Investigating the Effect of Finite Source Processes in Single Station Based On-Site Earthquake Early Warning System

Date: 4/25/2019

Time: 06:00 PM

Room: Grand Ballroom

Two consecutive moderate-sized earthquakes in southeast Korea, e.g., 2016 M 5.8 Gyeongju and 2017 M 5.4 Pohang events, highlight the need for comprehensive seismic hazard assessment and mitigation efforts in the Korean Peninsula. Earthquake early warning (EEW) system is used for the seismic hazard mitigation by issuing an alert in the region where strong ground shakings are expected before their arrival, using a modern seismic network. Caruso et al. (2017) developed an on-site P-wave based EEW algorithm, called on-Site Alert level (SAVE), which uses a single station to speed up the alert process especially in near-source regions. However, the single station based on-site EEW systems can be significantly affected by the relative location of the station used with respect to the spatio-temporal geometry of earthquake rupture process, including the rupture directivity effect.

In this study, we investigated the effect of finite source processes in an on-site EEW system by utilizing synthetic near-source ground motions obtained by the SCEC Broadband Platform (BBP). We simulated synthetic broadband ground motions at 30 stations surrounding an M 7.0 vertical strike-slip event at a distance of 20 km and 50 km, respectively. Then, we investigated the effect of the station locations in determining the magnitude, distance of the event and expected horizontal peak ground velocity (PGV) at each station, using the P-wave based on-site EEW algorithm (SAVE). Scaling relations for the on-site EEW parameters were obtained by analyzing a training dataset of the simulated ground motions at 169 seismic stations in the South Korea for Mw 5.5, 6.0, 6.5, and 7.0 earthquakes. Our preliminary results show that the SAVE algorithm can be significantly affected by the relative station locations mostly because of the difference of P- and S-wave radiation patterns and rupture directivity effect. It seems important to understand the range of uncertainty caused by the station location for a wide range of magnitude with various rupture scenarios to improve the P-wave based on-site warning system.

Presenting Author: Sangmin Kwak

Authors