基于ESMD方法的火山地震活动前后GNSS坐标异常分析

GNSS coordinate anomaly analysis before and after volcanic seismic activity based on ESMD method

火山地震活动对地面观测站的位置有很大影响。为了探究火山地震前后全球导航卫星系统(GNSS)测站的位移情况,以汤加火山地震事件为例,基于汤加(TONG)站2个月的观测数据,使用PRIDEPPP-AR软件对数据进行解算,引入极点对称模态分解(ESMD)方法对坐标时间序列进行分解,并对坐标位移进行了分析,结果显示:数据解算精度较高,北(N)和东(E)方向中误差在5 mm左右,垂直(U)方向精度在9 mm左右。在地震发生当天和前1~2 d,E方向坐标出现了0.1 m左右的明显扰动;在地震发生当天,U方向坐标时间序列异常不明显,但是在地震发生前1~2 d,可以观察到坐标的明显扰动。通过ESMD方法可以观察到E方向GNSS坐标时间序列的Model 1、Model 2信号振幅在震前和震后都有明显的异常扰动现象,同时也有明显的同震扰动。U方向Model 1~Model 3信号有着明显的同震振幅异常扰动,N方向坐标异常扰动不明显。从总能量信号来看,U方向和E方向可以观测到多次非常明显的能量异常,异常强度约为正常水平的3~10倍,N方向也能发现部分同震和震前能量异常,但是异常并不明显。

Volcanic seismic activity has a great influence on the location of ground observation stations.In order to explore the displacement of global navigation satellite system(GNSS)observation stations before and after volcanic earthquakes,this paper took Tonga’s volcanic seismic events as an example.Based on the observation data of Tonga(TONG)Station for two months,PRIDE-PPP-AR software was used to solve the data.The extreme-point symmetric mode decomposition(ESMD)was introduced to decompose the coordinate time series and analyze the coordinate displacement.The results show that the accuracy of the data solution is high,and the error in the north(N)and east(E)directions is about 5 mm.The accuracy in the vertical(U)direction is about 9 mm.On the day of the earthquake and 1-2 days before the earthquake,there was an obvious disturbance in the coordinates in the E direction,which deviated from the normal value by about 0.1 m.On the day of the earthquake,the coordinate time series in the U direction had insignificant anomalies,but a significant disturbance of the coordinates could be observed 1-2 days before the earthquake.Through the ESMD method,it could be observed that the signal amplitudes of Model 1 and Model 2 in the GNSS coordinate time series in the E direction had obvious abnormal disturbances before and after the earthquake,and there were obvious coseismic disturbances.The signals of Model 1-Model 3 in the U direction had obvious abnormal disturbances of coseismic amplitudes.The abnormal disturbance of the coordinates in the N direction was not obvious.From the perspective of the total energy signal,multiple prominent energy anomalies could be observed in the U and E directions,and the intensity of the anomaly was 3-10 times the normal level.Some coseismic and preseismic energy anomalies could also be found in the N direction,but they were not obvious.