redefinition of groundwater circulations for the Arcier hydrosystem.The results demonstrate a strong geological control of karstic hydrosystems on groundwater circulations, proving that classical hydrogeological methods, such as natural and/or artificial tracers, must be combined with rigorous geological analysis. Moreover, the multi-scale approach provides an explanation of groundwater circulation based on the intersection between 3D geometry of impervious layers delimiting the aquifers and their base water level, instead of the 2D view (section or map) requiring systematic recourse to inferred vertical faults to cross permeability barriers vertically or laterally. This study also brings a new vision to the local protection of the water resource.

Prolonged exhumation and preservation of the Yuku molybdenum ore field, East Qinling, China: Constraints from medium- to low-temperature thermochronology

Molybdenum (Mo) is an important globally strategic metal and mostly occurs as molybdenite (MoS2) in diverse Mo deposits. The Yuku ore field includes multiple porphyry-skarn Mo deposits and forms a significant world-class Mo cluster in the Qinling molybdenum belt, central China. Previous studies on the ore field were largely related to its genesis, and did not highlight the post-mineralization modifications that are important to formulate prospecting strategies. The exhumation and preservation processes of the ore field through multiple tectonic events also remain poorly understood. Here, we conducted multi-method apatite U-Pb, fission-track and (U-Th)/He and zircon (U-Th)/He medium- to low-temperature thermochronology and related thermal history modelling on granitoids from the ore-hosting Shibaogou and Yuku plutons in the Yuku ore field, and integrated published studies to unravel the post-mineralization exhumation and preservation of Mo deposits. The newly determined apatite U-Pb (158.3–104.9 Ma), zircon (U-Th)/He (158.2–115.0 Ma), apatite fission-track (90.8–63.1 Ma), and apatite (U-Th)/He (67.8–35.3 Ma) ages in this study document multiple cooling pulses during post-magma emplacement. The low-temperature thermochronological ages of 158.2–35.3 Ma also record the post-mineralization cooling and exhumation history. The thermal history modelling indicates an Early Cretaceous (132–125 Ma) rapid cooling pulse, two enhanced (or accelerated) cooling pulses at ca. 125–59 Ma and post-10 Ma, together with a slow cooling or reheating pulse at ca. 59–10 Ma in the Yuku ore field. The Early Cretaceous rapid cooling is related to the coeval collisional tectonics of the East Qinling Orogen. The enhanced cooling at ca. 125–59 Ma is triggered by the post-collisional assembly of the North China and Yangtze Blocks, the subduction of Paleo-Pacific Plate, and the sinistral strike-slip motion of the nearby Tan-Lu Fault Zone. The slow cooling during ca. 59–10 Ma and the post-10 Ma enhanced cooling are correlated with the extensional tectonics derived by the subduction of Pacific Plate and the far-field effects from India-Eurasia collision. The Yuku area underwent lower exhumation in comparison to the nearby Shibaoguo and Huangbeiling areas in the Yuku ore field, which thus is helpful to the preservation of Mo deposits. The un-exhumated areas within 1.0 km at the inner and outer contact zones between the Yuku pluton and its wall rocks are postulated to be favorable sites for Mo prospecting. In addition, the un-exhumated areas surrounding other Late Mesozoic plutons in the Luanchuan region are also suggested to have high potential for Mo exploration.

ANALISIS STRUKTUR GEOLOGI BERDASARKAN DATA PERMUKAAN DAERAH BANJARHARJO, KABUPATEN BREBES, PROVINSI JAWA TENGAH

The research area is administratively located in Banjarharjo Village, Banjarharjo District, Brebes Regency, Central Java Province. Geographically, the research area is located at coordinates 108o 49 '15.4 "- 108o 52' 30.8" East Longitude and 06o 59 "21.8" - 07o 02 '04.8 "LS. The research area is included in The North Central Java Basin (The North Serayu Through/Basin) which is a Back Arc Basin. Based on the stratigraphic and sedimentological composition, the research area is classified into five geological units, (old to young), namely: (1) Sandstone and Claystone Interchange Unit, (2) Carbonate Claystone Unit, (3) Sand Limestone Unit, (4) Volcanic Breccia Unit and (5) Andesite Intrusion Unit. According to Pulonggono and Martodjojo (1994) Java Island, there are three straight lines of dominant structure, including: (1) East Laur - Southwest (Meratus Pattern), (2) North - South (Sundanese Pattern) and (3) West - East (Pattern Java). Based on the strike dip and stockiness data at the research location, the results of the force with the direction of the main stress are relatively Northeast-Southwestern, with the combination of Harding modeling, (1977) and Moody and Hill, (1956). The structural arrangements in the research area that are formed are (1) Cibuluh thrust fault, (2) Maibah sinistral strike-slip fault, (3) Cikuya sinistral strike-slip fault, and (4) Cikuya dextral strikeslip fault.

Current active fault distribution and slip rate along the middle section of the Jiali-Chayu fault from Sentinel-1 InSAR observations (2017–2022)

The Jiali-Chayu fault, situated on the eastern side of the eastern Himalayan syntaxis, is the southeastern margin of the large strike-slip fault zone of the Jiali Fault. The study of the distribution and activity within this fault zone is imperative for a comprehensive understanding of the tectonic movement patterns in the southeastern Tibetan Plateau. Previous studies have established that the kinematic characteristic of the Jiali-Chayu fault diverges significantly from that of other segments within the Jiali fault. Nonetheless, the current tectonic characteristics, including the slip sense, slip rate, and geometric deformation of this fault, are still not well resolved, leading to divergent interpretations regarding its contemporary activity intensity. This paper introduced an optimized time-series InSAR method with phase compensation designed for regions characterized by low coherence and exhibiting slow deformation. Using Sentinel-1 SAR data from both ascending and descending orbits spanning the period between 2017 and 2022, we successfully derived deformation rates for the middle part of the Jiali-Chayu fault at a spatial resolution of 150 m. The slip and dip rates of active faults are determined by considering the fault movement rates from two different observation angles, in conjunction with strike angle and the assumed dip angle of the fault. The results show that the deformation rates of the three branches are very different, with F2-1 and F2-2 exhibiting notable activity, while other areas exhibit relatively weaker activity. The strike-slip rates for F2-1 and F2-2 faults range between 3.6 and 5.3 mm/a and 3.05 to 5.13 mm/a, respectively, while their respective dip-slip rates fall within the range of 1.1–2.7 mm/a and 2.99–5.02 mm/a. In accordance with the fault slip directions, we classify the F2-1 fault as a sinistral (left-lateral) strike-slip fault and the F2-2 fault as a dextral (right-lateral) strike-slip fault. This study addresses a gap in remote sensing methods for detecting active fault activity in this region, providing a systematic foundation for identifying weak activity characteristics within the fault zone.Graphical

New data on the Ben Levy anticline, with reverse reactivation on the Coolin Fault giving up-side-down Silurian rocks in Joyces Country, Connemara

Abstract: In Joyces Country in western Ireland, the ∼ E-W striking axial plane of the D7 Ben Levy anticline folded Dalradian and unconformable Silurian rocks. The north side of the fold is mostly coincident with the contemporaneous ESE-WNW striking steeply dipping Coolin Fault close to the Dalradian-basal Silurian contact. This fault was first initiated by sinistral strike-slip motion, probably of Ordovician age, and then secondly used by post-Wenlock down throw on the north side to form the D7 anticline. Later a newly recognised third motion of reverse reactivation on the fault uplifted the north limb of the fold and locally overturned the Silurian succession against irregularities in the SSW dip of the fault. Still later, but pre-374Ma (Devonian), NE-SW faulting exposed different previous levels of the Coolin Fault zone. The superb Dalradian rock exposure provides details not generally apparent on other reactivated faults in Connemara.

A Bayesian Source Model for the 2022 Mw6.6 Luding Earthquake, Sichuan Province, China, Constrained by GPS and InSAR Observations

Until the Mw 6.6 Luding earthquake ruptured the Moxi section of the Xianshuihe fault (XSHF) on 5 September 2022, the region had not experienced an Mw >6 earthquake since instrumental records began. We used Global Positioning System (GPS) and Sentinel-1 interferometric synthetic aperture radar (InSAR) observations to image the coseismic deformation and constrain the location and geometry of the seismogenic fault using a Bayesian method We then present a distributed slip model of the 2022 Mw6.6 Luding earthquake, a left-lateral strike-slip earthquake that occurred on the Moxi section of the Xianshuihe fault in the southwest Sichuan basin, China. Two tracks (T26 and T135) of the InSAR data captured a part of the coseismic surface deformation with the line-of-sight displacements range from ∼−0.16 m to ~0.14 m in the ascending track and from ~−0.12 m to ~0.10 m in the descending track. The inverted best-fitting fault model shows a pure sinistral strike-slip motion on a west-dipping fault plane with a strike of 164.3°. We adopt a variational Bayesian approach and account for the uncertainties in the fault geometry to retrieve the distributed slip model. The inverted result shows that the maximum slip of ~1.82 m occurred at a depth of 5.3 km, with the major slip concentrated within depths ranging from 0.9–11 km. The InSAR-determined moment is 1.3 × 1019 Nm, with a shear modulus of 30 GPa, equivalent to Mw 6.7. The published coseismic slip models of the 2022 Luding earthquake show apparent differences despite the use of similar geodetic or seismic observations. These variations underscore the uncertainty associated with routinely performed source inversions and their interpretations for the underlying fault model.