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我们研究了日本东北福岛县西南地区的剪切波偏振各向异性。研究的数据是从东北大学和字都宫大学的区域地震台网得到的。我们采用互相关方法,检测剪切波的分裂。对福岛县西南地区地下的浅源地震观测到的快剪切波振动方向(FSOD)呈NW-SE走向。观测到的延迟时间小于0.1s,在地震活动水平高的地区,(延迟时间)值趋向增大。对中等深度地震,观测的快剪切波振动方向平行于消减板块倾斜的方向,大部分观测到的延迟时间小于1s。在这些观测的基础上,我们估计了各向异性的位置和成因。在福岛县西南地区地下的上地壳中,估计各向异性主要是由构造应力控制的破裂的优势取向产生的。
We studied the shear wave polarization anisotropy in southwestern Fukushima, northeastern Japan. The data of the study are obtained from the regional seismological networks of Northeastern University and Shmatūsin University. We use a cross-correlation method to detect shear wave splitting. The fast shear-wave vibration direction (FSOD) observed by the shallow source earthquakes in the southwestern Fukushima area was NW-SE. The observed delay time is less than 0.1s, and the value of (delay time) tends to increase in areas with high seismicity. For moderate-depth earthquakes, the direction of the observed fast shear-wave vibration is parallel to the direction of slant of the slab, and most of the observed delay times are less than 1 s. Based on these observations, we estimate the location and cause of anisotropy. In the upper crust beneath the southwestern Fukushima prefecture, the estimated anisotropy is mainly due to the dominant orientation of tectonic stress-controlled rupture.