Seismogenic Fault Zone Research Articles

The rupture process of the Hualien M7.3 sequence on April 3, 2024

The Hualien M7.3 earthquake on April 3, 2024, was a significant and strong earthquake in Taiwan, China in the past two decades. The rupture process of the main shock and strong aftershocks is of great significance to the subsequent seismic activity and seismogenic tectonic research. Based on local strong-motion data, we used the IDS (Iterative Deconvolution and Stacking) method to obtain the rupture process of the mainshock and two strong aftershocks on the 23rd. The rupture of the mainshock was mainly unilateral, lasting 31 s, with a maximum slip of 2 m, and the depth of the large slip zone is about 41-49 km. There is a clear difference between the rupture depth of the main shock and the two strong aftershocks. The depths of the large slip zones of the latter two are 3-9 km and 8-10 km, respectively. There is also a significant difference in the seismogenic fault between the mainshock and the aftershocks, and we believe that there are two seismogenic fault zones in the study area, the deep and the shallow fault zone. The slip of the deep faults activates the shallow faults.

Topical issues in hydrogeology of seismogenic fault zones

The hydrogeology of fault zones, especially at considerable depth, is perhaps the most poorly developed area of earthquake source mechanics. This is due both to the insufficient data on the filtration characteristics of the geomaterial at large depths and to the complexity of the processes of mass transfer, fracture formation and healing under high temperatures and pressures. In these conditions, a fluid obviously has a very strong effect of on both the friction characteristics and the stress state in the vicinity of the slip zone. Fluids are carriers of dissolved matter and thermal energy, an effective catalyst for various types of metamorphic transformations. According to some models, fluid flows can be triggers for the start and stop of seismogenic ruptures. Constructing a complex computational model that adequately describes the processes of preparation, initiation, and stopping of various slip modes along faults, which is a recent trend in world seismology, requires developing the ideas about fluid dynamics of seismogenic faults. This review summarizes recent information on the hydrogeology of fault zones. Models and ideas about the role of fluids at different stages of the seismic cycle, derived from the field data, laboratory and in situ experiments, and numerical calculations, are analyzed.

On Fluid-Metamorphic Regime of Deep Fault Zones, in Connection with “Topical Issues in Hydrogeology of Seismogenic Fault Zones” by G. G. Kocharyan and I. V. Shatunov

On Fluid-Metamorphic Regime of Deep Fault Zones, in Connection with “Topical Issues in Hydrogeology of Seismogenic Fault Zones” by G. G. Kocharyan and I. V. Shatunov

Frictional Properties of Natural Granite Fault Gouge Under Hydrothermal Conditions: A Case Study of Strike‐Slip Fault From Anninghe Fault Zone, Southeastern Tibetan Plateau

AbstractThe Anninghe Fault (ANHF) is a major left‐lateral strike‐slip fault in southwestern China and one of the main seismogenic fault zones with a history of strong earthquakes. To understand the frictional properties of natural granitic gouges from the principal slip zone, we conducted hydrothermal friction experiments using both saw‐cut and ring shear methods. These experiments were performed at temperatures (T) of 25–600°C, pore pressures (Pf) of zero (dry), 30 and 100 MPa, sliding velocities (V) of 0.01–100 μm/s and effective normal stresses () of 68, 100, and 200 MPa. The (apparent) friction coefficient is low (μ < 0.5) at high T (600°C), high Pf (100 MPa) and low V (<1 μm/s); but high (μ > 0.6) under all other T, Pf and V conditions. Under high Pf, the velocity dependence of friction, (a‐b), displays three regimes with increasing temperature, from positive below ∼100°C to negative at 100–300°C (at V = 1–3 μm/s) or else 100–450°C (at V = 30–100 μm/s), becoming positive again above 300–450°C. At low Pf, the negative (a‐b) expands to the range ∼300–600°C. Microstructural observations and microphysical interpretation imply that the frictional weakening and transitions in (a‐b) are related to competition between dilatant granular flow and deformation of the fine‐grained gouge by intergranular pressure solution accompanied by healing phenomena (leading to cavitation‐creep‐like behavior). Our results provide a possible explanation for the distribution of earthquakes at different depths in the continental crust, in particular for the depth range of the seismogenic zone between 4 and 24 km along the ANHF.

In-situ rock shattering and strain localization along a seismogenic fault in dolostones (Monte Marine fault, Italian Central Apennines)

In-situ shattered rocks are often associated with seismogenic fault zones, but their mechanism of formation is still matter of debate, partly because of the limited number of field studies. Here we describe the characteristics of in-situ shattered rocks distribution along the NW-SE-striking seismogenic Monte Marine Fault (MMF) in the Italian Central Apennines. In the studied area, the MMF cuts through Mesozoic carbonates, is exhumed from <3 km depth and consists of two >5 km-long major hard-linked segments with normal kinematics. The linkage between the two fault segments occurs along a ∼2 km-long step-over zone with E-W trending faults and oblique-slip kinematics. To the northwest, fault-related shear deformation is localized in a ∼5 m-thick cataclastic fault core and off-fault deformation is dominated by in-situ shattered rocks up to ∼40 m-thick. Instead, in the step-over zone to the southeast, the in-situ shattered rocks are up to ∼500 m thick, particularly where MMF crosscuts older low-angle thrust faults.We integrated detailed field structural surveys with microstructural and grain size distribution analyses of the fault rocks to assess the mechanism of (1) formation of in-situ shattered rocks and, (2) progressive localization of shear deformation along the MMF. The obtained results, after the viability of several formation mechanisms (mechanical models) have been reviewed, support the hypothesis that the formation of in-situ shattered rocks was associated with the propagation of (multiple) seismic ruptures (mainshocks and aftershock sequences) within a mechanically heterogeneous fault zone. Heterogeneity is due to the occurrence of preexisting damage related to previous earthquakes, but also inherited from the older low-angle thrust faults. Therefore, we suggest that the origin of these shattered rocks is more compatible with seismic related processes than only with quasi-static fault growth models. On the other hand, the cataclastic fault core derived from the progressive accommodation of shear deformation within the in-situ shattered rock volumes during several seismic cycles. We conclude that the large volumes of in-situ shattered rocks are the result of seismic-related dissipative processes in a geometrically and mechanically heterogeneous fault zone. In this scenario, large volumes of in-situ shattered rocks are compliant low velocity zones which can influence the propagation of earthquake ruptures.

Slip-weakening friction controls coseismic displacements in a 3D fracture network: Implications for the long-term safety of nuclear waste repositories

During the long-term operational lifespan of nuclear waste repositories in crystalline rock formations, large earthquakes along nearby seismogenic fault zones may occur, coseismically triggering shear displacements of secondary fractures within the respository site. In addition, these secondary fractures that may be associated with slip-weakening friction could accommodate significant slip instabilities and large shear displacements. A cumulative shear displacement exceeding 50 mm could affect the integrity of waste canisters, potentially resulting in the escape of hazardous radionuclides into the groundwater system. To investigate this problem, we develop a novel 3D seismo-mechanical model to simulate the transient rupture of a primary seismogenic fault zone and coseismic slips in a network of secondary fractures located around the primary fault. A plausible postglacial earthquake scenario is studied, where the rupture along the seismogenic fault propagates outward from a predefined hypocenter, with the resulting static stress changes and dynamic ground vibrations captured. We explore different cases with secondary fractures having different degrees of slip-weakening friction, which is found to strongly control the spatial decay of coseismic fracture displacements in the system. The findings derived from our study have significant implications for assessing the long-term safety of nuclear waste repositories in faulted and fractured crystalline rocks.

Exothermic events in a fossil seismogenic fault acquiring thermoviscous remanent magnetization in an exhumed accretionary complex

Detecting exothermic events within fault rocks is key to understanding fault behavior. While paleo-temperature studies of fault rocks have been conducted via vitrinite reflectance or magnetic analysis, secondary remanent magnetization caused by exothermic events within fault rocks has not been examined directly. Direct detection of the secondary remanence has the advantage of revealing both paleo-temperature constraints and the paleomagnetic direction, which can help assess the relationship between secondary remanence and deformation. We conducted thermal and alternating-field demagnetization analyses and other rock–magnetic experiments on a fossil seismogenic fault zone and the surrounding host rocks in an exhumed accretionary complex. The fault zone comprises a few cataclastic zones, including thin-slip zones. The blocking temperature in the secondary magnetization site was detected at 300–360 °C only in cataclasite with magnetite or pyrrhotite as carriers. The paleomagnetic direction of the secondary magnetization is characteristic in the cataclasite, and the blocking temperature was higher than the paleo-maximum temperature of the host rocks. Therefore, the blocking temperature records a local exothermic event in the cataclasite. Thermoviscous remanent magnetization (TVRM) were suggested as candidate mechanisms for the blocking temperature.

Lowering of the kinetic barrier of clay-mineral reactions along a seismogenic fault: Example from the Nankai subduction zone, Japan

An analysis of clay minerals in core samples around the megasplay fault of the Nankai Trough, Japan, recovered during the Integrated Ocean Drilling Program Nankai Trough Seismogenic Zone Experiment reveals a local progression of the smectite-to-illite conversion (S–I) reaction in the slip zone, possibly associated with local thermogenesis caused by seismic slip on the fault. Our semiquantitative X-ray diffraction analysis demonstrates that the illite content in mixed-layer illite/smectite is ∼15% higher in the gouge than in the host sediments. The thermal history of the fault, constrained in a previous study, requires a reduction of the apparent activation energy by 20–30% compared with the literature value to explain the observed illitization. The Shirako Fault in the Miura–Boso accretionary complex, which is thought to have been activated in a tectonic setting similar to that of the megasplay fault of the Nankai Trough, also shows a 20–30% reduction in the apparent activation energy. These results suggest that the kinetic barrier of the smectite–illite reaction is lowered as a result of mechanochemical processes in seismogenic fault zones.

Active seismogenic faulting in the Tehran Region, north of Iran; state-of-the-art and future seismic hazard assessment prospects

This study summarizes the state-of-the-art investigation into active-seismogenic faulting in the Tehran Region, and presents new complementary data to provide an overall view on potential seismic sources to strike the capital of Iran. The study region lies in the central portion of the Arabia-Eurasia collision zone. The Tehran Region is located in a transitional zone between the seismically active regions of Central Iran to the south and Alborz to the north and exhibits a tectonic context characterized by both dip-slip and strike-slip E-striking fault systems such as the Mosha, Parchin, Garmsar and North Tehran faults. Seismic catalogues record numerous strong and moderate earthquakes in the Tehran Region. Although the mapping of active faults and paleoseismological records have defined the seismic sources of several historical and prehistorical earthquakes, still many of them need to be constrained. Based on successive fault displacements and related microseismicity, five previously unknown or poorly understood major active seismogenic fault zones in the Tehran Region were introduced. From the west to the east, and in both near- and far-field contexts, the Qezel Hessar, Mahdasht-South Karaj, Kuhak-Lavizan, Arakuh, and Kajan define the fault zones. Critically, in the last decades, the rapid urban development in Tehran, including the new settlements of Karaj, Hashtguerd, Pardis, and Parand, has covered some of the surface expressions of these fault zones. The Kuhak-Lavizan fault zone, however, is known to cut across inner city parts of Tehran. Within the Tehran Region, seismicity on these faults demonstrates ongoing active structural evolution. The active faults of Tehran City are generally discussed in three northern, central and southern ∼E-striking basement zones. The major zones, which contain deep-seated faults, are capable of producing moderate to strong seismic events near and within the metropolitan areas of Tehran and Karaj and nearby settlements.

Laboratory Study on Frictional Behavior of Rock Blocks of Meter Scale. Methods and Preliminary Results

—The paper introduces a new, unique for Russia, meter-scale laboratory setup created in the Institute of Geosphere Dynamics of the Russian Academy of Sciences (IDG RAS) to study the development of different sliding regimes on rock discontinuities. The experimental procedure is described and the results of the first series of tests aimed at studying the formation of different sliding regimes on rock faults are presented. The laboratory fault was a loaded contact of two 75-cm long blocks made of diabase. The fault was filled with granular material (a fault gouge). Normal stresses on the fault can reach 10 MPa. By varying fault gouge composition and loading rate, we reproduced a wide range of sliding regimes: sliding with constant velocity, regular stick-slip, and aperiodic slow slip episodes. It is shown that a variation in the loading rate can cause a significant change in the sliding regime. Intense frictional crushing of gouge grains is detected in the experiments at relatively low normal pressure of 2 MPa. In the case of high-amplitude stick-slip, besides crushing of the gouge material, also structural phase transformations of quartz grains corresponding to a local temperature increase up to 700°C are revealed. A possible set of the problems related to deformation processes in seismogenic fault zones that can be addressed by modeling on such setups—the pre-seismic stage of inelastic behavior of the main fault zone at critical stress—is outlined.

Structural fabrics of carbon grains in a natural fault gouge reactivated by the 2008 Wenchuan earthquake

AbstractNatural fault gouges reactivated by the 2008 Wenchuan earthquake are typically rich in carbon in shallow parts of the seismogenic fault zone. Although experimental evidence indicates that amorphous carbon can be changed to graphite during seismic slips, this transformation has not yet been observed in nature. We conducted a nanoscale investigation of a carbon‐rich co‐seismic gouge from a surface rupture related to the Wenchuan earthquake using high‐resolution transmission electron microscopy. We found that all mineral grains were wrapped in amorphous carbonaceous materials with sinuate and straight graphene layer stacks. The sinuate layer was the transient material (~0.3456 nm) formed by amorphous carbon transforming to graphite; the graphene layer was graphite flakes (0.3354 nm). This means that graphitization occurred on the mineral grain surfaces (asperities) in the shallow slip zones during previous earthquake cycles, which could decrease the friction strength of the co‐seismic fault gouge and explain the dynamic weakness of the shallow parts of the Longmenshan seismogenic fault zone.

Pronounced Changes in Thermal Signals Associated with the Madoi (China) M 7.3 Earthquake from Passive Microwave and Infrared Satellite Data

Thermal variations in surface and atmosphere observed from multiple satellites prior to strong earthquakes have been widely reported ever since seismic thermal anomalies were discovered three decades ago. These thermal changes are related to stress accumulation caused by the tectonic activities in the final stage of earthquake preparation. In the present paper, we focused on the thermal changes associated with the 2021 Madoi M 7.3 earthquake in China and analyzed the temporal and spatial evolution of the Index of Microwave Radiation Anomaly (IMRA) and the Index of Longwave Radiation Anomaly (ILRA) based on 8-year microwave brightness temperature (MWBT) and 14-year outgoing longwave radiation (OLR) data collected by satellites. We also explored their responses in different tectonic units (seismogenic fault zone and active tectonic block). Our results indicated that the enhanced IMRA was distributed along the seismogenic fault since mid-February and reappeared for a longer time and with stronger intensity in March and April 2021. The pronounced enhancement in the ILRA was observed within one month over Bayan Har tectonic and adjacent blocks. The higher ILRA over the tectonic blocks in the southern Tibet Plateau at the beginning of 2021 could be associated with the regional stress accumulation, as proven by the occurrences of two moderate earthquakes during this period.

Investigation on Two Mw 3.6 and Mw 4.1 Earthquakes Triggered by Poroelastic Effects of Hydraulic Fracturing Operations Near Crooked Lake, Alberta

AbstractA coupled approach of fluid flow and geomechanics is proposed in this study to quantitatively understand the hydraulic fracturing‐induced poroelastic effects that activate pre‐existing faults and trigger earthquake swarms near Crooked Lake, Alberta. The 3D poroelastic simulation of the seismogenic fault zone is then conducted to characterize the pressure diffusion and stress perturbation that led to fault activation. Results show that the poroelastic effects on the high‐permeable damage zones of a conductive‐barrier fault triggered the sequential activation of the seismogenic fault in the basement and Winterburn Formation. In addition, the high‐permeable damage zones act as conduits for pore pressure diffusion along the fault, whereas the fault core functions as a barrier to prevent crossing flow. The poroelastic effects in terms of pressure diffusion and stress perturbation in response to fluid injection facilitated the fault slip and hence triggered the Mw 3.6 earthquake in the basement formation 40 days after the fracturing operations. Moreover, the mainshock created negative Coulomb failure stress changes, inhibiting further fault slip in the basement formation. Subsequently, the stimulation of another well facilitated poroelastic effects on the fault damage zone in top Winterburn Formation, reactivating the same fault with an Mw 4.1 earthquake 8 days after the initiation of treatments. It is essential to optimize the injection site selection near the existing faults to reduce risks of the induced earthquakes near Crooked Lake.

Seismotectonics of Vlora-Elbasani-Dibra Transversal Fault Zone (Albania): A Review

The Vlora-Elbasani-Dibra transversal fault zone crosses from south-west to northeast the Albanides collision zone starting from Vlora area to the Dumre diapir and continuing from Elbasani Quaternary graben to Dibra area, within the internal Albanides extensional zone. The Vlora-Elbasani-Dibra seismogenic fault zone is expressed by an alignment of important historical and instrumental seismicity with 15 Ms > 6 earthquakes. The Vlora-Berati-Elbasani segment of this fault zone during the year 1851 has been activated along all is length. The geological and neotectonic investigations and the focal mechanism solutions of earthquakes that occurred along the Vlora-Elbasani-Dibra fault zone prove its division into two distinct fault zones: a) the Mali i Kanalit Block - Dumre diapir strike-slip fault zone NNE trending in transpression, and b) the Elbasan-Dibra normal fault zone NE trending in transtension. The Mali i Kanalit Block-Dumre diapir strike-slip zone NNE trending in transpression offsets dextrally and to SW the folds and thrusts of the Çika, Kurveleshi and Berati anticlinal belts of Ionian zone. The Neogene (mainly since Middle Miocene) offset of the Çika, Kurveleshi and Berati anticlinal belts from generally NW-SE trending to near N-S one has led to thrust’s steepening and turning into high-angle strike-slip faults due to NE-SW oblique compression from the Albanides collision zone. The Othoni Island-Dhermi strike-slip fault offsets the dextrally dragged Devolli (to the east of Dumre diapir), Osumi (near to Berati town), and Vjosa (west of Shkoza village) rivers’ valleys formed from the Middle Pleistocene (180,000 years) to historic times. The Othoni Island-Dhermi dextral strike-slip fault, that reaches the maximum velocity of greater than 5 mm/year to the south of it, is the only leading fault that shaped the Mali i Kanalit Block-Dumre diapir dextral strike-slip fault zone. Focal mechanism solutions of earthquakes that occurred on the Mali i Kanalit Block - Dumre diapir dextral strike-slip zone show their generation from strike-slip faults in transpressional motions. Focal mechanism solutions of earthquakes that occurred on the Elbasan-Dibra were generated from normal faults with dextral strike-slip movements.

Possible precursory anomalies in ground water level associated with the Wenchuan Ms 8.0 earthquake in 2008, Sichuan, China

We have examined the water level data from 16 wells in Sichuan province, China, recorded before the Wenchuan Ms8.0 earthquake occurred in 2008. We found that the data of 5 among these wells exhibit possible precursory anomalies, which are respectively named the Chuan No.08 well in Deyang, Chuan No.11 well in Pujiang, Chuan No.13 well in Luzhou, Chuan No.22 well in Qionglai and Beichuan. In time durations, these anomalies are of long-, intermediate- and short-term signals which are primarily distributed on the northeast (NE) trending Longmenshan fault zone as well as the parallel Huayingshan fault zone. It seems that the variations of the well levels on the Huayingshan fault zone imply compression while those on the Longmenshan fault zone reflect extension. These anomalies occurred first in the areas outside the epicenter region of the Wenchuan Ms8.0 earthquake, then migrated to the seismogenic fault zone. And they migrated from southwest to northeast in agreement with the rupture process of the main shock.

Geological and structural setting of the Vinodol Valley (NW Adriatic, Croatia): insights into its tectonic evolution based on structural investigations

The area of the Vinodol Valley and Bakar Bay represents a NW‒SE oriented valley in the NW Adriatic characterised by prominent historical and instrumentally recorded seismicity. As part of the greater geodynamic domain including the Ilirska Bistrica–Rijeka–Senj seismogenic fault zone, new geological and structural data addressing the tectonic evolution of the area were collected in order to better understand the focal mechanisms of previous earthquakes and to enable identification of potential seismogenic sources. Mapped informal lithostratigraphic units mostly correspond to the Upper Cretaceous, Palaeogene and Quaternary successions described in other parts of the External Dinarides. However, a shorter stratigraphic range of the Gornji Humac fm., the youngest Cretaceous unit in the study area, was determined and suggests that the uplifted area in the central NW part of the Adriatic Carbonate Platform already comprised several thousand km2 (from W and NW Istria to Krk and Vinodol area) at the end of the Turonian. Structural measurements of the fault planes in the study area generally correspond to the existing structural model of the tectonic evolution of the Dinarides. However, in contrast to the SW vergences typical of the Dinarides, NE-vergent reverse structures are common, especially along the SW margin of the Vinodol Valley. Cross-cutting relationships suggest that transpressional (NW–SE and NE–SW striking dextral and sinistral faults) and extensional features (NW–SE and NE–SW striking normal faults) are structurally concurrent or younger than the reverse faults, suggesting a change in the palaeostress field during the Neogene–Quaternary, with prevalent transpression and radial extension. Comparison of results of the palaeostress field analysis and the constructed synthetic focal mechanisms on one side, with available focal mechanism solutions for earthquakes within the Ilirska Bistrica–Rijeka–Senj seismogenic fault zone on the other, shows a favourable orientation of the observed NW‒SE and NE‒SW striking faults with respect to the recent compressional/transpressional stress field (N‒S oriented P-axis), indicating these as potential seismogenic sources within the study area.

Pseudotachylyte as field evidence for lower-crustal earthquakes during the intracontinental Petermann Orogeny (Musgrave Block, Central Australia)

Abstract. Geophysical evidence for lower continental crustal earthquakes in almost all collisional orogens is in conflict with the widely accepted notion that rocks, under high grade conditions, should flow rather than fracture. Pseudotachylytes are remnants of frictional melts generated during seismic slip and can therefore be used as an indicator of former seismogenic fault zones. The Fregon Subdomain in Central Australia was deformed under dry sub-eclogitic conditions of 600–700 °C and 1.0–1.2 GPa during the intracontinental Petermann Orogeny (ca. 550 Ma) and contains abundant pseudotachylyte. These pseudotachylytes are commonly foliated, recrystallized, and cross-cut by other pseudotachylytes, reflecting repeated generation during ongoing ductile deformation. This interplay is interpreted as evidence for repeated seismic brittle failure and post- to inter-seismic creep under dry lower-crustal conditions. Thermodynamic modelling of the pseudotachylyte bulk composition gives the same PT conditions of shearing as in surrounding mylonites. We conclude that pseudotachylytes in the Fregon Subdomain are a direct analogue of current seismicity in dry lower continental crust.

Thermal pressurization and fluidization of pulverized cataclastic rocks formed in seismogenic fault zones

Vein networks of pseudotachylytes and ultracataclastic rocks are composed mainly of ultrafine-to fine-grained materials, including fault gouge and microbreccia, and are widely considered indicators of past seismic faulting events. I show that such vein networks of pseudotachylyte with both melt and crush origins, as well as ultracataclastic rocks, form by the rapid injection of ultrafine-to fine-grained material sourced from pulverized ultracataclastic rocks in seismogenic fault zones under thermal pressurization and fluidization during seismic events. The thermal expansion of seismic slip zones caused by frictional heating results in the rapid fluidization of ultrafine-to fine-grained materials along with expanded fluids and gases (e.g., water vapor and melt) that are injected under pressure into fracture void spaces within fault zones in a gas–solid–liquid system during large earthquakes. I propose that the thermal expansion of water vapor and ultrafine-to fine-grained materials caused by frictional heating in the fault slip zone is the main mechanism responsible for the dramatic increase in pore pressure that results in the dynamic coseismic weakening of faults.

Fabric transition with dislocation creep of a carbonate fault zone in the brittle regime

Fabric transition by a switch in the dominant slip system of minerals in the plastic regime can be induced by changes in temperature, strain rate, or water content. We propose here this fabric transition by frictional heating in seismogenic fault zones in the brittle regime. The Garam Thrust in the Taebaeksan Basin of South Korea has a hanging wall of Cambrian dolostone juxtaposed against a footwall of Ordovician limestone and records a minimum displacement of ~120m. In a 10cm thick plastically deformed layer adjacent to the principal slip layer of the fault zone, the lattice preferred orientation of calcite grains suggests that the dominant slip system changes, approaching the principal slip layer, from r 〈02–21〉 and e-twinning, through r 〈02–21〉 and basal 〈a〉, to basal 〈a〉. This fabric transition requires a high temperature-gradient of 40°C/cm, which we infer to result from frictional heating of the seismic fault zone. We suggest that fabric transition within a thin plastically deformed layer adjacent to the principal slip layer of a fault zone indicates an unusually steep temperature gradient and provides strong evidence of seismic slip.

Millennium Recurrence Interval of Morphogenic Earthquakes on the Seismogenic Fault Zone That Triggered the 2016 Mw 7.1 Kumamoto Earthquake, Southwest Japan

Millennium Recurrence Interval of Morphogenic Earthquakes on the Seismogenic Fault Zone That Triggered the 2016 Mw 7.1 Kumamoto Earthquake, Southwest Japan