利用小波变换研究南天山地区流动重力异常特征——以2020年伽师M_(S)6.4地震为例

STUDY ON ANOMALY FEATURE OF MOBILE GRAVITY IN SOUTHERN TIANSHAN OF XINJIANG USING WAVELET TRANSFORM METHOD:CSAE STUDY OF JIASHI M_(S)6.4 EARTHQUAKE IN 2020

利用南天山地区2016~2019年的流动重力观测资料,获取伽师M_(S)6.4地震前不同时间尺度下区域重力场的动态演化特征,并通过功率谱分析方法,获取各阶小波重力细节对应的近似场源深度。结果表明:伽师M_(S)6.4地震前,巴楚至阿合奇一带一年尺度重力场变化呈现与断裂构造走向一致的正、负异常过渡带和梯度带特征,震源区为负变化高值集中区,两年尺度重力场变化显示柯坪块体皮羌断裂带两侧重力值出现显著异常变化,震源区为负变化高值集中区,3年尺度重力场变化显示震源区位于负值区。2018~2019年南天山地区重力场的小波变换结果显示,2020年1月19日伽师M_(S)6.4地震前,4阶小波重力细节中巴楚至阿合奇一带出现重力变化的高梯度带,量值约为80×10^(-8)m·s^(-2),地震位于负值集中区;利用功率谱分析方法,获取南天山地区各阶小波变换重力细节的场源近似深度,给予重力场变化具体的物理意义。

Based on mobile gravity observation data of Southern Tianshan from 2016 to 2019,the dynamic characteristics of regional gravity field in different scale were obtained before Jiashi M_(S)6.4 earthquake,and the depth of field source corresponding to each order of wavelet gravity details were obtained by power spectrum analysis.The results showed that before the Jiashi M_(S)6.4 earthquake,the one-year scale gravity field change in the Bachu Ahqi area was characterized by a positive and negative anomaly transition zone and gradient zone consistent with the strike of the fault structure.The source area was a high value concentration area of negative change.The two-year scale gravity field change showed that the gravity values on both sides of Piqiang fault zone in Keping block had significant abnormal changes.The source area was a high value concentration area of negative change.Three-year scale gravity field change showed that the source area was located in a negative value area.The wavelet transform results of the gravity field in the South Tianshan Mountains from 2018 to 2019 showed that before the Jiashi M_(S)6.4 earthquake on January 19,2020,there was a high gradient zone of gravity change in Bachu Ahqi area in the fourth order wavelet gravity details,with a magnitude of about 80×10-8 m·s-2,the earthquake was located in the negative concentration area.By using the power spectrum analysis method,the approximate depth of gravity field source of each order wavelet transform gravity detail in the South Tianshan was obtained,giving the specific physical significance of gravity field change.