GPS Seismology for a moderate magnitude earthquake: Lessons learned from the analysis of the 31 October 2013 ML 6.4 Ruisui (Taiwan) earthquake

Huang-Kai Hung,Ruey-Juin Rau,Augusto Mazzoni,Mattia Crespi,Mara Branzanti,Elisa Benedetti,Gabriele Colosimo

doi:10.4401/ag-7399

Abstract

The 31 October 2013 M L 6.4 Ruisui earthquake was well recorded by twelve 50-Hz, four 20-Hz and thirteen 1-Hz GPS receivers, and twenty-five strong motion stations located within the epicentral distance of 90 km in eastern Taiwan. Kinematic positioning solutions estimated by four GNSS software (TRACK, RTKLIB, GIPSY, VADASE) are used to derive the seismic waveforms and the co-seismic displacements for this event ; strong motion accelerometers are used to verify the capability of high rate GPS to detect seismic waves generated by this earthquake. Results show that the coordinate repeatability of the GPS displacements time series are ~6 mm and ~20 mm standard deviation in the horizontal and vertical components respectively, after applying spatial filtering. The largest co-seismic displacement derived from high-rate GPS is nearly 15 centimeter at 5 km northeast of the epicenter. S waves and surface waves are successfully detected by motions of high-rate GPS and double-integrated accelerometers within the 15 km epicentral distance. For the first time twelve 50-Hz and four 20 Hz GPS observations for seismological study were used and analyzed in Taiwan; a clear benefit was evidenced with regard to the seismic waves features detection, with respect to the 1-Hz GPS data, so that ultra-high rate (> 1-Hz) observations can compensate the sparse coverage of seismic data, provided proper monuments for the GPS permanent stations are realized. The 2013 Ruisui Taiwan earthquake recorded by the high-rate GPS permanent stations network in Taiwan demonstrates the benefits of GPS Seismology for a moderate size earthquake at a local scale.

Highlights

High-rate GPS has become an important sensor for the seismic wave detections and earthquake warning systems for moderate and large earthquakes
This is why waveforms retrieved from 10-Hz and 20-Hz sampling rates (Figure 3a) indicate similar ground motions, in the following we refer to the 10-Hz GPS solutions only instead of the original sampling rate
In this study, the first twelve 50-Hz, four 20-Hz and thirteen 1-Hz Continuous GPS Permanent Stations (CGPSs) epoch-by-epoch displacements in Taiwan are derived for seismological applications with respect to the 31 October 2013, ML 6.4 Ruisui earthquake, Taiwan

Summary

Introduction

High-rate GPS has become an important sensor for the seismic wave detections and earthquake warning systems for moderate and large earthquakes. The true ground displacements retrieved from the processing of high-rate GPS observations provide precise seismic waveforms to identify the wave property, the arrival time of the body waves and the surface wave [Kouba 2003, Larson et al 2003, Bock et al 2004, Langbein and Bock 2004, Kouba 2005, Ohta et al 2006, Larson et al 2007, Bilich et al 2008, Larson and Miyazaki 2008, Miyazaki and Larson 2008, Davis and Smalley 2009, Larson 2009, Shi et al 2010, Avallone et al 2011, Ohta et al 2012, Branzanti et al 2013, Li et al 2013, Benedetti et al 2014, Li et al 2014a,b]. Differently from the reconstruction of the entire waveforms, it was showed that co-seismic displacements can be accurately detected by the combination of the 1-Hz GPS solutions and co-located accelerometer [Bock et al 2011, Melgar et al 2013]

Objectives

Results

Conclusion