Thrust Faults Research Articles

Application of bivariate statistical techniques for landslide susceptibility mapping: A case study in Kaghan Valley, NW Pakistan

Landslides are dangerous events that threaten both human life and property. This research presents a case study of Kaghan valley catchment, which is an area of frequent landslide activity. We aim to present a comparison between the bivariate Landslide Numerical Risk Factor (LNRF), Statistical Index (SI) and Information Value (InfV) statistical models to evaluate landslide susceptibility. A total of 1556 landslides were identified using earlier reports, field surveys, and GOOGLE Earth imagery. The abundance of landslides is primarily controlled by acute deformation caused by a major thrust fault system and proximity to Hazara Kashmir Syntaxis (HKS). A landslide inventory was randomly partitioned into two datasets. 70% (1106) of landslides were used as a training phase of the models, whereas 30% (450) as validation of the three models. A spatial database of 11 conditioning factors was produced consisting of slope, aspect, elevation, lithology, land use, Topographic Wetness Index (TWI), rainfall, Stream Power Index (SPI), distance to faults, rivers and streams. All the landslide susceptibility assessment parameters were obtained from different sources and different landslide susceptibility maps were prepared on the GIS software. Performance of the three models was validated through the Receiver operator Characteristics (ROC) through success and prediction rate curves. Results show that the area under the ROC curve (AUC) for InfV, LNRF and SI models are 70.95, 83.99 and 67.56 for success rate curves and 70.75, 83.99 and 67.85 for prediction rate curves, respectively. LNRF having the highest AUC value proved to be superior for generating regional scale landslide susceptibility maps.

Correlation between the deformation of mineral crystal structures and fault activity: A case study of the Yingxiu-Beichuan fault and the Milin fault

Abstract The build-up and occurrence of earthquakes are due to the accumulation and release of stress in fault zones. When subjected to tectonic extrusion stress, the crystal structure of the minerals within a fault zone will change. In this study, Raman spectroscopy analysis was conducted on the concurrently deposited quartz veins from Shenxigou, along the Yingxiu-Beichuan fault, and from Niyang River mouth, in the southern section of the Milin fault. The test results reveal a 3.29 cm−1 shift in the characteristic 464 cm−1 peak of the quartz in the veins along the fault plane of the Yingxiu-Beichuan fault, which was significantly lower than the shifts in the quartz peaks of the quartz on both sides of the vein. The 464 cm−1 peak shifts of the samples collected 10 m to the NW and 21 m to the SE of the fault plane were approximately 4.40 and 4.62 cm−1. In the veins from the Milin fault, considerable shifts of the 464 cm−1 quartz peaks occurred at the fault plane and to both sides within 5.5 m of the fault plane. No significant change in the 464 cm−1 Raman peak of quartz was observed for the samples 5–28 m to the SE of the fault plane. These results indicate that the tectonic extrusion stress accumulated more easily in proximity to the fault plane, resulting in significant changes in the crystals near the fault plane. We conclude that there is a correlation between the degree of change in the crystal structures of the minerals in thrust fault zones and fault activity, and such a correlation can provide a new method for studying the activity of thrust faults in areas with bedrock.

Reconstruction of the proto-type basin and tectono-paleogeography of Tarim Block in the Mesozoic

The reconstruction of the proto-type basin and tectono-paleogeography of the Tarim Basin during the Mesozoic is crucial for hydrocarbon exploration, particularly for identifying hydrocarbon source rocks. This study reconstructs the position, thickness, and distribution of the original stratigraphy, the shortening amount by structural deformation, and the distribution of sedimentary facies in each Mesozoic period using paleomagnetic data, residual stratigraphy data, seismic profiles, and lithofacies distribution. During the Triassic period, a syn-collision thrust fault structure formed in the southern Tarim Block due to the successive collision of the Tianshuihai-Bayankara terrane, North Qiangtang terrane, and South Qiangtang terrane with the Tarim Block. The sedimentary strata mainly distributed in the Northern Depression and Kuqa Depression, and their sedimentary centers continuously moved northward. In the Early-Middle Jurassic, faulted basins representing post-collision extensional structures developed on the margins of the Tarim Block. In the Late Jurassic, the Tarim Block was compressed, and the faulted basin transformed into a depressional downwarped basin with red coarse clastic sediments due to the collision of the Amdo-Dongkacuo microcontinent with the Tarim Block. In the late Early Cretaceous, the collision between the Lhasa Block and the Tarim Block caused the entire uplift of the Tarim Block, which stopped accepting deposition except for the deposition of marine facies in the southwestern Tarim Basin influenced by a large-scale transgression event. The complex evolution of the Paleo-Tethys and Neo-Tethys Oceans during the Mesozoic significantly influenced the sediment distribution and structural features of the Tarim Basin.

Interaction of Segmental Tunnel Linings and Dip-Slip Faults—Tabriz Subway Tunnels

In some subsurface urban development projects, bedrock faults intersecting with the tunnel path are inevitable. Due to the high costs of urban tunnel projects, it is necessary to study the behavior of such concrete structures under fault movement risks. Using an advanced 3D numerical finite difference code and a plastic hardening constitutive model for the soil, this paper examined the performance of the straight and oblique segmented structures of Tabriz Subway Line 2 under large deformations. The Tabriz Line 2 tunnel passes through a reverse fault called the Baghmisheh Fault. The fault–tunnel simulations were validated by centrifuge tests on the segmental tunnel for normal faulting. In the centrifuge tests and validation models, there was a maximum difference of 15%. According to the results of the Tabriz Line 2 tunnel under reverse faulting, segmental structures outperform no-joint linings when it comes to fault movement. During reverse fault movement, line 2 segments did not collapse but showed slight deformations. However, continuous structures collapsed under faulting, i.e., the structural forces created exceeded the section strength capacity. Among the segmental structures, the lining with oblique joints showed better behavior against faulting than the lining with straight joints. For better tunnel performance under fault movement, oblique joints should be used in segmental structures in faulting areas.

Inversion of extensional basins parallel and oblique to their boundaries: inferences from analogue models and field observations from the Dolomites Indenter, European eastern Southern Alps

Abstract. Polyphase deformation of continental crust is analysed through physical analogue models for settings wherein platform–basin geometries at passive continental margins are subject to subsequent shortening and orogenesis. In a first stage, segmentation of the brittle and brittle–ductile models into basins and platforms is achieved by extension. Basins are partly filled with brittle material to allow for a strength difference between basin and platform realms, simulating relatively weaker, incompetent deposits of grabens surrounded by competent pre-rift basement or carbonate platform rock, respectively. In a second stage of deformation, contraction parallel and oblique (10 to 20∘) to the basin axes has been applied, leading to the inversion of basins formed earlier. The experiments show that strength contrasts across platform–basin transitions control the localisation and overall style of compressional deformation, irrespective of the nature of the basal décollement (frictional versus viscous), the rheology of the basin fill, or changing platform–basin thickness ratios. Orientations of thrust faults change laterally across inherited platform–basin transitions throughout all experiments; higher obliquity of basin inversion leads to stronger alignment of thrust curvature with the orientation of pre-existing rift axes. At individual thrust faults, variations in the strike of thrust fronts are accompanied by changes in the shortening direction during incremental phases of deformation. Reactivation of normal faults occurs in oblique basin inversion settings only, favourably at platform–basin transitions where the normal faults face the shortening direction. The amount and style of fault reactivation depend on the material used. Our experiments are relevant for natural cases such as the Dolomites Indenter of the eastern Southern Alps, underlining the importance of inherited geologic features for the subsequent shortening geometries. Field structural data from the western segment of the Belluno thrust of the Valsugana fault system support predicted variations of thrust fault orientation and a lateral change in shortening direction (from SSW to SSE along-strike) along one single fault. Based on our modelling results, we suggest that this variability of thrust fault orientation and shortening directions, controlled by inherited structures, is consistent with strain partitioning during a single phase of deformation and does not necessarily reflect different deformation phases.

Discovery of the large-scale Eocene Xiwu Pb–Zn–Ag deposit in the Tethyan Himalaya: Geochronology, geochemistry, and C–H–O–S–Pb–Sr–Nd isotopes

The known Pb–Zn–Sb–Au polymetallic deposits in the Himalaya mainly formed during the main-collisional convergence (65–41 Ma) and post-collisional crustal extension (25–0 Ma) tectonic settings. Here, we report the discovery and genesis of the large-scale Eocene Xiwu Pb–Zn–Ag deposit that formed during the late-collisional tectonic transition stage (40–26 Ma) in the eastern Himalaya. The surrounding ore-hosting rocks are mainly low-grade metamorphosed Jurassic clastic rocks and Early Cretaceous diabase. The most important ore-controlling structures are NE–SW thrust faults. The ore minerals include large amounts of galena, sphalerite, tetrahedrite and siderite, with minor chalcopyrite, pyrite, arsenopyrite, calcite and quartz. In this contribution, we analyzed the S–Pb isotopes of sulfides, fluid inclusions and the C–H–O–Pb–Sr–Nd isotopes of nonmetallic minerals. The results indicate that the ore-forming materials originated from deeper metamorphic rocks of the Greater Himalayan Crystalline Complex. This study infer that the source of ore-forming fluids was mainly metamorphic fluids with moderate temperatures and salinities, and S and C were mainly derived from microbial sulfate reduction and the decarboxylation of organic matter, respectively. The main ore-forming mechanism is fluid mixing between the deep ore-bearing metamorphic fluids and shallow formation waters. The Sm–Nd isotopic age of siderite is 37.4 ± 1.1 Ma, which is slightly younger than the zircon U–Pb age of the Zhunba leucogranite (38.9 ± 0.4 Ma) but is consistent with the main epoch of early prograde metamorphism (43–36 Ma) in the Himalaya. We propose a new metallogenic model for Himalayan Pb–Zn–Ag deposits that can greatly promote ore prospecting. The genetic type of the Xiwu deposit is a clastic-dominated subtype of sediment-hosted Pb–Zn deposits.

Polarity crossover regions of transient earth fault relays in non-radial resonant grounded networks

Transient-based earth fault protection is widely used in all types of resonant grounded networks, and though the operating principles of the commonly available relays are usually derived from radial networks, manufacturers claim applicability in meshed networks as well. This paper utilizes a laboratory setup to study the directional indication of four transient earth fault relays in non-radial resonant grounded networks. Two of the relays considered are widely used analog single-purpose transient earth fault relays, whereas the other two relays represent two transient-based earth fault functions found in modern protective devices. The paper verifies the location of crossover points according to the presented theory, i.e. fault locations for which relays transition between seeing faults as forward and reverse faults, and demonstrates the viability of the proposed theoretical analysis of crossover points. However, presented analytical formulae only describe the two analog relays accurately, whereas the two modern relays have a more complex operating principle which requires further analysis to quantify properly. Finally, it is shown that relay misoperation which is not easily fixed by communication between relays can occur, and it is suggested that network operators conduct detailed relay coordination when applying transient earth fault relays instead of relying on standardized settings.

Hosgri Fault Transpressional Slip Rates Reproduce Observed Central California Coast Uplift Rates

Abstract Coastal uplift is a common feature of Pacific Rim tectonic deformation. The 1989 Mw 7.0 Loma Prieta earthquake illustrated that reverse-oblique slip on a transpressive segment of the predominantly horizontal slip San Andreas transform fault produces coastal uplift. In west-central California the 400 km long San Gregorio-Hosgri fault coastal fault system of near-vertical to steeply northeast-dipping, reverse-oblique, dextral strike-slip faults also contribute to coastal uplift. Published southern Hosgri fault dextral slip rates are ∼4× reverse rates. Viscoelastic deformation modeling using published transpressional slip rates along the southern Hosgri fault reproduces observed emergent marine terrace uplift rates, offshore Hosgri fault deformation morphology, and crustal structure from San Luis Obispo Bay to Estero Bay. Our coastal uplift rate modeling is constrained by a unique combination of measurements: (1) offshore reverse- and strike-slip Hosgri fault zone (HFZ) slip rates, and (2) ≤125 ka onshore emergent terrace uplift rates adjacent to the HFZ. The previously proposed conceptual rigid block models of the southern central California coast (CCC) invoke local onshore thrust or reverse faults to explain coastal uplift. Observed transpressional offshore Hosgri fault deformation rates alone rigorously reproduce observed coastal uplift rates and crustal structure along the southern CCC.

Structural and geomorphological study of Bradost, Chinara, Shireen and Sare Musa anticlines, Iraqi Kurdistan Region

The Bradost and Chinara mountains are two well-known geomorphic features in the Iraqi Kurdistan Region (IKR), forming two anticlines, besides Shireen and Sare Musa anticlines, which are located north of the Bradost anticline, all four anticlines trend NW – SE. The four anticlines are dissected by the Greater Zab River that swings along its course within the anticlines due to tens of very old landslides and/or plunges. The four studied anticlines are dissected by different thrust faults, which extend for a few kilometers. The thrust faults trend NW – SE; however, locally they deflect from the main trend. The Lower Jurassic rocks are the oldest exposed rocks in the studied area, whereas the rocks of the Bekhme Formation form the carapace of the Bradost and Chinara anticlines. Different structural and geomorphological features were interpreted from satellite images and those which are accessible were checked in the field, all of them indicate the four anticlines exhibit lateral growth. We have measured different aspects to elucidate the type of folds. The four anticlines are Detachment folds, with shallow decollement, which ranges in depth between (100–250) m.

Estimation of Flores Sea Aftershock Rupture Data Based on AI

The earthquake catalog notes that there have been earthquakes with Mw > 7 that hit the Flores area, three of which occurred in the Flores Sea in 1992, 2015, and 2021. Revealed that the seismic activity of Eastern Indonesia is thought to be influenced by the isolated thrust fault segment of the island of Flores and the island of Wetar. The study of the rising fault segment on Flores Island and Wetar Island helps in further understanding the fault behavior, earthquake pattern, and seismic risk in the Flores Sea region. In earthquakes with giant magneto, an aftershock can occur due to the interaction of ground movements. This research analyzes and compares the data from the evaluation of the classification algorithm and the regression algorithm. The initial stages of this research include requesting IRIS DMC Web Service data. The data is then subjected to a cleaning process to obtain the expected feature extraction. The next stage is to perform the clustering process. This stage is carried out to label dependent data by adding new features as data clusters. The following procedure divides the validation value, which consists of training and test data. The estimation results show that the classification algorithm's evaluation value is better than that of the regression algorithm. The evaluation value of several algorithms indicates this, with an accuracy rate between 80% and 100%.

Tectonostratigraphic model of the Fila Costeña in southern Central America based on new biostratigraphic data: implications of a two-thrust-fault hypothesis

Biostratigraphic determinations in the surroundings of the Térraba River, Fila Costeña, Costa Rica, lead to a two-thrust-fault model to explain the distribution of sedimentary rocks. Eocene limestones of the Fila de Cal Formation appear as a single succession with a NE-SW predominant strike, and a thrust fault is required to explain their presence above other Oligocene rocks. Another thrust fault explains the outcrop of Oligocene rocks above presumable Miocene strata. A structural model based on surface data suggests a shallower basement to the southwest and deeper to the northeast; both parts are connected by a frontal thrust ramp, an oblique ramp (close to frontal) and a lateral ramp. In that sense, the superficial trend of thrust faults is interpreted as the result of slip along these thrust ramps. Based on these assumptions, minimum NE-SW shortening estimations vary between 8.3 and 22.2 km in the study area. This underlines the importance of geologic fieldwork and biostratigraphic determinations for structural modeling and minimum shortening estimations of the Fila Costeña and other sedimentary successions for which these approaches are possible.

The Identification of the Existence of a Fault Structure on Gravity and Audio Magnetotulleric Data in the Area of Mount Kubing, Belitung

Mount Kubing holds significant potential as a tourist attraction, despite being situated in a tectonic zone prone to faults. Its size and attractions make it suitable for both travel and exploration. Hence, the study has been conducted to identify subsurface structures that can identify the structural fault lines when the mitigation occurred during an earthquake or landslide. The derivative analysis method is used to determine the type of structures. The results of the derivative analysis indicate the direction of the fault structure on a Northwest-Southeast, and Southwest -Northeast that is controlled by two different faults. The fault caused by depression from granitic body and silt with FHD and SVD gravity value around -3 mGal until 1 mGal that showing the indication of normal fault and reverse fault in the research location with depth estimation curve (RAPS) approximately 500 meters in the subsurface of the earth. Whereas in 2D Audio Magnetotelluric modelling, it is identified that the groundwater reservoir layer is at a depth of 70-85 meters below the surface which is recognized as a semi-stressed reservoir with a value of 20-27 mv/nT in complex silt and sandstone.

Characteristics and controlling factors of petroliferous reservoirs in the Permian Lower Urho Formation, western Mahu Slope, Junggar Basin, Northwest China

Numerous hydrocarbon discoveries in the lower Urho Formation of the western Mahu Slope, China indicate that potential petroliferous reservoirs may exist in that region. However, issues concerning the reservoir characteristics and associated controlling factors remain unclear. To determine the characteristics and associated controlling factors of these reservoirs, we conducted integrated analysis of the 3D seismic volume, wireline logs, mud logs, cores, thin sections, porosity, and permeability data. Several lithologic types were identified from the core, casting thin section, and mud-log data (including mudstone, sandstone, gravity flow-derived glutenite, transitional glutenite, and traction flow-derived glutenite). The contact relationship was determined from the casting thin section data, and it included point contact and lineal contact, followed by concavo-convex contact and suture contact. We found the dominant pore types were found to be intergranular pores, followed by intragranular pores, intramatrix pores, and cracks. The porosity and permeability data reveal that sandstone and traction flow-derived glutenite commonly form low-porosity and low-permeability reservoirs, whereas transitional glutenite commonly forms low-porosity and ultralow-permeability reservoirs and gravity flow-derived glutenite generally forms low-porosity and ultralow-permeability reservoirs. This integrated analysis finds that tectonic movements and a sedimentary environment control the physical properties of the reservoirs. The tectonic movements control reservoir characteristics through thrust fault systems and large-scale provenance, and the sedimentary environment controls reservoir characteristics via facies distribution and lacustrine fluctuation. The insights gained from this study can provide knowledge about the characteristics and associated controlling factors of the reservoirs in the Permian Lower Urho Formation within the western Junggar Basin. These insights can also benefit petroleum reserve and hydrocarbon production exploration in the study area and further petroleum exploration in other areas with similar sedimentary/tectonic settings.

Active thrust tectonics along the western slope of the Central Andes southernmost Pampean flat-slab segment (∼33°S, Chile): The Cariño Botado fault system

Along the western slope of the Central Andes in the southernmost part of the Pampean flat-slab subduction zone segment (∼33°S), crustal Quaternary west-vergent reverse faults are found, but little is known about them. To better understand and characterize these faults, grouped as the Cariño Botado thrust fault system (CBF), we undertook a multidisciplinary study focused on remote sensing and field geomorphic and geologic mapping, sedimentary relationships, and fault characterization. Optically Stimulated Luminescence (OSL) and UPb dating samples were obtained from faulted deposits to constrain the timing of fault motion. We combined the mapping, fault relationship descriptions, and age control to understand this system better and quantify tectonic rates here for the first time. The main CBF is best expressed with Late-Cenozoic hanging wall fault rocks over thrusting Quaternary coarse-grained alluvial fan deposits, and the fault zone is found over a large area and with an altered fault zone (∼0.5–2 km wide). The principal reverse fault segment of the CBF is well exposed in creeks, with an average dip of 40°E and an associated vertical throw (up to the east) of the hanging wall from ∼3.2 m up to ∼30 m. Five OSL samples, taken from tilted and untilted alluvial fan deposits adjacent to the CBF's main fault, yielded ages between 2.5 ± 0.2 ka and 9.0 ± 0.7 ka, supporting Holocene activity and ∼4.9 m of fault slip in the last ∼8.7 ka. Ninety-nine detrital zircons from fluvial terrace deposits in the study area were dated using UPb ICPMS, giving mainly Oligo-Miocene ages. The youngest ages of detrital zircons are Quaternary (n = 3; ∼0.9–4.4 Ma), which indicates that CBF activity could have started as early as ∼0.9 Ma producing an accumulated hanging wall uplift of ∼130 m. The alignment of the fault profiles, creek and river knickpoints, and alluvial and fluvial deposits allows the most recent activity of the main CBF to be traced between 5 km and up to 15 km along the fault trace. Based on fault length, slip characteristics, and earthquake scaling relationships, earthquakes up to Mw 7.5 could be associated with the fault. Because of the clear relationship between the river incision, distribution of fluvial terraces, variation in sinuosity and stream power, and the location of the faults, we suggest that the tectonic uplift controls the hanging wall fluvial incision from ∼0.9 Ma to the present. The Quaternary (at least 0.9 Ma to present) active CBF shares geometric, structural, and rupture timing similarities with the nearby better-characterized San Ramón Fault system. The latter is located ∼50 km to the south along the eastern border of Santiago, the capital city of Chile. Both fault systems share a comparable morpho-structural setting with a consistent average N-S trend. Significant seismic hazard is associated with both the CBF and the San Ramon System, which may be linked structurally and temporally regarding previous surface ruptures and major earthquakes, and therefore remain important research targets.

Superimposed brittle structures in polyorogenic contexts: Variscan and Alpine faults in the Duje Valley (Picos de Europa, Cantabrian Mountains, NW Spain)

Abstract Detailed geological mapping of a highly fractured Paleozoic (pre-Permian) basement and the scarce outcrops of overlying Permian–Mesozoic cover in the surroundings of the Duje Valley (Picos de Europa Unit, Cantabrian Mountains, NW Spain), together with new field data, have allowed the separation of four genetic fault sets in a polyorogenic area, affected by the Variscan and Alpine cycles. These fault sets are, from oldest to youngest: Variscan thrusts (late Carboniferous), late Variscan strike-slip faults (late Carboniferous–earliest Permian), Alpine normal faults (Permian–Mesozoic) and Alpine reverse faults (Cenozoic). A structural analysis is reported here, based on the joint use of geometric, kinematic and deformational features, cross-cutting and tectono – sedimentary relationships between the structures. This analysis has allowed the recognition and full characterization of the four fault sets. These types of structural analyses are useful for unravelling complex tectonic histories in regions where massive limestone lithologies make reconstructing the timing of fault activity difficult, especially if the basement is affected by late deformation events that are not recorded by cover outcrops.

The damage mode and forced response characteristics of articulated lining structure: A case study of metro tunnel under a reverse fault action

With the continuous development of underground tunnel engineering, there have been a large number of engineering cases of tunnels crossing active faults, and the dislocation of active faults must have a greater impact on the structural safety of tunnels. Therefore, it is of great significance to study the stress characteristics and anti-dislocation design of tunnels crossing active faults. Based on the tunnel of Urumqi Metro Line 1 crossing the Wanyaogou reverse fault, a large-scale physical model test of shear dislocation of subway tunnel crossing the reverse fault is designed and carried out, and the mechanical behavior difference between conventional tunnel structure and articulated tunnel structure is compared and analyzed. The surface displacement, structural deformation, additional earth pressure, strain distribution, fracture distribution and other test results were monitored and recorded, and the forced response characteristics and failure mode of subway tunnel structure under the effect of stick–slip of reverse fault were studied in depth. The results show that the failure modes of conventional tunnel are mainly shear failure at the fault plane, while articulated tunnel is mainly large eccentric failure. Compared with the conventional tunnel, the deformation failure range, strain peak and total crack length of the articulated tunnel are obviously reduced. Besides, there is no spalling phenomenon similar to conventional tunnel. The structure still has a certain residual bearing capacity, that is, the articulated tunnel structure is more adaptable to the forced displacement of the fault, the stress state is better, and its rupture resistance is better. To sum up, the model test study reveals the forced response characteristics and rupture resistance of articulated tunnel structure under reverse fault conditions, which has guiding significance for similar tunnel engineering problems.

Submarine canyon morphology along the Chilean marine forearc (19°S–45°S)

Convergent margins host more than half of all global submarine canyons. In this environment, the lack of cognition of the canyon morphology variation and their controls in two different types of marine forearcs (erosive and accretionary) remains exists. Based on shipborne bathymetric maps, we systematically analyze width, incision depth and slope gradient of 17 submarine canyons along the Chilean marine forearc. We divide the study area into an erosive northern area, a transitional central area, and an accretionary southern area based on trench sediment cover and in line with previous tectonic interpretations. In the northern and central areas, limited sediment supply and little erosion from infrequent turbidity currents form narrow and shallow canyons that arrive at the toe of margin. Subduction erosion contributes to a simple and regular slope morphology where regional subsidence and trench-parallel faulting activities lead to vertical crustal movement and a steep thalweg of canyons' lower reach. In contrast, frequent canyon flushing/filling turbidity currents and slope failures on the canyon walls result in a wider range of canyon width and incision depth in the south. Here, the formation of an accretionary prism generates fold and thrust ridges at the seafloor that reduce the slope gradient of canyons' lower reach. Canyon morphology within the prism region has a larger range than the non-prism (backstop) region due to the higher erodibility of the less consolidated sediment. In addition, convex-up step-shaped bedforms develop along 14 canyon thalwegs, also suggesting regional uplift/subsidence and normal faulting in the north and central region but folding and thrust faulting in the south. This work not only reveals the difference of canyon morphology on active marine forearcs but also may help to understand controls on submarine canyon morphologies along the Chilean margin as well as in other convergent margins.

Precise Judgment of Reverse Fault-Induced Water Inrush Hazard under Influence of Roof Goaf Water

Previous research recognized the threat of faults to safe mining and the importance of identifying fault failure patterns, and began to use theoretical research and numerical simulations to study the activation laws of faults during mining. Conventional wisdom may suggest that the height of the fractured water-conducting zone (FWCZ) of the overburden strata over goaf will be increasingly caused by fault activation, thereby causing roof water inrush, in particular, goaf water existing in the roof of working face. Therefore, the FWCZ in the overburden strata make accurate judgments that are regarded as a key foundation to evaluate the safety of coal mining under water bodies. In view of this problem, the 15,103 working face of Wenzhuang Coal Mine in Shanxi Province were taken as the engineering background, the height of the FWCZ of the adjacent 15,100 working face was observed by drilling fluid leakage method and drilling television method, the observed results provided a reference for judgment of the height of the FWCZ of 15,103 working face. Additionally, the drilling method was adopted to conduct exploration on the terminal location of F6 reverse fault in overburden strata of No. 15 coal seam, the result showed that the disturbance range of F6 reverse fault was located in the FWCZ formed after mining the 15,103 working face. Furthermore, the method of numerical simulation analysis was used to study the failure height of overburden strata after mining the 15,103 working face through F6 reverse fault. The height of the FWCZ of F6 reversed fault was basically equal to that of the upper and lower plates, and F6 reverse fault had no influence on the height of the FWCZ after mining the 15,103 working face. There was a sufficient thick overburden strata between the maximal elevation of the fractured zone and the roof goaf water, and mining through F6 reverse fault under old goaf was safe and reliable. The research results can provide reference for the safe mining of passing through reverse faults under the influence of roof goaf water.

Late Medieval seismicity on the Himalayan Frontal Thrust Fault at Lal Dhang, Uttarakhand, India

The Himalayan Frontal Thrust Fault (HFT) lies at the active tectonic boundary between Eurasia and the Indian subcontinent. Past earthquakes on the HFT have resulted in significant ground displacement that is evidenced by sizable scarps along the fault. Here we present findings from an ~28-m-long x 5-m-wide x 8-m-deep paleoseismic trench excavated across an ~10-m-high fault scarp at the site of Lal Dhang in the Central Seismic Gap. Excavation exposed three recumbent fault-propagation folds that support occurrence of at least two earthquakes with >25 m of cumulative coseismic slip. Findings suggest that two great (Mw ≥ 8.0) earthquakes may have occurred in rapid succession at the site during the Late Medieval period. Radiocarbon dating of stratigraphic units that are modeled using the OxCal software program constrain timing of the events to 1317–1391 CE and 1447–1572 CE, which is coincident with historical earthquakes in 1344 CE and 1505 CE. With over 500 years of quiescence since the last great earthquake in the Central Seismic Gap, it is possible that another devastating rupture could be imminent.

Thermal architecture of the Salmon River suture zone, Idaho, USA: Implications for the structural evolution of a ductile accretionary complex during arc-continent collision

Abstract Documenting the tectono-thermal evolution of the exhumed ductile portions of orogenic systems is critical for interpreting orogen dynamics. Here, we utilize Raman spectroscopy of carbonaceous material thermometry to quantify the thermal architecture of the Salmon River suture zone in west-central Idaho, USA, which records the Cretaceous collision of the Wallowa island arc terrane with North America. We integrate this thermal architecture with published structural interpretations, geochronology, and pressure-temperature-time histories to interpret the evolution of deformation during arc-continent collision in this portion of the North America Cordillera. Mean peak temperatures within four, ~1–3-km-thick, penetratively deformed thrust sheets in the western part of the suture zone decrease moving structurally downward from 652 ± 28 °C (Pollock Mountain thrust sheet), to 577 ± 30 °C (Rapid River thrust sheet), to 426 ± 32 °C (Morrison Ridge thrust sheet), to 358 ± 18 °C (Heavens Gate thrust sheet). These ductile thrust sheets are separated by 100–500-m-thick intervals of inverted temperatures that surround the mapped positions of thrust faults. We interpret the western part of the suture zone as a ductile accretionary complex that records the progressive underplating and top-to-the-west translation of ductile thrust sheets that were derived from the Wallowa terrane during ca. 144–105 Ma collision-related deformation. Accretion of ductile thrust sheets began at ~30–35 km depths and completed at depths of ~10–20 km. Rocks at all structural levels in the suture zone exhibit distributed ductile fabrics, but the inverted thermal gradients that surround the mapped positions of thrust faults suggest that the majority of top-to-the-west displacement was accommodated within 100–500-m-thick, high-strain, thrust-sense ductile shear zones.