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A devastating earthquake with moment magnitude 7.5 occurred in the Noto Peninsula in central Japan on 1 January 2024. We estimate the rupture evolution of this earthquake from teleseismic P‐wave data using the potency‐density tensor inversion method, which provides information on the spatiotemporal slip distribution including fault orientations. The results show a long and quiet initial rupture phase that overlaps with regions of preceding earthquake swarms and associated aseismic deformation. The following three major rupture episodes evolve on segmented, differently oriented faults bounded by the initial rupture region. The irregular initial rupture process followed by the multi‐scale rupture growth is considered to be controlled by the preceding seismic and aseismic processes and the geometric complexity of the fault system. Such a discrete rupture scenario, including the triggering of an isolated fault rupture, adds critical inputs on the assessment of strong ground motion and associated damages for future earthquakes. Plain Language Summary: On 1 January 2024, a moment magnitude 7.5 earthquake occurred in the northern Noto Peninsula, Japan. The strong ground motion and tsunami associated with the earthquake caused severe damage to buildings and infrastructure, resulting in at least 245 causalities in the affected areas. The Noto Peninsula is affected by northwest‐southeast compression, and active reverse faults are known along the northern coast of the peninsula and its offshore region. Before the 2024 earthquake, the source region experienced long‐lasting earthquake swarm activity, which is a set of seismic events without an obvious mainshock‐aftershock pattern. Our seismological analysis found that there was a 10‐s‐long initial rupture episode around the hypocenter that overlapped with the earthquake swarm region. The initial rupture was followed by a series of three different rupture episodes on differently oriented fault segments. This earthquake highlights a multi‐scale rupture growth across a segmented fault network after a very quiet initial rupture process that was controlled by the preceding earthquake swarms and associated aseismic deformation related to fluid injection from depth. The rupture process advances our understanding of earthquake source physics and can lead to a better assessment of future earthquake hazards. Key Points: The 2024 Mw 7.5 Noto Peninsula earthquake involves a multi‐segmented rupture sequence on differently oriented faultsThe long and quiet initial rupture domain coincides with the preceding earthquake swarm regionFluid‐induced earthquake swarms and a segmented fault network control the complex earthquake rupture growth [ABSTRACT FROM AUTHOR]

Establishing the absolute age of palaeoearthquakes is of great significance for the assessment of the seismicity and seismic hazards of a region. As such, several different geochronological techniques to date earthquake-related material have been developed to provide answers on the time of past earthquakes. The present study is part of a wider palaeoseismic research project conducted in the Nojima Fault Zone (NFZ), where the 1995 Mw 6.9 Kobe (Japan) earthquake was triggered, to assess the suitability of the isothermal thermoluminescence (ITL) dating technique on fine-grained quartz and medium-grained feldspar and to provide a sequence of ages for fault-rock samples separated from a drilled core that was retrieved from a depth of ~506 m. Our analysis reveals that ITL can produce consistent dating results and can be considered a reliable luminescence technique for the absolute dating of fault-gouge material. The produced ITL ages signified the existence of repeated seismic events within the NFZ that took place through the late Pleistocene period, with gouge ages spanning from 78.6 ± 4.2 to 13.4 ± 1.4 ka; however, overestimation of the produced ITL dating results may be apparent. Nonetheless, even though some degree of overestimation is considered, ITL dating results denote the oldest possible age boundary of formation (or luminescence signal resetting) of the collected fault-gouge layers. [ABSTRACT FROM AUTHOR]

This study summarizes the findings of an attitude survey focused on people's perceptions of seismic hazard maps, which illustrate the risk of an earthquake in each location throughout Japan. These seismic hazard maps depict the likelihood of an earthquake with a seismic intensity of "6 Lower" or more within 30 years, with 3.0% being considered a high possibility. The 3.0% occurrence probability within 30 years can be reworded to 2.0% occurrence probability within 20 years, 0.1% occurrence probability within a year, 4.9% occurrence probability within 50 years, or 39.4% occurrence probability within 500 years when being converted according to a Poisson distribution. In this study, we convert the occurrence probability within 30 years in the seismic hazard maps to obtain that within a year up to that within 1000 years, present the involved risk and demonstrate the yearly probability of the people who see the maps becoming most convinced of the need for countermeasures. Although those are shorter than the occurrence probability within 30 years anyway, it is a characteristic that the peaks existed at the occurrence probability within 10–20 years, not at the occurrence probability within one year or five years. However, the results changed according to the age of the people viewing the maps, and it was when the risk was presented as the occurrence probabilities within 20 and 30 years for the people in their 20–40 s, while it was when the risk was presented the occurrence probabilities within 10 years for the people in their 50–60 s, the perception toward the need of countermeasures increased the most. In addition, regardless of gender and place of residence (coast of the Sea of Japan or the Pacific coast), the perception toward the need of countermeasures peaked at the occurrence probabilities within 10 and 20 years. [ABSTRACT FROM AUTHOR]

In order to reveal the secular deformation evolution and strain accumulation progress along subduction zone, we focus on high-precision Global Navigation Satellite System (GNSS) data processing, GNSS time series analysis and regional spatiotemporal filtering. The GNSS position time series is modeled as a combination of the long-term plate movements, short-term noise and the frequency-dependent variations and tectonic deformation information. Common Mode Errors (CME) is removed and the deformation signals is then extracted from the residual time series by Principal Component Analysis (PCA). Combing the filtered displacement array and the dynamic regional strain array derived from GNSS baseline, a spatiotemporal tectonic evolution map is exhibited obviously. We process the data recorded by GEONET over the 2003–2011 period in middle Japan island and reveal the dynamic evolution of crustal deformation along subduction zone. The results show that the regional reference frame transformation by constraining one site location and one stable GNSS baseline direction can further improve the Signal-to-Noise Ratio (SNR) of GNSS observations. A integrated analysis combining the baseline length with azimuth change can show the crustal motion feature more comprehensively. The observed behaviors agree well with the simulation experiment results of the rock rupture in the laboratory. We divide the pre-seismic deformation into four stages, the stable linear strain accumulation stage, the formation stage of the local locked area, local decoupling stage, and strain release stage. We also give an appropriate dynamical model for the interplate coupling to explain the observed deformation characteristics. Research result provides some of the observational new evidence for inter-seismic deformation anomaly detection and the medium- to longer-term seismic hazard assessments. [ABSTRACT FROM AUTHOR]

Thick sediment layers frequently cover the Japan islands' surface, and their frictional properties significantly affect the shallow slip behavior that occurs during earthquakes. However, laboratory data on the properties of the shallow zone remain limited. We collected tuff breccia samples from deep borehole cores in the Miocene "Green Tuff" formation, a major surface cover, and performed velocity-stepping friction tests on these samples under in situ stresses of 2 to 20 MPa to assess the velocity dependence of their frictional strength. The samples exhibit predominantly frictionally stable, velocity-strengthening behavior over the range of normal stresses tested, which supports the hypothesis that shallow sediment layers are seismically quiescent. This result is consistent with the low seismicity and attenuation of coseismic slip occurring in the shallow zone that is observed during regional earthquakes. Microstructural observations of the postmortem samples using optical and scanning electron microscopes indicate a fabric transition from boundary shear localization to distributed cataclastic flow with increasing normal stress. Our laboratory investigation of the depth-variable distribution of the frictional velocity dependence of a shallow sediment layer would provide further insight into the mechanical role for earthquake rupture dynamics and shallow seismicity. [ABSTRACT FROM AUTHOR]

Green's functions (GFs) for elastic deformation due to unit slip on the fault plane comprise an essential tool for estimating earthquake rupture and underground preparation processes. These estimation results are often applied to generate important information for public such as seismic and tsunami hazard assessments. So, it is important to minimize the distortion of the estimation results on the numerical models used for calculating GFs to guarantee assessment reliability. For this purpose, we here calculated GFs based on a numerical model that is of high fidelity to obtain realistic topography and subsurface structural models of the Earth. We targeted two well-known subduction zones in Japan, the Nankai Trough and the Japan Trench. For these subduction zones, databases for realistic topography and subsurface structural models of the Earth are available in the "Japan integrated velocity structure model version 1", which was proposed for earthquake hazard assessments conducted by the Japanese government. Furthermore, we eliminated the inconsistency in processing calculated GFs and space geodetic observation data for surface displacements, which is often overlooked, by using the same coordinate system. The ellipsoidal shape of the Earth, which is often approximated with a projected plane or a spherical shape, was also incorporated by faithfully following the definitions of the coordinate systems in Geodetic Reference System 1980, which is the global standard for space geodesy. To calculate elastic GFs based on such high-fidelity subduction zone databases with the ellipsoidal shape of the Earth, we introduced the finite element (FE) method. In the FE meshes, the resolution of the topography and subsurface structure is the same as that of the original databases. Recent development of the state-of-the-art computation techniques for the rapid calculation of crustal deformation using large-scale FE models allows for GF calculation based on such a high-fidelity model. However, it is generally not easy to perform such calculations. Thus, we released a library for the GFs calculated with 1-km grid spacing on the ground surface in this study to the geoscience community on a web server, aiming to contribute more reliable seismic and tsunami hazard assessment. [ABSTRACT FROM AUTHOR]

Near‐surface structure is crucial to assessing seismic hazards and understanding earthquakes and surface processes yet is a major challenge to robustly image. Recently, an approach based on body‐wave polarization was introduced for constraining shallow seismic structure, but the depth sensitivity of the polarization measurement has remained unclear. Using waveform simulations based on a layer over a half space, we find that the depth sensitivity of P wave polarization peaks at the surface and decreases abruptly over a depth range shorter than its wavelength. A strong frequency dependence provides constraints on local 1‐D structure, with frequencies between 0.1 and 10 Hz illuminating structure at depths of 10 m to several kilometers. Applying these results to teleseismic recordings in Japan provides constraints on structure at about 120 to 750 m, including a distinctive weak zone along the Median Tectonic Line in the Kii peninsula and Awaji Island. Plain Language Summary: Shallow structure controls the level of ground shaking and hence is critical in assessing seismic hazards. Conventionally, drilling or local seismic surveys are performed to image the near surface, but their high cost has resulted in extremely sparse coverage of studied sites worldwide. Here we demonstrate that the directions of P waves that are naturally generated by local or distant earthquakes constrain the structure immediately below the seismometer where the P waves are recorded. Our finding suggests that frequency‐dependent measurements of P wave directions is a promising tool for studying shallow structure that is noninvasive and cost effective. Application to data recorded in Japan reveals structure at about 120‐ to 750‐m depth, including a weak zone along a segment of the Median Tectonic Line. Key Points: The depth sensitivity of P wave polarization peaks at the surface and becomes negligible at a depth that is shallower than its wavelengthThe frequency content and the near‐surface shear wave speeds are the main factors that determine the depth sensitivityP wave polarization is a useful tool for constraining shallow 1‐D structure from about 10 m to several kilometers at 0.1 to 10 Hz [ABSTRACT FROM AUTHOR]

Strong ground-motion databases used to develop ground-motion prediction equations (GMPEs) and calibrate stochastic simulation models generally include relatively few recordings on what can be considered as engineering rock or hard rock. Ground-motion predictions for such sites are therefore susceptible to uncertainty and bias, which can then propagate into sitespecific hazard and risk estimates. In order to explore this issuewe present a study investigating the prediction of ground motion at rock sites in Japan, where a wide range of recording-site types (from soil to very hard rock) are available for analysis. We employ two approaches: empirical GMPEs and stochastic simulations. The study is undertaken in the context of the PEGASOS Refinement Project (PRP), a Senior Seismic Hazard Analysis Committee (SSHAC) Level 4 probabilistic seismic hazard analysis of Swiss nuclear power plants, commissioned by swissnuclear and running from 2008 to 2013. In order to reduce the impact of site-to-site variability and expand the available data set for rock and hard-rock sites we adjusted Japanese ground-motion data (recorded at sites with 110 m s-1 < Vs30 < 2100 m s-1) to a common hard-rock reference. This was done through deconvolution of: (i) empirically derived amplification functions and (ii) the theoretical 1-D SH amplification between the bedrock and surface. Initial comparison of a Japanese GMPE's predictions with data recorded at rock and hard-rock sites showed systematic overestimation of ground motion. A further investigation of five global GMPEs' prediction residuals as a function of quarter-wavelength velocity showed that they all presented systematic misfit trends, leading to overestimation of median ground motions at rock and hard-rock sites in Japan. In an alternative approach, a stochastic simulation method was tested, allowing the direct incorporation of site-specific Fourier amplification information in forward simulations. We use an adjusted version of the model developed for Switzerland during the PRP. The median simulation prediction at true rock and hard-rock sites (Vs30 > 800 m s-1) was found to be comparable (within expected levels of epistemic uncertainty) to predictions using an empirical GMPE, with reduced residual misfit. As expected, due to including site-specific information in the simulations, the reduction in misfit could be isolated to a reduction in the site-related within-event uncertainty. The results of this study support the use of finite or pseudo-finite fault stochastic simulation methods in estimating strong ground motions in regions of weak and moderate seismicity, such as central and northern Europe. Furthermore, it indicates that weak-motion data has the potential to allow estimation of betweenand within-site variability in ground motion, which is a critical issue in site-specific seismic hazard analysis, particularly for safety critical structures. [ABSTRACT FROM AUTHOR]

In this article, we investigate the challenges in designing a communication network robust against earthquake-induced disasters. Due to the heterogeneity of local geology conditions, an earthquake may cause different devastating effects on network links at different locations. Therefore, the aim of this research was to develop a network design method that, based on actual seismic hazard information, finds appropriate geographical routes for network links under a cost constraint to maximize the robustness of the network. We carried out experiments on local as well as nationwide networks considering many possible earthquake scenarios in Japan. The results suggest that the shortest route is often the optimal route, and, in some cases, long detour routes can significantly reduce the average endto- end disconnection probability compared to the shortest route solutions. This gives a network operator guidelines to design a network that is resilient against earthquake disasters at the lowest possible cost. [ABSTRACT FROM PUBLISHER]

Large earthquakes sometimes trigger local seismicity that is distal to their rupture zones. Various mechanisms for this triggered seismicity have been proposed, based on either the static stress change or ground shaking from seismic waves, but local geological structure is rarely studied to discern why this seismicity is remotely induced. We present the results of a joint three-dimensional resistivity and isotopic analysis of the groundwater system surrounding Mount Fuji, Japan, where increased seismicity was observed following the A.D. 2011 Tohoku- Oki megathrust earthquake. An electrically conductive zone and high concentrations of magmatic gases (He and CO2) correspond to the zone of triggered seismicity. In contrast, a contribution of magmatic water is not suggested from ²H (deuterium, D) and 18O isotope ratios. These results suggest that the earthquakes were triggered within a fractured zone through which magmatic gases preferentially migrated. We hypothesize that the upwelling of gas-rich hydrous fluids and/or gas bubbles occurred along this fracture pathway, causing an increase in the pore pressure and triggering the resultant earthquake sequence. [ABSTRACT FROM AUTHOR]

Kim, K.O., Choi, B.H., Pelinovsky, E. and Jung, K.T., 2013. Three-dimensional simulation of 2011 East Japan-off Pacific coast earthquake tsunami induced vortex flows in the Oarai port. The huge tsunami was generated by the 11 March 2011 off coast of the Pacific side of East Japan, recording a maximum 40 meter run up in Iwate prefecture. The tsunami wave attacked the Oarai port of Ibaraki prefecture within 30 minutes, and created an enormous vortex flow within the harbor. A similar feature was observed in the Imwon port, in the Eastern Korean coast during the 1983 tsunami event in the East (Japan) Sea. A set of simulations have been performed to investigate the generation of the powerful vortex caused by the 2011 tsunami event at the Oarai Port. The application of numerical models has successfully reproduced the formation of the vortex in the center of the port, which can be clearly identified in a photograph taken during the tsunami. The simulation of tsunami generation and propagation at the outer sea is performed with a hydrostatic model and, for the investigation of a more detailed transient pattern of water flows, the model which uses full Reynolds-averaged Navier-Stokes equations is applied. Examination of the Oarai and Imwon vortexes implies that the generation and strength of a vortex due to tsunami wave is strongly related in the size and the shape of port and breakwater layouts. The present work indicates that time-variation the inflow through the mouth of a harbor controls the transient pattern of the vortex. [ABSTRACT FROM AUTHOR]

By using network observation of subionospheric VLF (very low frequency)/LF (low frequency) signals in Japan and in Russia, we have found a significant ionospheric perturbation prior to the recent 2011 March 11 Japan earthquake (EQ) which occurred at sea proximate to the Tohoku area on the main island (Honshu) of Japan was an exceptionally huge plate-type EQ. A remarkable anomaly (with a decrease in the nighttime amplitude and also with enhancement in dispersion) was detected on March 5 and 6 along the propagation path from the NLK (Seattle, USA) transmitter to Chofu (together with Kochi and Kasugai). We also have observed the corresponding VLF anomaly during a prolonged period of March 1 - 6, with minima in the nighttime amplitude on March 3 and 4 along the path from JJI (Miyazaki, Kyushu) to Kamchatka, Russia. This ionospheric perturbation has been discussed extensively with respect to its reliability. (1) How abnormal is this VLF/LF propagation anomaly? (2) What was the temporal evolution of terminator times? (3) Were there any solar-terrestrial effects (especially the effect from geomagnetic storms) on the VLF/LF propagation anomaly? (4) The effect of any other EQs and foreshock activities on the VLF/LF anomaly? (5) Were there any correlations with other related phenomena? Finally, (6) are there any other examples of a VLF/LF propagation anomaly for oceanic EQs? We then compared the temporal properties of ionospheric perturbations for this EQ with those of a huge number of inland EQs and compared the corresponding spatial scale with the former result of the same oceanic 2004 Sumatra EQ with nearly the same magnitude. Finally, the generation mechanism of those seismo-ionospheric perturbations is briefly discussed. [ABSTRACT FROM AUTHOR]

In earthquake hazard assessment studies, the focus is usually on horizontal ground motion. However, records from the 14 June 2008 Iwate-Miyagi earthquake in Japan, a crustal event with a moment magnitude of 6.9, revealed an unprecedented vertical surface acceleration of nearly four times gravity, more than twice its horizontal counterpart. The vertical acceleration was distinctly asymmetric; the waveform envelope was about 1.6 times as large in the upward direction us in the downward direction, which is not explained by existing models of the soil response. We present a simple model of a mass bounding on a trampoline to account for this asymmetry and the large vertical amplitude. The finding of a hitherto-unknown mode of strong ground motion may prompt major progress in near-source shaking assessments. [ABSTRACT FROM AUTHOR]

Presents a study which focused on the development of empirical and analytical fragility curves for bridges using data from the 1995 Hyogo-ken Nanbu earthquake in Kobe, Japan. Methods needed for the development of fragility curves; Estimation of confidence intervals; Development of combined and composite fragility curves.

After a major earthquake, the rapid identification and mapping of co-seismic landslides in the whole affected area is of great significance for emergency rescue and loss assessment of seismic hazards. In recent years, researchers have achieved good results in research on a small scale and single environment characteristics of this issue. However, for the whole earthquake-affected area with large scale and complex environments, the correct rate of extracting co-seismic landslides remains low, and there is no ideal method to solve this problem. In this paper, Planet Satellite images with a spatial resolution of 3 m are used to train a seismic landslide recognition model based on the deep learning method to carry out rapid and automatic extraction of landslides triggered by the 2018 Iburi earthquake, Japan. The study area is about 671.87 km2, of which 60% is used to train the model, and the remaining 40% is used to verify the accuracy of the model. The results show that most of the co-seismic landslides can be identified by this method. In this experiment, the verification precision of the model is 0.7965 and the F1 score is 0.8288. This method can intelligently identify and map landslides triggered by earthquakes from Planet images. It has strong practicability and high accuracy. It can provide assistance for earthquake emergency rescue and rapid disaster assessment. [ABSTRACT FROM AUTHOR]

The earthquake rupture termination mechanism and size of the ruptured area are crucial parameters for earthquake magnitude estimations and seismic hazard assessments. The 2016 Mw 7.0 Kumamoto Earthquake, central Kyushu, Japan, ruptured a 34-km-long area along previously recognized active faults, eastern part of the Futagawa fault zone and northernmost part of the Hinagu fault zone. Many researchers have suggested that a magma chamber under Aso Volcano terminated the eastward rupture. However, the termination mechanism of the southward rupture has remained unclear. Here, we conduct a local seismic tomographic inversion using a dense temporary seismic network to detail the seismic velocity structure around the southern termination of the rupture. The compressional-wave velocity (Vp) results and compressional- to shear-wave velocity (Vp/Vs) structure indicate several E–W- and ENE–WSW-trending zonal anomalies in the upper to middle crust. These zonal anomalies may reflect regional geological structures that follow the same trends as the Oita–Kumamoto Tectonic Line and Usuki–Yatsushiro Tectonic Line. While the 2016 Kumamoto Earthquake rupture mainly propagated through a low-Vp/Vs area (1.62–1.74) along the Hinagu fault zone, the southern termination of the earthquake at the focal depth of the mainshock is adjacent to a 3-km-diameter high-Vp/Vs body. There is a rapid 5-km step in the depth of the seismogenic layer across the E–W-trending velocity boundary between the low- and high-Vp/Vs areas that corresponds well with the Rokkoku Tectonic Line; this geological boundary is the likely cause of the dislocation of the seismogenic layer because it is intruded by serpentinite veins. A possible factor in the southern rupture termination of the 2016 Kumamoto Earthquake is the existence of a high-Vp/Vs body in the direction of southern rupture propagation. The provided details of this inhomogeneous barrier, which are inferred from the seismic velocity structures, may improve future seismic hazard assessments for a complex fault system composed of multiple segments. [ABSTRACT FROM AUTHOR]

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]

In this article the author discusses the prediction of earthquake in Tokai, Japan. He is critical on the seismic and tsunami hazards warnings by the Japanese seismologists, especially Katsuhiko Ishibashi to the nuclear power plants safety. He argues that the government should stop using seismic hazard maps and flawed methods for long-term forecasts and scrap the system for predicting Tokai earthquake. He also suggests repealing the 1978 Large-Scale Earthquake Countermeasures Act (LECA).

The identification of capable faults is crucial for reliable seismic hazard assessments. To identify geochemical signatures characterizing recent, near-surface faulting, we analyzed the mineral and bulk-rock compositions of a range of fault rocks. We compare the compositions of two faults in central Japan that displace the same granitic unit, but record distinct geological histories: the capable Shiraki–Nyu Fault and a minor, incapable fault. Brownish gouge along the Shiraki–Nyu Fault (representing the principal slip surface) records MnO enrichment and FeO depletion and has a positive Ce anomaly, which was likely produced through oxidation reactions. Compositional mapping of outcrop and core samples from the Shiraki–Nyu Fault indicates that compositional changes (Mn- and Fe-oxide and/or oxyhydroxide precipitation along the principal slip surface) were driven by the fault-driven upward migration and oxidation of reduced fluids from depth to the near-surface. Mapping also indicates that Mn-rich gouge (and ultracataclasite) has undergone brecciation due to recent shallow-level faulting. In the Mn-rich gouge, Ce, Ba, and Y may have been enriched through co-precipitation and/or sorption onto the Mn oxide surfaces. Pale gray gouge from the principal slip surface of the minor incapable fault records no oxidation-related chemical changes. However, anastomosing/grid-like fractures filled with dark gray clay, which cut the pale gray gouge yield elevated MnO and Ba concentrations, low FeO concentrations and positive Ce anomalies, as well as high halloysite abundances. These chemical changes are attributed to post-faulting infiltration of oxidized surface water rather than repeated faulting. We show that geochemical analysis, combined with detailed geological observations, can be used to determine the spatial distributions of elements in heterogeneous fault zones, and contribute to the identification of recent, near-surface faulting events. • Chemical changes due to oxidation of upward migrated reduced fluids were detected. • The oxidation reaction prevails along a principal slip surface of a capable fault. • Geochemical analysis for fault rocks can contribute to identifying capable faults. [ABSTRACT FROM AUTHOR]

A probabilistic framework that considers the variability and uncertainty of the ground motions caused by earthquakes and the parameters of the slope material is proposed to assess the seismic stability of rock slopes. A stochastic ground motion simulation method, which reflects certain earthquake scenarios and site characteristics, was used to generate accelerograms as seismic inputs. Then, the probabilities of failure (P f) of the slopes when subjected to earthquake ground motions were computed via Monte-Carlo simulations based on the simulated ground motions and the decoupled Newmark permanent-displacement analysis. An example rock slope was used to illustrate the proposed procedure and verify its rationality. The results showed that the magnitudes of the earthquakes and the source-to-site distances had significant influences on the seismic stability of the slopes. For an earthquake of the same magnitude, the P f of the slope decreased rapidly as the source-to-site distance increased. In addition, given the same source-to-site distance, the P f of the slope increased steadily as the magnitudes of the earthquakes increased. Also, it was found that the influence of coefficient of variation of the slope's shear strength parameters (i.e., c , φ) was not negligible when the uncertainty of earthquakes was not considered. However, it may be overshadowed by the significant influence of a great earthquake, especially when the variability of ground motions is taken into account. The results that were obtained agreed well with observed earthquake-induced landslide phenomena and the statistical data of two typical earthquakes that occurred in Japan and China, which implies that the proposed method is accurate. • A probabilistic approach to assess rock slope seismic stability is proposed. • The uncertainties associated with earthquakes and slope were considered simultaneously. • Influence of earthquake and variability of slope's strength parameters was investigated. • The results agreed well with the observed earthquake-induced landslide phenomena. [ABSTRACT FROM AUTHOR]

Horizontal crustal strain in the Tohoku area during the twentieth century based on triangulation showed N-S extension and E-W contraction was not significant. This feature was one of the reasons why the 2011 Tohoku-oki earthquake was unexpected for many scientists. The first triangulation conducted in the late nineteenth century used a length scale defined by baseline surveys, direct measurements of short (2-10 km) baselines with steel rods. The Shionohara baseline in the Yamagata prefecture was measured in May-July 1894 and the 1894 Shonai (M7.0) earthquake occurred in its western neighbor 3 months after the measurement. The earthquake possibly elongated the baseline by as large as 5 cm or 10 ppm. However, the original length measured before the earthquake was used for the network adjustment of the entire triangulation network, causing extensive underestimation of the length scale of the network as large as 5-10 ppm in northeast Japan. The scale error effect was comparable to tectonic deformation signal over 100 years. The baseline length was re-surveyed in 2012, 1 year after the Tohoku-oki earthquake, and the result is consistent with the hypothesis of scale bias considering interseismic deformation. [ABSTRACT FROM AUTHOR]

The author discusses the need to effectively utilize the tools and geophysical knowledge of the world most particularly for the purpose of earthquake hazard mitigation in response to the 2011 magnitude-9 Tohoku-Oki earthquake devastated Japan. He also stresses the importance of developing a rapid tsunami-warning system that have an access to high-quality data at short distances as well as a method that can determine both the magnitude of the earthquake and the mechanism of faulting.

The article reports on the shortcoming experienced by the extensive earthquake warning system in Japan. It mentions that despite possessing the worlds densest seismometer, warning system and tsunami barriers, it underestimates the range of disaster coverage and damage. Masumi Yamada of Kyoto University states that the problem is attributed to the miscalculation of the point source of the earthquake.

The article discusses the March 11, 2011 Tohoku earthquake in Japan and assessments of further seismic risk in the area. Geological evidence was discovered of a larger earthquake and tsunami striking the coast of Japan in the year 869, strengthening concerns about the likelihood of a megaquake occurring in Japan. Topics include the limits of seismic forecasting, the utility of Japan's earthquake building codes, and the need for better communication between scientists and the public.