Earthquake‐Related Structures Beneath the Southernmost Portion of the Ryukyu Arc and Forearc

Wang, Shiou Ya; Hsu, Shu Kun; Yeh, Yun-Chi

doi:10.1029/2019gl082121

Cited by 7 publications

(2 citation statements)

References 40 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, based on the width, location, and depth of the structural uplift, there is a low possibility of an off-scraped part of the Luzon Arc beneath the Nanao Basin (Font et al 2001;Lallemand et al 2013), because the width of the Luzon Arc (~ 50 km) is larger than the width of the Gagua Ridge (~ 25 km). Moreover, the hypothesis of the Gagua Ridge being obliquely subducted can be used to explain the formation of an NW-SE right-lateral strike-slip fault below the Nanao Basin (Wang et al 2019, the black dashed line in Fig. 16).…”

Section: Structural Uplift By Obliquely Subducted Gagua Ridgementioning

confidence: 99%

Uplifted structures due to the obliquely subducted Gagua Ridge below the Nanao Basin imaged from MCS/OBS data

Deng

Wang

Wege

et al. 2022

Preprint

View full text Add to dashboard Cite

At the southernmost part of the Ryukyu subduction zone, data recorded by 28 ocean-bottom seismometers with active sources during the TAiwan Integrated GEodynamics Research (TAIGER) experiment in 2009 were re-analyzed. Additionally, six long-offset multi-channel seismic profiles across three forearc basins and the Yaeyama accretionary prism north of the southernmost Ryukyu Trench, obtained by the TAIGER experiment in 2009 and the TAICRUST project in 1995, were processed to generate pre-stack depth migration (PSDM) sections. Due to the NW convergence of the Philippine Sea Plate (PSP), the Gagua Ridge may have been obliquely subducting northwestward beneath the Yaeyama accretionary prism and below the Nanao Basin. The PSDM sections and the velocity-interface models show that the Yaeyama accretionary prism near the trench, the sedimentary basement and the lower crustal structure below the Nanao Basin were uplifted by the tip of the subducted Guagua Ridge. Furthermore, the sedimentary and crustal structures near ~ 122.5°E beneath the Nanao Basin were shown a north-trending uplift where shallow earthquakes had been occurred by the oblique subduction of the Gagua Ridge depicted in the isopach map of the crust. Moreover, a recent earthquake (Mw ~ 6.0) near the NE coast of Taiwan in 2018 at a depth of approximately 12 km below the Hsincheng Ridge was caused due to a thrust fault near the décollement that might have been formed by subduction of the PSP.

show abstract

Section: Structural Uplift By Obliquely Subducted Gagua Ridgementioning

confidence: 99%

Uplifted structures due to the obliquely subducted Gagua Ridge below the Nanao Basin imaged from MCS/OBS data

Deng

Wang

Wege

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…In the backarc region of the southern Ryukyu margin, the Okinawa Trough is rifting southward at a rate of 50 mm/yr (S. Nishimura et al., 2004). Previous studies of earthquake focal mechanisms, bathymetry, and seismic reflection profiles suggest that the relative plate motion in the southern Ryukyu margin is accommodated by the plate interface fault (Kao et al., 1998; Wang et al., 2019), trench‐parallel stretching and folding in the forearc (Lallemand et al., 1999, 2013), along with splay faults (Lallemand et al., 1999; Theunissen et al., 2010) and strike‐slip faults located within the accretionary wedge (Dominguez et al., 1998; Font et al., 2001; Lallemand et al., 1999, 2013). Numerical modeling of plate kinematics suggests plate convergence is partially taken up by intraplate deformation within the downgoing PSP (Chiao et al., 2001).…”

Section: Introductionmentioning

confidence: 98%

Strain Partitioning in the Southern Ryukyu Margin Revealed by Seafloor Geodetic and Seismological Observations

Chen

Hsu

Ikuta

et al. 2022

Geophysical Research Letters

View full text Add to dashboard Cite

The southern Ryukyu subduction zone is one of the potential sources for tsunamigenic earthquakes. Despite a great seismic risk, the deformation pattern remains poorly known, primarily due to the absence of seafloor constraints. With GNSS‐acoustic measurements over years, we characterize the convergence rate across this margin growing from 92 mm/yr offshore eastern Taiwan to 123 mm/yr near the Gagua Ridge. The new data suggest the subduction interface is capable of hosting Mw 7.5–8.4 earthquakes. The orientations of seafloor movement and P‐axes in the Nanao Basin are both subnormal to the trench, notably deviate from the direction of plate convergence. By considering the combined effect of plate convergence and backarc rifting, different trends between the forearc convergence, P‐axes, and seafloor movement may indicate some degree of slip‐partitioning. The trench‐parallel component is likely accommodated in part by earthquakes near Taiwan, lower plate deformation, and strike‐slip faults within the accretionary wedge.

show abstract

A hypothesis of the obliquely subducted Gagua Ridge below Nanao Basin based on uplifted structures in Ryukyu forearc

Deng

Wang

Wege

et al. 2023

Terr Atmos Ocean Sci

View full text Add to dashboard Cite

At the southernmost part of the Ryukyu subduction zone, six long-offset multi-channel seismic profiles were collected across three forearc basins and the southern Ryukyu accretionary prism during the TAIGER experiment in 2009 and the TAICRUST project in 1995. These profiles were reprocessed to generate pre-stack depth migration (PSDM) sections. In addition, two velocity-interface models were obtained by reanalyzing active source data recorded from 28 ocean-bottom seismometers during the same TAIGER experiment, in consideration of the PSDM sections and previous tomography models. Due to the northwest convergence of the Philippine Sea Plate (PSP), it is suggested that the Gagua Ridge may have been obliquely subducting northwestward beneath the Ryukyu prism and below the Nanao Basin. The PSDM sections and the velocity-interface models indicate the subducted Gagua Ridge causing the uplift of the sedimentary basement and the lower crustal structure below the Nanao Basin. The sedimentary and crustal structures near ~ 122.5° E beneath the Nanao Basin were also uplifted where shallow earthquakes had occurred by the oblique subduction of the Gagua Ridge depicted in the isopach map of the crust. Furthermore, a recent earthquake (Mw ~ 6.0) occurred near the northeast coast of Taiwan in 2018 at a depth of approximately 12 km below the Hsincheng Ridge. Our study suggests that this earthquake was caused by a thrust fault near the décollement, which might have been formed by the subduction of the PSP.

show abstract

Earthquake‐Related Structures Beneath the Southernmost Portion of the Ryukyu Arc and Forearc

Cited by 7 publications

References 40 publications

Uplifted structures due to the obliquely subducted Gagua Ridge below the Nanao Basin imaged from MCS/OBS data

Uplifted structures due to the obliquely subducted Gagua Ridge below the Nanao Basin imaged from MCS/OBS data

Strain Partitioning in the Southern Ryukyu Margin Revealed by Seafloor Geodetic and Seismological Observations

A hypothesis of the obliquely subducted Gagua Ridge below Nanao Basin based on uplifted structures in Ryukyu forearc

Contact Info

Product

Resources

About