2019年6月17日四川长宁MS6.0地震早期序列参数分析及强余震概率预测

2019年6月17日四川长宁发生M_S6.0地震, 之后发生了一系列的强余震, 为更好地分析此次地震的序列特征以及强余震的可预测属性, 采用国际上对复杂序列拟合相对较好的“传染型余震序列”(ETAS)模型以及基于Reseanberg-Jones(R-J)模型发展的Omi-R-J模型, 通过连续滑动、 拟合和余震发生率预测, 对地震序列的模型参数稳定性、 预测结果进行了比较研究, 并利用N-test、 T-test检验方法对预测结果进行了效能评估。 结果表明, 相比于其他中强震序列参数, 此次长宁M_S6.0地震序列参数中反映激发能力的αETAS较其他序列明显偏小, 而反映衰减能力的pORJ值和应力累积水平的bORJ值相对较小, 与此次余震序列丰富、 持续时间相对较长相吻合; ETAS和Omi-R-J模型对于复杂序列在3.0, 3.5, 4.0]三个震级档的强余震仍具有一定的预测能力; 总体的“每个地震的信息增益”(IGPE)计算结果显示, ETAS模型略优于Omi-R-J模型, 前者或更适合复杂地震序列的余震预测。

The Study on Early Sequence Parameters and Probability Forecasting of Strong Aftershocks of Changning MS6.0 Earthquake on June 17, 2019, Sichuan Province

An M_S6.0 earthquake occurred on June 17, 2019 in Changning, Sichuan Province, which was followed by a series of strong aftershocks. In order to better analyze the sequence characteristics and predictability of the strong aftershocks, this paper focuses on the comparative study of the applicability of the “Epidemic Type Aftershock Sequence” (ETAS) model which have been widely adopted internationally for complex sequence, the Omi-R-J model which based on the Reseanberg-Jones (R-J) model. We compare the stability of model parameters, forecasting results by continuous sliding, fitting and aftershock occurrence rate forecasting, and evaluate the effectiveness of forecasting by using the N-test and T-test with multiple time windows. The results show that the sequence parameters αETAS of response excitation ability of Changning M_S6.0 earthquake sequence is obviously smaller than other parameters of moderate-strong earthquake sequence, while the pORJ value of response attenuation ability and the bORJ value of response stress accumulation level are relatively small, which are consistent with the rich and relatively long duration of this aftershock sequence. ETAS and Omi-R-J models still have certain forecasting ability for strong aftershocks of complex sequence at three magnitude ranges 3.0, 3.5, 4.0]. The overall “Information Gain Per Earthquake” (IGPE) calculation results show that the ETAS model is slightly superior to the Omi-R-J model, thus the former is more suitable for aftershock forecasting of complex earthquake sequences.