Japan Geoscience Union Meeting 2015

Presentation information


Symbol S (Solid Earth Sciences) » S-CG Complex & General

[S-CG64] Ocean Floor Geoscience

Thu. May 28, 2015 11:00 AM - 12:45 PM A05 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Kyoko Okino(Ocean Research Institute, University of Tokyo), Keiichi Tadokoro(Research Center for Seismology, Volcanology and Earthquake and Volcano Research Center, Nagoya University), Osamu Ishizuka(Geological Survey of Japan, AIST), Tomohiro Toki(Faculty of Science, University of the Ryukyus), Narumi Takahashi(Research and Development Center for Earthquake and Tsunami, Japan Agency for Marine-Earth Science and Technology), Chair:Shiki Machida(独立行政法人 海洋研究開発機構), Yoshifumi Kawada(Japan Agency for Marine-Earth Science and Technology)

11:00 AM - 11:15 AM

[SCG64-23] Crustal thickness of the Ontong Java Plateau revealed from traveltime inversion analysis

*Seiichi MIURA1, Gou FUJIE1, Naoto NOGUCHI1, Shuichi KODAIRA1, Millard COFFIN2, Simon KAWAGLE3, Ronald VERAVE4 (1.JAMSTEC, 2.University of Tasmania, Australia, 3.University of Papua New Guinea, 4.Mineral Resource Authority, PNG)

Keywords:LIPs, OJP, MCS, OBS, traveltime, inversion

The Ontong Java Plateau (OJP) is the largest oceanic plateau on Earth, located in the western equatorial Pacific and delineated by the 4000-m bathymetric contour. It is five times as large as the Japanese islands. From the results of sampling and drilling, the OJP is a representative example of large igneous provinces (LIPs) (e.g. Coffin and Eldholm, 1994), which do not fit plate tectonic theory, and no formation model explains all existing observations from the OJP. Environmental impacts of OJP formation had the potential to be large scale as suggested by a geologically short interval of emplacement and the feature’s large area and volume. To understand its formation and environmental impacts, investigation of the crustal structure of the OJP is important. Structural studies of the OJP began in the 1960s. Since then, the few studies have determined the Moho depth beneath the OJP, which have varied according to survey method. For example, the Moho depths of seismic (Furumoto et al., 1976) and gravity (Sandwell and Renkin, 1988) studies are 35-42 km and 25 km, respectively. The Moho depth beneath the southernmost OJP is 35 km, as determined by a forward modeling approach (Miura et al., 2004), and an inversion analysis shows similar results (Korenaga, 2011). However, until recently the Moho depth at the center of the OJP has not been clearly determined and modern survey techniques were required. A seismic survey with 100 ocean bottom seismometers (OBS) across the center of the OJP was conducted in 2010 (Miura et al., 2011). First arrival traveltime tomography and forward modeling have been applied to the OBS data (Miura et al., 2013). Recently we have initiated traveltime inversion analysis of the OBS data using first arrivals and the largest amplitude later reflection phases (PmP), following noise reduction processing of reverberations from previous shots (Miura et al., 2014). Our analyses with initial models using various Moho depths show crustal thicknesses greater than those resulting from previous studies. Uncertainty analysis (Korenaga, 2011) will be applied to verify reliability of Moho depths.