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Experimental study of AE from rock under cyclic loading - in relation to the effect of oceanic tide to the earthquake swarm

循环荷载下岩石声发射的实验研究——与海潮对地震群影响的关系

基本信息

批准号：
03640374
负责人：
MOGI Kiyoo
金额：
$ 1.34万
依托单位：
Nihon University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

项目摘要

In the case of the 1980 Izu-hanto-toho-oki earthquake swarm, a very clear correlation between the seismic activity and the oceanic tide was found (Mogi, 1983). To obtain a clue to clarify this tide effect, laboratory measurements of AE from rock specimens under cyclic loadings were carried out. Since it is deduced that the swarm-type earthquakes in the Izu occurred in an extension stress field, cyclic loadings of a tensile type were applied to a rectangular parallelepipeds rock sample by a bending method. The amplitude of cyclic loadings were increased at successive intervals.According to this experiments, AE events occur both in the upward and the downward processes of loadings. It is concluded that AE events under cyclic loadings occur by the following two different mechanisms, (a) development of micro-fractures and (b) stick-slip along micro-crack surfaces.The experimental results show that there are some common character istics between AE and natural earthquakes under repeated loadings. They are: (1) The peak of activity dose not always coincide with the maximum point of loadings; (2) Both AE and seismic events occur at specific stress levels (the appearance of AE and earthquake families); (3) The activity in the earthquake swarm is high in the upward process of the oceanic tide, and the AE activity is also high in the upward process of loadings for the case of small amplitudes of cyclic loadings. These results may give a clue to make clear the effect of tidal stress to the earthquake occurrence.

在1980年伊豆半岛东北冲地震群的情况下，发现地震活动与海潮之间存在非常明显的相关性（Mogi，1983）。为了获得澄清这种潮汐效应的线索，进行了实验室测量循环荷载下的岩石标本的AE。由于推断出伊豆的震群型地震发生在拉伸应力场中，因此通过弯曲方法将拉伸型循环载荷施加到矩形平行六面体岩石样品上。试验结果表明，声发射事件发生在加载过程中的上升和下降过程中。结果表明，在循环荷载作用下，声发射事件是通过微裂纹的发展和沿着微裂纹面的粘滑两种不同的机制发生的，实验结果表明，在重复荷载作用下，声发射事件与天然地震有一些共同的特征。它们分别是：（2）AE和地震事件都发生在特定的应力水平上（AE和地震族的出现）;（3）在海潮上升过程中震群活动性强，在小幅值循环荷载作用下，荷载上升过程中AE活动性也强。这些结果可能为弄清潮汐应力对地震发生的影响提供线索。