Estimation of Strong Motion Generation Area Based on Acceleration Records During the 2011 Off the Pacific Coast of Tohoku Earthquake

Abstract eng:
Detailed parameters of source process are indispensable for precise evaluation of ground motion characteristics in nearsource region. Many studies have been devoted to development of inversion techniques based on observed waveforms such as far-field body waves, displacement motions, and acceleration envelopes. In those studies, however, less attention has been paid to short period contents of strong motions that have great influence on structures. The prompt estimation of the seismic intensity distribution based on the information on fault process is specially required for the initial and effective restoration program. For prompt estimation, the simulation of strong motion that used the source process is need. This study deals with the inversion technique of source process based on the acceleration envelope. In this study, the strong motion generation area is represented by the normalized coefficient for the superposition of the evolutionary power spectra for each sub-event in the EMPR(Earthquake Motion Prediction model on Rock surface). The validity of the technique is examined in the case of the 2011 off the Pacific coast of Tohoku Earthquake. During the 2011 off the Pacific coast of Tohoku Earthquake, strong motion records at many observation stations were obtained by KiK-net which is the observation network of National Research Institute for Earth Science and Disaster Prevention. In this study, the dataset of strong motion records that were observed by KiK-net stations, were used. Generally two seismometer both on ground surface and underground base rock level are set in the KiK-net system. Therefore, the records are converted to those for rock surface ground motion on the basis of the response analysis code, FDEL(Frequency Dependent Equi-Linearized technique). The inversion technique by use of the acceleration envelope is applied to this earthquake. The distribution of strong motion generation area on the fault plane, which represents the relative contribution ratio of acceleration power release, is obtained. The result was compared with those by other studies, and they were comparatively agreed with. The results demonstrate the validity of the estimated distribution using the inversion technique of the 2011 off the Pacific coast of Tohoku Earthquake.

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