Initial phase analysis of R waves from great earthquakes
Initial phase analysis of R waves from great earthquakes
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大地震R波初相分析
DOI：
10.1029/jb084ib12p06867
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发表时间：
1979
期刊：
影响因子：
--
通讯作者：
M. Furumoto
中科院分区：
文献类型：
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作者：
M. Furumoto
为了获得1963年千岛地震及其最大余震、1965年鼠岛地震和1968年十胜冲地震这4次地震的震源机制信息，对R波进行了相位均衡。初始相位采用相应的完整大圆相速度计算，从而大大减小了地球结构横向不均匀性的影响。根据一个简单的传播断层模型，由初相辐射图确定了千岛地震的断层长度。在这种方法中，断层长度和破裂速度之间没有折衷。这种折衷是传统方向性方法所固有的。得到的断层长度为250公里，几乎等于余震区的长度。我们已经引入了一个动态故障参数“源时间”，可以确定从相位测量使用完整的大圆相速度，而不是单个多个R波的平均相速度。该量对应于等效点源的源时间函数的上升时间。得到上述4次地震的震源时间分别为97、62、174和115 s。
Phase equalization was carried out for R waves in order to obtain information on source mechanisms of four earthquakes, the Kurile earthquake of 1963, its largest aftershock, the Rat Island earthquake of 1965, and the Tokachi-oki earthquake of 1968. The initial phase was computed using the corresponding complete great-circle phase velocity, so that influences of the lateral heterogeneity of the earth's structure were considerably reduced. The fault length of the Kurile earthquake was determined from the initial phase radiation pattern on the basis of a simple propagating fault model. There is no trade-off in this method between the fault length and the rupture velocity. Such a trade-off is inherent to the conventional directivity method. A fault length of 250 km was obtained, which was found to be nearly equal to the length of the aftershock area. We have introduced a dynamic fault parameter ‘source time’ that can be determined from the phase measurement using the complete great-circle phase velocity rather than the average phase velocity of the individual multiple R waves. This quantity corresponds to the rise time of the source time function of an equivalent point source. Source times of 97, 62, 174, and 115 s were obtained for the above four earthquakes.