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为了研究日本东北部宫城县境内1962年宫城北部 M6.5地震的孕震区大地电阻率结构,我们进行了大地电磁测量。二维反演表明,在该地区的地壳上部存在一个深的导电层,其上覆盖有高电阻带。该高电阻带之上还被认出有一个正航磁异常存在,人们把它解释为一个北上山地地下深成花岗岩岩体。通过与地震活动性进行比较我们发现,微震只发生在深导电层上方和高阻带里,并且几个s波反射体正好位于深导电区上方。由于s波反射体表明其下有流体存在,深导电层可以被解释为是一个充满流体的区带。而且我们认为,流体从导电性的充满流体的区带向高阻的深成花岗岩岩体的渗流可成为一种触发地震。
In order to study the earth resistivity structure of the seismogenic zone of the M6.5 earthquake in the north of Miyagi in 1962 in Miyagi, northeastern Japan, we conducted a geomagnetic survey. Two-dimensional inversion shows that there is a deep conductive layer in the upper part of the crust in the area, covered with a high resistance band. Above this high resistivity zone there is also recognized a positive aeromagnetic anomaly, which is interpreted as a deep granite pluton in the north upriver. By comparing with the seismic activity, we find that microseism occurs only above the deep conductive layer and in the high resistivity zone, and that several s-wave reflectors are located just above the deep conductive zone. The deep conductive layer can be interpreted as a fluid-filled zone because the s-wave reflector indicates the presence of fluid beneath it. Furthermore, we believe that the seepage of fluids from conductive fluid-filled zones to high-resistivity deep granitic rocks can be a triggering earthquake.