2003年民乐—山丹6.1和5.8级地震序列类型及地震学参数异常特征

Sequence Type and the Seismological Parameter Anomaly Characteristics of the Minle-Shandan M_S6.1, 5.8 Earthquakes in 2003

分析了2003年10月25日甘肃省民乐—山丹61,58级地震的序列类型及地震学异常特征,其最大余震震级为MS43,序列b值为069,h值为15;两次主要地震震级差为03级,释放的能量占整个序列能量的717%,序列判定为双震型。震前共出现了9项地震学参数异常,最为突出的是中等地震集中持续活动,为发震地点和震级提供了较好的短期判据。本次地震发生在甘肃省地震局圈定的2003年度祁连山中东段6级地震重点危险区边缘,震前作出了较好的短期预测。

The sequence and seismological parameter anomaly characteristics of the Minle-Shandan M_S6.1 and M_S 5.8 Earthquakes on Oct. 25, 2003 are studied in this paper. The maximum aftershock is M_S 4.3, b-value is 0.67 and h-value is 1.5. Because the magnitude difference of the two mainshocks is 0.3 and the ratio of their energy takes 71.7% of the total, the earthquake sequence is judged as double-shock type. There were the anomalies of nine seismological parameters before the earthquakes, and the most marked anomaly was the central and continuous activity of the medium earthquakes, which supplied good short-term criterion for the determination of the location and strength of the mainshocks. The earthquake occurred at the edge of the M6 earthquake risk region, which was in the middle-east section of the Qilian Mountains and predicted by the Earthquake Administration of Gansu Province in 2003. The good short-term prediction had been made before the shock.