Earthquake Directivity and Early Warning: The Response of P-Alert Network to the 2024 Mw 7.4 Hualien Event
Journal
Bulletin of the Seismological Society of America
Journal Volume
116
Journal Issue
1
Start Page
68
End Page
79
ISSN
0037-1106
1943-3573
Date Issued
2025-07-29
Author(s)
Abstract
On 2 April 2024, a major earthquake with a moment magnitude (Mw) of 7.4 struck the Hualien area of eastern Taiwan. Because of a significant directivity effect, with the rupture propagating from the south-southwest to the north-northeast direction, the earthquake caused damage, including in the Taipei metropolitan area, which is located approximately 120 km north of the epicenter. The Central Weather Administration (CWA) earthquake early warning (EEW) system issued two Public Warning Service alerts at 8 and 14 s after the earthquake’s origin. However, the system underestimated both the earthquake magnitude and ground-motion intensity in northern Taiwan, excluding the densely populated Taipei metropolitan area from the alerts. In contrast, the high-density P-Alert network, maintained by National Taiwan University, offered onsite EEW, delivering at least 3 s of lead time for areas near the epicenter and compensating for the missed warnings in the Taipei metropolitan area. The P-Alert network also generated detailed real-time shakemaps within 2.5 min, significantly aiding disaster response efforts and identifying the rupture’s directivity. Finally, testing of the ShakingAlarm demonstrated its effectiveness in filling the gap left by the CWA regional EEW system, providing an additional warning for the Taipei metropolitan area. This research demonstrates the critical role of the PAlert network in addressing the challenges posed by the earthquake’s directivity effect and enhancing early warning effectiveness.
Subjects
Hualien
Taiwan
Earthquake effects
Metropolitan area networks
Directivity effect
Early warning
Earthquake early warning systems
Earthquake magnitudes
Epicentre
Ground motion intensities
Metropolitan area
Moment magnitudes
National Taiwan University
Northern Taiwan
early warning system
earthquake epicenter
earthquake event
earthquake intensity
earthquake magnitude
earthquake rupture
ground motion
metropolitan area
Emergency services
Publisher
Seismological Society of America (SSA)
Type
journal article