Active Faults Research Articles

The uplift rate of Sulawesi East Arm and the activity of Batui Fault using a tectonic geomorphology approach in the Luwuk Area, Sulawesi

Sulawesi is a tectonically active area with convergent triple-junction amidst Eurasian, Indo-Australian and Pacific Plate. The study area is located in the suture zone of sedimentary Banggai-Sula Microcontinent and East Sulawesi Ophiolite. This research is aimed to determine fault activity and rate of tectonic uplift of Luwuk mountainous area. Field geological mapping had been done to determine lithology and geological structure along with morphometric analysis to measure definitive result of tectonic activities. Geological structure features which encountered in this area are Batui Thrust, Pasini Thrust, Lobu Balongan Fault Zone, and Lambangan Anticline. The sedimentary rocks have average N315oE dip direction with angle of 41o. Based on tectonic geomorphology and morphometric analyses are resulting the most active tectonic areas passed by the Batui and Pasini Thrust which have NE-SW direction and Lobu Balolang Fault Zone relative to others. The Batui Thrust is considered as active fault intersected the East Sulawesi Ophiolite and Banggai-Sula Microcontinent which segmented with wrench faults. Number of thrust faults parallel to the Batui Thrust generate Batui Thrust Belt which propagate from the ultramafic rocks to the sedimentary rocks within the suture zone. As a result, the presence of active fault is uplifting the East Arm of Sulawesi with 0.408 ± 0.008 mm and 0.213 ± 0.046 mm uplift rate per year by the presence of high altitude Celebes Molasses. These rates are getting higher to the west. Keywords: Batui Thrust, East Sulawesi Ophiolite, Luwuk, morphometry, tectonic geomorphology, uplift rate

Lithium and strontium isotope hydrogeochemistry in Okayama and Tottori Prefectures, southwest Japan: implications for tracing slab-derived fluid

Abstract Dehydration of the Philippine Sea Plate during subduction beneath the forearc region of southwest Japan releases fluids into the crust, potentially producing Arima-type fluids, which are characterized by anomalous hydrogen and oxygen isotopic compositions (δD and δ 18O). Arima-type fluids have been identified in limited hot springs near active faults, such as the Arima and Takarazuka hot springs. The aim of our study is to understand why there have been limited reports of Arima-type fluids, despite the likelihood of their formation during slab dehydration. δ 7Li data can be used to identify Arima-type fluids in samples with Cl– concentrations below 3400 mg/L, whereas δD and δ 18O data have difficulty to detect them. In this study, we collected and analyzed samples from Okayama and Tottori Prefectures in southwest Japan, focusing on their chemical compositions and δ 7Li and 87Sr/86Sr values. We found that the δ 7Li and 87Sr/86Sr compositions of some of the water samples from Okayama Prefecture were similar to those of Arima-type fluids and that they are unlikely to be explained by other sources (e.g., local reactions with host rocks, residual hydrothermal/magmatic fluids, or seawater altered by rocks). Our results therefore suggest there may be a more extensive distribution of Arima-type fluids in the forearc region of southwest Japan than has been previously reported.

Insights into temporal earthquake clustering from the Settlement Fault, southeastern Otago, Aotearoa New Zealand

ABSTRACT We combine previous studies, fieldwork, lidar data, and trenching to examine late Quaternary activity of the SE-dipping ≥23 km long Settlement Fault in the southeastern South Island. Trenching of a scarp crossing a small alluvial fan exposed a > 3 m thick sequence of folded sandy to silty fan alluvium. The uniformity of folding and four Optically Stimulated Luminescence dates indicate that these sediments were deposited relatively rapidly at ∼20 ka and subsequently accommodated 2.5 m of throw following ≥1 ruptures on an underlying buried reverse fault. Other key constraints on late Quaternary Settlement Fault activity are: (1) stranding of a shore platform at ∼3.7 ka, due to 1.5–2 m of fault uplift, and (2) a flat bedrock erosion surface overlain by loess and correlated to the last interglacial maximum (∼125 ka), indicating 0–4 m of fault uplift. From incorporating this information into a stochastic model of fault displacement accumulation we derive a slip rate of ∼0.02 mm/yr since 125 ka, and ∼0.27 mm/yr since 20 ka. We link the Settlement Fault’s current phase of heightened activity to a similarly timed increase in Akatore Fault activity, despite the tips of these faults being separated by between 9 and 25 km.

Geodetic data inversion to estimate a strain-rate field by introducing sparse modeling

Many studies have estimated crustal deformation from observed geodetic data. So far, because most studies have applied a smoothness constraint, which includes the assumption of local uniformity of a strain-rate field, localized strain rates near fault zones have tended to be underestimated when we invert spatially sporadic GNSS data. To overcome this difficulty, we introduce sparse modeling into the estimation of a strain-rate field. Specifically, we impose a sparsity constraint as well as the smoothness constraint on strain rates as prior information, which are expressed by the L1-norm and the L2-norm of the second-order derivative of the velocity field, respectively. To investigate the validity and limitation of the proposed method, we conduct synthetic tests, in which we consider an anti-plane strain problem due to a steady slip on a buried strike-slip fault. As a result, we find: (1) regardless of the locking depth of the fault, the proposed method reproduces localized strain rates near the fault with almost equal or better accuracy than the L2 regularization method (i.e., only the smoothness constraint); (2) the advantage of the proposed method over the L2 regularization method is clearer when data coverage is worse (i.e., when fewer observation points are available); and (3) the proposed method can be applied when observation errors are small. Next, we apply the proposed method to the GNSS data across the Arima-Takatsuki fault zone, which is one of the most active strike-slip faults in Japan. As a result, the proposed method estimates about 1.0×10-8/yr faster strain rates near the fault zone than the L2 regularization method, which corresponds to a 20–30% greater strain-rate concentration. The faster strain rates result in the estimation of a shallower locking depth: 11 km by the proposed method, compared to 17 km by the L2 regularization method. The former is closer to the depth of D90, 12–14 km, above which 90% of earthquakes occur.Graphical

The Central Mindoro Fault: An Active Sinistral Fault Within the Translational Boundary Between the Palawan Microcontinental Block and the Philippine Mobile Belt

The NNW-trending Central Mindoro Fault (CMF) is an active oblique left-lateral strike-slip fault as determined from offset morphotectonic features such as spurs and streams. Mapping of the trace and determination of the sinistral strike-slip sense of motion of the CMF is essential not only to the assessment of hazards but also to providing a clearer perspective of its role in accommodating deformation resulting from the NW relative motion between the Philippine Sea Plate and the Sunda Plate. Its sense of motion is also kinematically congruent with the NW-SE translation along a transcurrent zone between the Philippine Mobile Belt and the Palawan Microcontinental Block on the western part of the Philippine archipelago. It is also consistent with the left-lateral motion of other structures within the zone, such as the Verde Passage Fault—another structure believed to be accommodating the NW-SE translation. Mapping of the CMF provides a key constraint in identifying the possible mechanism(s) involved in the dextral strike-slip motion of the 1994 Mindoro Earthquake ground rupture, which is subparallel to the CMF.

Geomorphologic mapping and analysis of fault activities along the northern margin of the Yanfan Basin, China

Geomorphologic mapping and analysis of fault activities along the northern margin of the Yanfan Basin, China

A Study on the Controlling Effect of Geological Structures on Coalbed Methane Occurrence in the Northeast Margin of Qinshui Basin, North China

This study investigated the patterns of gas occurrence in the coal seam structural zones of the northeastern margin of the Qinshui Basin, with a focus on the Sijiazhuang Coal Mine. Using laboratory experiments, theoretical analysis, and field exploration, we examined how geological structures influence gas distribution. The results show that gas content and pressure near normal faults are generally higher than those in reverse fault areas. However, fault-induced gas occurrence is complex, with stress superposition potentially reversing this trend. When a normal fault intersects modern tectonic stress at a perpendicular or large angle, the fault zone may transition to a compressional state, enhancing gas preservation. Fold structures were found to play a significant role in gas distribution, with anticline zones exhibiting the highest gas content, followed by syncline and normal zones. Collapse columns were shown to affect gas occurrence within a range of 15 to 180 m, with the impact depending on factors such as surrounding rock properties, hydrogeological conditions, and fault activity during collapse formation. Additionally, mirror-like sliding surfaces, formed by multiple factors, are prevalent in the coal seam structures of this region. These sliding surfaces are closely linked to structural zones and serve as valuable indicators for geological predictions in coal seam development.

Role of Unloading Rate and Minimum Principal Stress on Fault Activation with Implication in Fault-Slip Rockburst

Role of Unloading Rate and Minimum Principal Stress on Fault Activation with Implication in Fault-Slip Rockburst

Research Progress on CO2 Geological Storage Reservoir and Caprock Mechanics: Methods and Status

ABSTRACTGreenhouse gas (GHG) emissions have caused serious global climate change, and countries worldwide are taking steps to mitigate the greenhouse effect caused by carbon emissions. CO2 geological storage (CGS) is emerging as a large‐scale technology for reducing GHG emissions and is gradually becoming one of the most important means of mitigating the greenhouse effect. There are several problems in the implementation of this technology, among which the geomechanical problems caused by injection sequestration cannot be ignored. This article reviews the impacts and hazards of geomechanical problems caused by injection and sequestration in CGS, which can lead to risks, including changes in reservoir and caprock mechanical properties, reservoir stability, caprock closure, fault activation, and induced seismicity during CO2 injection and sequestration. This article reviews the above studies and summarizes the research methods of CGS geomechanical problems and generation mechanisms, which can help to comprehensively understand the risks faced in the CGS process and provide references and guidance for the operation, monitoring, and research of CGS in the future.

Automatic speech recognition predicts contemporaneous earthquake fault displacement

Significant progress has been made in probing the state of an earthquake fault by applying machine learning to continuous seismic waveforms. The breakthroughs were originally obtained from laboratory shear experiments and numerical simulations of fault shear, then successfully extended to slow-slipping faults. Here we apply the Wav2Vec-2.0 self-supervised framework for automatic speech recognition to continuous seismic signals emanating from a sequence of moderate magnitude earthquakes during the 2018 caldera collapse at the Kīlauea volcano on the island of Hawai’i. We pre-train the Wav2Vec-2.0 model using caldera seismic waveforms and augment the model architecture to predict contemporaneous surface displacement during the caldera collapse sequence, a proxy for fault displacement. We find the model displacement predictions to be excellent. The model is adapted for near-future prediction information and found hints of prediction capability, but the results are not robust. The results demonstrate that earthquake faults emit seismic signatures in a similar manner to laboratory and numerical simulation faults, and artificial intelligence models developed for encoding audio of speech may have important applications in studying active fault zones.

Crystallization conditions and magmatic-hydrothermal evolution of syenite dykes spatially associated with gold mineralization: the example of the Dolodau syenite-carbonatite complex, Abitibi greenstone belt

The Dolodau syenite-carbonatite complex is one of several syntectonic intrusions of the Abitibi greenstone belt, Superior craton, Canada. It formed during the syntectonic period, which is the main deformation stage leading to craton stabilization. Such magma can be involved in intrusion-related gold systems (IRGS) and be overprinted by orogenic gold systems (OGS), with IRGS and OGS being the main gold mineralizing systems of the syntectonic period. Determining whether magmas of the syntectonic period can transport enough gold to fertilize the upper crust requires insights into the crystallizing conditions and the volatile content of these magmas. Retrieving such data from the altered rocks generally encountered in mineralized areas is best accomplished by accumulating case studies. This study focuses on the Au-W-Ag mineralization spatially associated with the Dolodau intrusive complex to evaluate its fertility for Au. Using field relationships, petrographic observations, whole rock geochemical analyses, and mineral chemistry (titanite, apatite), we show that Dolodau is a carbonatite-syenite-granodiorite intrusive suite that crystallized rapidly at shallow depth in an active fault zone. The magma was S- and Cl-poor according to apatite chemistry and it was likely incapable of transporting a significant amount of gold through the crust. It is concluded that the Dolodau Au-W-Ag mineralization is an OGS related to a major NE-SW oriented fault.

Global Research Trends in Performance-Based Structural Design: A Comprehensive Bibliometric Analysis

In the context of seismic hazard assessment and engineering design, a comprehensive understanding of local geological and geophysical factors is essential. However, previous studies have lacked crucial components such as local soil condition, ground response analysis, topographic influences, active fault characteristics, slip rates, groundwater behaviour, and slope considerations. To ensure the accuracy of the seismic hazard map of a country for the safe and cost-effective design of engineering structures in urban areas, a detailed analysis of these factors is imperative. Moreover, multidisciplinary investigations, such as logic-tree considerations, are needed to enhance seismic hazard maps. As a result, adopting a performance-based approach in structural design has become an essential priority. A performance-based approach allows engineers to design buildings to specified performance levels (IO, LS, CP) even without a reliable seismic hazard map. This approach is akin to a miracle for countries that do not have a reliable seismic hazard map. This study presents a systematic and comprehensive bibliometric analysis of the academic literature pertaining to performance-based design (PBD). By fostering collaborative efforts and expanding research networks, we aim to facilitate the development of coordinated initiatives within the field. Preferred journals, leading countries, leading organisations, and international institutions were identified utilizing the Scopus database. This study examined 3456 PBD-related publications spanning from 1969 to 2023 using VOSviewer version 1.6.19, a bibliometric mapping and visualization software tool. The analysis of co-citations revealed that performance-based design serves as the primary theoretical foundation for structural design and analysis. Furthermore, through a co-word analysis, we tracked the evolution of research topics within the PBD domain over time. This investigation uncovered noteworthy trends, including the steady growth of research output, the increasing prominence of the term “PBD”, and a focus on various types of performance-based analyses.

Relocation of Recent Shallow Seismic Activity in the Alboran Sea (Western Mediterranean Sea): The 2021–2024, 2016, and 2004 Seismic Series

ABSTRACT The Alboran Sea is a complex tectonic region and one of the most seismically active areas in the westernmost Mediterranean Sea. Its southern sector has been the scene of three significant earthquakes in the past 30 yr, the 1994 M 5.9 and 2004 M 6.3 Al Hoceima and the 2016 Mw 6.4 Alboran events. In this study, we perform a high-precision relocation of a selected subset of moderate-magnitude earthquakes of the three main seismic series that have occurred in this region in this century, the 2021–2024, 2016, and 2004 series, using all the available seismic data. We apply a two-step shared relocation procedure, first, a nonlinear probabilistic algorithm with a 3D velocity model for the Alboran–Betic–Rif system, and second, a double-difference relative method. Our results for the 2021–2024 and 2016 series show clustered epicenters along the nearby active fault systems in the area. The 2016 series displays an excellent spatial correlation with the Al-Idrisi fault and may be linked to it, whereas the 2021–2024 series could be associated to an unmapped structure to the east of Al-Idrisi, more fractured and of smaller dimensions, as inferred from its spatial–temporal magnitude distribution. Our solutions for the 2004 series confirm two clear and perpendicular epicentral alignments, which may be related to the Trougout fault. The overall depth distribution reveals shallow hypocenters mainly constrained in a seismogenic layer up to 15–20 km. Our results display a remarkable hypocentral clustering compared with the Instituto Geográfico Nacional (IGN) earthquake catalog solutions and an improvement in the accuracy and precision of earthquake locations, with mean horizontal and vertical uncertainties lower than ∼5 km, giving better constrained hypocenters over the IGN catalog. Our findings highlight the effectiveness of this methodology, especially in the case of offshore seismicity with poor azimuthal coverage, and may improve seismic hazard studies in the region.

High-resolution investigations of fault architecture in space and time

Heterogeneous fault architecture affects crustal seismotectonics and fluid migration. When studying it, we commonly rely on static conceptual models that generally overlook the absolute time dimension of fault (re)activation. Heterogenous faults, however, represent the end-result of protracted, cumulative and intricate deformation histories. This may lead to inaccurate reconstructions of tectonic histories and flowed models of fault hydro-mechanical behavior. We adopt here a multitechnique approach building upon the examination of now juxtaposed but not coeval brittle structural facies (BSF), which offer multiscalar insights in the spatio-temporal-thermal fault evolution. Our approach is applied to the Carboneras Fault, unveiling a ~ 25 Myr-long polyphase structural and thermal evolution. This led to a complex fault architecture, where BSFs exhibit a stark heterogeneity in fault rock and permeability, ultimately generating very different space- and time-dependent fault hydro-mechanical behaviors. Therefore, fault architectures shall be seen as dynamic features from which to extrapolate time-integrated comprehensive fault models accounting for the entire deformed rock volume and fault life span. We demonstrate that high-resolution studies of fault architectures are required to elucidate modes of fault growth and evolution, decipher long-lived, polyphase tectonic and thermal histories, and understand the influence of heterogenous fault architecture on hydraulic compartmentalization and earthquake rupture dynamics.

Applicability of electrical resistivity surveys for tracing and characterizing active faults: a case study in the Northern Gongju Fault Zone, Korea

Applicability of electrical resistivity surveys for tracing and characterizing active faults: a case study in the Northern Gongju Fault Zone, Korea

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.

New Insights on the Seismic Activity of Ostuni (Apulia Region, Southern Italy) Offshore

On 23 March 2018, an event of magnitude ML 3.9 occurred about 10 km from the town of Ostuni, in the Adriatic offshore. It was the most energetic earthquake in South–Central Apulia ever recorded instrumentally. On 13 February 2019, in the same area, a second ML 3.3 event was recorded. The analysis of the 2018 event shows that the ambiguity of the solution of the fault plane reported by INGV (Istituto Nazionale di Geofisica e Vulcanologia) on the Italian National Earthquake Centre website can be solved considering existing seismic profiles, exploration well logs and the Quaternary activity of faults in the epicentral area. A seismogenic source was identified in the rupture of a small portion of a 40 km length structure with strike NW-SE, dipping at a high angle toward the south. In this work, we have relocated the recent earthquakes by using the seismic stations managed by the University of Bari (UniBa), one of which is quite close to the event’s epicenter (about 20 km), together with data coming from the RSN (Rete Sismica Nazionale). Furthermore, we have determined the focal mechanism of some events, with implications on stress field of the area. Our results show right-lateral transtensional kinematics of the seismogenic faults along approximately E-W striking planes, with a tension, T, with a trend of about 60° (NE-SW direction) and a plunge of 20°. Finally, we have tried to correlate the location of the four best constrained earthquakes with their seismogenic structures.

Experimental Study on Tunnel Failure Mechanism and the Effect of Combined Anti-Dislocation Measures Under Fault Dislocation

Taking the tunnels crossing active faults in China’s Sichuan–Tibet Railway as the research background, experimental studies were conducted using a custom-developed split model box. The research focused on the cracking characteristics of the surrounding rock surface under the action of strike-slip faults, the progressive failure process of the tunnel model, and the mechanical response of the tunnel lining. In-depth analyses were performed on the tunnel damage mechanism under strike-slip fault action and the mitigation effects of combined anti-dislocation measures. The results indicate the following: Damage to the upper surface of the surrounding rock primarily occurs within the fault fracture zone. The split model box enables the graded transfer of fault displacement within this zone, improving the boundary conditions for the model test. Under a 50 mm fault displacement, the continuous tunnel experiences severe damage, leading to a complete loss of function. The damage is mainly characterized by circumferential shear and is concentrated within the fault fracture zone. The zone 20 cm to 30 cm on both sides of the fault plane is the primary area influenced by tunnel forces. The force distribution on the left and right sidewalls of the lining exhibits an anti-symmetric pattern across the fault plane. The left side wall is extruded by surrounding rock in the moving block, while the right side wall experiences extrusion from the surrounding rock in the fracture zone, and there is a phenomenon of dehollowing and loosening of the surrounding rock on both sides of the fault plane; the combination of anti-dislocation measures significantly enhances the tunnel’s stress state, reducing peak axial strain by 93% compared to a continuous tunnel. Furthermore, the extent and severity of tunnel damage are greatly diminished. The primary cause of lining segment damage is circumferential stress, with the main damage characterized by tensile cracking on both the inner and outer surfaces of the lining along the tunnel’s axial direction.

The Influence of Lithology and Fault Source Volume on the Magnitude–Frequency‐Distribution of Earthquakes

AbstractThe earthquake Magnitude‐Frequency‐Distribution is usually modeled with the Gutenberg‐Richter law, where the b‐value controls the relative rate of small and large earthquakes. b‐value shows an inverse dependence on differential stress, it increases with fault roughness and in areas with fluid involvement in faulting. b‐value analyses have been also applied to infer temporal evolution of the stress state along active faults or to discriminate between foreshocks and aftershocks. For the Mw 6.5 2016–2017 Central Italy seismic sequence, we show that: (a) away from the major earthquake faults, b‐values are controlled by lithology and style of deformation; (b) the absolute number of the b‐values depends on the adopted magnitude scale and catalog, but differences induced by lithology are preserved; (c) the selection of the fault source volume can strongly influence b‐value changes in time, highlighting some complexities on the applicability of the b‐value as fault stress meter.

A Review of Health Monitoring and Model Updating of Vibration Dissipation Systems in Structures

Given that numerous countries are located near active fault zones, this review paper assesses the seismic structural functionality of buildings subjected to dynamic loads. Earthquake-prone countries have implemented structural health monitoring (SHM) systems on base-isolated structures, focusing on modal parameters such as frequencies, mode shapes, and damping ratios related to isolation systems. However, many studies have investigated the dissipating energy capacity of isolation systems, particularly rubber bearings with different damping ratios, and demonstrated that changes in these parameters affect the seismic performance of structures. The main objective of this review is to evaluate the performance of damage detection computational tools and examine the impact of damage on structural functionality. This literature review’s strength lies in its comprehensive coverage of prominent studies on SHM and model updating for structures equipped with dampers. This is crucial for enhancing the safety and resilience of structures, particularly in mitigating dynamic loads like seismic forces. By consolidating key research findings, this review identifies technological advancements, best practices, and gaps in knowledge, enabling future innovation in structural health monitoring and design optimization. Various identification techniques, including modal analysis, model updating, non-destructive testing (NDT), and SHM, have been employed to extract modal parameters. The review highlights the most operational methods, such as Frequency Domain Decomposition (FDD) and Stochastic Subspace Identification (SSI). The review also summarizes damage identification methodologies for base-isolated systems, providing useful insights into the development of robust, trustworthy, and effective techniques for both researchers and engineers. Additionally, the review highlights the evolution of SHM and model updating techniques, distinguishing groundbreaking advancements from established methods. This distinction clarifies the trajectory of innovation while addressing the limitations of traditional techniques. Ultimately, the review promotes innovative solutions that enhance accuracy, reliability, and adaptability in modern engineering practices.