2023年土耳其双强震震源机制中心解及震源区构造应力场特征分析

Central Solutions of Focal Mechanisms and Characteristics of Tectonic Stress Field in the Source Area of Two Strong Earthquakes in Turkey in 2023

为理解2023年2月6日土耳其双震震源区的构造应力场特征,剖析双强震的孕育背景和发生条件,根据1976年1月至2022年10月全球CMT目录的震源机制解反演了土耳其双强震震源区及其邻区震前构造应力场,并模拟在其作用下各种形状断层上产生的相对正应力和剪应力分布情况。结果表明:(1)研究区域震前主要处于NNW-SSE向挤压和WWS-EEN向的拉张状态,且以拉张应力为主。这与阿拉伯板块向北运动,推挤安纳托利亚地块和安纳托利亚块体被迫向西逃逸相对应。(2)M_(W)7.8地震的断层破裂几乎沿应力场的最大剪应力平面发生,是在区域走滑型构造应力场作用下,沿应力场最大剪应力平面进行的正常能量释放。M_(W)7.5地震与背景构造应力相差较远,推测为M_(W)7.8地震产生的应力变化触发的结果。

Aiming to studying the characteristics of the tectonic stress field in the source area of the two strong earthquakes in Turkey on Feb.,6,2023 and analyzing seismogenic background and occurrence conditions of two strong earthquakes,we inverted tectonic stress field in the source area of two strong earthquake and its adjacent areas before two earthquakes on the basis of the source mechanism solutions of 87 M_(W)≥4.7 earthquakes in the global CMT catalogue from Jan.,1976 to Oct.,2022.In addition,we also simulated the distribution of relative normal stress and shear stress on faults of various shapes.The main conclusions of this paper are as follows:First,the study area was mainly in a NNW-SSE extrusion and WWS-EEN tensile state before the earthquake with dominant tensile stress state,which corresponds to the northward movement of the Arab Plate to push the Anatolian Block and forcing it to move westward.Second,the fault rupture of the M_(W)7.8 earthquake occurred along the maximum shear stress plane of the stress field,which appeared a normal energy release along the maximum shear stress plane of the stress field under the action of regional strike-slip tectonic stress field.The seismogenic fault of the M_(W)7.5 earthquake was significantly different from the background tectonic stress in the study area,and it is speculated to be the result of stress changes triggered by the M_(W)7.8 earthquake.