Application of ground motion model (GMM) considering rupture directivityto earthquake early warning (EEW) system in Taiwan

          Taiwan is situated in Circum-Pacific Seismic Belt, located on the boundary between the Eurasian Plate and the Philippine Sea Plate. Therefore, it is necessary to evaluate the ground motion intensity in various seismic designs or seismic disaster assessments. Ground motion model (GMM) is employed for this purpose. In addition, earthquake early warning (EEW) system detects seismic activity in real-time and sends alert, providing people with a few seconds of warning before the arrival of damaging seismic waves, i.e., S-waves. Ground motions result in an increase in peak ground values (e.g. PGA and PGV) during a large magnitude earthquake, especially for the region near the forward rupture direction. Most of current GMMs do not consider the effect of rupture directivity, and thus ground motions in the direction of forward rupture propagation may be significantly underestimated. Accordingly, this study utilizes a GMM with consideration of a rupture directivity function (Chao et al. 2020; Convertito et al. 2012) to predict PGA and PGV for several local earthquakes with magnitude larger than 5.5. We estimate rupture direction (Jan et al. 2018) and then apply the above GMM incorporating rupture directivity effect to predict ground motions near real-time for an EEW system in Taiwan. Our aim is to enhance the accuracy of predicting ground motions, especially for the region near the forward rupture direction in which more critical damages are expected in comparison to the opposite direction.