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AbstractThis study assesses sediment erosion rates in the Zhoukou River Basin in southern Taiwan over the past three decades, focusing on the impact of extreme rainfall events. While various established methods determine erosion rates over different temporal scales, we employ an independent approach for decadal-scale erosion rate calculation by utilizing open-source global and regional digital elevation models (DEMs) data for two distinct periods. We introduce a new method that applies Fourier analysis to vertically register the DEMs, significantly minimizing their vertical bias. Through spectral analysis, we identify long wavelength topography crucial for correcting vertical offsets. Erosion rates, computed through DEMs of Difference (DoD), exhibit a similar trend of significant reduction in sediment export rates from 1990–2010 to 2011–2020 due to decreased extreme rainfall events, aligning with erosion rate estimates derived from mean suspended load data at gauge stations. Over the entire period from 1990 to 2020, the calculated denudation rate was 14.19 mm/yr, whereas in the recent decade (2011–2020), it decreased to 10.46 mm/yr. Our study suggests that the improved DoD method can effectively estimate sediment transport rates by leveraging underutilized DEMs captured at distinct points in time, especially when the erosional signal dominates data noise.

A significant issue in the study of orogenic systems concerns the roles played by frontal and basal accretion in the construction of orogenic wedges. These different accretion mechanisms result in different thermal histories, with underplated materials experiencing significant heating and deformation during tectonic burial. This work provides new thermal data from Raman spectroscopy of carbonaceous material in combination with structural and stratigraphic observations of the northern Taiwan slate belt to address these questions of wedge development. Sedimentary rocks of the Northern slate belt were deposited on the Chinese continental margin immediately before the onset of the Neogene Taiwan arc‐continent collision. In the slates of the northern Hsüehshan Range, a large‐scale pop‐up structure on the prowedge of the Taiwan Orogen, synorogenic metamorphism has been investigated through analyses of peak temperatures and metamorphic field gradients. Results indicate underthrusting of the margin sediments to ~8‐km depth with significant folding in two major duplexes occurring before underplating. Such basal accretion is considered responsible for the distinct culmination of the Hsüehshan Range in central Taiwan and its relative uplift with respect to the Backbone Range to the east along the Lishan Fault. A similar underthrusting scenario is also suggested for the Backbone Range Slate Belt. We propose that basal accretion is the predominant mechanism in the growth and evolution of the Taiwan orogenic wedge and may have been achieved through inversion of a graben system on the ancient passive margin during continental subduction. Dynamic synorogenic thermal overprint over static basin diagenesis quantified through RSCM geothermometryTectonic underplating through duplex formation beneath frontal part of orogenic wedge responsible for dynamic heatingBasal accretion is key in the growth and evolution of the Taiwan orogenic wedge through margin basin inversion during continental subduction

Graphical Abstract:

Shallow slow slip events accompanied by seismicity has been increasingly reported in subduction zones during the last decade; however, the relationship between shallow slip events and seismicity is unclear. We report episodic slow slip events and seismicity at the southernmost Ryukyu Trench. The inversion results from GPS‐derived cumulative displacements indicate that the slow slip events occur offshore in northeastern Taiwan on the shallow subduction interface, where high seismic VP/VSratios applies. Seismicity is observed above the subduction interface for locations of significant variations in the VP/VSratio and does not follow the migration of peak slip along the subduction interface. We calculated the temporal evolution between the seismicity and the propagation of slow slip events and determined that seismicity is not primarily driven by slip propagation. The spatiotemporal relationship, coupled with the VP/VSratio, suggests that high‐pressure fluid activity may be crucial to episodes of slow slip events and seismicity. Slow slip events are a member of the slow‐earthquake family observed by geodetic measurements in global subduction zones in the past 15 years. Shallow slow slip events are considered to be important for the megathrust earthquake cycle of the shallowest locked zone. Recently, shallow slow slip events accompanied by different seismic behaviors has been increasingly reported. This paper reports episodic, shallow slow slip events accompanied by overlying plate seismicity at the southernmost Ryukyu Trench and analyzes their relationship. We discover that the spatiotemporal relationship between the propagation of slow slip and seismicity is weak, which infers that they may not have a causal relationship. We suggest that the initiation of shallow slow slip events and subsequent seismicity was probably caused by high‐pressure fluid activity. The interpretation may reveal the cause of many shallow slow slip events as a broad phenomenon. Relationship between shallow slow slip events and seismicity is reported at the southernmost Ryukyu Trench for the first timeSpatiotemporal seismicity does not adequately correlate with propagation of slow slip but is dominated by mainshock‐aftershock sequencesHigh‐pressure fluid activity likely has a key role in the initiation of episodic slow slip events and subsequent seismicity