Importance of real-time PGV in terms of lead-time and shakemaps: Results using 2018 M_L 6.2 & 2019 M_L 6.3 Hualien, Taiwan earthquakes

摘要

Two earthquakes having almost the same magnitude occurred in the Hualien area of Taiwan in 2018 and 2019. The 2018 earthquake had a magnitude M-L 6.2 produced severe destruction; however, the 2019 earthquake (M-L = 6.3) did not cause any severe damage. The P-Alert Strong Motion Network provides real-time shakemaps, in addition, to earthquake early warning (EEW) in terms of lead-time. Each instrument provides a different leadtime using peak ground acceleration (PGA) and peak ground velocity (PGV). During both the events, the instruments reported a lead-time of 1.5 to 8.0 s in the epicentral region. This network system also generated highquality shakemaps during both earthquakes. The shakemaps showed that the higher PGAs are concentrated in the epicentral region for the 2018 and 2019 earthquakes. The lower PGA contour (= 25 Gal) extended to a broader area, including Taipei, during the 2019 earthquake compared to the 2018 earthquake. However, PGV shakemaps display a different pattern. The higher PGV values (more than 17 cm/s) are observed in the epicentral region during the 2018 earthquake (locations suffering building collapse) compared to the 2019 earthquake, suggesting that PGV correlates better with damage distribution as compared to the PGA. The PGV shakemap, currently only available for the P-Alert network, provides crucial information that complements the PGA issued by the official agency in Taiwan.