Estimating crustal thickness in the northern Philippines: insights from ambient noise autocorrelation and receiver function analysis

Abstract The Philippine archipelago comprises accreted terranes, including ophiolites, island arcs, and continental fragments. It absorbs the approximately 9 cm/year convergence between the Sundaland Plate to the west and the Philippine Sea Plate to the east. Understanding the crustal thickness variations across the Philippines is crucial for distinguishing collision boundaries and comprehending the complexities of tectonic evolution. In this study, we conducted ambient noise autocorrelation combined with receiver function analysis to estimate crustal thickness in the northern Philippines. To resolve ambiguities in the PmP phase in autocorrelation signals, Moho depth information from receiver function was utilized. We successfully identified coherent signals of PmP autocorrelation from 20 vertical seismograms, with two-way travel time ranging from 6.64 s to 13.79 s. These times correspond to crustal thicknesses of 19.8 to 46.0 km, respectively, as derived from the average CRUST1.0 P-wave velocity model. Our main findings and interpretations indicate that the crust beneath Luzon is slightly thicker in the western regions compared to the eastern parts. This suggests a limited influence of magmatic processes in the latter. Furthermore, our observations identified a tear in the slab at 17°N and 14°N latitude, characterized by thinner crust. We observed that the crust beneath Mindoro thickens in proximity to the collision of the microcontinental fragments with Mindoro-Panay island, whereas it thins toward the extension of the Pleistocene Macolod Corridor rifting.