Hidden Fault Scarp Inferred from Gravity Analysis and Disaster Belt of the 1995 Hyogo-Ken Nanbu Earthquake
Dense gravity measurements were carried out together with the GPS positioning along five survey lines across the Rokko fault system. The subsurface structure relevant to the 1995 Hyogo-ken Nanbu earthquake was inferred from the Bouguer anomaly. A hidden fault was discovered on the southwestward extension of the Koyo fault underneath the sedimentary layer. The extension runs just on the edge of the earthquake disaster belt. The thickness of the sedimentary layer was estimated to decrease gradually toward the mountain side. The wedge-like structure of the soft layer and the hidden fault scarp under the Kobe plain may serve as a focusing lens of seismic rays during the earthquake.
KeywordsGravity Gradient Subsurface Structure Survey Line Fault Scarp Surface Trace
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