P波极性揭示的甘东南地区构造应力场特征  

The Tectonic Stress Field in Southeastern Area of Gansu Province Deduced from P Wave Polarity Data

作　　者：卜玉菲[1] 张元生[1] 万永革[2] 刘旭宙[1] 高见[1] 

机构地区：[1]中国地震局兰州地震研究所,甘肃兰州73000 [2]防灾科技学院,河北三河065201

出　　处：《地震工程学报》2013年第1期160-165,共6页China Earthquake Engineering Journal

基　　金：国家自然科学基金(40874029;41074072);地震行业专项(201208009);国家科技支撑计划项目(2012BAK19B03-4)

摘　　要：通过分析甘东南宽频带流动台阵以及周边固定台站2010年11月1日-2011年11月30日记录的大量近震资料,对区域地震进行了重新定位。根据P波极性数据推断了甘东南地区主应力轴方向,给出了0.25°×0.25°的构造应力场方向。结果显示,甘东南地区最大主压应力轴表现出旋转特性。最大主压应力轴由北部的NEE向逐渐向南部偏转为近EW向和SEE向。结合该区域其它结果讨论了本区域应力场的成因机制。To determine the crustal stress field based on the basis of earthquake waves,we analyze data from fixed seismic stations in Gansu and surrounding provinces and the broadband portable seismic array in southeast Gansu province,where three blocks converge to create complex tectonic conditions.Two methods used to directly obtain such stress fields include those based on focal mechanism data and p-wave first motion data.In order effectively use small and microscale earthquake data,the latter method is used in our study.On the basis of near earthquake observation data recorded from November 1,2010,to November 30,2011,we use Zhang＇s Method to relocate earthquakes occurring in this area.As a result,2 379 earthquakes and 12 129 p-wave polarity data are obtained through which the directions of principal stress axes are inferred.The inversion method and program are provided by Wan.Our study assumes a relative stress value of 0.5.We calculate only the 2-D stress field because most earthquakes have occurred in the research area at depths of 5~20 km;the average depth of 12 km was chosen as the calculating depth.The direction of tectonic stress field in a 0.25° × 0.25° grid in this area is presented for the first time.The orientation of P,B,and T axis azimuths are obtained by 1° × 1° × 1° grid searching.We treat these azimuths as stress flied directions when the contradictory ratio is the smallest.Results show that the maximum compressive stress axis strikes are presented in a radiated pattern;that is,they strike east-west from NEE in northern part to SEE in the east.These findings are similar to that reported in previous research,through which we can infer that the Qinghai-Tibet plateau moving to the northeast encountered the stable Ordos block and the South China block moving to the southeast;thus,the material moved southeast.The earthquakes occurring in this region were fewer and smaller than those west of 104° E;therefore,the stress field inversion result is primarily obtained from smoothing the results of surrou

关 键 词：P波初动 甘东南地区 构造应力场 流动台阵 

分 类 号：P315.12[天文地球—地震学]