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We calculated stress drops for 2875 small intraslab earthquakes at intermediate depths beneath Tohoku, Japan. We applied an S-coda-wave spectral ratio method to almost 900,000 event pairs. Detailed velocity values for the oceanic crust (OC) were adopted from previous observational studies. The median stress drops in the OC are about half those in the oceanic mantle (OM). The median stress drop for earthquakes in the OC decreases from depths of 70 to 120 km and increases from 120 to 170 km. Our preferred interpretation is that the rigidity in the OC decreases and then increases with depth due to combined effects of the dehydration associated with the eclogite formation and the increasing temperature with depth. These depth variations are consistent with results of a similar study beneath Hokkaido. The median stress drops in the oceanic plate beneath Tohoku are generally smaller than those beneath Hokkaido. Previous studies imaging the seismic structure at shallow depths and b-value analyses of intraslab earthquakes indicate that the near-trench region of the oceanic plate off Tohoku is more hydrated than that off Hokkaido. Taken together, these results suggest that differences in the degree of hydration of the oceanic plate in the near-trench regions could produce the different behaviors of stress drops of intermediate-depth earthquakes observed in Tohoku and Hokkaido. [ABSTRACT FROM AUTHOR]

For a more quantitative discussion of slow earthquake activity, we evaluated the detectable limits of very low frequency earthquakes (VLFEs), which are seismic slow earthquakes observed in very low-frequency (< 0.05 Hz) bands in the Nankai subduction zone. We performed numerical simulations using a local 3-D model and used the observed noise level of permanent broad-band seismometers. First, we investigated the effects of the source-time functions on the maximum amplitudes of the VLFE signals at a certain station. The maximum amplitudes of the VLFE signals were controlled by the VLFE moment rate. The detectable limit of VLFEs at each source location can be defined as the lowest moment rate of detectable VLFEs, which radiate signals larger than the noise levels of any component at ≥ 3 stations. For inland seismometers only, the detectable limits of VLFEs at deep (30–40 km) and shallow (≤ 10 km) depths were 1012–1012.3 and 1012.7 N·m s−1, respectively. Due to the geometrical spreading of VLFE signals and large noise levels in horizontal components, offshore seismometers improved the detectability of shallow VLFEs in regions where seismometers were densely deployed. Based on our detectability and published catalogues, shallow slow earthquakes are less active south-southwest off the Kii Peninsula, where geodetic studies expect mechanical coupling. [ABSTRACT FROM AUTHOR]

The catalog of moment tensor solutions, which contains the information on spatial location, origin time and fault mechanism type of earthquakes, has been interpreted by researchers based on a wealth of past knowledge. However, the long-term routine analyses have led to the accumulation of a huge amount of data in the moment tensor catalog, and it is worth considering moving away from the artisanal approach. In this study, using dimensionality reduction of unsupervised machine learning, we performed exploratory data analysis of the moment tensor catalog in Japan to objectively obtain comprehensive images of seismic activity and to acquire knowledge on the spatial and temporal characteristics of the earthquake mechanism. Source parameters of the moment tensor catalog in Japan, spatial location (latitude, longitude, and focal depth) and source-mechanism diagram information were embedded in two-dimensional space via a non-linear graph-based dimensionality-reduction method, Uniform Manifold Approximation and Projection. On the embedding map, earthquakes in eastern and western Japan are distributed separately and are further embedded to reflect their characteristic fault mechanism and focal depth in each region. The similarity degree of the earthquakes can be obtained as the distance on the embedding map. This study demonstrates that the data visualization using dimensionality reduction is useful for intuitively and objectively understanding the regional characteristics of earthquake mechanisms. The embedding map can also be employed to visualize temporal changes in regional seismic activity and to perform a similarity search with a past event. [ABSTRACT FROM AUTHOR]

Cross‐correlation analysis was applied to long‐term onshore broadband records from April 2004 to March 2021 to detect and relocate shallow very low frequency earthquakes (VLFEs) southeast off the Kii Peninsula, along the Nankai Trough, Japan. We then determined the moment rate functions of detected shallow VLFEs using the Monte Carlo‐based simulated annealing method. According to this new comprehensive catalog, shallow VLFEs are widespread beneath the accretionary prism toe, but shallow VLFEs with large cumulative moments are localized around the western edge of the paleo‐Zenisu Ridge, which is subducted beneath southeast off the Kii Peninsula. Our results from the long‐term shallow VLFE catalog are well consistent with previous studies in this region, suggesting that heterogeneous structures and stress conditions due to the subducted paleo‐Zenisu Ridge promote the occurrence of shallow slow earthquakes. The relocated shallow VLFE epicenters illustrated three major episodes characterized by a similar activity area and five minor episodes characterized by different areas. The three major episodes exhibited slow frontal migration with different initiation locations, directions, and speeds, as well as several rapid reverse migrations. Episodes of minor activity were distributed in different locations within part of the area of major activity. Different patterns of shallow VLFE migration could reflect temporal changes in the pore‐fluid distribution or stress conditions of the plate boundary. Plain Language Summary: Our knowledge of the physical characteristics of shallow slow earthquakes, which may provide frictional properties on plate boundaries and preparation processes of large interplate earthquakes, is still limited. Thus, we comprehensively analyzed shallow very low frequency earthquakes (VLFEs) southeast off the Kii Peninsula, in the Nankai subduction zone, where large tsunamigenic earthquakes have repeatedly occurred with intervals of approximately 100–200 yr. We found that shallow VLFEs occurred around the western edge of the subducted oceanic ridge. We considered that this ridge causes complex stress and subsurface structures around the plate boundary and consequently promotes slow earthquake activity. Key Points: We estimated the locations and moment rate functions of shallow very low frequency earthquakes (VLFEs) that occurred near the Nankai TroughLarge cumulative moments of shallow VLFEs were concentrated in the region with the subducted oceanic ridgeThe migration of shallow VLFEs exhibits various patterns in terms of initiation, migration direction, and area [ABSTRACT FROM AUTHOR]

Due to complex 3-D heterogeneous structures, conventional 1-D analysis techniques using onshore seismograms can yield incorrect estimation of earthquake source parameters, especially dip angles and centroid depths of offshore earthquakes. Combining long-term onshore seismic observations and numerical simulations of seismic wave propagation in a 3-D model, we conducted centroid moment tensor (CMT) inversions of earthquakes along the Nankai Trough between April 2004 and August 2019 to evaluate decade-scale seismicity. Green's functions for CMT inversions of earthquakes with moment magnitudes of 4.3–6.5 were evaluated using finite-difference method simulations of seismic wave propagation in the regional 3-D velocity structure model. Significant differences of focal mechanisms and centroid depths between previous 1-D and our 3-D catalogues were found in the solutions of offshore earthquakes. By introducing the 3-D structures of the low-velocity accretionary prism and the Philippine Sea Plate, dip angles and centroid depths for offshore earthquakes were well-constrained. Teleseismic CMT also provides robust solutions, but our regional 3-D CMT could provide better constraints of dip angles. Our 3-D CMT catalogue and published slow earthquake catalogues depicted spatial distributions of slip behaviours on the plate boundary along the Nankai Trough. The regular and slow interplate earthquakes were separately distributed, with these distributions reflecting the heterogeneous distribution of effective strengths along the Nankai Trough plate boundary. By comparing the spatial distribution of seismic slip on the plate boundary with the slip-deficit rate distribution, regions with strong coupling were clearly identified. [ABSTRACT FROM AUTHOR]

The spatiotemporal characteristics of shallow slow earthquake activity are linked to the tectonic environments of shallow plate boundaries. In this work, the spatiotemporal variations of shallow very low frequency earthquake (SVLFE) activity along the Nankai Trough were investigated using a cross‐correlation analysis. The SVLFEs migrated or spread eastward along the strike direction of the trench during large SVLFE episodes. Migrations and clusters of SVLFEs suggest the occurrence of shallow slow slip events. The observed lateral variations in SVLFE activity patterns reflect the heterogeneous distributions of effective strengths at the shallow plate boundary along the Nankai Trough. Migrations and clusters of SVLFEs tended to be concentrated in the regions surrounding the stress accumulation peaks on the Philippine Sea Plate boundary. The stress accumulated in the transitional regions between high‐strength and low‐strength zones can be released by shallow slow earthquakes. Plain Language Summary: Shallow slow earthquakes with rupture speeds between those of regular earthquakes and stable sliding often occur in the shallower extents of expected megathrust rupture zones. Such shallow slow earthquakes are useful for monitoring the slip behavior of shallow plate boundaries. The spatiotemporal variations of shallow slow earthquakes are related to tectonic characteristics including stress accumulation, friction properties, and the presence of pore fluids. To investigate the spatiotemporal variations of shallow slow earthquakes occurring along the Nankai Trough, the activities of shallow very low frequency earthquakes (SVLFEs) were examined using template matching and cross‐correlation relocation analysis. It was found that activity patterns of SVLFEs differed in each analyzed segment due to the different structural characteristics of the shallow Philippine Sea Plate boundary. A detailed spatial distribution revealed that SVLFEs tended to cluster or migrate in the regions surrounding the boundary stress accumulation peaks on the Philippine Sea Plate boundary. The obtained results suggest that shallow slow earthquakes occur and migrate to release accumulated stress in transitional regions between high‐strength (strongly locked) and low‐strength (stable sliding) zones on the shallow plate boundary. Key Points: Matched filter technique revealed details of activity patterns of shallow very low frequency earthquakes (SVLFEs) along the Nankai TroughThe characteristics of SVLFE clusters and migrations reflect frictional properties and possible slow slip events on the plate boundarySVLFEs tended to cluster or migrate in the regions surrounding the shear stress accumulation peaks on the Philippine Sea Plate boundary [ABSTRACT FROM AUTHOR]

The spatial distributions of shallow slow earthquakes are related to stress accumulation and structural characteristics of the shallow plate boundary, which are important for understanding megathrust earthquakes. To investigate spatiotemporal variation of shallow very low frequency earthquake (SVLFE) activity along the Nankai Trough, we conducted centroid moment tensor inversion method incorporating effects of offshore heterogeneous structures. By applying centroid moment tensor method into long‐term onshore seismograms, we obtained spatiotemporal variation of SVLFE activity occurred from June 2003 to May 2018. We find that SVLFE activities are related to the spatial variations of the slip‐deficit rate and pore fluid around the Philippine Sea plate boundary. SVLFEs are effectively activated by mechanical weakening due to rich pore fluid in areas surrounding strongly locked zones. Our results imply that spatial variations of long‐term SVLFE activity provide information on tectonic environments, which could constrain the rupture behavior of shallow plate boundaries during future megathrust earthquakes. Plain Language Summary: The spatial distributions of shallow slow earthquakes are related to stress accumulation and structural characteristics of the shallow plate boundary, which are important for understanding megathrust earthquakes. Despite this importance, conventional methods using onshore seismograms and one‐dimensional Earth models cannot well constrain the location and magnitude of shallow slow earthquakes due to the effects of three‐dimensional (3‐D) offshore subsurface structures. Moreover, offshore observations near hypocenters are still limited. By applying a method incorporating the effects of 3‐D subsurface structures into long‐term onshore seismograms, we show the spatial variations of well‐constrained shallow very low frequency earthquakes (SVLFEs) along the Nankai Trough, including events that occurred prior to offshore observations. We find that SVLFE activities are related to the spatial variations of the slip‐deficit rate and pore fluid around the Philippine Sea plate boundary. SVLFEs are effectively activated by mechanical weakening due to rich pore fluid in areas surrounding strongly locked zones. Our results imply that spatial variations of long‐term SVLFE activity provide information on tectonic environments, which could constrain the rupture behavior of shallow plate boundaries during future megathrust earthquakes. Key Points: We conducted CMT inversions of shallow very low frequency earthquakes (SVLFEs) occurred from June 2003 to May 2018 along the Nankai TroughSpatiotemporal variation of SVLFE activity are related to slip‐deficit rate and pore fluid along the Philippine Sea plate boundarySVLFEs are effectively activated by mechanical weakening due to rich pore fluid in areas surrounding strongly locked zones [ABSTRACT FROM AUTHOR]

Applying deconvolution interferometry technique to surface‐borehole (down to 300 m) seismogram pairs of KiK‐net, we retrieved temporal changes in S wave velocities and polarization anisotropies associated with the 2016 Kumamoto earthquakes, Japan. The average S wave velocity decreased after the largest foreshock (Mw 6.2) and again after the Mw 7.0 mainshock, in the latter case, by as much as 6.4%. The seismic velocity susceptibility (SVS), defined as the ratio of the relative S wave velocity change to the maximum dynamic strain, ranged from −170 to −13. The absolute value of the SVS was larger at the sites near the ocean or covered by an embankment. Systematic changes were not observed for SVSs obtained after the largest foreshock and mainshock. At most sites, the average S wave velocity continued to recover for at least 1 year, proportional to the logarithm of the lapse time after the mainshock. The speed of the log‐time recovery (m‐value) appears to be independent of the maximum dynamic strain of the mainshock. Large m values were observed at the sites of large absolute SVS values, indicating that a more susceptible medium is more resilient. The strength of the S wave polarization anisotropy (anisotropy coefficient) increased by up to 0.8% after the mainshock, which was much smaller than the relative change in the average S wave velocity and was below the background change due to phenomena other than earthquakes. These observations can be explained qualitatively by considering fracture theory in a medium that contains many vertical cracks with randomly oriented polarizations. Key Points: A reduction in shallow subsurface S wave velocity and subsequent recovery were observed after the 2016 Kumamoto earthquakesAt sites near the ocean or covered by an embankment, the S wave velocity reduction was more susceptible to ground motionChanges in the S wave anisotropy coefficient were much smaller than changes in S wave velocity [ABSTRACT FROM AUTHOR]

An M 6.8 ( Mw 6.5) deep-focus earthquake occurred beneath the Bonin Islands at 21:18 (JST) on June 23, 2015. Observed high-frequency (>1 Hz) seismograms across Japan, which contain several sets of P- and S-wave arrivals for the 10 min after the origin time, indicate that moderate-to-large earthquakes occurred sequentially around Japan. Snapshots of the seismic energy propagation illustrate that after one deep-focus earthquake occurred beneath the Sea of Japan, two deep-focus earthquakes occurred sequentially after the first ( Mw 6.5) event beneath the Bonin Islands in the next 4 min. The United States Geological Survey catalog includes three Bonin deep-focus earthquakes with similar hypocenter locations, but their estimated magnitudes are inconsistent with seismograms from across Japan. The maximum-amplitude patterns of the latter two earthquakes were similar to that of the first Bonin earthquake, which indicates similar locations and mechanisms. Furthermore, based on the ratios of the S-wave amplitudes to that of the first event, the magnitudes of the latter events are estimated as M 6.5 ± 0.02 and M 5.8 ± 0.02, respectively. Three magnitude-6-class earthquakes occurred sequentially within 4 min in the Pacific slab at 480 km depth, where complex heterogeneities exist within the slab. [ABSTRACT FROM AUTHOR]

We estimate high-frequency (4-20 Hz) energy release due to the 2016 Kumamoto, Japan, earthquake sequence, within a time period from April 14 to 26 through envelope inversion analysis applied to the Hi-net continuous seismograms. We especially focus on energy releases after each of the April 14 M 6.5 and the April 16 M 7.3 earthquakes. The cumulative energy release from aftershocks of the April 14 event reaches 60% of that from the April 14 event itself by the lapse time of 27 h (pre-April 16 period). On the other hand, the cumulative energy release from aftershocks of the April 16 event reaches only 11 and 13% of that from the April 16 event itself by the lapse times of 27 h and 10 days (post-April 16 period), respectively. This discrepancy in the normalized cumulative energy release (NCER) indicates that the April 14 event was followed by much larger relative aftershock productivity than the April 16 event. Thus, NCER would provide information that reflects relative aftershock productivity and ongoing seismicity pattern after a large earthquake. We also find that the temporal decay of the energy release rate obeys the power law. The exponent p of the power-law decay is estimated to be 1.7-2.1, which is much larger than the typical p value of the Omori-Utsu law: slightly larger than 1. We propose a simple relationship given by p = βp/ b, where p value, b value of the Gutenberg-Richter law, and β value of the magnitude-energy release relationship are combined. [ABSTRACT FROM AUTHOR]

To estimate the seismic velocity changes at different depths associated with a large earthquake, we apply passive image interferometry to two types of seismograms: KiK-net vertical pairs of earthquake records and Hi-net continuous borehole data. We compute the surface/borehole deconvolution waveform (DCW) of seismograms recorded by a KiK-net station and the autocorrelation function (ACF) of ambient noise recorded by a collocated Hi-net station, 26 km from the epicenter of the 2014 Northern Nagano Prefecture earthquake, Japan ( M 6.2). Because the deeper KiK-net sensor and the Hi-net sensor are collocated at 150 m depth, and another KiK-net sensor is located at the surface directly above the borehole sensors, we can measure shallow (<150 m depth) and deep (>150 m depth) velocity changes separately. The sensitivity of the ACF to the velocity changes in the deeper zone is evaluated by a numerical wave propagation simulation. We detect relative velocity changes of −3.1 and −1.4% in the shallow and deep zones, respectively, within 1 week of the mainshock. The relative velocity changes recover to −1.9 and −1.1%, respectively, during the period between 1 week and 4 months after the mainshock. The observed relative velocity reductions can be attributed to dynamic strain changes due to the strong ground motion, rather than static strain changes due to coseismic deformation by the mainshock. The speed of velocity recovery may be faster in the shallow zone than in the deep zone because the recovery speed is controlled by initial damage in the medium. This recovery feature is analogous to the behavior of slow dynamics observed in rock experiments. [ABSTRACT FROM AUTHOR]

Many earthquakes with various types of focal mechanisms occur along the subducting Philippine Sea slab (PHS) beneath southwest Japan, and the hypocentre distribution is quite inhomogeneous. In this region, distinct non-volcanic deep low-frequency tremors are often observed. To clarify the cause of these apparently complicated and peculiar seismic activities, we first construct a detailed configuration of the oceanic Moho (slab Moho) within the PHS based on a receiver function (RF) analysis. To convert the time-domain RFs into their depth-domain equivalents, we adopt a fine-scaled velocity model based on the traveltime tomography. The depth contours of the oceanic Moho exhibit complexities, but the active region of the intraslab earthquakes corresponds well to the oceanic Moho geometry. In the western part of Shikoku, the intraslab seismicity is very high and the focal mechanisms mainly exhibit normal faults with east–west extension axes. Since the PHS is subducting to the west and the dip angle of the slab becomes steep in the western part of this region, the stress field in this region can be attributed to the slab pull induced by the westwards slab subduction. Similar types of focal mechanisms are observed in the Tokai district with a focal depth greater than 35 km. Since the oceanic Moho exhibits a ridge shape in this region, its stress field can be attributed to the slab pull and the effect of slab bending. Shallow earthquakes in the Tokai and eastern Shikoku regions have strike-slip focal mechanisms and their extension axes are parallel to the strike of the oceanic Moho. These focal mechanisms may be influenced by both the oblique subduction of the slab and low slab dip angle. Earthquakes beneath the Kii Peninsula exhibit strike-slip or downdip compression focal mechanisms with east–west compression axes. Since the Moho beneath this peninsula shows a valley shape, compressional stress occurs around the Moho. Moreover, the slab convergence compresses this valley. This also induces the east–west compression field in this region. We have newly confirmed the existence of an aseismic slab beneath the northern part of the Kinki district, central part of Japan. In this aseismic region, the dip direction of the slab is parallel to that of the slab convergence direction. This tendency is observed in the central part of Shikoku, where the slab seismicity is relatively low. These features imply that the intraslab seismicity is constrained by the interaction between the slab geometry and slab motion. We also revealed the possibility that the oceanic Moho beneath not only Ise Bay but also the Kii Channel has a ridge shape. In both these regions, the non-volcanic low-frequency tremor activity becomes low. More than 80 per cent of the tremor epicentres are distributed within contour depths of 38 ± 3 km of the oceanic Moho. We find that the interaction between the Moho geometry and the plate motion of the subducting PHS plays an important role in determining the local stress field and the location of both seismicity and low-frequency tremors. [ABSTRACT FROM AUTHOR]

Abstract: The Philippine Sea plate is subducting under the Eurasian plate beneath the Chugoku-Shikoku region, southwestern Japan. We have constructed depth contours for the continental and oceanic Mohos derived from the velocity structure based on receiver function inversion. Receiver functions were calculated using teleseismic waveforms recorded by the high-density seismograph network in southwestern Japan. In order to determine crustal velocity structure, we first improved the linearized time-domain receiver function inversion method. The continental Moho is relatively shallow (∼30km) at the coastline of the Sea of Japan and at the Seto Inland Sea, and becomes deeper–greater than 40km–around 35°N and 133.8°E. Near the Seto Inland Sea, a low-velocity layer of thickness 10km lies under the continental Moho. This low-velocity layer corresponds to the subducting oceanic crust of the Philippine Sea plate. The oceanic Moho continues to descend from south to northwest and exhibits complicated ridge and valley features. The oceanic Moho runs around 25km beneath the Pacific coast and 45km beneath the Seto Inland Sea, and it extends to at least to 34.5°N. The depth variation of the Moho discontinuities is in good qualitative agreement with the concept of isostasy. From the configurations of both the continental and oceanic Mohos, we demonstrate that the continental lower crust and the subducting oceanic crust overlap beneath the southern and central part of Shikoku and that a mantle wedge may exist beneath the western and eastern part of Shikoku. The southern edge of the overlapping region coincides with the downdip limit of the slip area of a megathrust earthquake. [Copyright &y& Elsevier]

National Research Institute for Earth Science and Disaster Resilience (NIED) integrated the land observation networks established since the 1995 Kobe earthquake with the seafloor observation networks established since the 2011 Tohoku earthquake and tsunami as MOWLAS (Monitoring of Waves on Land and Seafloor) in November 2017. The purpose of MOWLAS is to provide comprehensive, accurate, and rapid observation and monitoring of earthquake, tsunami, and volcano events throughout Japan and its offshore areas. MOWLAS data are widely utilized for long-term earthquake forecasting, the monitoring of current seismic activity, seismic and tsunami hazard assessments, earthquake early warning, tsunami warning, and earthquake engineering, as well as earthquake science. Ocean bottom observations provide an extension of observations to areas where no people are living and have the advantage of increasing lead time of earthquake early warning and tsunami warning. The application of recent technology advancements to real-time observations as well as the processing of MOWLAS data has contributed to the direct disaster mitigation of ongoing earthquakes. These observations are fundamental for both science and disaster resilience, and thus it is necessary to continue ceaseless operation and maintenance. [ABSTRACT FROM AUTHOR]

The southeast offshore Mie earthquake occurred on April 1, 2016 near the rupture area of the 1944 Tonankai earthquake, where seismicity around the interface of the Philippine Sea plate had been very low until this earthquake. Since this earthquake occurred outside of seismic arrays, the focal mechanism and depth were not precisely constrained using a one-dimensional velocity model, as in a conventional approach. We conducted a moment tensor inversion of this earthquake by using a three-dimensional velocity structure model. Before the analysis of observed data, we investigated the effects of offshore heterogeneous structures such as the seawater, accretionary prism, and subducting oceanic plate by using synthetic seismograms in a full three-dimensional model and simpler models. The accretionary prism and subducting oceanic plate play important roles in the moment tensor inversion for offshore earthquakes in the subduction zone. Particularly, the accretionary prism, which controls the excitation and propagation of long-period surface waves around the offshore region, provides better estimations of the centroid depths and focal mechanisms of earthquakes around the Nankai subduction zone. The result of moment tensor inversion for the 2016 southeast offshore Mie earthquake revealed low-angle thrust faulting with a moment magnitude of 5.6. According to geophysical surveys in the Nankai Trough, our results suggest that the rupture of this earthquake occurred on the interface of the Philippine Sea plate, rather than on a mega-splay fault. Detailed comparisons of first-motion polarizations provided additional constraints of the rupture that occurred on the interface of the Philippine Sea plate. [ABSTRACT FROM AUTHOR]

We have generated a high-resolution catalog called the “Japan Unified hIgh-resolution relocated Catalog for Earthquakes” (JUICE), which can be used to evaluate the geometry and seismogenic depth of active faults in Japan. We relocated > 1.1 million hypocenters from the NIED Hi-net catalog for events which occurred between January 2001 and December 2012, to a depth of 40 km. We apply a relative hypocenter determination method to the data in each grid square, in which entire Japan is divided into 1257 grid squares to parallelize the relocation procedure. We used a double-difference method, incorporating cross-correlating differential times as well as catalog differential times. This allows us to resolve, in detail, a seismicity distribution for the entire Japanese Islands. We estimated location uncertainty by a statistical resampling method, using Jackknife samples, and show that the uncertainty can be within 0.37 km in the horizontal and 0.85 km in the vertical direction with a 90% confidence interval for areas with good station coverage. Our seismogenic depth estimate agrees with the lower limit of the hypocenter distribution for a recent earthquake on the Kamishiro fault (2014, Mj 6.7), which suggests that the new catalog should be useful for estimating the size of future earthquakes for inland active faults. [ABSTRACT FROM AUTHOR]