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Earthquake swarms are most commonly composed of small‐magnitude earthquakes. However, a recent study by Yoshida, Uchida, et al. (2023, https://doi.org/10.1029/2023GL106023) analyzed a swarm beneath the Noto Peninsula in Japan that, after more than two years of moderate‐magnitude seismicity, triggered the moment magnitude (Mw) 6.2 Suzu mainshock in May 2023. Based on high‐precision earthquake locations and a slip inversion of the mainshock, these authors found that the Mw 6.2 Suzu earthquake occurred on the updip extension of a fault that was active during the swarm, likely driven by increased fluid pressure. After publication of that paper, a much larger and more destructive Mw 7.5 event occurred nearby on 1 January 2024. These events underscore the potential for swarms to be precursors to large, damaging earthquakes. Forecasting the eventual evolution of swarms is currently very challenging but could be aided in the future by new observations and models. Plain Language Summary: Although earthquake swarms often only contain small earthquakes, occasionally they can trigger large, damaging earthquakes. Yoshida, Uchida, et al. (2023, https://doi.org/10.1029/2023GL106023) examined the triggering of a magnitude 6.2 earthquake in Japan, which caused extensive damage, following two years of smaller earthquakes. This sequence, like many swarms, may have been driven by elevated fluid pressure migrating upwards within the crust. After publication of that paper, a much larger and more destructive Mw 7.5 event occurred nearby. Forecasting the eventual evolution of ongoing swarms is currently very challenging but could be aided in the future by new observations and models. Key Points: Earthquake swarms can be precursors to damaging earthquakes, including the 1 January 2024, Mw 7.5 Noto Peninsula, Japan eventFluid pressure changes often drive swarm activity, and their degree of confinement may influence swarm evolutionDirect observations of fluids in fault zones combined with numerical modeling may aid swarm forecasting in the future [ABSTRACT FROM AUTHOR]

Rupture size is a fundamental earthquake source parameter that is challenging to infer independently from far‐field seismological observations. Here, we develop a novel observational constraint on source size based on the decay rate of wavefield coherence across a seismic array. For a given earthquake, waveform coherence decays with increasing interstation distance or, more precisely, with increasing projection difference defined as the difference between the takeoff vectors associated to the two stations projected along the rupture direction. We find that coherence generally falls off with projection difference faster for earthquakes of larger magnitudes. The magnitude dependence of the coherence decay rate can be explained by a finite source effect: larger source sizes cause larger differences of phase delays between waves arriving from different parts of the rupture at different stations, hence a stronger spatial variability of the wavefield, resulting in a breakdown of waveform coherence. Assuming a 1‐D Haskell's source model, the rupture size can be estimated from the coherence decay rate. We apply this method to USArray data of earthquakes in three subduction zones, the Sea of Okhotsk, South America and Japan. The source sizes inferred from the coherence decay patterns are consistent with scaling relations intermediate between width‐saturated L‐models and quasi equi‐dimensional rupture models. Our observation captures a unique pattern of array waveform coherence and demonstrates the potential of utilizing waveform coherence to study earthquake source parameters. Plain Language Summary: In this paper, we observe that for a given earthquake, the similarity of the waveform (coherence) recorded by stations in a far‐field array decays with increasing interstation distance. The waveform coherence generally falls off with interstation distance faster for earthquakes of larger magnitudes and therefore, larger rupture sizes. We develop a novel method using array waveform coherence to estimate the earthquake rupture size, and apply this method to USArray data of earthquakes in three geological regions: the Sea of Okhotsk, South America and Japan. The source sizes inferred from the coherence decay patterns are consistent with previous studies using different methods. According to our observation, there is a potential to infer earthquake rupture independently from far‐field observations by waveform coherence. Key Points: Waveform coherence decays as a function of interstation distance faster for large earthquakes (Mw > 7)The waveform coherence pattern is governed by earthquake source sizeRupture sizes inferred from waveform coherence satisfy empirical scaling relations [ABSTRACT FROM AUTHOR]

The literature often reports space–time relations between the abnormal variations of different kinds of nonseismological (i.e., geophysical, geochemical, and atmospheric) parameters and the occurrence of earthquakes. The integration of such observations with seismological ones could improve the quality of the seismic hazard assessment in the medium‐short term (months to days). Each considered parameter has, in principle, its capabilities to provide useful (and utilizable) information about seismic processes. Therefore, to define a system based on different observations, the first step is to estimate the informative contribution that each considered parameter could provide. In this paper, we will evaluate the potential of Significant Sequence of Thermal Anomalies (SSTAs). In particular, we adopted the broadly used Robust Satellite Techniques (RST) data analysis methodology to identify SSTAs over 11 years (June 2005 to December 2015) of nighttime satellite images acquired by MTSAT satellites over Japan. Aiming at reducing the false‐positive rate, we introduced and tested an innovative configuration of the RST, which is here presented. We executed a correlation analysis between SSTAs and Japanese earthquakes with MJMA ≥ 6 by applying suitable constraints concerning space, time, and magnitude. The analysis highlights (a) the occurrence of just 29 SSTAs in the 11‐year period of observation, (b) 18 SSTAs (i.e., 62%) occur in an apparent space–time relation to earthquakes, and (c) 13 of them occur before the quake. Results of the random test analysis, based on error diagrams, confirm a noncasual correlation between "RST‐based satellite thermal anomalies" and earthquake occurrences. In particular, for MJMA ≥ 6.5 earthquakes, probability gain is up to better than 4.3 as compared with the random guess. Key Points: We present an innovative version of the Robust Satellite Techniques able to reduce the proliferation of false‐positive thermal anomaliesA noncasual relation between satellite thermal anomalies and MJMA ≥ 6 earthquakes affecting Japan in the time span 2005–2015 was foundMultiparametric approach could accelerate the set‐up of a system for time‐dependent assessment of seismic hazard [ABSTRACT FROM AUTHOR]

Coseismic and postseismic crustal deformations caused by earthquake episodes are important in understanding the mechanisms of these episodes as well as the fault rheology near an epicentral area. Specifically, interferometric synthetic aperture radar (InSAR) and synthetic aperture radar (SAR) pixel tracking can depict high‐resolution crustal deformation fields associated with earthquakes and volcanic activities without installing on‐site observation instruments. In this study, we investigate the coseismic and postseismic near‐fault crustal deformations associated with the 2016 Kumamoto earthquake sequence in southwest Japan using ALOS‐2/PALSAR‐2 (Phased Array‐type L‐band SAR‐2) data. Coseismic three‐dimensional (3‐D) displacement fields inferred from PALSAR‐2 pixel tracking data showed 1.6 m of horizontal displacements and 2 m of subsidence at maximum, despite the mainshock focal mechanism that was dominated by strike‐slip components with N‐S extension axes. The locations of large displacement variations along surface ruptures due to the mainshock were almost identical to a region where infrastructure was damaged, thus implying the generation of strong ground seismic waves. By using conventional InSAR stacking, we inferred two independent quasi‐east‐west and quasi‐vertical displacement fields as cumulative postseismic deformations following the mainshock over a period of about 2 years. The near‐fault postseismic deformation represented complicated displacement characteristics that could not be explained by a single physical process. Deformation signals around Aso volcano were interpreted by the effects of postseismic physical processes as well as geological heterogeneous structures. Plain Language Summary: Coseismic and postseismic crustal deformation fields provide information for inferring slip distributions occurring along a fault, and these data are helpful for understanding the geological characteristics around an epicentral area. By using satellite synthetic aperture radar (SAR) images, we can derive crustal deformation maps with high spatial resolutions and high measurement accuracy without installing on‐site observation instruments. In this paper, we offer coseismic and postseismic crustal deformation maps associated with the 2016 Kumamoto earthquake sequence on Kyushu Island, SW Japan, which were derived using the Japanese SAR satellite ALOS‐2/PALSAR‐2 data. Measurements of displacements along with details on Earth surface ruptures due to earthquakes also allow us to understand the variations in rupture processes along seismogenic faults. Furthermore, comparisons of the spatial and temporal variations of coseismic and postseismic deformations can provide information on the geophysical mechanisms of long‐term deformations following a mainshock. Key Points: PALSAR‐2 pixel tracking and InSAR revealed near‐fault coseismic and postseismic deformations due to the 2016 Kumamoto earthquake sequenceSignificant coseismic displacement variations along the surface ruptures imply complicated fault rupture processes during the mainshockPostseismic deformations can be interpreted by multiple physical processes and geological heterogeneous structures [ABSTRACT FROM AUTHOR]

The three‐dimensional (3‐D) deformation field associated with the 2016 Central Tottori earthquake is retrieved from advanced land observing satellite 2 interferometric synthetic aperture radar (InSAR) observations with four different viewing geometries, that is, ascending/descending tracks and left‐/right‐looking modes. The strain model and variance component estimation (SM, VCE, SM‐VCE) method is exploited and improved to integrate the InSAR observations with different viewing geometries so that the 3‐D deformation field is not affected by the inconsistent coverage of SAR footprints or the gross errors in InSAR observations. The obtained results are consistent with GNSS observations, indicating that the improved SM‐VCE method, known as SM‐RVCE in this paper, is capable of retrieving an accurate and spatially complete 3‐D deformation field for this earthquake. In addition, the precision of the InSAR observations and the estimated 3‐D deformation are quantitatively assessed by the SM‐RVCE method. Finally, on the basis of the estimated 3‐D coseismic deformation, the source parameters of this event are inverted, revealing an asperity with a maximum strike‐parallel slip of ~1.1 m concentrated at depths between 2 and 10 km. The estimated seismic moment is 2.4 × 1018 Nm, which corresponds to a Mw 6.2 event. Key Points: We retrieve the 3‐D deformation field of the 2016 Central Tottori earthquake from left‐ and right‐looking InSAR observationsWe conduct a precision assessment for InSAR observations based on the variance component estimation (VCE) methodWe employ the robust VCE method to mitigate the effects of gross InSAR errors such as unwrapping errors on the 3‐D deformation [ABSTRACT FROM AUTHOR]

The devastating earthquake that struck the City of Kobe on 17 January, 1995, created many critical issues for the government of Japan. The Kobe shock pointedly revealed that both the central and local governments had neglected to develop the administrative skills necessary for managing major disasters. This paper, first, provides brief background information on the Kobe disaster. It is followed by a discussion of the problems of the Self-Defense Forces and its involvement in Japan’s crisis management. The paper then describes the function of executives at a time of crisis. In the final section, the paper outlines subsequent government efforts to improve the quality of crisis control in Japan. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper uses firm-level data to examine how supply chain networks affected the recovery of firms from the Great East Japan Earthquake. Extensive supply chains can negatively affect recovery through higher vulnerability to network disruption and positively through support from trading partners, easier search for new partners, and general benefits of agglomeration. Our results indicate that networks with firms outside of the impacted area contributed to the earlier resumption of production, whereas networks within the region contributed to sales recovery in the medium term. The results suggest that the positive effects of supply chains typically exceed the negative effects. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to propose a new index for the seismic damage estimation of service lines. The proposed index is based on the tension of each service line due to an earthquake event. Because the tension is evaluated using not only the seismic intensity, but also the dynamic properties of the major components of the distribution equipment, including poles, lines, transformers, and service lines, the proposed index makes it possible to quantitatively differentiate the seismic damage level of every distribution pole. Using the records of seismic damage caused by the 2007 Niigata-ken Chuetsu-oki earthquake, the estimation accuracy of the proposed index is compared to that of existing damage indices. It is shown that the proposed index is more suitable than existing indices for equipment damage estimation. © 2012 Wiley Periodicals, Inc. Electron Comm Jpn, 95(9): 17-26, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.11400 [ABSTRACT FROM AUTHOR]

This paper provides a framework for assessing empirical patterns of urban disaster recovery through the use of statistical indicators. Such a framework is needed to develop systematic knowledge on how cities recover from disasters. The proposed framework addresses such issues as defining recovery, filtering out exogenous influences unrelated to the disaster, and making comparisons across disparate areas or events. It is applied to document how Kobe City, Japan, recovered from the catastrophic 1995 earthquake. Findings indicate that while aggregate population regained pre-disaster levels in ten years, population had shifted away from the older urban core. Economic recovery was characterised by a three to four year temporary boost in reconstruction activities, followed by settlement at a level some ten per cent below pre-disaster levels. Other long-term effects included substantial losses of port activity and sectoral shifts toward services and large businesses. These patterns of change and disparity generally accelerated pre-disaster trends. [ABSTRACT FROM AUTHOR]

The Shinanogawa Seismic Belt in the Northern Fossa Magna, Honshu Island, Japan, extends along the Shinano River, bounding the Eurasian Plate and the Okhotsk Plate. The geopressured hydrothermal system occurs widely in the Northern Fossa Magna region. Many destructive earthquakes are related to the activity of this system in the Shinanogawa Seismic Belt. Expulsion of a geopressured hydrothermal system and rising from depth along an active fault triggers the occurrence of an earthquake and opens the fault as a pathway. Anomalous areas in temperature, electrical conductivity and Cl­ concentration of groundwater trend north­east in a linear distribution, and convincingly demonstrate the presence of a buried active fault at the epicentral area of the destructive earthquake in the Shinanogawa Seismic Belt. The distribution of the major axis of the anomalous area in groundwater temperature shows a strong positive relationship with earthquake magnitude, which means that the distribution of this area may indicate the scale of earthquake fault. The linearly anomalous areas in groundwater temperature, resulting from the percolation of a geopressured hydrothermal system, that have no record of previous destructive earthquake are predicted to be areas where destructive earthquakes could occur in the future. Four potential earthquake areas are proposed and discussed in this paper, based on re-examination of active faults and seismicity in the Shinanogawa Seismic Belt. [ABSTRACT FROM AUTHOR]

A magnitude 7.2 earthquake hit one of the major metropolitan areas of Japan at 5:46 am on 17 January 1995. This paper examines the behaviour of public organizations during this event in four municipal governments. Opening and managing shelters, reception of relief goods and cooperation with volunteers are, especially, studied in detail. Some of the programmes implemented by the national government and Hyogo prefectural government are also studied. Based on these studies, characteristics of the organizations' responses during the emergency are analyzed. It is argued that the structure of organizations or the disaster response programmes are formulated or changed by using more stable structures or procedures. [ABSTRACT FROM AUTHOR]