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In this paper, a scalable end-to-end tree boosting system called XGBoost has been applied for predicting the magnitude of an earthquake from the early part of earthquake waveform data. This model uses the features extracted from the early P wave phase of the records as an input. The model's effectiveness has been verified by using data on earthquakes occurring in the Eurasian plate of Japan Islands from 1996 to 2021. Feature engineering has given 29 new features identified from the early P wave phase of the record, which show a high correlation with the magnitude of an earthquake. The comparison of predicted and actual magnitude shows that a trained XGboost model, which uses a single input record for magnitude prediction, gives an average prediction error of 0.004 ± 0.57 for earthquakes in the test dataset. In contrast, the average prediction error of –1.1 ± 0.80 and –0.65 ± 0.69 has been obtained for the magnitude estimated from conventional τc and Pd methods using the same test dataset. It is further seen that the average predicted magnitude of a single earthquake of magnitude 4.5 and 6.1 (MJMA) obtained by using multiple nearfield records using XGBoost model is 4.58 ± 0.33 and 6.32 ± 0.29, which is close to the actual magnitude of the earthquake. The results presented in this paper clearly show that the structured data can be effectively used by complex machine learning or deep learning models to predict earthquake magnitude from single or multiple records. [ABSTRACT FROM AUTHOR]

A cross-region prediction model named SeisEML (an acronym for Seismological Ensemble Machine Learning) has been developed in this paper to predict the peak ground acceleration (PGA) at a given site during an earthquake. The SeisEML model consists of hybridized models, kernel-based algorithms, tree regression algorithms, and regression algorithms. The model ablation study is conducted to examine the performance and the selection of meta-machine learning models in the SeisEML. The training and testing dataset consists of 20852 and 6256 accelerograms recorded by the Kyoshin Network, Japan. The mean absolute error (MAE) and root mean square error (RMSE) have been utilized to compare the predicted peak ground acceleration (PGA) for the test data. The SeisEML model yields approximately half the MAE and RMSE values obtained with conventional attenuation relations. The SeisEML model has been used to compute Japan's iso acceleration contour map of three earthquakes ( M JMA 7.4, 6.6, and 6.1). The qualitative comparison of iso acceleration contours obtained from actual and predicted PGA using SeisEML clearly shows that the model can reliably predict the PGA distribution during an earthquake compared to the regional ground motion prediction equation (GMPE). The cross-region prediction was performed on the datasets of the Iranian earthquakes using SeisEML. The comparison of predicted and observed peak ground acceleration in terms of MAE and RMSE shows that the machine learning model's performance is superior to the regional attenuation relation. The predictions of PGA from the developed ML model indicate that this trained model has the potential for predicting regional and global scenarios with similar tectonic setups. The ML model developed in this paper can considerably enhance the reliability of PGA prediction for seismic hazard mapping of any region and can serve as a reliable substitute for GMPEs. [ABSTRACT FROM AUTHOR]

This paper discusses the relationship between the vertical ground motion and ionospheric disturbances before the Kumamoto earthquake on 16 April 2016, in Kyushu, Japan, using the vertical ground motion measured by slant gauges widely distributed in Kyushu, and the NmF2 observed by ionosondes in Japan and another region. We provide evidence that vertical ground motion excites internal gravity waves (IGWs) that disturb changes in the ionospheric plasma density. From the spectral analysis results of the vertical ground motion data, the summation of various period (frequency) components analyzed from the original data of the slant gauge shows a possible correlation with the change of NmF2 before the earthquake. On the other hand, the influence of the geomagnetic disturbance on vertical ground motion seems to exist. However, we cannot confirm that vertical ground motion is influenced by the geomagnetic disturbance (Kp index) and that the earthquake is triggered by the geomagnetic disturbance. There are two conditions for the vertical ground motion to disturb variations in the ionospheric plasma density: (1) The effective vertical ground motion period should be shorter than 5 h. In addition, (2) vertical ground motion should continue to exist so that wave energy can be continuously injected into the atmosphere. A possible mechanism with which to modify the ionosphere is discussed. The results of this study can provide a basis for the future ionospheric precursors of earthquakes by using the vertical ground motion. [ABSTRACT FROM AUTHOR]

The motivation of this study stems from a retaining wall made of waste tires. The wall did not suffer any earthquake or tsunami-induced damage during the 2011 Off the Pacific Coast of Tohoku Earthquake, Japan. This paper deals with a case study on this tire retaining wall. Results from a series of field and laboratory investigations are first described. A numerical simulation is also described in which whole tires were used as protective layers in an embankment. The results show that confining effect of each tire, friction between the tires, ductility, and damping inherent in tires contribute towards the excellent performance of the retaining wall during the earthquake loading. The case study also reveals that it is the isolation mechanism due to the vibration absorption capability of rubber particles in tires, which could protect tire retaining structure during the earthquake. [ABSTRACT FROM AUTHOR]

Real‐time tsunami prediction is necessary for tsunami forecasting. Although tsunami forecasting based on a precomputed tsunami simulation database is fast, it is difficult to respond to earthquakes that are not in the database. As the computation speed increases, various alternatives based on physics‐based models have been proposed. However, physics‐based models still require several minutes to simulate tsunamis and can have numerical stability issues that potentially make them unreliable for use in forecasting—particularly in the case of near‐field tsunamis. This paper presents a data‐driven model called the tsunami runup response function for finite faults (TRRF‐FF) model that can predict alongshore near‐field tsunami runup distribution from heterogeneous earthquake slip distribution in less than a second. Once the TRRF‐FF model is trained and calibrated based on a discrete set of tsunami simulations, the TRRF‐FF model can predict alongshore tsunami runup distribution from any combination of finite fault parameters. The TRRF‐FF model treats the leading‐order contribution and the residual part of the alongshore tsunami runup distribution separately. The interaction between finite faults is modeled based on the leading‐order alongshore tsunami runup distribution. We validated the TRRF‐FF modeling approach with more than 200 synthetic tsunami scenarios in eastern Japan. We further explored the performance of the TRRF‐FF model by applying it to the 2011 Tohoku (Japan) tsunami event. The results show that the TRRF‐FF model is more flexible, occupies much less storage space than a precomputed tsunami simulation database, and is more rapid and reliable than real‐time physics‐based numerical simulation. Plain Language Summary: Timely tsunami warning is important to save lives and property. Existing physics‐based models require a lot of time to predict tsunamis. For this reason, many countries rely on a precomputed tsunami simulation database for tsunami warning. However, such databases do not include all possible tsunami scenarios, because in the real world there is almost an infinite number of possible tsunamigenic‐earthquakes. The present study introduces a new data‐driven model that can rapidly predict the maximum onshore tsunami height along the coast from the earthquake information. Once the model is trained based on physics‐based model simulations, the new model can be applied to any possible tsunami scenario. This new model captures the leading‐order contribution and the residual part of the alongshore tsunami runup distribution separately. This new model can account for complex large earthquakes with different land movements depending on location. We tested this new model using artificial earthquake scenarios as well as the historic Japan earthquake from 2011. The results show that the new model can handle wider variety of scenarios than the traditional database approach, and the new model takes up less storage space. Moreover, the new model is more rapid and reliable than a physics‐based model. Key Points: A rapid data‐driven model is proposed that can predict tsunami runup distribution from heterogeneous earthquake slip distributionThe data‐driven model is validated based on synthetic tsunami scenarios and the 2011 Tohoku tsunamiThis model has potential for supporting real‐time tsunami forecasting [ABSTRACT FROM AUTHOR]

Japan has an established tradition of museums commemorating its long history of disasters, which memorialize lives lost and convey the scientific mechanisms of natural hazards, disaster history, and people's experiences during and after disasters. The first part of this paper provides an overview of seven modern disaster museums in Japan established before 3.11, starting from the museum of the 1923 Great Kanto Earthquake. These seven museums commemorate disasters of different types, time, and scales of damages. Considering their shared commonalities and individual characteristics, it describes the components and approaches of exhibits that these museums use to convey experiences and stories of disasters, passing on local knowledge toward future disaster risk reduction. The second part of the paper provides an overview of new museums and exhibit facilities established to commemorate the 3.11 Great East Japan Earthquake, tsunami, and nuclear disaster of March 11, 2011. The scale of the devastation of 3.11, as well as an explosion of interest and support for activities of memorialization, documentation, and exhibition, has resulted in a variety and decentralization of new museums and exhibit spaces throughout the area affected by the 3.11 disaster. Spanning various combinations and types of exhibit facilities, this paper concludes by considering emergent trends compared to pre-3.11 disaster museums and potential future developments. [ABSTRACT FROM AUTHOR]

Coastal regions around the Pacific Ring of Fire share the risk of massive earthquakes and tsunamis. Along with their own political-economic, cultural and biophysical contexts, each region has their own history and experiences of tsunami disasters. Coastal areas of Washington State in the U.S. are currently at risk of experiencing a tsunami following a massive Magnitude 9 (M9) earthquake anticipated in the Cascadia Subduction Zone (CSZ). Looking ahead to consider adaptive planning in advance of a tsunami following this M9 event, this paper explores how lessons from recent megaquake- and tsunami-related experiences of risk-based planning and relocation in coastal areas of Japan and Chile could inform anticipatory action in coastal Washington State. Based on a comparison of earthquake and tsunami hazards, social factors, and the roles of government, this paper outlines a framework to compare policy contexts of tsunami risk-based planning and relocation in three Ring of Fire countries, including factors shaping the possible transfer of approaches between them. Findings suggest some aspects of comparative significance and commonalities shared across coastal communities in the three countries and at the same time highlight numerous differences in governance and policies related to planning and relocation. Although there are limitations to the transferability of lessons in disaster adaptive planning and anticipatory action from one national/regional context to another, we believe there is much more that Washington and the Pacific Northwest can learn from Japanese and Chilean experiences. In any context, risk reduction policies and actions need to garner political support in order to be implemented. Additional case study research and detailed analysis is still needed to understand specific lessons that may be applied to detailed risk-based planning and relocation programs across these different national contexts. [ABSTRACT FROM AUTHOR]

This paper examines the effects of the 2012 revisions to the damage predictions of an anticipated Nankai Trough megathrust earthquake on subsequent inter-municipality migration in Japan's coastal areas. We find that an increase in predicted tsunami height—rather than anticipated seismic movements—after the 2012 revision is associated with a subsequent reduction in net migration. While the reducing effect of tsunami predictions on in-migration persisted throughout the study period, the effect on out-migration was only temporary. Moreover, working-age people are more likely to respond to tsunami risk and avoid moving to municipalities with a high tsunami risk after the revisions. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of the Great Hanshin-Awaji earthquake on plant input, output, total factor productivity (TFP) and exit using Japanese plant-level manufacturing data. We employ the difference-in-differences (DID) estimation method to identify the effects of the quake and find that the quake had an impact on manufacturing. The results suggest that production was influenced by the quake, particularly in the first year after the quake. Furthermore, the quake did not influence manufacturing industries uniformly. The effects are different based on specifications, variables, and industries. However, the quake had little impact on the exit of plants. [ABSTRACT FROM AUTHOR]

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Copyright of Regional Science Policy & Practice is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The 2007 Chuetsu Oki earthquake (M = 6.6) triggered more than one hundred slope failures in the northwest part of Niigata prefecture, Japan. A reconnaissance survey conducted by the authors revealed that although most of the failures were only a few meters deep, they still caused significant damage to roads, railways, and houses. It was also found that a vast number of shallow slides were concentrated along the coastal line of the Japan Sea, while only few, but relatively larger failures occurred in a mountainous part of the study area, which is located in a considerable distance from the earthquake's epicenter. This paper summarizes the reconnaissance observations, describes the geologic characteristics of the area covered by landslides, provides characterization of major types of the landslides, and examines the causes and mechanisms of typical failures. In addition, this paper seeks to investigate the mechanism of the Ohzumi landslide, the largest slide triggered by the Chuetsu Oki earthquake. For this purpose, a comprehensive analysis that included field investigation and laboratory testing of soils samples was performed. Results of field investigation suggested that the failure plane of the Ohzumi landslide formed in a saturated layer of sandy soil near a boundary with bedrock. Data from undrained cyclic loading triaxial compression tests indicated that the sandy material was highly susceptible to generation of high excess pore-water pressures during earthquake loading. On the basis of the obtained results and the outcome of seismic response and slope stability analyses, the authors posited an explanation on the mechanism of the Ohzumi landslide. [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]

This paper discusses the origins of torsion and its effect on the response of structures with a focus on the contribution of experimental data. The fact that torsion increases the stresses in structures, augmenting strain and damage during earthquakes, was confirmed in the 1960s. Over the years, the torsional response of structures has mainly been analysed through numerical studies, because few buildings are equipped with translational sensors, and even fewer are equipped with rotational sensors. This is likely to change as building instrumentation becomes more widespread and new generations of rotational sensors are developed. Therefore, this paper focusses on a number of scientific questions concerning the rotational response of structures during earthquakes and the contribution of experimental data to the understanding of this phenomenon. [ABSTRACT FROM AUTHOR]

To create effective risk mitigation policies and improve risk communications, it is important to understand how individuals perceive ambiguity about certain risks. A significant number of studies have demonstrated that an individual's behavior is sensitive to ambiguity. Therefore, this study explores how Japanese homeowners perceive ambiguity about earthquake and house destruction risks by focusing on two research questions: (1) To what degree do people perceive ambiguity? and (2) What are the factors that affect the degree of perceived ambiguity? We administered a survey to 1200 homeowners in Japan. Respondents were asked to state their subjective probabilities and ambiguities about earthquake and house destruction risks. Next, we examined the socioeconomic characteristics affecting their perceived ambiguities by applying a sample selection model. The findings reveal four aspects related to ambiguity. First, some homeowners perceived considerable ambiguity, while the majority observed small degrees of it. Second, on average, homeowners perceived less ambiguity about house destruction risk compared to earthquake risk. Third, socioeconomic characteristics and house attributes had an effect on the perception of ambiguity. Finally, from the perspective of creating policies that mitigate house destruction risks due to earthquakes, seismic diagnoses can help correct subjective risks and reduce the perceived ambiguity regarding them. [ABSTRACT FROM AUTHOR]

Conveying a comparative approach, with both cultural and technical elements, of earthquake management in Japan and Romania, this paper engages in channelling the existing global discussion around this natural disaster towards an understanding of discrepancies. Based on the available literature on social and technical dynamics of earthquakes, as well as on our own surveys and fieldwork experiences on earthquake representation and education carried out from 2012 in Romania and Japan, we argue that, whereas safe infrastructure represents an important financial effort for a developing country, education could be easily improved. [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 seismic catastrophe in Japan was forecasted far ahead of time by scientists from the Russian Academy of Sciences. The most reliable forecast was made by A.A. Lyubushin, a leading researcher at the Schmidt Institute of Physics of the Earth. Over the 2008-2010 period, at a number of the most important international conferences, including that of the Seismological Society of Japan, Lyubushin warned that an earthquake with a magnitude of 8.5-9.0 could occur in Japan; it was published in English in leading scientific journals all over the world. On April 26, 2010, Lyubushin officially informed the Russian Advisory Council on Earthquake Prediction and Seismic Hazard Assessment of his forecast. One distinctive feature of this forecast is that it is based on large bodies of data on microseismic oscillations for the territory of Japan, which were mathematically treated using present-day methods. This forecast has a reliable physical justification and a visual interpretation. Brief information on the results of other Russian studies on the precursors of the main shock and aftershocks of the earthquake of March 11, 2011, in Japan is given. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to: explore major and potential challenges facing healthcare facilities operation specifically those related to utility supplies; and quantify the impact of utility supplies interruption on the operation of healthcare facilities through the development of an estimation model. Design/methodology/approach – A pluralistic qualitative and quantitative research approach benefiting from an online computer program that applies the discriminant function analysis approach. Information was collected from 66 hospitals following three major earthquakes that struck northeast Japan in 2003. Findings – Analysis demonstrated that healthcare utilities face three major challenges: vulnerability of infrastructure to natural hazards; low performance of alternative sources; and lack of consideration of healthcare utility supplies in resilience codes and legislations. The study also proposed a method to estimate the impact of utility interruption of healthcare facilities. A model has been developed for the case study hospitals in Northern Japan following three major earthquakes in 2003. Practical implications – The findings are expected to raise the awareness of the critical role utilities play for the operation of healthcare facilities which will potentially lead to upgrading resilience codes and legislations. The findings are also expected to pool the literature with more information about the resilience of healthcare utility publications. Originality/value – The topic and issues discussed in this research are original based on authors’ investigations following three major earthquakes that took place in northeast Japan. The study followed a statistical approach in addressing the inter-relationship between the utility systems post disasters to develop an innovative unique index to predict the impact of utility shortage on healthcare. [ABSTRACT FROM AUTHOR]

In the spring of 2011, Japan was struck by a massive earthquake and tsunami that brought in its wake devastation and a severe threat of a nuclear crisis. The threat of this crisis took the world by storm because it had implications not only for the people of Japan but for other parts of the world. This paper analyzes how an US-based online news source, CNN.com and a Japan-based online news source, Asahi.com, framed the 3/11 disaster. This comparative analysis of how online news sources from two parts of the world covered the crisis offers a unique understanding of how culture and medium might impact reporting of an environmental crisis that happened locally but had global implications. An examination of loss, threat, cause, responsibility and solution frames of the CNN.com and Asahi.com coverage documented that while both outlets were similar in how they stressed the responsibility and solution frames, CNN.com talked significantly more about the threat frame compared to Asahi.com. Similarly, Asahi.com talked significantly more about the cause and loss frames than CNN.com. Through its findings, this paper offers insights into cross-cultural crises framing by online sources and expands the literature on media framing of environmental crises. [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]

Copyright of Tecnura is the property of Tecnura and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To clarify the relationship between earthquakes and electrical phenomena, signals of three parameters were observed continuously at Sennan in Akita Prefecture, Japan: ground acceleration (GAC), earth potential difference (EPD), and electrostatic field in the atmosphere (EFA). A large metal plate was used as an electrostatic antenna to observe EFA variation. For this paper, we used the digital natural observation (D-NOB) method as a signal processing technique and found clear EPD and EFA waveforms during seismic wave propagation. Our observation and examination results show that GAC causes EPD variation. Subsequently, the EPD variation induces EFA variation. [ABSTRACT FROM AUTHOR]

During the Great Kanto Earthquake, fire ravaged the city beyond its firefighting capabilities at that time. This also applies to contemporary society. Today, as Japan is facing a declining birthrate and an aging population, resources for public assistance-led disaster prevention measures are also dwindling. We have experienced the limitations of public-assistance-led disaster reduction measures for numerous disasters; for example, the Great East Japan Earthquake. Following the background, in recent years, the concept of "phase-free" has attracted the consideration as a means of preparing for disasters that exceed the scope of our corresponding range. The purpose of this study was to formulate a process of disseminating disaster prevention education that is effective in terms of both children's learning ability and disaster preparedness through an analysis of a case study on the application of the phase-free concept (PFC) to school disaster prevention education. In PFC, disaster prevention and mitigation considerations are integrated into daily life. In Japan, several companies and local governments have begun to implement this concept. This study is based on a case study of phase-free efforts in school disaster prevention education in Naruto City, Japan. Through qualitative surveys conducted from the stakeholders, this research is focused to answer the question "Why was the PFC able to spread in actual schools throughout Naruto City?" These findings indicate that the PFC helps explain Naruto City's proactive approach to disaster management as well as explains actors' dynamic participation in phase-free activities. Furthermore, the research findings suggest that the term "phase-free" has become a marker of the perception of quality (Merkmal in German) in disaster prevention that promotes collaboration among diverse stakeholders. [ABSTRACT FROM AUTHOR]

Many buildings in Japan currently have a base-isolation system with a low stiffness that is designed to shift the natural frequency of the building below the frequencies of the ground motion due to earthquakes. However, the ground motion observed during the 2011 Tohoku earthquake contained strong long-period waves that lasted for a record length of 3 min. To provide a novel and better solution against the long-period waves while maintaining the performance of the standard isolation range, the exploitation of the characteristics of nonlinear damping is proposed in this paper. This is motivated by previous studies of the authors, which have demonstrated that nonlinear damping can achieve desired performance over both low and high frequency regions and the optimal nonlinear damping force can be realized by closed loop controlled semi-active dampers. Simulation results have shown strong vibration isolation performance on a building model with identified parameters and have indicated that nonlinear damping can achieve low acceleration transmissibilities round the structural natural frequency as well as the higher ground motion frequencies that have been frequently observed during most earthquakes in Japan. In addition, physical building model based laboratory experiments are also conducted, The results demonstrate the advantages of the proposed nonlinear damping technologies over both traditional linear damping and more advanced Linear-Quadratic Gaussian (LQG) feedback control which have been used in practice to address building isolation system design and implementation problems. In comparison with the tuned-mass damper and other active control methods, the proposed solution offers a more pragmatic, low-cost, robust and effective alternative that can be readily installed into the base-isolation system of most buildings. [ABSTRACT FROM AUTHOR]

• Curie point depth analysis by magnetic data reveals thermal structure of the Japanese islands. • The map of Curie depth was upgraded from the previous hand-writing map to a digital map. • Drillhole data provides local temperature data, while the map of Curie depth provides regional thermal structure. • It may be possible to estimate heat sources by combining Curie depths, drillhole data, and seismic data. This paper shows results of Curie point depth (CPD) analysis of the Japanese Islands using magnetic data. The analysis method is Bouligand et al. (2009) based on fractal theory. This analysis result was combined with the cutoff depth of ordinary earthquakes, low frequency earthquakes and drillhole data. CPD by magnetic data (Dcmag) performed in the case of 50 km window size ranges 6–9 km deep in volcanic areas and is deeper than 9 km in non-volcanic areas. The results are concordant with the previous study by Okubo et al. (1989). Cutoff depths calculated by JMA unified catalog are 10 km or shallower in the volcanic area, deeper than 20 km in the forearc side and concordant with Dcmags. Dcmags across the Kakkonda GP gradually become shallower from 6.8 km west Akita-Komagatake toward to 4.6 km near Iwate volcano. The depth-to-temperature curves from drillhole database around the Kakkonda GP show that thermal gradients between Iwate volcano and the Kakkonda GP range 0.157 - 0.222 K/m. Assuming that these thermal gradients continue from the bottom of hole to the deeper part, the depths reaching 580 °C (Dchole) are determined. Dchole is concordant with Dcmag in the west side of the Kakkonda GP and much shallower than Dcmag in the east side. This suggests that Dcmags may miss to delineate a local high temperature area smaller than 50 km square in the east because of the average effect of CPD analysis. Dchole is shallower than 3 km west Iwate volcano and deepens at about 5 km west the Kakkonda GP. Combining the low frequency earthquakes data from the JMA unified earthquake catalog and the drillhole data of the Kakkonda geothermal field, we find the Curie point depths are consistent with those data. [ABSTRACT FROM AUTHOR]

A numerical model of the influence of a strong earthquake on disturbances to the geomagnetic field is proposed. The impact on the epicentral region of the Earth's ionosphere of wave atmospheric disturbances caused by a seismic event is considered as the main mechanism of the magnetic effect. The estimates made on the basis of the proposed model using the example of a strong earthquake on March 11, 2011 (Japan, M = 9.1), are consistent with the results of instrumental observations. [ABSTRACT FROM AUTHOR]

As of mid-2014, the main organizations of the earthquake (EQ hereafter) prediction program, including the Seismological Society of Japan (SSJ), the MEXT Headquarters for EQ Research Promotion, hold the official position that they neither can nor want to make any short-term prediction. It is an extraordinary stance of responsible authorities when the nation, after the devastating 2011 M9 Tohoku EQ, most urgently needs whatever information that may exist on forthcoming EQs. Japan’s national project for EQ prediction started in 1965, but it has made no success. The main reason for no success is the failure to capture precursors. After the 1995 Kobe disaster, the project decided to give up short-term prediction and this stance has been further fortified by the 2011 M9 Tohoku Mega-quake. This paper tries to explain how this situation came about and suggest that it may in fact be a legitimate one which should have come a long time ago. Actually, substantial positive changes are taking place now. Some promising signs are arising even from cooperation of researchers with private sectors and there is a move to establish an “EQ Prediction Society of Japan”. From now on, maintaining the high scientific standards in EQ prediction will be of crucial importance. [ABSTRACT FROM AUTHOR]

The causes for forearc basin and megathrust rupture zone segmentation are controversial. The Nankai forearc, Japan, is separated into five domains based on topography: Enshu, Kumano, Muroto, Tosa, and Hyuga. The boundaries of these domains correspond to the rupture limits of large earthquakes. We examined the geologic structure of the boundary region between the Kumano and Muroto domains off the Kii Peninsula using multichannel seismic reflection data to evaluate the role of upper plate composition in controlling segmentation. The results suggest that thick cover sediments and underlying accretionary prism are obliquely thrust landward over the igneous basement complex rock in the region of offshore of Cape Shionomisaki and separate the forearc basin. The igneous basement complex rocks directly overlying the plate interface in the hypocentral regions of 1944 Tonankai and 1946 Nankai earthquakes. The 1944 earthquake originated at the base of the complex, and the rupture extent slipped past its basement boundary, whereas the 1946 event nucleated at the updip boundary of the basement complex. The dense igneous rocks might have worked as a heavily loaded barrier on the seismogenic megathrust and separated the rupture area of both the earthquakes. Upper plate geology may be an important factor in controlling seismogenesis in the Nankai Trough and may serve as an example for understanding the controls on megathrust slip in other subduction zones. Plain Language Summary: The Nankai Trough, Japan is the place where quakes nucleate in the margin and tsunamis repeatedly devastated circum‐Pacific societies. When, where, why, and how the quakes were started in the trench is a central scientific question but unsolved. The historical records of earthquakes suggest that the rupture started around Cape Shionomisaki of the Kii Peninsula, where there is also a topographic segment boundary of the ∼2,000 m deep basin in the middle continental slope. Our research of the geologic structure beneath the earthquake epicenters indicates a dense and hard rock mass situated upon the hypocenters of 1944, and 1946 megaquakes off Cape Shionomisaki. The rock mass might have worked as a heavy load and barrier on the low angle dipping plate boundary fault when the fault slipped the large rupture was propagated in the Nankai Trough. Key Points: The Nankai forearc basin is separated off the Kii Peninsula owing to the existence of middle Miocene igneous basement in the upper plateThe rupture areas of the 1944 Tonankai, 1946 Nankai, and 2016 off‐Mie earthquakes appear to be controlled by the igneous basementThe shallow distribution of very low‐frequency earthquakes and tremors are related to the geological heterogeneity of the upper plate [ABSTRACT FROM AUTHOR]

Electromagnetic emissions (EMEs) associated with earthquake (EQ) epicenters are found to be one of the most reliable phenomena for the short-term pre-seismic mechanism of earthquakes. The detection mechanism of such emissions can have both direct and indirect techniques. In this manuscript, we attempted to present the signature of such emissions before two strong EQs, one in Fukushima on November 21, 2016, and another in Kumamoto on April 15, 2016, in Japan. We use the lithospheric emission in the range of ultra-low frequency (ULF) waves as observed from the Kakioka observatory in Japan for direct measurement. For the indirect investigation, we use the concept of energetic particle precipitation in the inner radiation belt due to wave–particle interaction through the pitch angle scattering processes. We use the particle enhancement (electron and proton) observed from the space-based National Oceanic and Atmospheric Administration (NOAA) satellites. The ULF results found an abnormal increase in lithospheric radiation for Kumamoto and Fukushima EQs on three days and ten days before the EQs, respectively, and an ionospheric depression on six days before both the cases. The satellite observations related to the EMEs from these EQs exhibit electron particle bursts (PB) on the day of the Fukushima EQ. We observe particle bursts 4–5 and 10 days before the mainshock for the Kumamoto EQ. We are not found any proton precipitation for the Fukushima EQ where signatures of proton count number are observed for the Kumamoto EQ. This type of simultaneous observation from the ground and satellite-based instruments establishes that EMEs are observed before the EQs and can be a potential candidate for short-term precursory studies. [ABSTRACT FROM AUTHOR]

Damage and performance of railway bridge structures during the 2011 Tōhoku Earthquake are reported. Although the scale of the earthquake was historically the largest known, seismic damage to structures was smaller and less time was required for recovery of service compared with an earlier major earthquake. Upgrading of seismic code and planned seismic retrofits performed after the 1995 Kobe Earthquake were found effective for reducing seismic damage to bridges and civil structures; damage to bridge superstructure, with complex geometry and damage to secondary structural systems such as electric-power poles, now became the prominent type. Enormous structural damage observed for areas affected by severe tsunami forces (which had offered great challenge to structural engineering) is also reported. Following this, bridge performance (under the force of the 2011 Tōhoku earthquake and subsequent tsunami) is studied using data recorded by monitoring systems installed on bridges that were located in strong motion areas. Based on this experience, advantages of and challenges to the structural health monitoring system are also discussed. [ABSTRACT FROM AUTHOR]

Abstract: The key point of this paper is that for the first time we successfully observed “co-rupturing” Earth''s magnetic field changes due to the piezomagnetic effect caused by earthquake rupturing. Electromagnetic changes associated with earthquakes have been investigated previously. Most of them are “coseismic” step-like offsets in the geomagnetic field, which are regarded as the piezomagnetic effect caused by the total static stress changes resulting from an earthquake. Proton precession magnetometers have so far been mainly used to detect seismomagnetic effects, for which the measurement interval was usually 1 or 10min and the measurement accuracy was 0.1nT. For seismomagnetic observations we employed flux-gate magnetometers whose specifications are the measurement with accuracy of 0.01nT and with the sampling interval of 0.5 or 1s. By virtue of such highly sensitive magnetometers, we show observations of magnetic signals accompanying fault movement. Our observation site happened to be situated at an epicentral distance of 26km from the 2008 Iwate-Miyagi Nairiku earthquake of M 7.2, in NE Japan. Magnetic field components began to change almost simultaneously with the onset of the earthquake rupture and grew non-linearly until the first P wave arrival. Such magnetic signals are most probably generated by the changing stress field due to rupturing, i.e. the piezomagnetic effect, rather than the seismic dynamo effect or electromagnetic induction within the conducting crust, because they lack oscillatory features like seismic waves. We attempt to interpret the observations with the aid of quasi-static piezomagnetic-model calculation which strongly supported our observation results. [Copyright &y& Elsevier]

Abstract: This paper presents a case study that assessed spatial variations in the tectonic uplift rates of beach deposits in the relict Kujukuri strand plain, situated on the northeastern coast of the Boso Peninsula, eastern Japan. The southern Boso Peninsula is tilted downward to the northeast due to plate subduction along the Sagami Trough. However, the cause of the northeastern coast uplift creating the relict strand plain is unclear, due to the absence of a Holocene raised marine terrace sequence. Elevations and ages of beach deposits were collected from drilled cores and ground-penetrating radar profiles along three shore-normal sections in the southern Kujukuri strand plain. From this, alongshore variations in the relative sea level since the mid-Holocene could be seen. These corresponded to north-to-northeast downward tilting at a rate of 0.4m/ka for an interval 10km and are concordant with the longer term tilting of the last interglacial marine terrace surrounding the plain. Although it is difficult to assess shore-normal variations of uplift based on the present dataset, the recognized tilting apparently continues to the tilting of the southern Boso Peninsula, implying the Sagami Trough probably affects the uplift of the Kujukuri coast. [Copyright &y& Elsevier]

Abstract: Precursory changes in the radon concentration of groundwater were observed by prior to the 1978 Izu-Oshima-Kinkai earthquake of magnitude 7.0. Mechanisms for interpreting the anomalous radon decrease are examined in this paper. The SKE-1 well is situated in a volcanic-rock fractured aquifer of limited recharge. Given these geological conditions, the dilation of brittle rock mass occurred at a rate faster than the recharge of groundwater and gas saturation developed in newly created cracks preceding the earthquake. Radon volatilization into the gas phase can explain the anomalous decrease of radon precursory to the 1978 earthquake. To support the hypothesis, vapor–liquid two-phase radon-partitioning experiments were conducted at formation temperature (14°C) using formation water from the SKE-1 well. Experimental data indicated that the decrease in radon concentration from 483±3 count/min to 439±7 count/min required a gas saturation of 2.35% developed in rock cracks through the dilatancy process. [Copyright &y& Elsevier]

Deep-sea turbidites have been utilized to understand the history of past large earthquakes. Surface-sediment remobilization is considered to be a mechanism for the initiation of earthquake-induced turbidity currents, based on the studies on the event deposits formed by recent great earthquakes, such as the 2011 Tohoku-oki earthquake, although submarine slope failure has been considered to be a major contributor. However, it is still unclear that the surface-sediment remobilization has actually occurred in past great earthquakes. We examined a sediment core recovered from the mid-slope terrace (MST) along the Japan Trench to find evidence of past earthquake-induced surface-sediment remobilization. Coupled radiocarbon dates for turbidite and hemipelagic muds in the core show small age differences (less than a few 100 years) and suggest that initiation of turbidity currents caused by the earthquake-induced surface-sediment remobilization has occurred repeatedly during the last 2300 years. On the other hand, two turbidites among the examined 11 turbidites show relatively large age differences (~ 5000 years) that indicate the occurrence of large sea-floor disturbances such as submarine slope failures. The sedimentological (i.e., of diatomaceous nature and high sedimentation rates) and tectonic (i.e., continuous subsidence and isolated small basins) settings of the MST sedimentary basins provide favorable conditions for the repeated initiation of turbidity currents and for deposition and preservation of fine-grained turbidites. The MST small basin is a suitable site for examining deep-sea turbidite paleoseismology. [ABSTRACT FROM AUTHOR]

Kinematic finite‐extent models of earthquake sources can be determined by inverse modeling of observed waveforms and/or geodetic data. Such models are subject to significant uncertainty as a result of inaccurate observations and imperfect physical description of the complex properties of the Earth's crust. For slip inversions of large earthquakes, the major source of uncertainty is related to the uncertainty of Green's functions due to the imperfect description of the crustal model and selected parameterization of the source model. To account for both, we introduce an effective nonlinear Bayesian slip inversion with transdimensional source parameterization, including analytical representation of uncertainties of Green's functions. Our nonlinear slip inversion method relies on a self‐adapting spatial parametrization of the slip distribution by means of a varying number of spline control points on the assumed fault. For the temporal parameterization, it utilizes the regularized Yoffe function with spatially varying rise time and rupture velocity. Rake angle is also treated as an unknown spatially dependent parameter. The Green's function uncertainties are included using full covariance matrices. The posterior probability density function is sampled by the transdimensional Markov chain Monte Carlo algorithm with parallel tempering. The performance of our slip inversion method is demonstrated on a synthetic test from the Source Inversion Validation project and real‐data inversion of the 2016 Mw7.1 Kumamoto earthquake. In the latter test, we infer an ensemble of ~7,300,000 possible rupture models, representing samples of the posterior probability density, and inspect which features of these models are reliable and which are rather artifacts. Plain Language Summary: Large damaging earthquakes are caused by a rapid slip movement on large fractures in the Earth's crust. Earthshaking is then caused by a combination of released energy by the slip on the fracture (i.e., the source), propagation of generated waves through the Earth, and site‐specific conditions at the place of an observer. Having observations of the earthquake from multiple locations, we can discriminate the source parameters (i.e., kinematic description of the slip) of the earthquake. We focus in this work on the inference of large earthquakes' parameters, which would take into account also the imperfect knowledge of the medium between the source and the observer. For this purpose, we utilize mathematical relations between the observed ground shaking and the description of the source to obtain a statistical description of the source model uncertainty. The spatial smoothness of source is governed by Occam's razor. Features of the earthquake source having small uncertainties are labeled as certain and vice versa. We apply this method to the destructive earthquake that happened in the Japanese prefecture Kumamoto in 2016. The interpretation supports major features as described by other researchers while pointing on some uncertain aspects of the source of this earthquake. Key Points: Novel probabilistic self‐adapting fault slip inversion method is introducedStatistics from the ensemble of solutions allow estimating the fault slip model reliability and uncertaintyWe inspect which features of the 2016 Kumamoto earthquake source model are reliable and which are artifacts [ABSTRACT FROM AUTHOR]

In a report to the International Atomic Energy Agency (IAEA), the Japanese government stated that the Fukushima Daiichi nuclear disaster was caused not by the Tohoku earthquake but by the tsunami it generated, resulting in a loss of power for the station's cooling systems and, consequently, three core meltdowns. The tsunami countermeasures taken when Fukushima Daiichi was designed in the 1960s were, arguably, marginally acceptable considering the scientific data then available. But, between the 1970s and the 2011 disaster, new scientific knowledge emerged about the likelihood of a large earthquake and resulting tsunami; however, this was ignored by both the plant operator, Tokyo Electric Power Company, and government regulators. The regulatory authorities failed to properly review the tsunami countermeasures in accordance with IAEA guidelines and continued to allow the Fukushima plant to operate without sufficient countermeasures, despite having received clear warnings from at least one member of a government advisory committee. The lack of independence of government regulators appears to have contributed to this inaction. The anzen shinwa (“safety myth”) image portrayed by the Japanese government and electric power companies tended to stifle honest and open discussion of the risks. Japan's seismological agencies are locked into outdated and unsuccessful paradigms that lead them to focus on the hazard of a supposedly imminent earthquake in the Tokai district, located between Tokyo and Nagoya, while downplaying earthquake hazards elsewhere in Japan. Consequently, regulators and the plant operator missed many opportunities to avert the calamity at the Fukushima Daiichi Nuclear Power Station. [ABSTRACT FROM PUBLISHER]

This article empirically examines the effectiveness of earthquake early warning (EEW) in Japan based on experiences of residents who received warnings before earthquake shaking occurred. In Study 1, a survey (N = 299) was conducted to investigate residents' experiences of, and reactions to, an EEW issued in Gunma and neighboring regions on June 17, 2018. The main results were as follows. (1) People's primary reactions to the EEW were mental, not physical, and thus motionless. Most residents stayed still, not for safety reasons, but because they were focusing on mentally bracing themselves. (2) Residents perceived the EEW to be effective because it enabled them to mentally prepare, rather than take physical protective actions, before strong shaking arrived. (3) In future, residents anticipate that on receipt of an EEW they would undertake mental preparation as opposed to physical protective actions. In Study 2, a survey (N = 450) was conducted on another EEW issued for an earthquake offshore of Chiba Prefecture on July 7, 2018. Results were in line with those of Study 1, suggesting that the findings described above are robust. Finally, given people's lack of impetus to undertake protective action on receipt of an EEW, this article discusses ways to enhance such actions. [ABSTRACT FROM AUTHOR]

We investigate 3‐D seismic structures (Vp, Vs, and Poisson's ratio) and Vp azimuthal anisotropy in the source area of the 2018 Eastern Iburi earthquake (M 6.7) in Hokkaido, Japan. Its mainshock occurred at the edge of a high‐Vp (2–4%) seismogenic zone. Significant low‐Vs (−1% to −3%) and high Poisson's ratio (2–7%) anomalies are imaged in and below the source zone and extend to the upper surface of the subducting Pacific slab, most likely reflecting ascending fluids released by the slab dehydration. A high consistency between the fault plane and the low‐Vs and high Poisson's ratio anomalies indicates that the fluids may have entered the fault and affected the rupture nucleation. A high‐V (1–3%) anomaly is revealed in the fore‐arc mantle wedge and connects with the high‐V seismogenic zone, probably reflecting a lithospheric fragment and contributing to cool down the mantle wedge. Complex seismic anisotropy is revealed in the crust in and around the source area, which may reflect complicated stress regime and strong structural heterogeneities there. Key Points: The 2018 Eastern Iburi earthquake occurred at the edge of a high‐Vp seismogenic zoneAscending fluids from slab dehydration affected rupture nucleation of this earthquakeA high‐V anomaly exists below the source zone, which may cool down the mantle wedge [ABSTRACT FROM AUTHOR]

Background: Antenatal common mental disorders (CMDs) including anxiety, depressive, adjustment, and somatoform disorders are prevalent worldwide. There is emerging evidence that experiencing a natural disaster might increase the risk of antenatal CMDs. This study aimed to synthesise the evidence about the prevalence and determinants of clinically-significant symptoms of antenatal CMDs among women who had recently experienced an earthquake. Methods: This systematic review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The search included both electronic and manual components. Five major databases were searched. A data extraction table was used to summarise study characteristics and findings. Two authors examined the quality of studies independently using a quality assessment tool. A narrative synthesis of the findings reported. Results: In total seven articles met inclusion criteria. Quality scores ranged from six to seven out of ten. All the studies were cross-sectional surveys and were conducted in high and middle-income countries. Sample sizes varied among studies. The prevalence of clinically-significant symptoms of antenatal CMD ranged from 4.6% (95% CI, 3.2; 6.5) experiencing 'psychological stress' in Japan to 40.8% (95% CI, 35.5; 46.4) 'depression' in China. While all studies were conducted in an earthquake context, only four examined some aspect of earthquake experiences as a risk factor for antenatal CMDs. In multivariable analyses, higher marital conflict, poor social support, multiparity, stresses of pregnancy and the personality characteristic of a negative coping style were identified as risks and a positive coping style as protective against antenatal CMDs. Conclusions: This systematic review found that women who have recently experienced an earthquake are at heightened risk of antenatal mental health problems. It indicates that in addition to the establishment of services for safe birth which is recognised in post-disaster management strategies, pregnancy mental health should be a priority. The review also revealed that there is no evidence available from the world's low-income nations where natural disasters might have more profound impacts because local infrastructure is more fragile and where it is already established that women experience a higher burden of antenatal CMDs. Trial registration: PROSPERO-CRD42017056501. [ABSTRACT FROM AUTHOR]

A quick response to a large-scale natural disaster such as earthquake and tsunami is vital to mitigate further loss. Remote sensing, especially the spaceborne sensors, provides the possibility to monitor a very large scale area in a short time and with regular revisit circle. Damage ranges and damage levels of the destructed urban areas are extremely important information for rescue planning after an event. Rapid mapping of the urban damage levels with synthetic aperture radar (SAR) is still challenging. Compared with single-polarization SAR, fully polarimetric SAR (PolSAR) has a better potential to understand the urban damage from the viewpoint of scattering mechanism investigation. In radar polarimetry, the dominant double-bounce scattering mechanism in an urban area is primarily induced by the ground-wall structures and can reflect the changes of these structures. In this sense, urban damage level in terms of destroyed ground-wall structures can be indicated by the reduction of the dominant double-bounce scattering mechanism, which is the basis of this study. This work first establishes and validates the linear relationship between the urban damage level and the proposed polarimetric damage index using polarimetric model-based decomposition. Then, efforts are focused on the development of a rapid urban damage level mapping technique which mainly includes two steps of urban area extraction and polarimetric damage level estimation. The 3.11 East Japan earthquake and tsunami inducing great-scale destruction are adopted for study using L-band multitemporal spaceborne PolSAR data. Experimental studies demonstrate that the estimated damage levels are closely consistent to the ground-truth. The final urban damage level map for the full scene is generated thereafter. Results achieved in this study further validate the necessity of exploring fully polarimetric technique for damage assessment. [ABSTRACT FROM PUBLISHER]

We report precursory seismic patterns prior to the 2016 Kumamoto earthquakes, as measured by four different methods based on changes in seismicity that can be used for earthquake forecasting: the b-value method, two methods of seismic quiescence evaluation, and an analysis of seismicity density in space and time. The spatial extent of precursory patterns differs from one method to the other and ranges from local scales (typically, asperity size) to regional scales (e.g., 2° × 3° around the source zone). The earthquakes were preceded by periods of pronounced anomalies, which lasted in yearly scales (1.5 years), or longer (>3 years). We demonstrate that a combination of multiple methods detected different signals prior to the Kumamoto earthquakes. This indicates great potential to reduce the hazard at possible future sites of earthquakes relative to long-term seismic hazard assessment. We also found that the seismic quiescence in a regional-scale area, detected by using the two methods of seismic quiescence evaluation, was a common precursor to the 2016 Kumamoto earthquakes and 2015 Off Satsuma Peninsula earthquake. The result allows us to interpret both events as the onset that occurred at a section along the tectonic line from the Okinawa Trough through the Beppu-Shimabara graben. [ABSTRACT FROM AUTHOR]

In the present study, we have developed a numerical method which can simulate the dynamic behaviour of a seabed ground during gas production from methane hydrate-bearing sediments. The proposed method can describe the chemo-thermo-mechanical-seismic coupled behaviours, such as phase changes from hydrates to water and gas, temperature changes and ground deformation related to the flow of pore fluids during earthquakes. In the first part of the present study, the governing equations for the proposed method and its discretization are presented. Then, numerical analyses are performed for hydrate-bearing sediments in order to investigate the dynamic behaviour during gas production. The geological conditions and the material parameters are determined using the data of the seabed ground at Daini-Atsumi knoll, Eastern Nankai Trough, Japan, where the first offshore production test of methane hydrates was conducted. A predicted earthquake at the site is used in the analyses. Regarding the seismic response to the earthquake which occur during gas production process, the wave profiles of horizontal acceleration and horizontal velocity were not extensively affected by the gas production. Hydrate dissociation behaviour is sensitive to changes in the pore pressure during earthquakes. Methane hydrate dissociation temporarily became active in some areas because of the main motion of the earthquake, then methane hydrate dissociation brought about an increase in the average pressure of the fluids during the earthquake. And, it was this increase in average pore pressure that finally caused the methane hydrate dissociation to cease during the earthquake. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY In the disconnecting switch of 300 kV or less single pole structure, the Great East Japan Earthquake received much damage at the former by the rotation insulator base metal which damage experience had. Conventionally, we carried out a simple desk evaluation about earthquake-proof evaluation of insulator base metal. However, there is deviation with the damage actual condition and it became clear that it was an apparatus weak point part. Then, we worked on the analysis accuracy improvement of insulator base metal, and we built the analysis technology of the single pole structured disconnecting switch. [ABSTRACT FROM AUTHOR]

In this article, we develop statistical models to predict the number and geographic distribution of fires caused by earthquake ground motion and tsunami inundation in Japan. Using new, uniquely large, and consistent data sets from the 2011 Tōhoku earthquake and tsunami, we fitted three types of models-generalized linear models (GLMs), generalized additive models (GAMs), and boosted regression trees (BRTs). This is the first time the latter two have been used in this application. A simple conceptual framework guided identification of candidate covariates. Models were then compared based on their out-of-sample predictive power, goodness of fit to the data, ease of implementation, and relative importance of the framework concepts. For the ground motion data set, we recommend a Poisson GAM; for the tsunami data set, a negative binomial (NB) GLM or NB GAM. The best models generate out-of-sample predictions of the total number of ignitions in the region within one or two. Prefecture-level prediction errors average approximately three. All models demonstrate predictive power far superior to four from the literature that were also tested. A nonlinear relationship is apparent between ignitions and ground motion, so for GLMs, which assume a linear response-covariate relationship, instrumental intensity was the preferred ground motion covariate because it captures part of that nonlinearity. Measures of commercial exposure were preferred over measures of residential exposure for both ground motion and tsunami ignition models. This may vary in other regions, but nevertheless highlights the value of testing alternative measures for each concept. Models with the best predictive power included two or three covariates. [ABSTRACT FROM AUTHOR]

The geomagnetic fields in the atmosphere can be affected by phenomena in the Earth, so that changes of geomagnetic intensity might be used as an indicator of earthquake occurrences. Variations of geomagnetic data have been analyzed in association with the Tohoku Earthquake on March 11th 2011. The Geomagnetic data have been derived from Memambetsu (MMB), Kakioka (KAK) and Kanoya (KNY) Observatories, which are INTERMAGNET observatories. The analysis was performed by calculating the power spectral density (psd) of the ULF signal of Z and H components and then polarizations are observed by comparing the psd of Z and of H. The results showed the difference psd of Z and of H between the KAK observatory (the nearest position to the epicenter) with MMB and KNY (at some greater distance from the epicenter) is quite significant, which can be observed over a period of 10 days before the earthquake occurrence. The polarizations of Z/H in KAK indicate a highest change of intensity which occurred at 18 days prior to the earthquake. [ABSTRACT FROM AUTHOR]

Large-scale landslides along the Kubusu and Besso rivers in Toyama Prefecture are developed in the Miocene Iwaine Formation, which is composed of andesitic lava, tuff, and tuff breccia. In the middle member of this formation, the tuff is easily altered to montmorillonite-bearing rock, and subsequently plays an important role in the development of landslides events, which tend to be large-scale events, as the massive lava of the upper member forms a cap rock over the tuff. The Kiritani and Koinami basins, which are flat intermontane basins located along the Kubusu and Besso rivers, respectively, are interpreted as landslide-dammed lakes, later filled with sediment. Accelerator mass spectrometry C ages show that the landslides forming each dam occurred simultaneously, at approximately 2500 BP. These ages were measured from wood fragments embedded in the landslide material of Kiritani, and from an in situ stump drowned during the impoundment of Koinami. If the trigger of these landslides was an earthquake, it is most likely to have been the penultimate event along the Atotsugawa fault zone. [ABSTRACT FROM AUTHOR]

Three washover sand beds, ranging from 15 to 34 cm in thickness, were recorded in a lagoonal mud sequence on the Shizuoka coast of central Japan, which faces the Suruga Trough. The sand beds were composed of well-sorted and well-rounded beach sand derived by a marine inundation. The basal erosion surface, mud clasts, and presence of both inverse and normal grading suggest that the sand beds formed as a result of high-energy deposition. The sand beds are multilayered, with fine alternations of sand sheets and mud drapes, which are consistent with deposition from a long-period wave train. Radiocarbon dates obtained from the three washover deposits are around ad 1000, 3565–3486 cal. yr BP, and 4000 cal. yr BP. Vertical changes in the diatom assemblages suggest a gradually increasing inflow of seawater up to the second sand bed, followed by a rapid change to freshwater conditions just above the bed. The gradual increase of seawater inflow begins again just above the second sand bed. We conclude that this series of sequential environmental changes indicates interseismic subsidence and coseismic uplift. The study area experienced around 1 m of uplift during the ad 1854 Ansei Tokai earthquake (Mw 8.4). In contrast, the area has subsided gradually (c. 6 mm/yr) during the present interseismic period. The youngest sand bed may be correlated with the ad 1096 Eicho earthquake, which caused severe damage along the Shizuoka coast. [ABSTRACT FROM AUTHOR]

We have observed and recorded the neutral current of a 500-kV transformer at a substation in the Chubu region since 2008 in order to detect electromagnetic anomalies associated with earthquakes. In this study, we could not find any particular anomalous change of the neutral current before and after earthquakes (e.g., for the Suruga Bay Earthquake of August 11,2009). However, from the results of a quantitative analysis between geomagnetic field data and neutral current data, we would be able to investigate the underground electric conductivities near the substations. It would be possible to monitor changes of subsurface electromagnetic structure before and after earthquakes. [ABSTRACT FROM AUTHOR]

Tide gauge observations along the coastline of Japan have recorded the land sinking due to the continuous subduction of the oceanic plates, indicating that stress and strain energies have been accumulating at the plate boundary, which would eventually cause large oceanic trench earthquakes like the 2011 Great East Japan Earthquake. The proposed method extracts such long-term activities of the Earth's crust together with rapid displacements related to earthquakes, even before the establishment of the global positioning system, from monthly mean data of the sea levels. A state space model decomposes the tide gauge time series into trend, seasonal, autoregressive and observation noise components, each of which are estimated using the particle filter algorithm. The spatial and temporal distributions of the extracted trend component clearly indicate high-risk regions, near which giant earthquakes have occurred or are predicted to occur. A multivariate analysis of the observatories located at the northeast coast of Japan successfully determines the past crustal displacement in the case of the 1978 Off-Miyagi Earthquake. The proposed method has the potential application for monitoring crustal activities related to the accumulation of earthquake energy. [ABSTRACT FROM PUBLISHER]