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The complexity of the young Taiwan orogen mainly resulting from arc‐continent collision is manifold. As the Moho and crustal properties are crucial to unravel the still‐debated orogenic models, we adopt a H‐V stacking method jointly utilizing P and S receiver functions for simultaneously reliable determination of crustal thickness and average P‐ and S‐wave velocity, their ratio (Vp/Vs), and bulk sound speed (Vb) beneath 50 stations in Taiwan and offshore islands. Results indicate the Moho is inclined from ∼20 km in the north and west coastal areas to ∼47 km in the midwest of the Central Range (CR), and abruptly elevated >25 km at the eastern edge of the CR and adjacent collision suture zone. The uplifted Moho along with exclusively high Vp/Vs (2.1) suggest the subducted Eurasian crust may have been exhumed and compositionally modified by the accreted ophiolite complex of oceanic affinity during forearc basin closure. Our Moho mostly lies in the depths of the sharpest positive velocity gradient, a few to a dozen kilometers shallower than the Vp = 7.5 km/s isosurface assumed in the tomographic models. The unusually thin crust (∼20 km) with high Vp/Vs (1.9–2.0) is observed in the northern Taiwan volcanic zone, plausibly attributed to the post‐orogenic extensional thinning and induced melting in the sublithospheric mantle producing magmatic fluids trapped in the crust. Moreover, Vb apparently decreases from the coasts to the middle CR coinciding with the thickest crust, implying the crust under the central mountain range is more compressible and easily deformed/thickened by ongoing collisional compression. Plain Language Summary: Taiwan is known for one of the most seismically hazardous and rapidly growing orogens in the world. The mountain building processes would involve the crustal deformation and disturbance of the boundary between the crust and underlying chemically distinct mantle, called the Moho, with sudden jumps in seismic velocities. Therefore, it is of vital importance to constrain the Moho depth and crustal velocity variations across Taiwan for advancing our understanding of orogenic and seismotectonic processes in Taiwan. We jointly use the arrival times of seismic phases converted at the Moho from direct P‐ and S‐ waves of distant earthquakes and their associated reverberations to robustly determine the Moho depth and average seismic velocities of the crust beneath permanent broadband seismograph stations across Taiwan. Our results indicate that the Moho is inclined toward the central Taiwan mountain ranges, and uplifted swiftly across the collision suture between the Eurasian continental margin and the Luzon arc of Philippine Sea Plate. The most thickened crust in the central Taiwan orogen reveals the lowest average bulk modulus or the highest compressibility, implying the crust therein is weaker and less resistant to compressional deformation. Key Points: Lateral variations of the Moho and average crustal velocities in Taiwan first studied by H‐V stacking of joint P and S receiver functionsThe Moho lying in the sharpest positive velocity gradient zone, not on the isovelocity surface assumed in prior tomographic modelsVariations of average Vp/Vs and bulk velocity providing key constraints on crustal composition and compressibility in the Taiwan orogen [ABSTRACT FROM AUTHOR]

The Philippine Sea Plate is converging against the Eurasian Plate near Taiwan at a velocity of 7–8 cm yr−1; this has caused the Taiwan orogenesis and induced abundant earthquakes. In this study we examine the corresponding change of gravitational potential energy (ΔGPE) using 757 earthquakes from the earthquake catalogue of the Broadband Array in Taiwan for Seismology (BATS) from 1995 July to 2003 December. Our results show that the variation of the crustal ΔGPE strongly correlates with the different stages of the orogenesis. Except for the western Okinawa Trough and southern Taiwan, most of the Taiwan convergent region exhibits a gain of crustal ΔGPE. In contrast, the lithospheric ΔGPE in the Taiwan region exhibits a reverse pattern. For the whole Taiwan region, the earthquake-induced crustal ΔGPE and the lithospheric ΔGPE during the observation period are and , respectively. The average rate of the whole ΔGPE in the Taiwan region is very intense and equal to , corresponding to about 1 per cent of the global GPE loss induced by earthquakes. [ABSTRACT FROM AUTHOR]

The active convergence between the northwest corner of the Philippine Sea Plate and the southeast margin of the Eurasian Plate has given rise to the Taiwan mountain-building and produced numerous earthquakes. Among the earthquakes, the 1999 Chi-Chi earthquake is the largest one recorded in the century. In this study, we examine the crustal gravitational potential energy (GPE) change in the Taiwan orogen caused by the Chi-Chi earthquake sequence, which was catalogued by the regional broadband seismometer array for a whole year. As a result, we find that the crust was going up and down randomly during the earthquake sequence, but an overall cumulative gain of the crustal GPE, +1.82×1016 J, was rapidly achieved in 1 month after the main shock. The crustal GPE was nearly still afterwards and reached +1.90×1016 J in 1 year. Spatially, although the main surface faulting has occurred in western Taiwan, the crustal GPE gain is mainly distributed in central Taiwan at the area where the existing crustal GPE is high and the existing lithospheric GPE is relatively low. The crustal GPE loss by the Chi-Chi earthquake sequence can also be observed and is generally distributed at both sides of the crustal GPE gain area. The crustal GPE gain mainly found in central Taiwan corroborates that the uplift of the Taiwan orogen is principally taking place in central Taiwan, rather than in the more hazardous western Taiwan. [Copyright &y& Elsevier]