Slab Morphology Around the Philippine Sea: New Insights From P‐Wave Mantle Tomography

Abstract

The Philippine Sea Plate (PSP) is located at the intersection of the Eurasian, Pacific and Indo-Australian plates, and is almost entirely surrounded by subduction zones (Zhang et al., 2016). The PSP eastern boundary is the Izu-Bonin, Mariana, Yap, and Palau trenches and the Ayu Trough. The PSP western border is the Nankai Trough and the Ryukyu, Manila, and Philippine trenches. The Kyushu-Palau Ridge divides the Philippine Sea Basin into the West Philippine Basin and the Shikoku-Parece Vela Basin. The latter is further divided into the Shikoku Basin (SB) in the north and the Parece Vela Basin (PVB) in the south by the Sovgan Fault. In the easternmost part of the PSP, the Izu-Bonin-Mariana (IBM) block is composed of the Izu-Bonin and Mariana islands arcs (Figure 1). The PSP has rotated clockwise three times during 40-50 (or 55) Ma, 5-25 Ma, and 0-5 Ma Hall, Fuller et al., 1995;Sdrolias et al., 2004), and then expanded to its present form with complex structures and tectonics. The PSP is a complex region where the bathymetry, plate shape and seafloor age have undergone significant changes (Müller et al., 2008;Yamazaki et al., 2010). The PSP has become one of the major research targets in geosciences because of its special geological location and complex tectonic features.Seismic imaging has become a crucial tool for studying the interior structure of the Earth. To date, many tomographic studies have been made to investigate the 3-D velocity structure of the crust and upper mantle beneath the PSP region (e.g.,

Detached Pacific Slab Beneath the Philippine Sea Plate and Its Geodynamical Implications

“…Our Vp tomographic images at different depths and along different profiles are presented in Figures 4–8, which are generally consistent with the previous tomographic models in and around the study region (e.g., Amaru, 2007; Barklage et al., 2015; Cao et al., 2014; Chen et al., 2017; Fan & Zhao, 2018, 2021a, 2021b; Fan et al., 2015, 2016, 2017, 2022; Fukao & Obayashi, 2013; Hasegawa et al., 2013; Huang & Zhao, 2006; Huang et al., 2013; Isse et al., 2004, 2006, 2009, 2010; Koulakov et al., 2014; Kuo‐Chen et al., 2012; Lallemand et al., 2001; Li et al., 2008; Liu & Zhao, 2016; Lu et al., 2019; J. Ma et al., 2019; Pyle et al., 2010; Qiao et al., 2021; She et al., 2023; Tao et al., 2018; Toyokuni et al., 2021, 2022; van der Hist et al., 1991; Wei et al., 2012, 2015, 2022; Zhao, 2004; Zhao et al., 1992, 2012, 2017). The most distinct feature of the upper mantle is linear and continuous high‐velocity (high‐V) anomalies around the PSP, which indicate the subducting Eurasian slab along the Manial Trench, the Pacific slab along the Japan and IBM trenches, and the Philippine Sea slab along the Nankai Trough and the Ryukyu and Philippine trenches (Figures 4b–4i).…”

Structure and Tectonic Evolution of the NW Sulu Sea Basin (SE Asia)

“…Thereby, the opening of the South China and Sulu Sea basins could be related to a slab under the Philippine Sea to the East (Rangin et al., 1999; She et al., 2023). Slab roll‐back accounts for the sequential opening of back‐arc basins in the SW Pacific (Schellart et al., 2006) and the Mediterranean (Faccenna et al., 2001).…”

“…Proposed geodynamic models (see Xu et al., 2014 for a review) include back‐arc opening (Karig, 1971; Li et al., 2020; Rangin, 1989). Global seismic tomography models (Rangin et al., 1999; She et al., 2023; Simmons et al., 2019; Wu & Suppe, 2018), gravity modeling (Liu et al., 2014), and large‐scale geodynamic models (Lin et al., 2020) have been used to propose a PSCS slab offshore Palawan‐Borneo and under the Sulu Sea Basin. Although all those models do not resolve a clear mantle structure supporting the presence of a slab, subduction of a PSCS plate has been proposed as the mechanism that led to the opening of the South China Sea and Sulu Sea basins (Liu et al., 2014).…”