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通过估计震源分布的空间分维D随时间的变化,并把这些结果与震源区及其周围区域的地震活动性进行比较,研究了2000年鸟取县西部地震(M_J=7.3)之前震源分布的分维结构。在用1983年1月到2001年2月期间的日本气象厅地震目录数据计算分维D值的过程中,运用了相关积分法和移动时间窗法。本文得出如下结论:(1)主震之前在震源区及其周围区域的D值急剧下降。估计的前兆持续时间为1～3年,时间窗不同,结果也不同。(2)D值的下降肯定是由震源的丛集和震源区及其周围广泛区域内的异常地震活动所致。(3)因此,与大地震相关的D值随时间变化作为地震的一项前兆是有效的。
By comparing the time-dependent changes of spatial fractal dimension D of the source distribution with the time, and comparing these results with the seismicity of the source area and its surrounding area, the source distribution of the western Tottori earthquake in 2000 (M_J = 7.3) was studied Fractal structure. In the calculation of the fractal dimension D using the data of the Japan Meteorological Agency’s earthquake catalog from January 1983 to February 2001, the related integral method and the moving time window method were used. The main conclusions of this paper are as follows: (1) The value of D in the source area and the surrounding area before the main shock sharply drops. Estimated precursor duration of 1 to 3 years, the time window is different, the result is also different. (2) The decrease of D value is certainly caused by the cluster of focal sources and the anomalous seismic activity in the focal area and its surrounding area. (3) Therefore, it is effective that the D value related to a large earthquake changes with time as a precursor of an earthquake.