Super deep earthquake

点击翻译按钮获取中文摘要

(1) Slow deformation which has low rupture velocity and long rise-time can make a earthquake which has a large moment of the low frequency components comparing to the scaling law as omega-square model. These earthquakes are called "slow earthquakes" . The small slow earthquakes observed only in the local network may have a possibility of earthquake prediction.In this study, we present the "multi-station method" of the crustal movement data for finding the slow earthquakes which are occurred in the Kii peninsula and the Hida region. We use the strain-meter and water-tilt meter records located in the small network in the Kii peninsula and larger network located in the Southwest Japan, from 1990 to 1991. Within time series from 4 minutes to 256 minutes, no slow events was detected in this study. However, considering that there occurred the local slow earthquakes in the previous studies and that there occurred no large earthquakes, this result has possibility that there is no local slow earthquake when there is no large earthquake.(2) Micro-earthquakes which lack high frequency waves have been found in the crust in the Hida region, central Japan. During a period of 12 years within an area of 150 X 200 km, eleven events were detected which radiated low-frequency waves predominantly. Eight of these events are located in aseismic zone, with depth of 10-30 km.Most of these events occurred beneath the northern part of the Hida Mountain region. This means these low frequency earthquakes were caused by transportation of liquid-magma in solid rocks.