基于速率-状态依从摩擦定律的前郭震群余震活动率及模型参数相关性研究

基于速率-状态依从摩擦定律的地震活动率时空预测模型,以同震库伦应力变化作为模型初始应力扰动,模拟了2013年吉林前郭MS5.8震群的余震活动率变化。考虑模型参数相关性,在模拟中采用2种不同的拟合方案,一是余震持续时间t_a不固定条件下的拟合,二是余震持续时间t_a固定条件下的拟合。结果显示,t_a不固定条件下的拟合方式可获得较好的AIC评价,适用于震后早期的趋势判定; t_a固定条件下的拟合计算耗时更短,拟合误差更小,理论模拟结果与前郭震群实际地震时序特征更为吻合。采用该方案对截至2016年10月24日的余震活动率变化进行了回溯性预测检验,结果显示模型预期的余震日频次与实际记录呈较好的正相关关系。研究还发现,主震破裂面附近的同震应力影区导致震后早期模型预测值相对于实际偏低,说明前郭序列余震活动可能还存在其他触发机制。

Aftershock Rate Forecasting of the Qianguo Seismic Swarm Based on the R-S Model and Parameter Correlations Analysis

Dieterich physics-based approach build up a seismic rate forecasting model based on rate- and state-dependent friction law. According to previous research,we modeled the aftershock rate of the Qianguo seismic swarm in 2013 based on the R-S model. We considered coseismic Coulomb stress changes to be the initial stress perturbation. And,based on logarithm maximum likelihood best fit method,we present two different fitting mode. One is a fitting considering fixed aftershock duration fixed t_a. Another is considering a non-fixed aftershock duration non-fixed t_a. We found,fixed t_a mode provide a faster procedure calculation and a more correct parameter fitting results,while non-fixed t_a mode provide a larger lnL and a smaller AIC value. Finally,we consider the aftershock rate forecasting of the Qianguo seismic swarm based on the fixed t_a mode. The forecasted aftershock number per day has a well positive correlation with observation. The stress shadow near the mainshock failure leads to a lower forecasted value compared with observation,which means more other trigger mechanisms for aftershock activity.