Stress estimate for the highest mountain system in Japan
Stress estimate for the highest mountain system in Japan
复制标题
日本最高山脉系统的应力估计
DOI：
10.1029/tc002i005p00453
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发表时间：
1983
期刊：
影响因子：
--
通讯作者：
K. Yamaoka
中科院分区：
文献类型：
--
作者：
Y. Fukao;K. Yamaoka
飞驒山脉是日本最大的山系，是一个现代隆升特征（隆升速度约1-5毫米/年）。在这个山脉中没有发现大地震和活动断层，但是在它的轴向部分经常发生小地震，通常是成群的。震源机制为走滑型，P轴方向为NW-SE ~ WNW-ESE。这个方向垂直于山脉的走向，与现在在日本岛屿的大部分地区引起板内地震的构造压缩方向一致。与太平洋板块和欧亚板块的汇聚方向重合。横跨希达山脉的布格异常剖面表明，在它下面有一个上地壳根。根据布格异常剖面，计算出与此上部地壳根部相关的浮力载荷，发现浮力载荷不足以承受地表地形均衡载荷。如果任何构造力从山系中移除，山脉就会通过非弹性变形而下沉。提出了利用已知地形荷载和浮力荷载计算构造力虚移瞬间应力差的公式。假设牛顿流体具有均匀粘度。计算的应力差为水平拉伸，约290巴，在山脉的轴向部分。这种水平张力必须在构造上加以克服，才能保证山的隆升和地震的发生。我们认为，飞驒山脉现在是在板块构造起源的水平压缩作用下抬升的，其压应力至少在300巴数量级。在隆升过程中，山系似乎保持了其上地壳结构，处于应力差最小的相当接近状态。
The Hida range, the largest mountain system in Japan, is a contemporary uplifting feature (uplifting rate∼1–5 mm/yr). No large earthquakes nor active faults have been located in this mountain range but small earthquakes occur rather frequently, often as swarms, in its axial portion. Their focal mechamisms are found to be of strike slip type with the P axes in the NW-SE to WNW-ESE direction. This direction is perpendicular to the trend of the mountain chain and coincides with the orientation of the tectonic compression now causing intraplate earthquakes in most regions of the Japanese islands. It also coincides with the convergence direction of the Pacific plate and the Eurasian plate. The Bouguer anomaly profile across the Hida range suggests an upper crustal root beneath it. A buoyancy load associated with this upper crustal root is calculated from the Bouguer anomaly profile, which is found to be not large enough to sustain the surface topographic load isostatically. If any tectonic forces were removed from the mountain system, mountains would subside through inelastic deformation. A formula is presented to calculate, using the known topographic load and buoyancy load, the stress differences arising at the virtual instant of removal of tectonic forces. The Newtonian fluids of uniform viscosity are assumed. The calculated stress difference is horizontally tensile, about 290 bars, at the axial portion of the mountain range. This horizontal tension must be overcome tectonically to ensure the mountain uplifting and the earthquake occurrence. We suggest that the Hida range is now uplifting by horizontal compression of plate tectonic origin with a compressive stress at least of the order of 300 bars. During uplifting, the mountain system seems to maintain its upper crustal configuration as the one in a fairly close state of minimum stress difference.