郯庐断裂带南段及邻区中小地震视应力的时空特征研究

Temporal and Spatial Characteristics of Small to Moderate Earthquake Apparent Stresses in the South Part of Tanlu Fault Belt and Adjacent Areas

利用安徽地区测震台网记录的波形资料,采用波形分析和反演的方法计算了郯庐断裂带南段及邻区中小地震的视应力,分析研究视应力的时空变化特征,并讨论其与地震矩等震源参数之间的关系。结果表明:①利用提取的地震震源谱数据计算得到郯庐断裂带南段及邻区中小地震的视应力值为0.05～0.9MPa,平均为0.20MPa,以此可作为该区域的背景应力水平;②时间变化显示视应力在黄海ML5.1、江西九江ML6.0及河南太康ML5.0地震前呈现持续高值异常状态,震后趋于正常水平,而江西九江6.0级地震后视应力再次出现高值异常,随后发生了安徽定远ML4.7地震,一定程度上说明郯庐断裂南段及邻区中小地震的高视应力水平与华东地区中强震有较好的对应关系;③空间分布显示高视应力集中区与地震高辐射能区域具有一定的相关性,主要位于嘉山—滁州段的皖、苏交界区附近和庐江县附近,该区域相继发生过定远4.7级和安庆4.8级地震,并推断认为庐江县附近发生破坏性地震的危险性可能更大,值得高度关注;④视应力随着地震矩增加而增加的趋势不明显,拐角频率与地震矩大体呈负相关。

Based earthquake data recorded by the Anhui seismic network,using waveform analysis and inversion,we calculated small to moderate earthquake apparent stresses in the south part of the Tanlu fault belt and adjacent areas,analyzed their variation characteristics in time and space,discussed the corresponding relationship with earthquake moment and source parameters.The results show： ① Using earthquake source spectrum data,the obtained apparent stress value in the south part of Tanlu fault belt and adjacent areas is between 0.05~0.9 MPa,averaging 0.20 MPa,which is the background stress level of the region;② Temporal change shows apparent stresses continued to present abnormally high values before Huang Hai ML5.1 earthquake,Jiangxi Jiujiang ML6.0 earthquake and Henan Taikang ML5.0 earthquake,to be normal after earthquake.But after Jiangxi Jiujiang magnitude 6 earthquake,apparent stresses have again a high value anomaly,subsequently Anhui Dingyuan ML4.7 earthquake happened,to a certain extent show that the high level of apparent stress in the south part of the Tanlu fault belt and adjacent areas have a good corresponding relationship with strong earthquakes in East China;③ Spatial distribution shows high value area of apparent stress is relevant to the seismic radiation energy higher area,mainly lied in Jiashan-Chuzhou section and Lujiang county nearby,where Dingyuan magnitude 4.7 earthquake and Anqing magnitude 4.8 earthquake happened in succession;④ It is not obvious that apparent stress increases with earthquake moment,corner frequency basically has a negative correlation with earthquake moment.