The interferometric SAR coherence-change technique with coherence filter and polarization (HH and HV) has been used to detect the parts of buildings damaged by the 2015 Gorkha Earthquake. A survey of the building damage was conducted in every house to evaluate the detection accuracy in the Khokana and Sankhu urban areas in the Kathmandu Valley of Nepal. The damaged parts of the urban area were adequately detected using coherence-change (∆γ) values obtained before the earthquake (γ pre ) and during the inter-seismic stage of the earthquake (γ int ). The use of a coherence filter effectively increased overall accuracy by ~2.1 to 7.0 % with HH polarization. The incorporation of HV polarization marginally increased the accuracy (~0.9 to 1.2 %). It was confirmed that road damage due to liquefaction was also observed using the interferometric SAR coherence-change detection technique. The classification accuracy was lower (27.1-35.1 %) for areas that were damaged. However, higher accuracy (97.8-99.2 %) was achieved for areas that were damage-free, in ∆γ obtained from HH and HV polarization with a coherence filter. This helped to identify the damaged urban areas (using this technique) immediately after occurrence of an earthquake event.

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Vein structure, a distinctive structure in deep-sea hemipelagic clayey and siliceous mudstones at convergent plate boundaries, consists of closely spaced mud-filled veins forming an array usually parallel to the bedding plane. This structure has been regarded as a seismite that formed during earthquake shaking by resonance of fractures. Our detailed field observations and shaking model experiments verified that both basic (first-stage) and advanced (developed-stage) vein structures can be explained by a systematic theory. Essentially, a vein structure forms in an array of fractures as a result of shearing, not by push waves but by shear waves of very short wavelength, by a mechanism very similar to that which forms ripple marks. We found the height of a vein array (H) to be systematically related to vein spacing (S) such that H = 5S, suggesting that the shear strength of the sediment is proportional to the thickness of the standing wave part of a sediment layer. Shear or oscillatory flow occurs in the top part of a sediment layer, under which standing waves with wavelengths on the order of millimeters to centimeters lead to vein structure formation. Vein structure can develop not only in response to earthquake shaking but also by propagation of shear waves along a large fault or by other kinds of shears associated with density or debris flows, landsliding, or faulting.

An earthquake with a magnitude of 7.8 (M w) occurred at 11:56 NST (local time) on 25 April 2015, in the central part of Nepal (Gorkha).We organized a damage survey team and dispatched it to the affected area for several periods following the earthquake (May 26 to June 3: first trip, June 17 to 24: second trip, August 16 to 21: third trip and October 27 to November 2: forth trip) to investigate the damage and collect data. We found traditional construction methods are stronger than imagined. Many traditional earthquake-resistance technologies exist in Nepal. The first and second surveys were to collect timely statistical information on the damage to brick and stone masonry buildings and to confirm the availability of data and their sources for subsequent surveys. We also carried out a first-hand building damage survey in selected areas. The investigation of the strong-motion data set from the USGS Center for Engineering Strong Motion Data includes information from stations in Nepal that continued to function throughout the main shock and the several subsequent strong aftershocks of the 2015 earthquake. The third and fourth surveys were to collect the every building damage survey in selected areas. The motivation behind the survey was to obtain ground truth data for the calibration and improvement of a wide-area damage estimation system that uses satellite data; the system is currently under development by National Research Institute for Earth Science and Disaster Prevention (NEID) and the Japan Aerospace Exploration Agency (JAXA). A survey of the degree of damage was conducted for every house in Sankhu and Khokana by the European Macroseismic Scale (EMS)-98. This report outlines the findings of this investigation team into various aspects of the earthquake disaster in the Kathmandu Valley. The motivation behind the survey was to obtain ground truth data for the calibration and improvement of a wide-area damage estimation system that uses satellite data. Field surveys confirmed that the severely damaged urban area was well detected by the decrease derived from the ALOS-2 satellite SAR data. The higher classification accuracy for non-damaged area helps to detect the damaged urban area using this technique, immediately after a disaster. Keywords Gorkha Á Nepal earthquake Á Kathmandu Á Masonry Á Ground truth 1 Introduction An earthquake with a magnitude of 7.8 (M w) occurred at 11:56 Nepal Standard Time (NST), (local time) on 25 April 2015, in the central part of Nepal (Gorkha).

The purpose of this study is to verify fault modeling in the source region of the 1940 Shakotan-Oki earthquake using active faults offshore of Japan. Tsunami heights simulated in previous studies are found to be lower than observed levels, which makes it difficult to explain historical tsunami records of this earthquake. However, the application of appropriate slip magnitudes in the fault models may explain these differences. In the “Project for the Comprehensive Analysis and Evaluation of Offshore Fault Informatics (the Project),” a new fault model is constructed using marine seismic data and geological and geophysical data compiled by the Offshore Fault Evaluation Group, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) as part of the Project for Fault Evaluation in the Seas around Japan (Ministry of Education, Culture, Sports, Science and Technology, MEXT). Single-channel and multichannel reflection seismic data were used that includes information from a new fault identified in previous surveys. We investigated fault geometries and their parameters using the above data. Here, we show that the geometric continuity of these faults is adjusted by increasing the magnitude of fault slip. Standard scaling laws are applied on the basis of strong ground motion of the fault parameters, and the validity of the fault model is examined by comparing tsunami heights along the Japanese coastline from historically observed records with tsunami height from simulation analysis. This verification quantitatively uses Aida’s K and κ scale and variance parameters. We determine that the simulated tsunami height determined using the new model approach the heights observed historically, which indicates that the model is valid and accurate for the source region.