高频GNSS实时地震学与地震预警研究现状

High-rate real-time GNSS seismology and early warning of earthquakes

为实现从注重灾后救助向注重灾前预防转变,如何提高地震灾害监测预警和风险防范能力成为我们关注的重点.本文给出了国际上GNSS位移记录、强震动加速度记录、测震速度记录在地震预警中的应用现状,并总结了各自的特点,归纳出围绕高频GNSS地震学在震级与破裂过程实时反演中的几个需要进一步研究的关键问题:(1)引入北斗系统,基于高频GNSS(GPS/BDS)双系统的实时位移解算方法来提高实时单站位移解算精度,使实时解算精度达到厘米级;(2)开展强震仪加速度记录基线偏移校正研究,弥补地震近场GNSS站密度不足问题;(3)强震仪加速度记录与GNSS位移记录特点不同,开展强震仪加速度数据与GNSS位移数据实时融合处理研究,快速获得包含丰富地震形变和速率的波形数据;(4)测震学方法可快速估算震级,但是在强震发生时会出现震级饱和现象,造成震级估算偏低.需要开展基于GNSS位移时间序列的多种方法相结合的实时震级估算方法研究,通过与地震学方法比较和结合,来得到精度高、计算快的震级估值算法;(5)基于高频GNSS、断层初始模型快速选取、断层尺度、参数自适应调整是快速判断断层破裂方向的基础,在断层破裂过程自适应准实时反演算法方面需要进一步加强.通过国内外研究现状调研、分析,表明基于高频GNSS地震学的震级快速确定、震源破裂过程准实时反演算法的发展将对我国地震预警系统从“二网融合”到“三网融合”提供坚实的技术支撑.

In order to realize the transform from emphasizing earthquake relief to focusing earthquake prevention,we should pay more attention on how to improve the early warning and risk prevention capability.This paper reviews the application status of GNSS displacement,acceleration and velocity data in earthquake early warning in the world and the characteristics of each technique,and finally summarizes several critical problems on magnitude estimation and real-time inversion for source rupture process by high-rate GNSS seismology.(1)we plan to use combined North Stars(Beidou)and GPS observations to improve the accuracy of real-time displacement solution of single stations to centimeter-level.(2)As accelerometer data and high-rate GNSS displacements have different characteristics,we will try to combine these two types of data to rapidly estimate 3-D seismogeodetic waveforms in displacement and seismic velocity.(3)In view of the low density of GPS stations,we intend to develop an empirical baseline correction for accelerometer data to derive large near-source static displacements.(4)The seismic method permits to rapidly estimate the magnitude of an event,but when a large earthquake happens,the magnitude tends to be saturate,leading to underestimates of this parameter.We need to develop a new real-time method of magnitude estimation that uses a variety of methods based on GNSS displacement time series,and combines GNSS and seismic methods to acquire precise and magnitude estimation very soon.(5)Based on high-rate GNSS,fault parameters selection and self-adapting adjustment make it possible to perform rapid determination of rupture direction,and the self-adaptive quasi-real-time inversion algorithm of source rupture process need to be further strengthened.Investigating and analyzing current situation and development trends suggest that the development of rapid magnitude estimation and the inversion algorithm of source rupture process will provide a powerful technical support to the national earthquake early warning system,which is under the transforming process from“two systems”fusion(using both velocity and acceleration data)to“three systems”fusion(using velocity,acceleration and displacement data).