Liquefaction Hazard Mapping Based on Regional Geology, Local Geotechnical Data, and Cyclic Stress Ratio (CSR) Values: Dagupan City, Pangasinan, Philippines

Abstract

The presence of the Philippine Fault, Iba Fault, East Zambales Fault, and the Manila Trench makes the central Luzon plains one of the most seismically active areas in the Philippines. Given its geology, which consists primarily of quaternary alluvial deposits, it is known that the magnitude and intensity of the earthquakes induced by some of these faults may be accompanied by liquefaction. Dagupan City has been selected as a study area for this liquefaction hazard mapping since it is situated within the region and has historically experienced the effects of liquefaction, as proven by accounts from PHIVOLCS. In the study’s methodology, a map will be produced utilizing the features provided in QGIS to determine degrees of susceptibility in liquefiable areas using regional and local geology and geotechnical data with cyclic stress ratio (CSR) values. The results show the entirety of Dagupan to be highly susceptible to liquefaction, with the CSR values ranging from +0.30 to +0.70 in contrast to existing hazard maps where liquefaction is generally susceptible in all areas. The study implies that even with the results, liquefaction is not guaranteed to occur in every seismic event. Peak ground acceleration (PGA), earthquake generators, and the recurrence interval of the earthquake magnitude must be kept in mind.