Earthquake Magnitude Estimation from High-Rate GNSS Data: A Case Study of the 2021 Mw 7.3 Maduo Earthquake

Zhiyu Gao,Yanchuan Li,Chuanhua Zhu,Xinjian Shan

doi:10.3390/rs13214478

Abstract

Peak ground displacement (PGD) and peak ground velocity (PGV) are critical parameters during earthquake early warning, as they can provide rapid magnitude estimation before rupture end. In this study, we used the high-rate Global Navigation Satellite System (GNSS) data from 55 continuous stations to estimate the magnitude of the 2021 Maduo earthquake in western China. We used the relative positioning method and variometric approach to acquire real-time GNSS displacement and velocity waveforms, respectively. The results showed the amplitude of displacement and velocity waveforms gradually decreased with increasing hypocentral distance. Our results showed that the fluctuation of PGD magnitudes over time is smaller than that of PGV magnitudes. Nonetheless, the earthquake magnitudes estimated from both methods were consistent with their counterparts (Mw 7.3) reported by the United States Geological Survey (USGS). The final magnitude estimated from the PGD and PGV methods were Mw 7.25 and Mw 7.31, respectively. In addition, our results highlighted how the number of high-rate GNSS stations could influence the stability and convergence time of magnitude estimation.

Highlights

According to the China Earthquake Network Center, at 18:04:13 (UTC) on 21 May2021, an Mw 7.3 earthquake occurred in Maduo County, Qinghai Province, China
To investigate the applicability of Global Navigation Satellite System (GNSS) in magnitude estimation of large earthquakes in the Tibetan Plateau, in this study, we focused on the recent Maduo earthquake
We obtained a maximum and minimum value of Peak ground displacement (PGD) magnitude of Mw 8.0 and Mw 6.8, respectively. These results indicate that, at different high-rate GNSS stations, PGD magnitude varies to a sizable extent, which might be related to site effects and/or radiation pattern

Summary

Introduction

According to the China Earthquake Network Center, at 18:04:13 (UTC) on 21 May2021, an Mw 7.3 earthquake occurred in Maduo County, Qinghai Province, China. This unexpected earthquake was the largest earthquake to have occurred in. China since the 2008 Mw 7.9 Wenchuan earthquake [6,7,8], challenging the conventional perspective that the Bayan Har block acts as a quasi-stable block. During the Maduo earthquake, the densely distributed high-rate GNSS stations (Figure 1) around the epicenter recorded ground displacement and velocity waveforms, providing valuable data to investigate the source process of the earthquake. These data can help in testing algorithms, such as the rapid estimation of magnitude, in the geodetic-based earthquake early warning (EEW) system that is under development [9]

Results

Discussion

Conclusion