2020年1月19日新疆伽师MS6.4地震及余震序列定位研究

LOCATION STUDY OF XINJIANG JIASHI M S6.4 EARTHQUAKE AND AFTERSHOCKS SEQUENCE ON JANUARY 19TH,2019

利用此次伽师地震序列震相数据,通过走时曲线得到震源区的初始一维速度模型。结合此速度模型,利用单纯形法测定了新疆伽师M S6.4地震参数。使用双差定位方法对伽师地震和M L≥1.8的297次余震事件进行了重新定位,得到结论:①伽师M S6.4地震参数为39.841°N、77.151°E、深度14.4 km。②伽师地震的破裂是非均匀、迁移的。主、余震整体分布呈“T”字型展布,主震位于“T”字底部,“T”字的横长竖短,多数余震向主震的正北方向延伸,余震整体呈近东西方向展布,东西方向长约40 km,南北方向长约20 km。前震、主震发生在震源区近南面的隐伏断层,可能是受塔里木盆地的阻碍,余震并没有向南发展,而是逐渐向北延伸至位于北面的隐伏断层,后又沿北面的断层向东发展。③通过序列整体分布呈“T”字型展布,初步判断伽师地震是一次共轭断层破裂事件。余震一边向主震正北方向发展,一边继续向东发展,表明发震断层是一条近EW向北倾断层,同时证明了塔里木盆地向北插入南天山。④地震震源深度主要集中在10~20 km,占73%,优势破裂深度在中地壳,中地壳积累和释放的能量居多。伽师地震位于塔里木盆地边缘,地表覆盖有7~8 km的低速沉积层。

Based on the phase data of this Jiashi Earthquake sequence,the initial one-dimensional velocity model of the focal area is obtained through the travel time curve.Combined with this velocity model,the seismic parameters of Jiashi M S6.4 in Xinjiang are measured by simplex method.The 297 aftershock events of Jiashi Earthquake and M L≥1.8 were relocated by using double difference positioning method.The conclusion is as follows:(1)The parameters of Jiashi M S6.4 earthquake are 39.841°N,77.151°E and 14.4 km in depth.(2)The fracture of Jiashi Earthquake is non-uniform and migrated.The overall distribution of main and aftershocks is in the form of“T”.The main shock is located at the bottom of“T”.The horizontal length and vertical length of“T”are short.Most of the aftershocks extend to the north direction of the main shock.The aftershocks are distributed nearly in the East-West direction,about 40 km in the east-west direction and about 20 km in the north-south direction.The foreshock and main earthquake occurred in the concealed fault near the south of the focal area,which may be hindered by the Tarim Basin.The aftershock did not develop southward,but gradually extended northward to the concealed fault in the north,and then developed eastward along the fault in the north.(3)According to the“T”distribution of the whole sequence,it is preliminarily judged that Jiashi Earthquake is a conjugate fault rupture event.The aftershocks developed to the north of the main earthquake and to the east at the same time,indicating that the seismogenic fault is a fault dipping to the north near EW,and that the Tarim Basin is inserted into the South Tianshan Mountain to the north.(4)The focal depth of the earthquake is mainly 10~20 km,accounting for 73%.The dominant fracture depth is in the middle crust,and the energy accumulated and released in the middle crust is mostly.Jiashi Earthquake is located at the edge of Tarim Basin,and the surface is covered with 7~8 km low-speed sedimentary layer.