Fault Movement Research Articles

Quaternary Segmentation Characteristics of the Hunhe Fault, Northeast China

The northern segment of the Tanlu fault zone, which encompasses the Dunhua–Mishan and Yilan–Yitong fault zones, plays a critical role in the tectonic framework of Northeast China. This study focuses on the Hunhe fault, part of the Liaoning segment of the Dunhua–Mishan fault zone, which exhibits concealed characteristics and an NE–NEE orientation. We employ remote sensing and field investigations to accurately delineate the Hunhe fault’s location, scale, and tectonic activity. The findings indicate that the Hunhe fault displays significant spatial variability in tectonic activity. Some segments show evidence of late Quaternary activity, contradicting prior research that classified the Hunhe fault as an active fault during the MIS (Marine Isotope Stages) 20-103MIS 20-103- MIS6-19MIS6-19 period and assessed its seismic potential differently. Recent field investigations suggest considerable spatial variability in tectonic activity, indicating segmental characteristics. In this study, the Hunhe fault is divided into segments based on five aspects: the fault structure and movement characteristics of the fault; transverse faults and obstruction structures; geological and geomorphological characteristics; seismic features; and fault activity. The detailed segments are as follows: the Shenyang segment, the Fushun segment, the Zhangdang-Nan Zamu segment, and the Nan Zamu to Ying Emeng East section. These findings aim to enhance the understanding of the seismic hazard potential associated with the Hunhe fault, highlighting the need for ongoing research to address its complexities and implications for regional seismic risk assessment.

Numerical investigation on failure mechanism of tunnel lining with different fault dip angles and Geological Strength Index under geohazard of fault movement and seismic action

In this article, the failure mechanism of the tunnel under geohazard fault movement and non-uniform seismic load was studied. The study area considered was Atal Tunnel in Himachal Pradesh, India, in the North-West of the Himalayas. A normal fault of 10 m width was considered by varying the fault dip angles of 30°, 45°, 60°, 75°, and 90° along with Geological Strength Index (GSI) values of 20, 40, 60, and 80. The finite element models were analysed under fault movement and 4 ground motions. A fault movement of 0.5 m was applied at the bottom of the fault and hanging wall area. The results showed that fault with 60° dip angle produced more structural forces in tunnel lining under fault movement. The fault with 20 GSI rock mass exhibited higher structural forces in the tunnel lining, irrespective of dip angle. In the case of seismic load, a smaller dip angle generates more structural forces. The tunnel lining in the hanging wall experienced more tensile damage, especially in the direction of seismic wave propagation. The left and right sides of the lining in the footwall area underwent tension, whereas the tunnel crown and bottom experience compression under seismic load.

SEISMICITY of the BAIKAL REGION and TRANSBAIKALIA in 2020

We consider a character of the seismic process in the Baikal region and Transbaikalia in 2020. A total number of registered earthquakes with KR≥5.6 was 7711. Most of them (94 %) occurred in the Baikal rift zone where the South Baikal and Baikal-Muya regions were the most active (by number of earthquakes). The strongest seismic events – the September 21, 2020 Bystraya (Mw=5.6) and December 9, 2020 Kudara (Mw=5.5) earthquakes – were localized in the Hovsogol-Tunka and South Baikal regions respectively. Both events in the near-field zone (∆≤19 km) were felt with an intensity of 6–7. Noticeable macroseismic effects with less intensity were observed from another 34 earthquakes with KR≥8.4. Focal mechanisms were determined for 77 earthquakes (KR≥9.1) using two methods: from P-wave first-arrival polarities on regional seismic stations and during calcula tions of a seismic moment tensor (in a double-couple approximation) based on surface wave amplitude spectra. It has been shown that normal fault movements, which are often combined with strike-slips, are dominated in sources of regional earthquakes. In general, the region is characterized by moderate seismic activity in 2020, total seismic energy is estimated as 573∙1012 J that is two times higher than the same parameter calculated in 2018–2019.

Landslide Prediction Validation in Western North Carolina After Hurricane Helene

Hurricane Helene triggered 1792 landslides across western North Carolina and has caused damage to 79 bridges to date. Helene hit western North Carolina days after a low-pressure system dropped up to 254 mm of rain in some locations of western North Carolina (e.g., Asheville Regional Airport). The already waterlogged region experienced devastation as significant additional rainfall occurred during Helene, where some areas, like Asheville, North Carolina received an additional 356 mm of rain (National Weather Service, 2024). In this study, machine learning (ML)-generated multi-hazard landslide susceptibility maps are compared to the documented landslides from Helene. The landslide models use the North Carolina landslide database, soil survey, rainfall, USGS digital elevation model (DEM), and distance to rivers to create the landslide variables. From the DEM, aspect factors and slope are computed. Because recent research in western North Carolina suggests fault movement is destabilizing slopes, distance to fault was also incorporated as a predictor variable. Finally, soil types were used as a wildfire predictor variable. In total, 4794 landslides were used for model training. Random Forest and logistic regression machine learning algorithms were used to develop the landslide susceptibility map. Furthermore, landslide susceptibility was also examined with and without consideration of wildfires. Ultimately, this study indicates heavy rainfall and debris-laden floodwaters were critical in triggering both landslides and scour, posing a dual threat to bridge stability. Field investigations from Hurricane Helene revealed that bridge damage was concentrated at bridge abutments, with scour and sediment deposition exacerbating structural vulnerability. We evaluated the assumed flooding potential (AFP) of damaged bridges in the study area, finding that bridges with lower AFP values were particularly vulnerable to scour and submersion during flood events. Differentiating between landslide-induced and scour-induced damage is essential for accurately assessing risks to infrastructure. The findings emphasize the importance of comprehensive hazard mapping to guide infrastructure resilience planning in mountainous regions.

On the anatomy of acoustic emission.

Abrupt, local frictional fault failure comprises a displacement that is normally accompanied by acoustic emission (AE)-an impulsive elastic wave broadcast with an amplitude proportional to particle velocity. The aggregate of these displacements is the basic fault motion. In laboratory shear experiments, the examination of a sequence of laboratory earthquakes includes continuous measurements of fault motion and the associated AE that is broadcast. From these measurements, connections between the fault motion and cumulative sum of the AE amplitude can be identified. The composition of the AE broadcasts reveals inhomogeneity in the fault mechanical structure from which they arise. This inhomogeneity can be decomposed into a time invariant AE component and an articulated AE component. The articulated AE component serves as a "state of the fault diagnostic" that follows a distinctive pattern to fault failure. Thus, the articulated AE component can be used directly to monitor the state of the fault.

Evidence for a Late Cretaceous to Paleogene basement-involved retroarc wedge in the southern U.S. Cordillera: A case study from the northern Chiricahua Mountains, Arizona

Late Cretaceous to Paleogene contractional deformation in the southern U.S. Cordillera is commonly attributed to the Laramide Orogeny, in part because of the prevalence of moderate- to high-angle, basement-involved reverse faults. However, it is unclear if the tectonic models developed for the archetypal Laramide foreland belt in the U.S. Rocky Mountain region are applicable to the southern U.S. Cordillera. New geologic mapping of the northern Chiricahua Mountains in southeast Arizona, USA, indicates the presence of an originally sub-horizontal thrust fault, the Fort Bowie fault, and a thin-skinned ramp-flat thrust system that is offset by a younger thrust fault, the Apache Pass fault, that carries basement rocks. Cross-cutting relationships and new geochronologic data indicate deformation on both faults occurred between 60 Ma and 35 Ma. A biotite 40Ar/39Ar plateau age of 48 Ma from the hanging wall of the basement-involved Apache Pass fault is interpreted to record erosion related to reverse fault movement and rock uplift. The presence of thrust faults in southeast Arizona raises the possibility of a latest Cretaceous−Eocene retroarc orogenic wedge that linked the Sevier and Mexican thrust belts to the north and south, respectively. Basement-involved deformation does not rule out the presence of a retroarc wedge, and many Cordilleran orogenic systems include basement-involved thrusting.

Topographic ridges express late Quaternary faulting peripheral to the New Madrid seismic zone, intraplate USA: Their tectonic implications

Northeast-trending linear topographic ridges in Pliocene and Quaternary sediments adjacent to the New Madrid seismic zone (NMSZ), intraplate North America, have been long speculated to be neotectonic landforms related to reactivation of basement faults of the eastern Mississippi Valley Rift margin. Earthquake epicenters and paleoseismological studies show that eastern rift margin faults (ERMF) were active during late Quaternary south of a restraining bend in the Mississippi Valley Rift fault complex, but the ERMF zone north of the restraining bend (ERM-N) and underlying the linear ridges is seismically quiescent. A previous P-wave seismic reflection survey across the most prominent linear ridge (Rives lineament) revealed that it overlies a horst in Eocene sediment. To ascertain whether the Rives lineament could have been produced by surface faulting/folding, we collected electrical resistivity tomography (ERT) and ground penetrating radar (GPR) profiles to image the ridge's shallow subsurface features. We interpret shallow folding and faulting of late Pleistocene sediment in our ERT and GPR images. Additionally, convexity of multiple topographic profiles of scarps along margins of the Rives lineament was quantified and compared to the convexity of profiles of known neotectonic scarps and of fluvial terrace riser profiles within the region. Comparison of these profiles reveals a high degree of similarity between the scarps along the Rives lineament margins and the Holocene Reelfoot thrust scarp. When combined, our results strongly suggest late Pleistocene or Holocene folding and faulting created this ridge despite its current seismic quiescence, and thus they provide useful insight for assessing the seismic hazard potential of quiescent faults in strike-slip systems in general. We conclude that the late Quaternary series of movements documented on the Reelfoot thrust was initiated to accommodate crustal shortening after transpressional fault movements on the ERM-N became inactive in late Pleistocene or early Holocene and that movement along the ERM-N may resume if the Reelfoot thrust has an interval of inactivity in the future. Our results suggest how fault interactions within a strike-slip system can change, making faults with significant amounts of seismic potential appear as though they are inactive.

Relocation and Stress Analysis of the 2018 Mandali-Sumar Earthquake Sequence, Iraq-Iran Border

The 2018 Mandali-Sumar earthquake sequence started in January 2018 at the Iraq – Iran border within the Low Folded Zone of the Zagros Fold-Thrust Belt. To study the fault that is responsible for this earthquake sequence, the relocation of 32 earthquakes was conducted. In addition, moment tensor solutions of 9 large earthquakes were collected to know the fault motion and stress regime in the study area. The Computer Programs in Seismology (CPS) was used to analyze waveform data taken from 33 seismic stations located in Iraq and Iran to relocate earthquakes. The location of the earthquake sequence based on the IRSC bulletin shows a scattered spatial distribution, but the results of the relocations show that the earthquakes of the sequences are aligned in a longitudinal feature parallel to an anticline limb located in Ilam and Kermanshah provinces near the Iraqi border. The moment tensor solutions indicate that the sequence is related to a thrust fault with a 342º strike direction, 35º NE dip angle, and 76º rake angle. The TENSOR program was used to perform formal stress inversion of moment stress axes, which revealed that the azimuth of the maximum horizontal stress axis is 63º. The epicenters of the sequence are located between the Mountain Front Fault to the NE and the Zagros Foredeep Fault to the Southeast. We believe that the 2018 Mandali-Sumar earthquake sequence is related to displacement on the surface of the Zagros Foredeep Fault within the uppermost basement and the lowermost Phanerozoic cover.

Seismic Wave Detectability on Venus Using Ground Deformation Sensors, Infrasound Sensors on Balloons and Airglow Imagers

AbstractThe relatively unconstrained internal structure of Venus is a missing piece in our understanding of the formation and evolution of the Solar System. Detection of seismic waves generated by venusquakes is crucial to determine the seismic structure of Venus' interior, as recently shown by the new seismic and geodetic constraints on Mars' interior obtained by the InSight mission. In the next decade multiple missions will fly to Venus to explore its tectonic and volcanic activity, but they will not be able to conclusively detect seismic waves, despite their potential to detect fault movements. Looking toward the next fleet of Venus missions after the ones already decided, various concepts to measure seismic waves have been proposed. These detection methods include typical geophysical ground sensors already deployed on Earth, the Moon, and Mars; pressure sensors on balloons; and imagers of high altitude emissions (airglow) on orbiters. The latter two methods target the detection of the infrasound signals generated by seismic waves and amplified during their upward propagation. Here, we provide a first comparison between the detection capabilities of these different measurement techniques and recent estimates of Venus' seismic activity. In addition, we discuss the performance requirements and measurement durations required to detect seismic waves with the various detection methods. Our study clearly presents the advantages and limitations of the different seismic wave detection techniques and can be used to drive the design of future mission concepts aiming to study the seismicity of Venus.

Imaging and modelling the subsurface structure of the Rungwe Volcanic Province in SW Tanzania with aeromagnetic data: An improved structural map to support geothermal exploration

The Rungwe Volcanic Province (RVP) in the East African Rift System, SW Tanzania, provides a unique opportunity to investigate geothermal resources in the context of particularly complex continental rifting processes. To support geothermal resource targeting in the RVP, we present a revised neotectonic structural map based on an interpretation of aeromagnetic data constrained by 2D-forward modelling of magnetic anomalies integrated with the distribution of previously reported faults, seismic epicentre locations, 3D magnetotelluric resistivity models and surface geothermal manifestations. Magnetic anomalies in the RVP, including the nationally prominent Mbeya anomaly, are related to the high magnetic susceptibility or remanent magnetism of Precambrian rocks and Cretaceous carbonatite intrusions buried in the rift under a varying thickness of non-magnetic sediments and volcanic rocks. Magnetic lineaments are related to structures controlling the geometry of the Precambrian rocks and concealed dikes and the thickness of the sediments and volcanics. The recent Ngozi and Rungwe trachyte volcanics have relatively low magnetic susceptibility comparable to the low susceptibility of the sediments in the rift basins. The revised neotectonic structural map shows prominent NW, NE and NS-trending magnetic lineaments that correlate with previously reported faults and alignments of seismic epicentres in the study area and with the regional trend of the rift segments. The NE-trending magnetic lineaments are consistent with interpretations of the current stress field in the RVP. The main volcanoes in the RVP, Ngozi, Rungwe and Kiejo (also known as Kyejo and Kieyo), are aligned with the NW-trending linear magnetic feature joining the Lupa and Livingstone rift border faults. This lineament is intersected and frequently displaced by the NE and NS-trending lineaments, suggesting that the NE to NS-striking structures are younger. The Rungwe and Ngozi volcanoes as well as numerous ‘‘monogenetic’’ eruption centres and the Mwakaleli caldera, which originated ca. 2 Ma ago (Ebinger et al., 1989) following a large explosive eruption emplacing widespread ignimbrite deposits, are located within a zone of low-intermediate magnitude magnetic features forming a basin-like structure surrounded by magnetic high anomalies of the Precambrian basement structures. We interpret the intersections between the NW-trending intra-rift faults and the NS and NE-trending faults as favourable locations for wells to target high permeability within the geothermal resource conceptual models previously constructed using 3D MT resistivity imaging integrated with supporting geoscientific data. The intersections provide a focus area for follow-up ground mapping of subtle features that may be associated with very recent fault movement.

Constraints of the regional deformation on the hydrothermal veins in Ousdrat and Aït Ahmane ore deposits (Bou Azzer-El Graara inlier, central Anti-Atlas, Morocco): Implications for mineral exploration

The overlap of tectonic and magmatic events in the Bou Azzer-El Graara inlier causes a complexity for understanding the absolute and/or relative chronology between the deformation and the hydrothermal system. In the central northern part of the Bou Azzer-El Graara inlier, syn-orogenic ca. 650 Ma Aït Ahmane and Ousdrat plutons have been deformed under NE-SW shortening and with metamorphic conditions. These plutons are affected by fault systems with four mains directions: N015, N090, N140, and N040. The last two fault systems are the most mineralized and they are weakly constrained in the frame of deformation phases affecting the Bou Azzer inlier, and filling style. In addition, Pan-African, WACadomian or Hercynian origin of NE-SW faults is not yet reached. This contribution aims to clarify these issues based on structural, textural and morphological of these faults and veins. Our analyses highlight that most of these structures were formed through open-space filling and crack-seal-slip mechanisms. N140 contacts faults between serpentinite and quartz diorite experienced multiple reactivations during the WACadomian stages. The oldest activation was in ductile condition and later reactivated in a transpression to transtension regime leading to the development of N040 faults as sinistral antithetic faults due to NNE stress evolution. Field observations suggest that N040 structures affect late Ediacaran Ouarzazate Group, but not the Adoudounian Formation, highlight their WACadomian origine. The N040 structures preserve metric to microscopic cataclastic shear zones. This evolution suggests that the hydrothermal system in the Bou Azzer inlier shifted from ductile-brittle hydrothermal style along the N140 foliated contact to a brittle regime along the N040 sinistral-normal faults. Some intra-vein microtextures suggest that this hydrothermal fluid was emplaced in a predominantly extensional and tectonically active environment, as evidenced by extensional relay, syntaxial and antiaxial textures, and elongated grains. Consequently, a detailed analysis of the morphology, textures, filling types, and fault movements is an essential and important tool for establishing the relative chronology of deformation in front of the N140 and N040 veins.

Experimental study on mechanical behavior and countermeasures of mountain tunnels under strike-slip fault movement

In the seismic mountainous regions such as western China, it is usuallly inevitable to construct tunnels near active fault zones. Those fault-crossing tunnel structures can be extremely vulnerable during earthquakes. Extensive experimental studies have been conducted on the response of continuous mountain tunnels under reverse and normal fault movements, limited experimental investigations are available in the literatures on mountain tunnels with special structural measures crossing strike-slip faults. In this study, a new experimental facility for simulating the movement of strike-slip fault was developed, accounting for the spatial deformation characteristics of large active fault zones. Two groups of sandbox experiment were performed on the scaled tunnel models to investigate the evolution of ground deformation and surface rupture subjected to strike-slip fault motion and its impact on a water conveyance tunnel. The nonlinear response and damage mechanism of continuous tunnels and tunnels incorporated with specially designed articulated system were examined. The test results show that most of slip between stationary block and moving block occurred within the fault core, and significant surface ruptures are observed along the fault strike direction at the fault damage zone. The continuous tunnel undergoes significant shrinkage deformation and diagonal-shear failure near the slip surface and resulted in localized collapse of tunnel lining. The segments of articulated system tunnel suffer a significant horizontal deflection of about 5°, which results in opening and misalignment at the flexible joint. The width of the damaged zone of the articulated system tunnel is about 0.44 to 0.57 times that of the continuous tunnel. Compared to continuous tunnels, the articulated design significantly reduces the axial strain response of the tunnel lining, but increases the circumferential tensile strain at the tunnel crown and invert. It is concluded that articulated design provides an effective measure to reduce the extent of damage in mountain tunnel.

Constraining timing of Proterozoic fault movement in the Capricorn Orogen, Western Australia

Ancient faults dissect low-grade Mesoproterozoic sedimentary rocks of the 1673–1455 Ma Edmund Basin and the 1455–1075 Ma Collier Basin in the Capricorn Orogen, Western Australia, and reveal a protracted history of basin formation and subsequent deformation. K–Ar dating of illite from fine-grained fault gouge separates (ideally <0.1 µm) provide robust dates of the most recent fault movement. From the Godfrey–Mount Vernon Fault, a sample of siltstone from the Kiangi Creek Formation (1590–1514 Ma) in the Edmund Basin, which was collected adjacent to faulting, provided a whole-rock date of 1506 ± 30.2 Ma. This is interpreted as a mixed age, encompassing modification of the depositional age by subsequent faulting during the extensional opening of the Edmund Basin. A fault gouge sample dated at 1141.4 ± 58.6 Ma, also from the Godfrey–Mount Vernon Fault, is consistent with the tectono-thermal 1321–1171 Ma Mutherbukin Tectonic Event identified in underlying high-grade Gascoyne Province basement rocks. Fault gouge sample dates of 885.5 ± 45.9 Ma from the Godfrey–Mount Vernon Fault and 782.2 ± 40.1 Ma from the Quartzite Well Fault define the younger newly identified crustal shortening during the Kuparr Tectonic Event. Concomitant tectonic activity in eastern Australia and South China has been considered as a possible precursor of the breakup of Rodina. In southern Africa, the Zambezi Supracrustal Sequence has been dated at 880–820 Ma and the Munali Intrusive Complex at 862–857 Ma also identified as rift-related.

Syntectonic Late Devonian terrestrial sedimentation in the southern Bonaparte Basin, Western Australia

Late Devonian sedimentation in the southern Bonaparte Basin was controlled by, and provides a record of, contemporaneous fault movements in the Halls Creek Orogen. An important episode of Late Devonian faulting caused uplift and southward tilting of the Carr Boyd Ranges block and uplift and northward tilting of the O’Donnell Ranges block forming the Galloping Creek and Ragged Ranges sub-basins, respectively. Uplift of the Carr Boyd Ranges provided the eastern source of the Ragged Range Conglomerate, while the south-dipping Carr Boyd Ranges and the uplifted O’Donnell Ranges and Bow River blocks formed the northern and western sources of the Galloping Creek Formation. Conglomeratic facies on both the northern and southwestern margins of the Galloping Creek Sub-basin record interaction with a fault-controlled topography. The apparent lack of unconformities within the northern Galloping Creek Formation and the progressive increase in siltstone content towards the centre of the sub-basin suggest that faulting was no longer an active driver for sedimentation. While alluvial fan deposition infilled the southwestern part of the sub-basin, the remainder of the Galloping Creek Formation was deposited by fluvial systems that changed from an initial proximal braided stream character to a later distal character with more extensive floodplain deposition. Post-depositional folding and faulting of the Galloping Creek Sub-basin were confined to movement on the Halls Creek and Glenhill faults with a probable 10+ km of sinistral offset and uplift of the western block along at least the latter.

Topographic metrics for unveiling fault segmentation and tectono-geomorphic evolution with insights into the impact of inherited topography, Ulsan Fault Zone, South Korea

Abstract. Quantifying today's topography can provide insights into landscape evolution and its controls, since present topography represents a cumulative expression of past and present surface processes. The Ulsan Fault Zone (UFZ) is an active fault zone on the southeastern Korean Peninsula that was reactivated as a reverse fault around 5 Ma. The UFZ strikes NNW–SSE and dips eastward. This study investigates the relative tectonic activity along the UFZ and the landscape evolution of the hanging-wall side of the UFZ, focusing on neotectonic perturbations using 10Be-derived catchment-averaged denudation rates and bedrock incision rates, topographic metrics, and a landscape evolution model. Five geological segments were identified along the fault, based on their relative tectonic activity and fault geometry. We simulated four cases of landscape evolution to investigate the geomorphic processes and accompanying topographic changes in the study area in response to fault movement. Model results reveal that the geomorphic processes and the patterns of topographic metrics (e.g., χ anomalies) depend on inherited topography (i.e., the topography that existed prior to reverse fault reactivation of the UFZ). On the basis of this important model finding and additional topographic metrics, we interpret the tectono-geomorphic history of the study area as follows: (1) the northern part of the UFZ has been in a transient state and is in topographic and geometric disequilibrium, so this segment underwent asymmetric uplift (westward tilting) prior to reverse faulting on the UFZ around 5 Ma, and (2) its southern part was negligibly influenced by the asymmetric uplift before reverse faulting. Our study demonstrates the utility of topographic metrics as reliable criteria for resolving fault segments. Together with landscape evolution modeling, topographic metrics provide powerful tools for examining the influence of inherited topography on present topography and for the elucidation of tectono-geomorphic histories.

Analysis of Magnitude–Frequency Distribution of Earthquakes in the Sichuan Basin, Southwest China

Abstract The Sichuan basin is characterized by underdeveloped active geological structures and low seismic activities. In recent years, an increase in seismicity has been observed in the southern Sichuan basin, which includes small earthquakes induced by water injection during shale gas exploitation and M ≥ 5.0 earthquakes, causing unexpected damage and casualties. This necessitates a comprehensive analysis of the magnitude–frequency distribution of the current seismicity. In this study, we examined the current seismicity using instrumental earthquake records at different periods and estimated the temporal and spatial variations in b-value. We found that the b-values widely vary in the Sichuan basin and analyzed the spatial differences in b-value in seven different earthquake clusters. The results show that the intense fault movement on the western boundary of the Sichuan basin might be the main controlling factor of the increased seismicity in the southern basin instead of being induced by water injection. Furthermore, earthquakes in the Sichuan basin follow the same size distribution as the events on the boundary faults and the Sichuan–Yunnan rhombus active block. Thus, it is appropriate to consider the magnitude–frequency distribution of earthquakes for the Sichuan basin and the Sichuan–Yunnan rhombus block together rather than separately. These results may help improve the recurrence models in probabilistic seismic hazard assessment of the region.

Travertine and calcareous tufa occurrences as an indicator of the ongoing tectonic activity of the Central Slovak Fault System inferred from airborne laser scanning data, geomorphometric, and structural analysis (Northern Slovakia)

The travertine formation process, active over the Quaternary, has enabled the origin of one of the largest travertine accumulations in the Western Carpathians. Travertines and calcareous tufas are associated with the tectonic activity of the Central Slovak Fault System, a 45 km wide and 140 km long N-S oriented fault zone. As the geological mapping, structural analysis, geomorphometric and isobase surface analysis revealed, the development of faults was polyphase and the travertine/tufa precipitation was not a continuous process. In addition, numerous travertine/tufa morphofacial varieties have been recognized within the study area, such as travertine/tufa terraces and tufa cascades, hillslope paludal tufa crust, phytoherm framework tufa barrages, lacustrine microdetrital tufas, bryophyte-dominated self-built channel, and fluvial tufa crust, reflecting its local geomorphology and precipitation factors. In the Revúcka dolina Valley, the travertine/tufa geobodies thus represent a reliable indicator of the tectonic activity over the Neogene up to Quaternary. The structural data provided relevant evidence confirming the character of orogen-parallel extension for the current tectonic/neotectonic regime in the Inner Western Carpathians. High-resolution topography derived from airborne laser scanning and the subsequent application of various geomorphometry techniques allowed quick identification of the edges of the terrace cascade systems and morpholineaments. Based on our observations, in this zone, the significant vertical movements of normal faults took place with a maximum estimated offset of 800–1000 m. The achieved results also support the use of the presented multifaceted methodology to understand the interplay between geomorphogenesis, hydrology, and tectonics.

Depositional, stratigraphic and structural controls on the geometry of Montney Formation reservoirs: Lower Triassic, northeast British Columbia, northwest Alberta

Abstract The Lower Triassic Montney Formation is a world-class unconventional hydrocarbon reservoir that spans the border of northeast British Columbia and northwest Alberta. Integrated sedimentological and ichnological analyses suggest that the Montney Formation was deposited in a predominantly prodeltaic setting that was commonly influenced by both river flood and storm processes. Riverine processes include the local occurrence of normally- and inversely-graded siltstone and sandstone interbeds, interpreted as the record of sediment-laden hyperpycnal flows. Episodic storms are recorded by the local occurrence of hummocky cross-stratified interbeds, as well as normally graded, parallel and wave-ripple laminated beds, which are commonly draped by structureless carbonaceous mudstones. These mudstone drapes represent river-flood-derived fluid muds that collapsed from hypopycnal plumes following the passage of the storms and suggest the intimate linkage between storms and heightened fluvial discharge. The basin in which the Montney Formation was deposited began as three sub-basins, northern, central and southern, each of which experienced different patterns of subsidence and uplift that varied both spatially and temporally during sedimentation. Subsidence of the northern sub-basin was compartmentalized by deep seated faults that provided accommodation for the basal sequence of the Montney Formation, Sequence 1. Subsequent fault movement resulted in reduced accommodation in the northern sub-basin and accelerated subsidence in the central sub-basin, providing accommodation for deposition of Sequence 2, the basal sequence in the central sub-basin. The northern sub-basin remained paleotopographically elevated throughout deposition of Sequence 2 and early Sequence 3 successions, and these younger units did not extend beyond the northern limit of the central sub-basin. During subsequent deposition of the late Sequences 3 and Sequence 4 successions, compartmentalization between the north and central sub-basin was greatly reduced and these intervals were deposited relatively more uniformly along-strike. The unconventional and conventional reservoirs in both the northern and central sub-basins occur at the scale of systems tracts within the four depositional sequences of the Montney Formation. Reconstructing the depositional history of the component systems tracts of Sequence 1 through early Sequence 3 reveals the dynamic interplay between syndepositional tectonism, fluctuating relative sea-level and deltaic depositional processes in controlling the character, geometry and distribution of prolific Montney Formation reservoirs. The recognition of these key geological controls enhances predictability in this valuable resource and may be applicable to other fine-grained reservoirs elsewhere.

SITE-SPECIFIC DISAGGREGATION ANALYSIS OF RECENT EARTHQUAKE ON THE AMBON COAST

Seismic activity in the eastern region of Indonesia, particularly in Ambon, has been a matter of great concern because of its high tectonic activity. The devastating magnitude 6.5 earthquake in September 2019, which resulted in fatalities and significant damage, highlighted the region’s vulnerability and emphasized the importance of understanding the area’s seismic hazards. Although previous studies have been conducted, this study aims to fill critical gaps in the literature by using the latest seismic data until 2022 and updated attenuation equations. Disaggregation analysis is employed to identify ground motion characteristics, that are crucial for calculating synthetic ground motion acceleration. Under risk-targeted maximum considered earthquake (MCER) conditions, the study results show a peak ground acceleration of 0.444 g, with spectral acceleration at 0.2 s reaching 1.093 g, which decreases to 0.350 g at 1.0 s. Notably, background earthquake sources play a dominant role in contributing to the region’s high seismic hazard potential. The results of this study highlight the urgency of updating Indonesia’s national seismic hazard map. The study also recommends future studies to explore additional parameters of newly discovered faults to enhance understanding of fault movements and their impacts in the study area.

Dynamic rupture modeling in a complex fault zone with distributed and localized damage

Active fault zones have complex structural and geometric features that are expected to affect earthquake nucleation, rupture propagation with shear and volumetric deformation, and arrest. Earthquakes, in turn, dynamically activate co-seismic off-fault damage that may be both distributed and localized, affecting fault zone geometry and rheology, and further influencing post-seismic deformation and subsequent earthquake sequences. Understanding this co-evolution of fault zones and earthquakes is a fundamental challenge in computational rupture dynamics with consequential implications for earthquake physics, seismic hazard and risk. Here, we implement a continuum damage-breakage (CDB) rheology model in our MOOSE-FARMS dynamic rupture simulator to investigate the interplay between bulk damage and fault motion on the evolution of dynamic rupture, energy partitioning, and ground motion characteristics. We demonstrate several effects of damage (accounting for distributed cracking) and breakage (accounting for granulation) on rupture dynamics in the context of two prototype problems addressed currently in the 2D plane-strain setting: (1) a single planar fault and (2) a fracture network. We quantify the spatio-temporal reduction in wave speeds associated with dynamic ruptures in each of these cases and track the evolution of the original fault zone geometry. The results highlight the growth and coalescence of localization bands as well as competition between localized slip on the pre-existing faults vs. inelastic deformation in the bulk. We analyze the differences between off-fault dissipation through damage-breakage vs. plasticity and show that damage-induced softening increases the slip and slip rate, suggesting enhanced energy radiation and reduced energy dissipation. These results have important implications for long-standing problems in earthquake and fault physics as well as near-fault seismic hazard, and they motivate continuing towards 3D simulations and detailed near-fault observations to uncover the processes occurring in earthquake rupture zones.