鲁甸M_S6.5地震前地震活动性分析及川滇东边界中部未来地震危险性研究

本文努力探索地震活动性定量化前兆的检测方法,针对Region-Time-Length(RTL)算法在空间异常分析中的不足,根据新提出的综合衡量区域地震活动水平的物理参数——RTL面积分(I_(RTL)),定量分析了2014年鲁甸M_S6.5地震前地震活动时空变化,并与2012年彝良M_S5.7、5.6地震作了对比,研究结果显示这些地震前都检测到地震活动增强.彝良地震前地震活动增强异常主要分布在则木河断裂和昭通—莲峰断裂带西段的交汇区,鲁甸地震前异常主要分布在昭通—莲峰断裂带、马边断裂带及周边地区.以上地震活动增强异常区的I_(RTL)随时间呈现由小变大,至峰值后回落的特征.彝良地震和鲁甸地震均发生于I_(RTL)峰值后数月,这表明I_(RTL)峰值对地震发生可能有一定的指示意义.鲁甸地震后,对周边地区地震活动跟踪研究检测到地震活动增强现象,且自2015年I_(RTL)呈上升趋势,目前I_(RTL)值已超过鲁甸地震前的峰值水平,也许更强的地震正在孕育,所以川滇交界东边界中部仍存在发生强震的可能.以上研究为我们认识鲁甸地震的孕震过程和地震前兆研究提供了新的认识.

Analysis of the seismicity changes prior to the MS6.5 Ludian earthquake and study on the potential strong-earthquake risk for the middle part of eastern boundary of Sichuan-Yunnan

For lacking physical parameters to analyze space anomalies of seismic activity which detected by Region-Time-Length (RTL) algorithm, an effort to explore the precursory parameter for quantifying seismic activity in space was conducted. The RTL algorithm and the new physical parameter-surface integral of RTL (I_RTL), which could synthetically evaluate the space-time changes of seismicity in a region, were applied to analyze the seismicity changes prior to the 2014 Ludian M_S 6.5 earthquake and the 2012 Yiliang M_S5.7, M_S5.6 earthquakes. An enhancement of seismic activity was detected prior to the above earthquakes. Space anomalies mainly distributed in Zemuhe fault and west part of Zhaotong-Lianfeng fault prior to Yiliang earthquakes. Before Ludian earthquake, anomalies were detected in Zhaotong-Lianfeng fault, Mabian fault and surrounding areas. The parameter I_RTL of anomalous region changed from small to large, after reaching its peak value, then reduced. Several months after the peak points, Yiliang and Ludian earthquakes occurred. I_RTL may be an indicator for earthquake occurrence. After Ludian earthquake, an enhancement of seismic activity was detected in the middle part of eastern boundary of Sichuan-Yunnan, and I_RTL was increasing since January 2015. Now, the value of I_RTL was larger than the peak value prior to Ludian earthquake. Perhaps a stronger earthquake may be preparing in the middle part of the eastern boundary of Sichuan-Yunnan in the future. The above studies may provide some new evidence for better understanding the seismogenic process of Ludian earthquake and earthquake precursors.