Super deep earthquake

(1)与ω - 2模型的标度律相比，低破裂速度和长上升时间的慢变形可以产生低频分量矩较大的地震。这些地震被称为“慢震”。仅在局地台网中观测到的小而慢的地震也有预报地震的可能。本文提出了用地壳运动资料的“多站法”寻找喜井半岛和飞驒地区发生的慢震。我们使用了1990 - 1991年位于纪井半岛的小网和位于日本西南部的大网的应变仪和水倾斜仪记录。在4分钟至256分钟的时间序列中，本研究未检测到慢事件。但是考虑到以往的研究中都发生了局部慢震，没有发生大地震，这个结果有可能在没有发生大地震的情况下没有发生局部慢震。(2)在日本中部飞驒地区地壳中发现了缺乏高频波的微地震。在12年的时间里，在150 × 200公里的范围内，检测到11次以低频波为主的事件。其中8次地震位于地震带，震源深度为10-30公里。这些事件大多发生在飞驒山北部地区的地下。这意味着这些低频地震是由固体岩石中的液体岩浆运输引起的。

(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.