Creep rates of the Philippine fault on Leyte Island based on offset cultural features

Abstract Recent space–geodetic analyses revealed that the central Philippine fault on Leyte Island creeps aseismically. We obtained the first verifiable evidence of surface creep on the northernmost and central Leyte Island based on surveys of offset cultural features (e.g., roads, buildings, and curbs). The creep rates derived from offset cultural features in the past 10–35 years are 20.9 ± 4.3 mm/year for northernmost Leyte and ~ 15 mm/year for central Leyte. These rates are comparable with the lower bound of the rates obtained from GNSS and InSAR analyses and are in good agreement with the geologic fault slip rates. On 15 January 2023, a moderate earthquake (M w 4.7) ruptured the creeping section on the northernmost Leyte Island, where we measured ~ 20 mm/year creep rate. The left-lateral motion of the Philippine fault in the northernmost Leyte appears to be mainly accommodated by creeping with relatively little contributions from coseismic displacement related to a small locked patch on the fault plane. The observed fault behavior, aseismic creeping with moderate surface-rupturing earthquakes, is similar to that observed on Masbate Island. Surface creeping has been identified for the Philippine fault from Masbate Island to northern Mindanao Island, and it is essential to estimate the creep rate and the ratio between creep and coseismic displacement to better characterize the fault mechanics and seismic hazards of the Philippine fault.