Fault configuration produced by initial arc rifting in the Parece Vela Basin as deduced from seismic reflection data

Abstract

The Parece Vela Basin (PVB), which is a currently inactive back-arc basin of the Philippine Sea Plate, was formed by separation between the Izu-Ogasawara Arc (IOA) and the Kyushu-Palau Ridge (KPR). Elucidating the marks of the past back-arc opening and rifting is important for investigation of its crustal structure. To image its fault configurations and crustal deformation, pre-stack depth migration to multichannel seismic reflection was applied and data obtained by the Japan Agency for Marine-Earth Science and Technology and Metal Mining Agency of Japan and Japan National Oil Corporation (Japan Oil, Gas and Metals National Corporation). Salient results for the pre-stack depth-migrated sections are: (i) deep reflectors exist around the eastern margin of KPR and at the western margin of IOA down to 8 km depth; and (ii) normal fault zones distributed at the eastern margin of the KPR (Fault zone A) and the western margin of the IOA (Fault zone B) have a total displacement of greater than 500 m associated with synrift sediments. Additional normal faults (Fault zone C) exist 20 km east of the Fault zone B. They are covered with sediment, which indicates deposition of recent volcanic products in the IOA. According to those results: (i) the fault displacement of more than 500 m with respect to initial rifting was approximately asymmetric at 25 Ma based on PSDM profiles; and (ii) the faults had reactivated after 23 Ma, based on the age of deformed sediments obtained from past ocean drillings. The age of the base sediments corresponds to those of spreading and rotation after rifting in the PVB. Fault zone C is covered with thick and not deformed volcanogenic sediments from the IOA, which suggests that the fault is inactive.

The formation and tectonic evolution of Philippine Sea Plate and KPR

“…GPS measurements indicate that the KPR is still moving northward with Philippine Sea Plate and subducts beneath the Nankai Trough (Kobayashi., 2004). Okino et al (1998), Yamashita et al (2007), Haraguchi et al (2003), and Kobayashi, (2004)]. …”

Facies architecture, detrital provenance, and tectonic modulation of sedimentation in the Shikoku Basin: Inputs to the Nankai Trough subduction zone

“…Shikoku Basin occupies the northeastern part of the Philippine Sea plate (Fig. 1), and the Parece Vela Basin represents its extension to the south (Kasuga and Ohara, 1997;Okino et al, 1999;Yamashita et al, 2007). Such basins typically originate through rifting of an island arc and spreading between the remnant and active volcanic edifices (Karig, 1974;Taylor and Karner, 1983;Martinez et al, 2007;Stern, 2010).…”

Multi-channel seismic reflection survey in the northern Izu-Ogasawara island arc –KR07-09 cruise–

“…In order to clarify these unknown issues in the IBM arc, multi-channel seismic (MCS) reflection survey is one of best tools. In particular, MCS is strongly useful to discuss seismic stratigraphy of the sedimentary layer and the deformation of the basement, and to image reflectivity within the crust (e.g., Yamashita et al, 2007).…”