A low velocity zone beneath the Hida Mountains derived from dense array observation and tomographic method
A low velocity zone beneath the Hida Mountains derived from dense array observation and tomographic method
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DOI：
10.1186/bf03351623
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发表时间：
2000-01-01
影响因子：
3
通讯作者：
Kawasaki, I
中科院分区：
文献类型：
--
作者：
Matsubara, M;Hirata, N;Kawasaki, I
地震波在日本本州岛中部的希达山脉下传播时会受到强烈的衰减。为了详细地研究这一地区，我们于1996年夏天在希达山及其周围地区进行了三种密集地震台阵观测。从101个台站的54个地震中拾取P波和S波到时数据，获得3175个P波和2335个S波到时数据用于层析成像研究。同时确定了震源位置和速度结构。我们用棋盘格分辨率测试评估了速度结构的射线覆盖和分辨率。射线路径的模型所获得的速度结构进行了详细检查。有两个低P波速度区，一个在4公里的深度和另一个在15公里。P波速度在0-20公里深度分辨率良好，S波速度在0-15公里深度分辨率良好。高的V-P/V-S比值（2.7）表明在希达山脉下存在部分熔融的岩石。深部低速带位于上、下地壳边界之上。这些观测结果表明，在希达山下的上地壳中存在着岩浆库。
Seismic waves suffer strong attenuation when propagating beneath the Hida Mountains in Central Honshu, Japan. In order to study this region in detail, we conducted three kinds of dense seismic array observations in and around the Hida Mountains in the summer of 1996. Picking P- and S-wave arrival time data from 54 events at 101 stations, 3175 P- and 2335 S-wave arrival time data were obtained for our tomographic study. Hypocenter locations and velocity structure were determined simultaneously. We assessed ray coverage and resolution of the velocity structure with checkerboard resolution tests. Ray paths for the model of the obtained velocity structure were examined in detail. There are two zones of low P-wave velocity, one at a depth of 4 km and the other at 15 km. The resolution is good at depths of 0-20 km for P-wave velocities and at depths of 0-15 km for S-wave velocities. A high V-P/V-S ratio (2.7) indicates that a partially melting rock exists beneath the Hida Mountains. The deep low velocity zone is located just above the upper/lower crustal boundary. These observations indicate that a magma reservoir exists in the upper crust beneath the Hida Mountains.