DETERMINISTIC LANDSLIDE MODELING OF THE JULY 1990 EARTHQUAKE IN CARRANGLAN NUEVA ECIJA USING NEWMARK METHOD

摘要

Nueva Ecija, Philippines is one of the towns showing traces and evidence of faulting as a consequence of the devastating July 1990 earthquake in Central Luzon, thus many houses, infrastructures, and lives were affected. In this study, a deterministic landslide modeling using Newmark Method was executed in order to produce a more detailed attributes for landslide susceptibility classification. The geotechnical properties of rock were obtained using Slope Stability Probability Classification (SSPC) while the reconstituted soil samples had undergone Direct Shear Test. Three rock exposures show cohesion values of 20,170 Pa, 25,350 Pa, 11, 700 Pa, and friction angle values of 40.22°, 49.22°, and 24.43°. Two soil samples show cohesion values of 12, 944.78 Pa and 8,041 Pa, and friction angle values of 29.41° and 44.69°. The factor of safety, critical acceleration, and peak ground acceleration, was computed using the cohesion and friction angle as parameters, generating a slope stability model. In the output slope stability model, 42.92% of the area is categorized as unstable, 20.27% is slightly stable, 30.51% is moderately stable, and 5.85% of the area is stable. Compared to the output prepared by PHIVOLCS, the slope stability model generated showed a difference in the classification of the landslide susceptible areas in the vicinity. This study discusses the efficiency of a deterministic landslide modeling based on Newmark's sliding-block model and producing a more detailed landslide slope stability model.