SEGJ Technical Conference

An Ultra high Density Questionnaire Seismic Intensity Survey in Ichinoseki City of Iwate Prefecture, for the aftershock occurred at April 7 in 2011, of the 2011 off the Pacific coast of Tohoku Earthquake

Abstract To clarify the vibration characteristics in Ichinoseki City of Iwate Prefecture, where many houses were dameged by both the 2011 off the Pacific coast of Tohoku Earthquake and the aftershock occurred at April 7, 2011, the survey of seismic intensity was done using questionnaires for both the main shock and the aftershock ,2011.JMA reported that the seismic intensities at the observation site of Ichinoseki City were 6 weak for the main shock and same for the aftershock. The questionnaire revised by Ohta et al. (1998) was used for calculating seismic intensities. About 10,000 questionnaires were distributed for residents for each earthquake.Calculating seismic intensities for aftershock April 7 has been finished.The seismic intensities estimated from questionnaires were averaged for 1km to 250m square meshes to clarify the distribution of seismic intensity for Ichinoseki City. As a result, it was revealed that the seismic intensity in Akogi area, where was at the west area of Ichinoseki area, was large.In this area, the meshes where seismic intensities were 7 were recognized for the 250m square mesh mapping.