采用新疆地区1990年以来的浅源地震目录，利用扩散链法去除余震，在小震空间集中度C值的研究基础上，进一步发展了C值变化量，即ΔC值的时空扫描计算方法，针对2000年以来天山地震带11次6级以上地震前ΔC值的演化过程，进行回顾性研究。结果表明，2012年新源—和静交界MS 6.6地震、2017年精河MS 6.6地震和2020年伽师MS 6.4地震之前，均出现较为明显的区域ΔC值异常，且3次地震前ΔC值异常演化时间均小于6个月，属于震中附近区域震前中短期异常变化。
Based on the Xinjiang earthquake catalog since 1990, we studied the spatio-temporal variation of seismic concentrative degree C and developed a method of calculating the variation of C value, i.e., ΔC value. The earthquake catalog was declustered by the diffusion chain method. Then we calculated the magnitude of completeness Mc. The result shows that the Mc for Tianshan earthquake zone varies from ML 1.0 to ML 3.0 since 2000 and keeps around ML 3.0 from 1990 to 2000. Therefore, our study is based on the events with magnitude larger than ML 3.0 in the catalog. Our method calculates C values in a step of one month and puts the results in a database. The current C value is subtracted from the average C value of the previous 10 years and then divided by the standard deviation to calculate the current ΔC value. Based on retrospective studies of 11 MS ≥ 6.0 earthquakes that occurred in the Tianshan seismic belt since 2000, we found that there were ΔC value anomalies around the epicentral areas before the Xinyuan-Hejing MS 6.6 earthquake in 2012, the Jinghe MS 6.6 earthquake in 2017, and the Jiashi MS 6.4 earthquake in 2020. The three earthquakes occurred in the vicinity of the high ΔC area according to the spatio-temporal scanning results. The anomaly-time curves show that the evolution time of the ΔC anomaly is less than half a year, indicating that the ΔC value anomaly is a short to medium-term anomaly that appeared before an earthquake.
2021,42(3): 15-24 收稿日期：2020-06-28
DOI：10.3969/j.issn.1003-3246.2021.03.002
基金项目：国家重点研发计划课题（项目编号：2017YFC1500502）；中国地震台网中心青年科技基金（项目编号：QNJJ201905）
作者简介：马亚伟(1990-),男,硕士,主要研究方向:地震活动性
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