The Taiwan Strait, along with the southeastern continental margin of the Eurasian plate, Fujian in SE China, is not far from the convergent boundary between the Eurasian plate and the Philippine Sea plate. Although this region is considered tectonically relatively inactive, many small earthquakes still occur, and normal faults are well developed in the strait. To better understand the geological processes in this region, we use 2 years of ambient noise data from more than 100 stations in Fujian and Taiwan to obtain a 3‐D crustal shear‐wave velocity model using a direct surface‐wave inversion method. Our results show that the low‐velocity zone beneath the Zhenghe‐Dapu suture zone plays an important role in the tectonic evolution of the Fujian area. The relatively high velocity in the eastern part of the suture zone and low velocity in the west correspond to the Mesozoic magmatic zone and the Wuyi‐Yunkai orogenic belt in Fujian, respectively. The coastline of Fujian presents a high‐velocity anomaly in the upper crust, which is related to the Mesozoic Pingtan‐Dongshan metamorphic belt. The long strip‐like high‐velocity zone through the rift basins in the strait is interpreted as igneous rocks due to extension of the lithosphere in the Cenozoic. Two‐stage extension with different extensive centers in the strait may be the reason for the high‐ and low‐velocity anomalies in the middle to lower crust and uppermost mantle of the strait.
Rifting along southeastern Eurasia in the Late Cenozoic led to the formation of a magma-poor rifted margin facing the South China Sea to the southeast and the Philippine Sea to the east. Further rifting along the outer part of the margin during the middle to late Miocene was accompanied by an extensive episode of intraplate flood volcanism that formed the Penghu Archipelago. Previous geophysical studies in the area of the strait have focused primarily on the shallow structures of the rift basins and the depth to the Moho. In this study we present the regional-scale 3-D S wave structure of the Taiwan Strait that is derived from a joint Chinese and Taiwanese 3-D ambient noise tomography study. The S wave model shows a thinning of the crust beneath the rift basins where, locally, thin high-velocity layers suggest the presence of intrusive bodies. The rift basin and the foreland basin along the west coast of Taiwan are imaged as low-velocity zones with thicknesses between 5 and 10 km and extending eastward beneath the Taiwan mountain belt. In the upper 10 km of the crust, the basaltic rocks of the Penghu Archipelago are imaged as a high-velocity zone that, with depth, becomes a relatively low-velocity zone. We interpret this low-velocity zone in the lower crust and upper mantle beneath the Penghu Archipelago to image a thermal anomaly related to the still cooling magma feeding system and the melt reservoir area that fed the flood basalts at the surface. Penghu Archipelago and its relationship to what is otherwise defined as a magma-poor rifted margin CHEN ET AL.AMBIENT TOMO ACROSS THE TAIWAN STRAIT 1782
M w 6.4 Meinong earthquake occurred on 6 February 2016 in southern Taiwan, resulting in more than one hundred casualties and several collapsed buildings. The aftershocks occurred mostly at mid-to-lower crustal depths (10-30 km), related to a blind fault system. However, several centimeters of cosesimic surface uplift within the Liushuang, Erhchungli, and GutingKeng Formations, composed mainly of mudstone, was recorded from the InSAR results. The uplifted pattern is similar to that of GPS and leveling data from 2000-2010, which indicates the deformation is accomplished by creeping due to the shallow mudstone structure related to mud diapir. Previous studies have shown limited information about the shallow structure in this region due to few deployed seismic stations. We deployed 36 temporary seismic stations (~5 km spacing) in this study around one month after the main shock to obtain a 3-D shear wave shallow crustal velocity structure using ambient noise tomography. The reliable periods of group and phase velocities from Rayleigh waves were 0.6-5 s, corresponding to around 0-5 km at depths. As a result, the low S-wave pattern speeds at 0-4 km depths correspond to the uplift region from both InSAR data for the coseismic period and GPS and leveling data for the interseismic period. The results from this study are compatible with the reflected seismic profile. The results show that with dense seismic array deployment we can obtain high subsurface image resolution to link the relationship between the surface observations to the subsurface structures.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.