云南地区地壳速度模型研究及应用

Study on Crustal Velocity Model and Its Application in the Yunnan Region

摘要:

选取2009～2014年发生在云南地区、每个地震均在10个以上台站有记录的7412个地震数据，作走时曲线。同时为提高精度，重点对其中每个地震均在80%以上台站有记录的、M_L≥3.0的83个地震数据，再作线性分析、折合走时曲线和区间稳定性分析，结合前人研究成果得到了研究区的初始地壳速度模型。选取2010～2014年云南省内M≥3.0的200次地震，采用Hyposat批处理方法迭代初始速度模型，以及对S波作分层速度拟合，得到云南地区的地壳速度模型，即2015云南模型：v_P1=6.01km/s，v_P2=6.60km/s，v_Pn=7.89km/s，H₁=20km，H₂=21km，v_S1=3.52km/s，v_S2=3.86km/s，v_sn=4.43km/s。基于新模型的地震重定位分析表明，云南地区地震事件大多发生于20km内的上地壳；对2011年3月10日盈江M5.8和2014年8月3日鲁甸M6.5典型地震进行重定位，得出震源深度分别与精定位结果和震中强震台震源距接近，表明新的一维速度模型能更好地反映研究区平均速度结构。

Abstract:

We selected the records of 7,412 earthquake data from more than 10 seismic stations during 2009~2014 in the Yunnan region and turned them into a travel time curve. Meanwhile to improve the precision,we focused on the 83 earthquake data with M_L>3.0 from the stations with over 80% of the records. We then do the linear analysis,the travel time curve and the interval stability analysis,and combined with the previous research results obtained the initial crustal velocity model of the study area. The results of the Hyposat batch determination of 200 earthquakes over M3.0 and the stratified velocity fitting of the S wave were searched to obtain the crustal velocity model in Yunnan Province,that is,the 2015 Yunnan model:v_P1=6.01km/s and v_P2=6.60km/s, v_Pn=7.89km/s, H₁=20km, H₂=21km,v_S1=3.52km/s, v_S2=3.86km/s, v_Sn=4.43km/s. Seismic relocation analysis based on the new model shows that most of the earthquake events in Yunnan region occur in the upper crust within 20km. The typical seismic relocation of March 10,2011 Yingjiang M5.8 and August 03,2014 Ludian M6.5 are close to their focal strong earthquake stations respectively. The results show that the new one-dimensional velocity model can better reflect the average velocity structure in the study area.