Evaluating the Seismic Hazards in Metro Manila,Philippines

Abstract eng:
We have performed site-specific probabilistic seismic hazard analyses (PSHA) for four sites in the Manila metropolitan area. The Philippine Islands lie within a broad zone of deformation between the subducting Eurasian and Philippine Sea Plate. This deformation is manifested by a high level of seismicity, faulting, and volcanism. The Philippines fault zone is a major left-lateral strike-slip fault that remains offshore east of Manila. The Marikina Valley fault system (MVFS) is the closest active fault to Manila and represents the most likely near-field source of large damaging earthquakes. The largest earthquake that has struck Manila historically, surface wave magnitude (MS) 7.5, occurred in 1645. Manila has experienced other historical damaging earthquakes numerous times. We have included 14 crustal faults, and the Manila Trench, Philippines Trench, and East Luzon Trough subduction zones (both megathrusts and Wadati-Benioff zones) in our seismic source model. We also have accounted for background crustal seismicity through the use of an areal source zone and Gaussian smoothing. Very little paleoseismic data is available for crustal faults in the Philippines including the MVFS so we have included a large amount of epistemic uncertainty in the characterization of these faults using logic trees. New empirical ground motion predictive equations were used in the PSHA. Based on our analyses, the hazard in the Manila metropolitan area for soil sites and a 2,475-year return period can exceed peak horizontal accelerations of 1.0 g almost solely due to the MVFS. At 1.0 sec spectral acceleration, the MVFS still dominates the hazard in Manila with a small contribution from the Manila Trench megathrust.

• Export as: BibTeX | MARC | MARCXML | DC | EndNote | NLM | RefWorks
• Add to your basket