The seismic time series of 10 high-rate GNSS stations during the 2021 Maduo M W 7.4 earthquake were acquired using GPS and BDS/GPS fusion PPP based on the GREAT program, and the velocity time series 30 minutes before the earthquake were obtained based on the variometric approach.The analysis found that the BDS/GPS relative to GPS velocity RMS values in the EW,NS and UP orientation can be improved by 14.8%,15.2% and 3.5% respectively.The seismic wave’s first arrival-time was extracted from the BDS/GPS time series of each station using the STA/LTA method, the location of the epicenter of the Maduo earthquake was（34.63°N,98.51°E）,and the earthquake’s original time was 18:04:29（UTC）,calculated from the time of first arrival of seismic waves at each station.This article refers to the time of the Maduo earthquake, using the Coordinated Universal Time.The epicenter of the Maduo earthquake calculated by GPS time series is（34.6°N,98.54°E）,and the original time is 18:04:28.8.Using GPS and BDS/GPS peak ground displacement, the Maduo earthquake magnitude was inverted according to the empirical formula, and the obtained magnitudes were M W 7.36 and M W 7.34,respectively.The BDS/GPS magnitude was closer to the result published by GCMT.The results show that the BDS/GPS fusion PPP solution can improve the stability of time series and reduce noise, which can more realistically describe the surface displacement changes during the earthquake, thus improving the accuracy of the magnitude solution and providing better data support for earthquake early warning and post-earthquake rescue.

2022年1月15 日汤加火山剧烈喷发产生了波及全球的大气重力波,距离火山8 736～12 758 km的中国大陆所有地应变观测站清晰记录到由此产生的短时地表应变变化.应用小波分析方法系统分析了中国近200个地应变观测站记录数据的时空响应与频率特征,主要表现为:由大气重力波激发的短时地表应变变化的持续时间约为1.5 h,其中能量最强的变化集中在前40 min,面应变平均变幅约为186×10-10,呈现出单脉冲起伏状变化,形态具有很强的一致性,具备兰姆波传播属性;短时地表应变变化的平均传播速度约为310 m/s,与大气重力波传播速度基本一致.部分观测站还记录到绕地球一圈后再次到达的大气重力波对地表的作用.这是首次通过大范围布设的高精度地应变观测仪记录到大气重力波作用于地表的痕迹,有助于认识地壳运动和大气圈层相互影响的机制.

针对实际GNSS地壳形变流动监测中信号遮挡比较严重,GPS可视卫星数较少等问题,采用BDS/GPS双系统观测,分析了BDS/GPS双系统在实际流动测站观测中对精密单点定位(PPP)性能的改善.基于四川石棉地区GNSS地壳形变监测网实际流动测站观测数据,分析了在实际观测环境以及模拟更恶劣观测环境下BDS单系统、GPS单系统和BDS/GPS双系统等3种定位模式的可视卫星数、几何精度衰减因子(GDOP)、定位精度和历元利用率.结果表明:在观测环境较差的山区,BDS/GPS双系统可大大提高可视卫星数,几何精度衰减因子降低,显著改善卫星空间几何结构,提高收敛速度和定位精度;与BDS单系统、GPS单系统相比,BDS/GPS双系统收敛速度可提高50％～80％,定位精度可提高20％～50％;单系统定位精度受高度角影响较大,BDS/GPS双系统在较高高度角时仍可保持较高精度,稳定性更强;在遮挡严重地区,为保证有充足双频观测值,可视卫星数需有6颗或6颗以上.BDS/GPS双系统因其高稳定性和高精度,更有利于在地形起伏剧烈区域捕捉地壳形变及地震产生的微弱位移信号,在复杂观测环境(山区、树林、建筑物密集区)具有更好的应用价值.

通过Sentinel-1卫星升降轨数据获取谢通门地震的同震形变场,并基于均匀弹性半无限位错模型反演地震的同震滑动分布模型.InSAR同震形变场表明,升降轨视线向最大形变量分别为0.049 m和0.051 m,形变场长轴大致呈南北方向,位于甲岗-定结断裂西侧.通过对倾角和倾向进行格网搜索发现,西倾节面更可能为该地震的发震节面.反演结果表明,滑动分布主要位于2～10 km深度范围内,平均滑动量为0.02 m,最大滑动量为0.10 m,发震断层倾角为47°,平均滑动角为-81.60°,显示该地震以正倾滑动为主.大地测量数据约束的该地震震中为30.27°N、87.75°E,震源深度为6.58 km,释放地震矩为5.056×1017 Nm,对应矩震级为Mw5.7,与GCMT、USGS公布的震级基本一致.综合分析震中位置和滑动机制认为,甲岗-定结断裂的分支断层为本次谢通门地震的发震断层.