基于模拟高频GNSS数据的安宁河断裂强震滑动分布快速反演研究

Rapid Inversion of Fault Slip Distribution for Strong Earthquakes Along the Anninghe Fault Based on High-Rate GNSS

为了探讨现有的高频全球导航卫星系统(global navigation satellite system,GNSS)连续台站在强震潜能较高的安宁河断裂未来强震发生时震级快速预估、滑动分布快速反演的可靠性与时效性,利用以震间闭锁模型为约束的运动学数值模拟方法,合成1100个Mw 6.5~7.5地震事件或破裂情景,模拟得到带有随机噪声信号的高频GNSS位移波形,结合最速下降法进行分析与讨论。统计结果表明,利用现有的GNSS连续台站能够在8 s左右反演得到初始震级(Mw 6.2),并能够在较短时间内或破裂完成之前反演得到准确的震级结果与滑动分布结果。在中国地震科学实验场即将加密建设的GNSS连续台站,能够为区域内强震震级快速估计、滑动分布快速反演甚至断层破裂优势方向予以更加有效地刻画。研究结果证实了利用高频GNSS数据在安宁河断裂强震震级快速估计和有限断层滑动分布快速反演中的可行性和适用性,为该区域强震速报预警提供理论依据与技术支撑。

Objectives:Infrequent strong earthquakes which occur on subduction and intraplate faults world⁃wide can be extremely destructive.The exploration on the reliability and timeliness of high-rate global navi⁃gation satellite system(GNSS)continuous stations can help rapid inversion of slip distribution and rapid esti⁃mation of earthquake magnitude.Especially for the Anninghe fault with high potential for strong earth⁃quakes,this research has important practical significance for early warning of strong earthquakes in this re⁃gion.Methods:We adopt a kinematic simulation method to synthesize stochastic rupture scenarios by incor⁃porating the geodetic fault coupling model as prior constraints.For the Anninghe fault,we synthesize 1100 earthquake events from Mw 6.5 to 7.5 and rupture scenarios,and simulate displacement waveforms by using random noise signals from the existing and newly built GNSS stations.These waveforms are analyzed the reliability of fault slip distribution along the Anninghe fault in combination with the steepest descent method.Results:For these events along the Anninghe fault,the initial inversion magnitude of Mw 6.2 can be determined in about 8 s after the earthquake using the existing GNSS continuous stations.And the mag⁃nitude and slip distributions can be obtained within a short time or before the rupture completes.The GNSS continuous stations of the China earthquake science experimental field,which is about to be built,can not only effectively obtain the magnitudes and slip distributions,but also determine the dominant directions of fault rupture.Conclusions:The feasibility and usefulness of the high-rate GNSS data are confirmed in mag⁃nitude estimation and finite-fault slip inversion of strong earthquakes along the Anninghe fault.It can pro⁃vide theoretical basis and technical support for earthquake early warning in this region.