Active Fault System Research Articles

Segmentation of the Active Fault on the Cirebon-Semarang Segments as Revealed by DEM-Derived Geomorphic Indices

This research focuses on the segmentation and tectonic activity of the Baribis-Kendeng Fault across the Cirebon to Semarang segments, revealed through the analysis of geomorphic indices derived from Digital Elevation Models (DEM). Utilizing geomorphic indices such as the Hypsometric Integral (HI), Stream Length-Gradient Index (SL), and SL/K ratio, the analysis was conducted on 33 streams crossing ten segments. The results indicate that the landscape in the research area is predominantly in the youthful stage, with HI values ranging from 0.459 to 0.492, indicating active tectonic uplift. Segments such as Ungaran and Pemalang exhibit significant tectonic activity, with high SL/K values, particularly in the Ungaran segment, where the SL/K value reaches 344.872. These findings suggest that fault activity in the region is ongoing, with stronger uplift patterns observed at the western and eastern ends of the fault, while relatively lower activity is found in the central area. This research highlights the ongoin tectonic processes shaping the region’s geomorphology and contributes to a better understanding of the active fault system in Java Island.

Seismicity and Present‐Day Crustal Deformation in the Southern Puna Plateau

AbstractThe Southern Puna plateau in the central Andes has a complicated tectonic history that includes episodes of distributed shortening and extension, lithospheric delamination, uplift and Quaternary backarc volcanism. In this study, the upper crustal structure and present‐day deformation in this area is investigated using a new regional earthquake catalog derived with a deep‐learning‐based phase picker. Results show abundant strike‐slip seismicity at shallow depths in the eastern Southern Puna plateau that reveals active fault systems in the area and indicates N‐S extension/E‐W compression that changes orientation and relative magnitude from north to south. A broad zone of seismic quiescence in the western plateau may indicate a zone of upper crustal decoupling from large‐scale deformation. The region separating the western and eastern plateau exhibits a complex stress field that can be related to the boundary of east/west oriented middle‐to‐lower crustal flow in the main volcanic arc. Southeast of the plateau in the Sierras Pampeanas, crustal seismicity deepens and is dominated by conjugate reverse faulting structures associated with the direction of plate convergence. Vp and Vs seismic velocity models of the upper crust obtained through local earthquake tomography with the improved seismic catalog show low‐velocity anomalies near intermontane basins, except in the Antofagasta basin where a high‐velocity anomaly possibly represents shallow intrusive component of Quaternary basaltic volcanism. Below the Cerro Galan caldera, an upper crustal 10‐day long earthquake swarm is observed which may indicate local stress perturbations from fluids at the top of the crustal magmatic system that feeds this volcano.

Source Analysis of April 2, 2023, Magnitude 5.6 Flores Sea Earthquake North of Bima, Sumbawa, Indonesia

Abstract The seismotectonic setting and the potential of significant earthquakes from the Flores Sea region in eastern Indonesia are not well understood. On April 2, 2023, a magnitude 5.6 earthquake occurred north of Bima (Sumbawa), specifically under the Flores Sea. This area has a complex tectonic setting with a Flores back-arc thrust and some local active faults. Our study aims to analyze the source mechanism of this earthquake using moment tensor inversion and hypocenter relocation methods. We utilized five (5) three-component regional BMKG seismic stations for the moment tensor inversion and analyzed aftershocks within one month following the main event for hypocenter relocation purposes. Our findings indicate that the earthquake was generated by an unidentified fault segment with a strike-slip mechanism, either an N/NW-S/SE west-dipping fault segment or an E-W north-dipping fault segment. Through hypocenter relocation, we found that aftershocks were oriented directly to the N/NW-S/SW north of the Flores Thrust fault zone. We interpreted that this earthquake was not directly associated with the activity of the Flores Thrust system. This study can help update our understanding of the active fault system around the Flores Sea and as a constraint to support seismic hazard mitigation.

Active, long-lived upper-plate splay faulting revealed by thermochronology in the Alaska subduction zone

The lack of subaerial forearc geological records in active subduction zones has hindered our understanding of the roles of upper-plate structures and their interactions with plate interface processes in accommodating forearc deformation. Forearc splay faults, a type of upper-plate structure, are of particular interest due to their high efficiency in triggering tsunamis during great earthquakes. The coastal area of the Kodiak Islands, Alaska, USA exhibits stratigraphic and geomorphologic records of Miocene to Recent vertical tectonism and Quaternary thrust faults, suggesting potential splay-fault-involved deformation over geological timescales. To better understand the mechanisms of forearc long-term strain accumulation and the roles of splay faults, we investigate the spatial and temporal pattern of recent forearc exhumation in the Kodiak accretionary prism by conducting zircon and apatite (U-Th)/He (ZHe and AHe) thermochronologic analyses and thermal history modeling. These results are supplemented by field investigations, detrital zircon geochronology analyses and offshore active fault mapping. Most of the ZHe ages record cooling through the ZHe closure temperature in the late Eocene-early Oligocene, temporally and spatially consistent with the Eocene-early Oligocene broad antiformal exhumation previously documented by zircon and apatite fission track thermochronological ages. However, the AHe ages record cooling through the AHe closure temperature from early Miocene to Pliocene and exhibit an overall trenchward younging trend, with all the Pliocene ages (3-5 Ma) in the regions closest to the trench. Our thermal history modeling and field survey suggest that the trenchward coastal area of the Kodiak Islands experienced a change from early-middle Miocene basin subsidence to recent deformation and rapid uplift from 6-7 Ma to recent, while the rest of the island experienced an early-middle Miocene decrease in the prolonged exhumation from the Eocene-Oligocene. The newly revealed long-term exhumation pattern resembles the estimated uplift patterns based on elevated marine terraces and geodetic data. The early-middle Miocene change in exhumation pattern might be caused by a change in the dominant deformation mechanism affecting the Kodiak Islands, from broad underplating along the subduction interface mainly during the Eocene-Oligocene to hanging-wall uplift due to an active crustal splay thrust fault system since the late Miocene (the Kodiak Shelf Fault). We further discuss the dip-slip rate and geometry of the Kodiak Shelf Fault system and how inherited forearc upper-plate structures and lithology may affect forearc fluid distribution and facilitate the development and persistent deformation of the Kodiak Shelf Fault system.

Strain Partitioning, Interseismic Coupling, and Shallow Creep Along the Ganzi‐Yushu Fault From Sentinel‐1 InSAR Data

AbstractThe Ganzi‐Yushu fault (GYF) is one of the most seismically active fault systems in eastern Tibet, having experienced five M > 7.0 earthquakes over the past 300 years. Here, we use Sentinel‐1 InSAR data spanning from 2014 to 2023 to derive the interseismic velocity fields along the GYF. We calculate the strain rate fields for the entire fault system, which reveal localized strain accumulation along the GYF as well as along two secondary faults within the Bayan Har block. The inversion results obtained from the elastic block model indicate left‐lateral strike slip rates of 4.0–6.5 mm/yr along the GYF and five locked segments distributed along strike. Furthermore, we identify two shallow creeping segments on the InSAR velocity maps. Based on the locations of the creeping sections and their temporal decay characteristics, we infer that the shallow creep along the GYF is afterslip of the 2010 Yushu earthquake.

Tectonic activation and the risk of Ilisu Dam collapse to Iraq through modelling and simulation using HEC-RAS

Floods caused by dam failures can cause huge losses of life and property, especially in estuarine areas and valleys. In spite of all the capabilities and great improvements reached by man in the construction of dams and their structures, they will remain helpless before the powerful forces of nature, especially those related to tectonic activation, and the occurrence of earthquakes of different intensities.The region extending from the Ilisu Dam in Turkey to the Mosul Dam in Iraq was chosen as an area for this study, and the HEC-RAS application was used to simulate the collapse of the Ilisu Dam due to a major earthquake, to know the magnitude of the risks and losses that could result from this. The Ilisu Dam was built very close to a highly tectonically active fault system, particularly the East Anatolian Fault (EAF), which is one of the largest tectonically active faults in the world with a length of 500 km. This region has witnessed past and present earthquakes of high magnitude (M > 7), especially in the EAF, so the construction of the Ilisu Dam near the EAF fault system is of great concern, as it was built in a basin with very complex seismic activity and geology.Using the HEC-RAS simulation application, the study found that the flood resulting from the collapse of the Ilisu Dam would reach the edges of the Mosul Dam Lake in just 13 h. With a flow of more than 100,000 m3/s, more than 10 billion m3 of water will flow into the Mosul Dam Lake within four days of the disaster. This will lead to the collapse of the Mosul Dam and direct the flood wave of the collapse of these dams towards Baghdad through Mosul, Tikrit, and Samarra. This could pose risks to all Iraqi cities located within the Iraqi sedimentary plain (Mesopotamia), from south of the Mosul Dam up to Basra, in a scenario similar to Noah’s Flood.

Active Fault Interaction in the Eastern Betic Cordillera: A Model of Coseismic and Postseismic Stress Transfer Following Historical Earthquakes in SE Spain

AbstractThe Spanish historical earthquake catalog reveals a significant number of destructive earthquakes (Mw 6.0) that have occurred along the Eastern Betic Shear Zone (EBSZ), a major active fault system at the Eastern Betic Cordillera. However, during the last century, seismic activity in this region has been characterized by the absence of large‐magnitude events, complicating yet underlining the importance of understanding active fault interaction in the EBSZ. In this work, we focus on the northeastern half of the EBSZ and apply a similar method to Yazdi et al. (2023, https://doi.org/10.1029/2023tc007917). We model a series of consecutive earthquakes ( VII; Mw 5.0) between the and centuries occurring along the Alhama de Murcia, Carrascoy and Bajo Segura faults, and assess their coseismic impact as well as explore the evolution of Coulomb stress changes due to the postseismic viscoelastic relaxation on the surrounding faults. Our results support a stress‐triggering connection between subsequent events and shed light on identifying the responsible faults for some. Our findings indicate that 1673 Mw 6.0 Orihuela and 1674 Mw 6.2 Lorca earthquakes, seemingly unrelated, could have both contributed to the forthcoming Mw 5.0 earthquake clustering along the Carrascoy fault. We show that attributing the 1829 Mw 6.6 Torrevieja earthquake to the Bajo Segura fault better describes the occurrence of earthquake sequences between the mid‐ and early centuries. Finally, we propose the Alhama de Murcia and the Carrascoy faults as responsible initiators for the early ‐century earthquake sequence in the Segura Medio valley. These findings provide valuable insights for seismic hazard modeling in the region.

Exploring seismic fragility and strengthening of masonry built heritage in Lisbon (Portugal) via the Applied Element Method

Although mainland Portugal has been spared from large magnitude earthquakes in recent years, it faces a threat due to the presence of several active fault systems. In such a framework, Portuguese pre-code masonry construction is believed to be the most vulnerable in the existing building stock. Given the lack of information on earthquake damage to this stock, the use of detailed numerical models is a viable strategy to comprehend its seismic behavior. This paper provides an updated fragility characterization of Lisbon pre-code masonry buildings based on their seismic assessment through the Applied Element Method. To limit the computational time, a promising pushover strategy, known as Incremental Ground Acceleration, was adopted. After the characterization of the current fragility, two retrofit layouts based on piers strengthening were modeled and assessed for the building stock whose seismic capacity does not meet expected demand. The aim of the paper is to derive updated fragility curves for the Lisbon region to support risk analysis incorporating the latest hazard studies and to offer insights into potential retrofit interventions.

Earthquake-induced deformation structures along Trans-Yamuna active fault system: Doon Valley, NW Himalaya

Earthquake-induced deformation structures along Trans-Yamuna active fault system: Doon Valley, NW Himalaya

Large-Depth Ground-Penetrating Radar for Investigating Active Faults: The Case of the 2017 Casamicciola Fault System, Ischia Island (Italy)

We conducted large-depth Ground-Penetrating Radar investigations of the seismogenic Casamicciola fault system at the volcanic island of Ischia, with the aim of constraining the source characteristics of this active and capable fault system. On 21 August 2017, a shallow (hypocentral depth of 1.2 km), moderate (Md = 4.0) earthquake hit the island, causing severe damage and two fatalities. This was the first damaging earthquake recorded on the volcanic island of Ischia from the beginning of the instrumental era. Our survey was performed using the Loza low-frequency (15–25 MHz) GPR system calibrated by TDEM results. The data highlighted variations in the electromagnetic signal due to the presence of contacts, i.e., faults down to a depth larger than 100 m below the surface. These signal variations match with the position of the synthetic and antithetic active fault system bordering the Casamicciola Holocene graben. Our study highlights the importance of employing large-depth Ground-Penetrating Radar geophysical techniques for investigating active fault systems not only in their shallower parts, but also down to a few hundred meters’ depth, providing a contribution to the knowledge of seismic hazard studies on the island of Ischia and elsewhere.

Evaluation of the tectonic activity of faults with mineral alterations: A case of East Anatolian Fault-Palu Segment, Turkey

Palu segment is a part of the Eastern Anatolian Fault Zone (EAFZ), the most important active left-lateral strike-slip fault system in Turkey, and there are different mineral alterations in this zone. In the study, the spatial relationship between tectonic activity and mineral alterations was tested with the Getis-Ord Gi* statistic in and around Palu segment. Mineral alterations at the pixel level were determined from ASTER images by Ratio, Relative Band Depth (RBD), Mineral Indices, CROSTA, Constrained Energy Minimization (CEM), Mixed Tuned Matched Filter (MTMF) methods. According to the results, the spatial distribution of alteration minerals extending parallel to tectonically active fault lines and/or partially bounded by faults in the area. RBD, Mineral Indices, CROSTA, CEM, and MTMF image processing algorithms applied in the study gave consistent results in the spatial determination and mapping of hydrothermal alterations in the study area. At 99% and 95% confidence intervals, statistically significant cold spot clusters indicate the proximity of alterations to faults concentrated around fault lines. This degree of clustering of mineral alterations indicates regions with high alteration rates close to fault lines and areas with tectonic activity along fault lines.

High-resolution 3D ambient noise tomography around the Meishan-Chiayi active fault system of western Taiwan

The Meishan-Chiayi area of western Taiwan has a large probability of producing a major earthquake in the near future. Historically, one of the largest and most damaging of Taiwan’s earthquakes occurred there. It is, therefore, important to have a well-constrained upper crustal 3-D shear-wave velocity model that can be used to accurately determine ground motion predictions and fault geometry models used in seismic hazard and risk modelling. In this study, we carried out an ambient noise tomography experiment using 100 seismometers deployed with a ∼2 km spacing on a 20 by 20 km grid. The reliable periods of phase velocity from Rayleigh waves are 0.6 to 6.8 s, providing a well-resolved Vs structure from the surface to a depth of around 4 km. The velocity model displays a prominent, roughly northeast-striking change in Vs that follows the projected surface trace of the blind Chiayi thrust. The uplift of relatively higher Vs rocks in its hanging wall, together with a negative to positive change in dVs suggests that it dips gently eastward across the study area. A northward thickening of the lower Vs crust, together with a high negative dVs in the north of the study area is related to an increased thickness of foreland basin rocks across the Meishan fault. The Vs and dVs models provide reasonable evidence that the Meishan fault can be traced at a high angle from its surface rupture to the base of the model at 4 km depth. It cuts the Chiayi thrust.

Reappraising the seismogenic potential of a low-strain rate region: Active faulting in the eastern Siena Basin (southern Tuscany, Italy)

We investigated the active tectonics and earthquake potential of the eastern Siena Basin, a slowly deforming portion of southern Tuscany in the inner Northern Apennines. This region hosts several historical settlements and valuable cultural heritage, but also frequent background seismicity and rare damaging earthquakes in the Mw range 5.0–6.2. We describe in detail an active, capable, and seismogenic fault system that we identified in the eastern Siena Basin, a few kilometers south-east of the city of Siena, thanks to the presence of an active quarry (Cava Capanni) that exploits travertines of Middle Pleistocene-Holocene age. Travertines are unique rock masses that may preserve living evidence of active and seismogenic faulting, thus providing remarkable seismotectonic insight. The active fault system consists of at least two segments rupturing travertines younger than 45 ka, with a cumulative vertical displacement of 111 cm, and an estimated minimum slip rate of 0.02–0.03 mm/y. We maintain that this displacement is the result of at least three coseismic movements accompanied by clastic dykes injected within the fault damage zone due to liquefaction phenomena. The fault system is seen to extend east of the quarry, affecting Pliocene and Mesozoic deposits.The Cava Capanni fault system is evidence of a poorly understood but potentially seismogenic tectonic mechanism of regional extent. Its orientation and kinematics are compatible with the activity of faults that are oriented obliquely or orthogonally to the main chain axis, in contrast with the setting of the axial and outer zone of the Northern Apennines, where extension and compression are accommodated by Apennines-parallel faults.

Assessing the relative activity of faulting along both flanks of the Ou Backbone Range, Tohoku Region, Japan, from fluvial geomorphic analyses

The Ou Backbone Range in the Tohoku Region of Japan is bounded on its both sides by two major active fault systems: the Western Fault Zone of Kitakami Lowland in the east and the Eastern Fault Zone of Yokote Basin in the west. Although these two systems are primary active fault systems in the region, information on their long-term activity characteristics is still quite limited. Therefore, we analyzed the normalized channel steepness indexes of river valleys trending perpendicular to the range front along both flanks of the Ou Backbone Range. Our results show that the eastern flank has gentler river valleys, whereas rivers along the northwestern flank are steeper. Our field investigation shows that knickpoints in this area are mostly related to local lithologic boundaries or are check dams along the valleys, thus the river systems are likely under steady-state conditions. Hence, the steeper river valleys in northwestern Ou Backbone Range indicate a higher uplift rate of the area. Because both fault systems are primarily dip-slip reverse faults and do not have significant variations in their subsurface geometry, the faster uplift suggests that the northern segment of the Eastern Fault Zone of Yokote Basin has a higher slip rate. This is consistent with results of previous studies, and the fact that the rupture of the 1896 Rikuu earthquake, the only historical surface-rupturing event in this region, was only limited along the northern segment of this fault system.

Morphometric Evaluation of the Relative Uplift Rates along the Vigan–Aggao Fault in Ilocos Norte, Philippines

The Vigan–Aggao Fault (VAF) in northern Luzon Island is a NNE-trending sinistral fault divided by fault bends, which are associated with local variations in the fault’s kinematics. In this study, we examined the relative uplift rates across the fault bend in the San Juan–Vintar segment of the VAF using morphometric indices. Basin-based indices, namely hypsometric integral, basin shape, basin elongation ratio, and basin asymmetry factor, and non-basin-based indices, namely stream length-gradient index, normalized stream length-gradient index, and mountain front sinuosity were calculated to isolate and examine the surface processes that influence landscape development. We then integrated the basin-based results with geological data to create a relative tectonic activity index (RTAI). Clustering analysis of the results revealed hotspots along the bent section of the fault indicating more values that suggest higher relative uplift rates during the development of the landscape. The morphometric indices showed that the highest uplift rates are along the central VAF strands. This study described and evaluated the relative uplift rates of a known active fault system in Ilocos Norte, in the absence of detailed field structural data. This study also reinforces the utility of morphometry in identifying priority sites for detailed paleoseismic and seismic hazard analyses.

Coupled Detachment Faulting and Hydrothermal Circulation at 49.7°E Southwest Indian Ridge Revealed by Seafloor Magnetism

AbstractDetachment faults at slow‐ and ultraslow‐spreading mid‐ocean ridges are essential for lithosphere‐hydrosphere interactions. However, their coupling with subseafloor hydrothermal circulation is poorly understood. Here, we investigated shallow hydrothermal fluid circulations in the active Dragon Horn detachment fault system of the Southwest Indian Ridge using combined near‐bottom magnetic anomaly data and rock magnetic analyses. We observed enhanced magnetic anomalies related to the high magnetization of basaltic country rocks and highly serpentinized (>80%) peridotite, whereas the hydrothermally altered basalts and sulfide deposits had weak magnetization and reduced magnetic anomalies. Therefore, the low‐magnetization zone was interpreted as a proxy for the hydrothermal fluid channel. The spatial distribution of the low‐magnetization zone revealed that the inactive Suye field expanded more than 500 m in diameter horizontally and ∼100 m vertically, and the active Longqi hydrothermal field had a >1 km fluid channel, both centered around the detachment fault fracture zone. Our results establish a robust link between detachment faulting and shallow hydrothermal circulation in which the detachment fault system provides critical fluid paths. Therefore, detachment tectonics are important elements for evolving seafloor hydrothermal fields along the Southwest Indian Ridge and possibly other slow‐ and ultraslow‐spreading mid‐ocean ridges globally.

Probabilistic estimation of the source component of seismic hazard in North-Eastern Brazil

Stable continental regions pose unique challenges for conducting Probabilistic Seismic Hazard Analysis because the earthquake activity driving mechanisms are poorly understood. For instance, the lower seismicity (hence the paucity of data) and the absence of well-defined active fault systems complicate accurately determining seismic source parameters. Northeastern Brazil is a stable continental region exhibiting moderate-size events recorded with significant seismic intensities and provoking the collapse of poorly constructed buildings in the last century. Thus, assessing the seismic hazard is critical for seismic risk mitigation. The seismic hazard depends on three components: source, path, and site, and here, we present the probabilistic seismic hazard analysis of the source component for NE Brazil. Spatial aggregation of earthquake sources outlined four areal seismic zones. A goodness-of-fit test rejected the Gutenberg-Richter model of magnitude frequency distribution in one of the studied seismic zones. For this reason, we estimated the magnitude probability distribution function in that zone using a nonparametric adaptive kernel estimator. In other zones the Gutenberg-Richter magnitude frequency model was applied. In either way of the magnitude probability distribution modelling we considered the upper bound for magnitude equal to 6.6 mR, based on the upper bound of a 95 % confidence interval for the standard normal distribution of palaeoearthquake sizes. Our findings suggests that potentially damaging events are likely to occur, and we cannot neglect chances for the occurrence of earthquakes exceeding 5.2 mR. The calculated mean return periods indicate significantly shorter intervals between consecutive large events than palaeoseismic records.

Assessing the hazard of fault triggering by deep geothermal energy production in an active fault system via a 1D stress model and 3D fault mapping

Borehole image data and a 1D-stress model built on open hole logs, leak-off tests (LOT) and image logs are used to evaluate the potential of seismicity caused by fault triggering during geothermal heat production in the city of Vienna. Data were derived from a 4220 m deep geothermal exploration well that investigated the geothermal potential of fractured carbonates below the Miocene fill of the Vienna Basin. The well penetrated several normal faults of the Aderklaa Fault System (AFS) that offset Pleistocene terraces at the surface and hence are regarded as active. Stress-induced borehole failures and 1D geomechanical modeling proves that the potential reservoirs are in a normal fault stress regime with Sv > SHmax > Shmin. While stress magnitudes in the upper part of the well (down to about 2000 m) are significantly below the magnitudes that would trigger the rupture of critically oriented faults including the AFS, stresses in the lower part of the drilled section in the pre-Neogene basement (below about 3300 m) are not. Data evidence a rotation of SHmax for about 45° at a fault of the AFS at 3694 m to fault-parallel below the fault suggesting that the fault is active. Critical or near-critical stressing of the fault is corroborated by the stress magnitudes calculated from the 1D geomechanical model. The safety case to exclude unintended triggering of seismic fault slip by developing geothermal reservoirs in close vicinity to one of the branch faults of the AFS may therefore be difficult or impossible to make.Graphical

A large fault partially reactivated during two contiguous seismic sequences in Central Italy: The role of geometrical and frictional heterogeneities

Earthquakes can rupture multiple fault segments as well as faults with complex geometry, or heterogeneous pre-stress and frictional properties. These observations have been documented mainly for moderate-to-large earthquakes by inverting geodetic and seismic data and by studying the influence of fault orientation and rheology within the regional stress field.In this work we have studied the Gorzano fault, GF, a large normal fault within the active fault system of Central Italy that during the last two largest Italian seismic sequences, L'Aquila (2009) and Amatrice-Visso-Norcia (2016–2017), was reactivated via a series of 5.0 < Mw < 6.0 events. We calculated moment tensor solutions for 134 M > 3 events and evaluated their normalized slip-tendency. Merging these results with high resolution earthquake catalogs, available M > 5 earthquake slip distributions, and frictional properties characterizing the activated fault, we develop a mechanical model and discuss potential earthquake rupture scenarios.The GF is an optimally oriented fault within the regional stress field and from, the reactivation via aftershock or mainshock slip of complementary fault portions from 2009 to 2017 indicates that the fault behaves as a single fault structure. The geometrical and mechanical heterogeneities suggest that the most likely slip behavior of GF is the reactivation of different fault portions with M > 5.0. However, due to favorable initial stress conditions, we suggest that a seismic rupture can produce the complete reactivation of the fault, resulting in a M 6.5–6.6 earthquake as documented in paleoseismological data.

Distinct response of deep and shallow geothermal reservoir temperature following earthquakes in the Kangding Fault zone hydrothermal system

Study regionAs part of the active Xianshuihe Fault system, the Kangding geothermal field is a representative high-temperature hydrothermal system in the southeastern Tibetan Plateau, China. The strong tectonic and hydrothermal activity serves as a unique location to study the interaction between earthquakes and geothermal fluids. Study focusWe have collected water samples taken from thermal springs and boreholes in the geothermal field to identify fluid composition and reservoir temperature of the deep granite and shallow metamorphic rock using geochemical analysis and the Integrated Multicomponent Geothermometry (IMG) method. Two typical thermal springs that offer long-term hydrochemical data were selected to investigate the effect of earthquakes on the shallow and deep reservoir temperatures. New hydrological insights for the regionThe deep reservoir temperature in the Kangding geothermal field is in the range 222 ℃ to 256 ℃, while the shallow reservoir temperature ranges from 128 ℃ to 171 ℃. Both thermal springs show changes in reservoir temperature following the 2008 Wenchuan, the 2013 Lushan, and the 2014 Kangding earthquakes. The temperature changes are similar in the deep reservoir of the two springs but different in the case of the shallow reservoir. We propose that the changes in reservoir temperature, steam fraction, and dilution factor indicate that the deep reservoir is more sensitive to earthquake-induced permeability changes than the shallow reservoir.