Che-Min Lin

Performance of the NCREE's on‐site warning system during the 5 February 2016 Mw 6.53 Meinong earthquake

The National Center for Research on Earthquake Engineering in Taiwan has developed an on-site earthquake early warning system (NEEWS). The Meinong earthquake with a moment magnitude of 6.53 and a focal depth of 14.6 km occurred on 5 February 2016 in southern Taiwan. It caused 117 deaths, injured 551, caused the collapse of six buildings, and serious damage to 247 buildings. During the Meinong earthquake, the system performance of 16 NEEWS stations was recorded. Based on a preassigned peak ground acceleration (PGA) threshold to issue alarms at different stations, no false alarms or missed alarms were issued during the earthquake. About 4 s to 33 s of lead time were provided by the NEEWS depending on the epicenter distance. In addition, the directivity of the earthquake source characteristic and also possibly the site effects were observed in the diagram of the distribution of PGA difference between the predicted PGA and the measured PGA.

Strong Ground Motion and Pulse‐Like Velocity Observations in the Near‐Fault Region of the 2018 Mw 6.4 Hualien, Taiwan, Earthquake

The maximum observed peak ground acceleration (PGA) and peak ground velocity (PGV) at various stations during the 2018 Hualien,Taiwan earthquake were 594 Gal and 146 cm=s, respectively. Pulse-like velocities were observed at all stations within a distance of 4 km from the Milun fault. The horizontal spectral accelerations of the pulse-like records indicated two obvious amplifications at periods of roughly 1 and 2 s. Natural frequencies of 0.8–1.5 Hz were observed in the region near the Milun fault using microtremor measurements. The spectral acceleration peak at periods of roughly 2 s is mostly seen in the east–west direction, indicating a typical fault-normal seismic radiation from the fault rupture. Consequently, we contend that the amplifications of spectral acceleration at approximately 1 and 2 s were caused by site amplification and the rupture front, respectively. The site amplification at approximately 1 s may have been one reason for the collapse of medium-rise buildings during this earthquake. Evident soil nonlinearity resulted in smaller horizontal than vertical PGA at many stations in the near-fault region.