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云南地区GNSS应变场时空演化与地震事件关联分析
王伶俐, 洪敏, 张勇, 高涵, 徐良叶, 牛甜
云南省地震局, 昆明 650041
摘要:
采用GAMIT/GLOBK软件对云南境内及邻区近400个GNSS测点1999~2018年的观测数据进行解算,在各个测点时间序列和速度场的基础上,采用克里金插值方法分时段估计该区域在1999~2004年、2004~2007年、2009~2013年、2013~2015年、2015~2018年共计5个时间区域应变率场;根据区域地壳面应变率和最大剪应变率的空间变化以及相应时段之后3年内的MS ≥ 5.0地震事件分布特征,分析发现:绝大部分震例发生在面应变高梯度带的张压转换区和最大剪应变高值区,可见研究区各个观测时段GNSS应变率场对后期1~3年内的中强震发生区域有一定的指示意义;以2014年盈江6.1级、鲁甸6.5级和景谷6.6级地震为样本,建立监视块体获取应变时间序列,分析发现:地震前三个月左右均出现震中附近短期应变趋势改变、快速增强、转折的现象,这些形变异常变化或许反映了发震区应力-应变积累在接近临界破裂状态时的非线性调整,为地震短临预测尤其是时间要素的判断提供参考。
关键词:  GNSS  速度场  应变率场  地震预测  时间序列
DOI:
分类号:P315
基金项目:云南省地震局地震科技专项基金(2017ZX03)、地震地磁分析与地震预报创新团队共同资助
Analysis of the Relationship between the Spatiotemporal Evolution of GNSS Strain Field and Earthquake Events in Yunnan Region
Wang Lingli, Hong Min, Zhang Yong, Gao Han, Xu Liangye, Niu Tian
Yunnan Earthquake Agency, Kunming 650041, China
Abstract:
GAMIT/GLOBK software was used to calculate the observed data of about 400 GNSS sites in Yunnan and neighboring regions from 1999 to 2018. Based on the time series and velocity fields of each measuring point,kriging interpolation method was used to estimate the strain rate fields in 5 periods(from 1999 to 2004,2004 to 2007,2009 to 2013,2013 to 2015,2015 to 2018). Based on the spatial variations of surface expansion rate and maximum shear strain rate,as well as the distribution characteristics of MS>5.0 seismic events within 1~3 years after the corresponding periods we found that the most seismic cases in following 3 years were occurred in the transition zone between extension and compression of high gradient belt,as well as the high value zone of the maximum shear strain gradient belt. Therefore,the GNSS strain rate field of each observation period has certain significance for predicting the occurrence of earthquakes in future. In this paper we also carry out high-precision data processing on the continuous GNSS data since 2011,and obtain the coordinate time series of all stations. The analysis of the strain time series of the tectonic blocks where Yingjiang MS6.1 earthquake Nudian MS6.5 earthquake and Jinggu MS6.6 earthquake occurred,we find that trend changes,rapidly intensifies and turns of the strain about three months before the earthquakes may reflect the nonlinear adjustment of the stress-strain accumulation in the seismic region. The above results provide a reference for the short and imminent earthquake prediction,especially for the determination of time factors.
Key words:  GNSS  Velocity field  Strain rate field  Earthquake prediction  Time series