Fig. 1: Regional maps and profiles illustrating geological features, seismicity, and variations in Moho depth.
A displays a regional map. PHP refers to the Philippine Sea Plate, EUR represents the Eurasia Plate, and SCS denotes the South China Sea. The two orange lines mark key boundaries: the upper line indicates the continental-to-thinned continental transition, while the lower line marks the oceanic-to-continental boundary, as defined by Wang et al.17. The red box outlines the area shown in the (B). B illustrates the study area, including profiles’ (C–E) locations, seismic stations, transition boundary between continental and thinned continental crust and deformation front (DF). The red box identifies the region depicted in Fig. 2 (A). On both the profiles (C-E) and the map (B), the locations of the 2006 Pingtung offshore earthquake doublet are indicated by red stars, determined by Central Weather Administration of Taiwan25. Slab interfaces from the Slab2 model95 are shown as blue lines. The Moho depth from multiple studies are plotted: from the wide-angle seismic tomography (Vp = 7.8 km/s contour) by yellow squares12,15,16, from gravity inversion by red diamonds14, and from onshore receiver function by green triangles13. Relocated background seismicity from 1990 to 2020 and their depth uncertainties are plotted9,96.
