A Hazard to Lead to a Flood Risk Caused by Ground Deformation Due to the Uemachi Fault Zone Earthquake in the East Area of the Osaka Plain

Abstract

This paper shows a hazard to lead to a flood risk caused by ground deformation due to the Uemachi fault zone earthquake in the east area of the Osaka plain. First, the ground is assumed a homogeneous semi-infinite elastic medium, the fault parameters are set based on results of study and research of the past, and vertical displacement of earth's surface caused by dislocation of a rectangular fault in this medium is analyzed by numerical simulation based on the Okada's formula (the Okada's Dislocation Model). Next, it is grasped that a trend of ground deformation in the east area of the Osaka plain due to one event in the Uemachi fault zone. And, we paid attention to sedimentation situation of Ma12 and Ma10 layer which is diluvial clay formation make up the Osaka plain, and analyzed this situation and numerical simulation results with deformation based on the estimated number of activity times after formation of these layers started. As a result, about tilting rate of strata in these periods, we found that numerical simulation results are correlated well with analysis results of geologic strata by geotechnical data in the east area of the Osaka plain. Moreover, it makes clear that wide area ground deformation in this area due to one event in the Uemachi fault zone can become a hazard to lead to a flood risk because this ground deformation will cause reverse gradient of some rivers in this area.