摘要
以1992年美国南加州Landers MW7.3地震为例,通过利用主震前后应力场和主震位错引起的应力变化来约束背景应力场差应力的方法,系统研究了数据不确定性与差应力约束可靠性的关系.通过实际地震数据结合数据模拟研究,发现由于数据的不确定性(主要是震源机制解不确定性和发震节面的难确定性),该方法得到的原始约束结果与真实差应力存在系统偏差,原始约束值不能反映真实的差应力水平.数据模拟统计曲线表明,原始约束值和真实差应力存在两段线性关系:上升段和水平段,上升段对差应力有约束能力,水平段对差应力没有约束能力.利用上升段的线性关系对原始差应力约束值调整,得到的调整约束值在一定区间消除了与真实差应力的系统偏差.在不同的分析地点(分析点),本质上是主震位错引起的不同应力变化,数据不确定性对差应力约束结果影响也不同,不同分析点在差应力约束上有优劣性.本文采用Rv、Tv、λ等三个客观评价参数来挑选分析点,在Rv≤9,|Tv|≥17.5,λ<1的条件下挑选出24个分析点,得到Landers地震背景应力场差应力的最佳约束结果是-12.2±2.6 MPa.通过对评价参数的不同取值来检验约束结果的稳定性,以及通过数据模拟的综合分析来检验约束结果的可靠性,发现该最佳约束结果是稳定和可靠的.
Taking the 1992 MW7.3 Landers,California,earthquake as an example and using the stress fields before and after the mainshock and the stress changes caused by the mainshock dislocation to constrain the background differential stress,the relationship between the data uncertainty and reliability of the differential stress constraint was studied systematically.Using actual seismic data in combination with data simulation research found that the uncertainty of the data(mainly uncertainty of the focal mechanism and focal plane ambiguity)results in a systematic deviation between the original constraint results obtained by this method and the real differential stress.Thus,the original constraint value does not reflect the true differential stress level.The statistical curve of data simulation showed that there were two linear relationships between the original constraint value and the true differential stress:the rising segment and the horizontal segment,with the rising segment having the constraint capacity for the differential stress and the horizontal segment having no constraint capacity for the differential stress.The original differential stress constraint value was adjusted using the linear relationship of the rising segment,and the obtained adjusted constraint value eliminates the systematic deviation from the true differential stress in a certain interval.At different analysis locations,which are essentially different stress changes caused by mainshock dislocations,data uncertainty also has different effects on the differential stress constraint results,and different analysis locations vary greatly in constraint capability for differential stress.We used three evaluation parameters,Rv,Tv,andλ,to select analysis locations objectively.Twenty-four analysis locations were selected under the conditions of Rv≤9,|Tv|≥17.5,andλ<1,and the best differential stress constraint result of the Landers earthquake was-12.2±2.6 MPa.The stability of the constraint results was checked by using different values of the evaluat
作者
郝平
HAO Ping(Institute of Earthquake Forecasting,China Earthquake Administration,Beijing 100036,China)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2023年第10期4176-4188,共13页
Chinese Journal of Geophysics
基金
国家自然科学基金项目(41874045)资助。
