Bouguer Anomalies and Crustal Structure Models around the Atotsugawa Fault, Central Japan

Abstract

Crustal structure models from the Noto Peninsula to the Hida mountains area crossing the Atotsugawa fault were estimated based on both detailed gravity anomaly and explosion seismological data. The results are as follows;
(1) Minor changes of short wavelength Bouguer anomalies were observed across the Atotsugawa fault. This is due to small density differences of rocks around the fault. However, a locally high anomaly zone remained along the fault.
(2) Variation of long wavelength Bouguer anomalies across the fault was about 12 to 20 mgal per 10km.
(3) Estimated crustal structure models indicated that the deeper subsurface structure changes suddenly under the fault. It suggests that the Atotsugawa fault is situated at the border of large scale variation of crustal structure between the Hida mountains and the Noto peninsula regions.