工业开采诱发地震的应力降研究现状和主要科学议题

诱发地震及其灾害风险已成为非常规油气资源开发和废水回注等新型工业活动顺利实施的重要威胁。应力降是反映地震破裂前后断层上平均应力差的物理量,对诱发地震中应力降的系统研究有助于揭示诱发地震的震源特征、高频地震动特征、构造背景和地震危险性。本文系统地总结了近20年来工业开采诱发地震中应力降的相关研究进展,分别从计算所用理论方法、获得的平均应力降数值、影响应力降数值的主客观因素、围绕应力降的重要科学讨论等方面做了归纳分析。介绍了直接进行谱拟合、经验格林函数(EGF)、谱叠加和广义反演3种适用性的计算方法,通过案例考察了工业开采诱发地震的应力降平均值,分析影响应力降测定数值的主客观因素,并总结应力降空间分布依赖性、与震源机制类型相依性、自相似性、深度依赖性等4个主要科学问题。同时,阐述了诱发地震应力降的测定可靠性仍未突破、主要科学问题存在广泛争议、在新型工业开采活动中具有重要应用潜力等现状。本文的总结分析可为从事新型能源开发、地震安全监管和科学研究领域的企业、管理人员和科学研究人员提供参考。

Research Status and Major Scientific Issues in Stress Drop in Mining-induced Earthquake

Induced earthquake and the disaster risk have become serious threats to the smooth implementations of newly industrial activities such as unconventional oil and gas extraction and wastewater reinjection. The stress drop,which reflects the average stress difference on the fault before and after the earthquake rupture,is helpful to reveal the source characteristics,high-frequency ground motion characteristics,tectonic setting and seismic risk of induced earthquake. In this study,we systematically summarize the research progress of stress drop that is related to mining-induced earthquake during the past 20 years,referring to the theory and method used in calculation,the estimated average stress drop values,the subjective and objective factors that affect the stress drop,and important scientific issues. We introduce three applicable calculation methods,including direct spectral fitting,the Empirical Green''s function(EGF),and spectrum superposition and generalized inversion. We study the average stress drop that is caused by mining-induced earthquake through case investigation,analyze the subjective and objective factors affecting the estimation of stress drop,and summarize four major scientific issues,including the space dependency,focal mechanism type dependency,self-similarity,and depth dependency. We also mention that there is no breakthrough in the reliability of measured stress drop;the main scientific issues are widely disputed;and it has important application potential in newly mining activities. We hope the summary and analysis in this study will provide some scientific references for enterprises,managers and researchers who are engaged in the fields of new energy development,seismic safety supervision and scientific research.