Single station moment tensor inversion for near earthquakes
Single station moment tensor inversion for near earthquakes
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近震单站矩张量反演
DOI：
10.4294/jpe1952.36.125
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
I. Nakanishi
中科院分区：
文献类型：
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作者：
Takeshi Fukushima;D. Suetsugu;I. Nakanishi
结果表明，近震（震中距约500 km）后单站持续时间约6 min的二分量或三分量地震动记录足以确定事件的初步震矩和震源机制，通常利用纵波初动资料和远震波形来确定震源机制。不过，上述数据最多还需要几天时间才能获得。对于日本附近的海洋地震，即使地震发生后立即获得内陆台站的纵波初动数据，台站覆盖范围也不足以确定震源机制。如果设计出一种快速可靠的地震震级和机制同时测定方法，将成为在海啸到达沿海地区之前估算附近海洋地震海啸潜力的重要工具。福岛等人。 (1987a)通过数值实验表明，基于简正模态理论的矩张量反演方法对于快速确定地震规模和断层参数是有用的。实验中，假定了适合日本地区的假设震源站几何结构，并反演了根据三场海啸地震的双偶模型计算出的震中距离为100至1,300公里的长周期垂直分量地震图。反演结果表明，只要获得日本至少两个台站的长周期垂直分量数据，所得解与真实解几乎相同。 BULAND 和 GILBERT (1976 a) 以及 GILBERT 和 BULAND (1976) 已经表明，理论上可以通过使用一台水平地震仪或两台垂直地震仪来找到埋藏点震源的地震矩张量的六个独立元素。
It is shown that the twoor three-component record of ground motion at a single station of the duration of about 6 min following a near earthquake (epicentral distance of about 500 km) may be sufficient to determine the preliminary seismic moment and source mechanism of the event, Earthquake source mechanism has usually been determined by using P-wave first-motion data and teleseismic waveforms. However, it still takes a few days at best until the above data become available. For an oceanic earthquake near Japan, even if the P-wave first-motion data from inland stations become available immediately after the earthquake occurrence, the station coverage is rather insufficient to determine the source mechanism. If a rapid and reliable simultaneous determination method of earthquake size and mechanism is devised, it will become an important tool to estimate the tsunami potential of nearby oceanic earthquakes before tsunami arrivals at coastal regions. FUKUSHIMA et al. (1987 a) have shown by a numerical experiment that the moment tensor inversion method based on normal mode theory is useful for the rapid determination of earthquake size and fault parameters. In the experiment, a hypothetical source-station geometry appropriate to the Japanese region is assumed and the long-period vertical component seismograms at epicentral distances of 100 to 1,300 km computed from double couple models of three tsunamigenic earthquakes are inverted. The inversion result shows that the obtained solutions are almost equal to the true ones, provided that the long-period vertical component data are obtained from at least two stations in Japan. BULAND and GILBERT (1976 a) and GILBERT and BULAND (1976) have shown that it is theoretically possible to find the six independent elements of the seismic moment tensor of a buried point source, by using one horizontal seismometer or two vertical seismometers.