近年來高頻GPS (HRGPS)已經被成功應用在許多地球科學相關的研究，例如監測地質災害及測量大地震的同震變形，以及結合加速度觀測資料(e.g., from強地動SM或加速度儀)而獲得地震的位移地振動資訊，這些成果也逐步地擴展到即時地振動監測與相關的地震或海嘯災害預警。台灣地區在過去20年間建立了一個相對密集的連續GPS觀測網(>400站)，且許多的GPS接收儀也在近數年間陸續的升級到可收集高頻數據(>1 Hz)。然而，台灣HRGPS資料的使用及相關研究仍不普遍。近期的一些中大型地震，如2016的美濃與2018的花蓮地震，其靜態同震位移多是利用地震前後數天或數小時的平均解位移進行估算。若地震於24小時內就有明顯震後變形，這種的同震位移測量就會產生偏差，並同時影響到地震相關的斷層模型及滑移量估算。此外，針對未來的即時預警，以地震數天後資料為主的觀測方式也將無法適用。本研究計畫將嘗試使用訊號分析中常用的平滑先驗信息方法(Smoothness Priors Method)將靜態偏移從HRGPS的同震時間序列分離出來，做為測量地表同震位移的依據，並將結果與以每日座標解平均值所得的同震位移進行分析比較。此外，分離後剩下的訊號可視為位移地震波，未來也可嘗試將它們與鄰近的強震站或寬頻站紀錄比較，提供HRGPS資料在seismogeodesy上的應用。 ;In recent years, high-rate GPS (HRGPS) had been widely used in earthquake monitoring, and it was successfully utilized to measure the coseismic crustal deformations for many large earthquakes and to perform real-time inversion of seismic source parameters and coseismic fault slip distribution for achieving the aim of early warning for large earthquakes and tsunamis. A dense GNSS array of >400 stations has been deployed in the past 20+ years and many of the instruments have been upgraded to be able to collect high-rate (>1 Hz) GPS records. Despite this, the rich Taiwan HRGPS data had not been widely implemented to analyze earthquake ground motion, for example the estimations of coseismic displacement for recent Taiwan large earthquakes were still based on the daily or hourly averaged coordinate solutions, which may be not reasonable if there is obvious post-seismic deformation in the first 24h. Here we propose the Smoothness Priors Method (SPM) to rapidly extract static offset from GPS displacement waveforms for recent large Taiwan earthquakes, and the results will be compared with the past solutions from daily-based measurements. Moreover, the separated high-frequency GPS displacement waveforms, which did not suffer from the saturation effects, can be used to rapidly estimate source parameters and provide important applications on seismogeodesy.
