AUTHOR=Li Jiawei , Böse Maren , Feng Yu , Yang Chen 

TITLE=Real-Time Characterization of Finite Rupture and Its Implication for Earthquake Early Warning: Application of FinDer to Existing and Planned Stations in Southwest China

JOURNAL=Frontiers in Earth Science

VOLUME=9

YEAR=2021

URL=https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2021.699560

DOI=10.3389/feart.2021.699560

ISSN=2296-6463

ABSTRACT=<p>Earthquake early warning (EEW) not only improves resilience against the risk of earthquake disasters, but also provides new insights into seismological processes. The <underline>Fin</underline>ite-Fault Rupture <underline>De</underline>tecto<underline>r</underline> (FinDer) is an efficient algorithm to retrieve line-source models of an ongoing earthquake from seismic real-time data. In this study, we test the performance of FinDer in the Sichuan-Yunnan region (98.5<sup>o</sup>E–106.0<sup>o</sup>E, 22.0<sup>o</sup>N–34.0<sup>o</sup>N) of China for two datasets: the first consists of seismic broadband and strong-motion records of 58 earthquakes with 5.0 ≤ <italic>M</italic><sub>S</sub> ≤ 8.0; the second comprises additional waveform simulations at sites where new stations will be deployed in the near future. We utilize observed waveforms to optimize the simulation approach to generate ground-motion time series. For both datasets the resulting FinDer line-source models agree well with the reported epicenters, focal mechanisms, and finite-source models, while they are computed faster compared to what traditional methods can achieve. Based on these outputs, we determine a theoretical relation that can predict for which magnitudes and station densities FinDer is expected to trigger, assuming that at least three neighboring stations must have recorded accelerations of 4.6 cm/s<sup>2</sup> or more. We find that FinDer likely triggers and sends out a report, if the average distance between the epicenter and the three closest stations, <italic>D</italic><sub>epi</sub>, is equal or smaller than log<sub>10</sub> (<italic>M</italic><sup><italic>a</italic></sup> + <italic>b</italic>) + c, where <italic>a</italic> = 1.91, <italic>b</italic> = 5.93, and <italic>c</italic> = 2.34 for <italic>M = M</italic><sub>W</sub> ≥ 4.8, and <italic>c</italic> = 2.49 for <italic>M = M</italic><sub>S</sub> ≥ 5.0, respectively. If the data used in this study had been available in real-time, 40–70% of sites experiencing seismic intensities of V-VIII (on both Chinese and MMI scales) and 20% experiencing IX-X could have been issued a warning 5–10 s before the <italic>S-</italic>wave arrives. Our offline tests provide a useful reference for the planned installation of FinDer in the nationwide EEW system of Chinese mainland.</p>