天山地区流动重力重复测量资料前兆异常识别判据、地震预报指标及效能评价

EARTHQUAKE ANOMALY RECOGNITION CRITERION,PREDICTION INDEX FROM REPEATED MOBILE GRA-VITY SURVEY DATA IN TIANSHAN AREA AND EVALUATION OF ITS PREDICTION ABILITY

通过对 1 5年以来的流动重力重复测量资料的统计分析 ,认为在 MS5.0左右及大于 MS5.0地震前重力资料有显著的前兆异常。异常识别判据定为相邻两期段差变化绝对值大于、等于 40× 1 0 -8m· s-2 。预报指标 :发震时间为测出异常后 1 2 (± 6)个月内 ;地点在异常测段周围 1 50 km(特殊地质构造关系 2 50 km)范围内 ;震级一般为 MS5.0左右 (异常量大于 70× 1 0 -8m· s-2 时为 5— 6级 )。预报效能评价为 66.1 3%。

Take the absolute value of gravity difference between two neighboring surveying points more than 40×10 -8m.s -2 as anomaly criterion, fifteen years' mobile gravity data that were repeatedly surveyed by Lacoste-Rombeg gravimeters in Tianshan area was made a total time-space scanning and statistical analysis. The obvious precursory anomalies had been found before the M-S4.5 or so and M-S≥5.0 earthquakes. The prediction indexes are determined as follows: the earthquake occurring time is 12(±6) months after anomaly appearing, the location in an area of 150 km from the anomalous survey segment,the magnitude generally about 5 (5-6 when anomalous amount over 70×10 -8m.s -2). The prediction ability is evaluated to be 66.13%.