2009年青海大柴旦M_S6.4地震前中小地震震源机制前兆特征分析

Analysis on Precursory Characteristics of Focal Mechanism Solutions of Mid-small Earthquakes before Qinghai Dachaidan M_S6.4 Earthquake in 2009

2009年8月28日青海省大柴旦MS6.4地震发生前,在震中附近发生了30多个1.0≤ML≤3.9地震。针对这些中小地震,采用青海省区域地震台网观测资料,利用矩张量反演理论和格林函数库技术对主震及震前中小地震进行快速矩张量反演,计算出了其中15个ML≥1.5地震的震源机制解。结果表明,主震发生前中小地震震源参数的一致性较好,断层面走向、倾角的一致性达到86%,其初至P波波形相关系数也较高。中小地震应力P、T轴的优势方向与该区域应力场方向基本一致。

The MS6.4 earthquake occurred in Qinghai Dachaidan area on Aug.28 in 2009,and there occurred more than thirty 1.0≤ML≤3.9 earthquakes before the main shock around the epicenter.Using the observation data in Qinghai Regional Seismic Network,we quickly inversed the moment tensor for the main shock and the midsmall earthquakes before the main shock to calculate the focal mechanism solutions of 15 ML≥1.5 earthquakes by moment tensor inversion theory and Green function database technology.The results showthat the focal mechanism solutions of mid-small earthquakes before main shock showed the good consistency,the consistency of the strike and dip of the fault plane reached to 86%,and the correlation coefficient of the initial P wave was higher.The advantage direction of the P、T axis of stress of mid-small earthquakes was consistent with the direction of stress field in the study region.