Japan Geoscience Union Meeting 2016

Presentation information


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

[S-CG59] Ocean Floor Geoscience

Wed. May 25, 2016 3:30 PM - 5:00 PM 301B (3F)

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:Yojiro Yamamoto(Japan Agency for Marine-Earth Science and Technology), Mikiya Yamashita(Japan Agency for Marine-Earth Science and Technology)

4:30 PM - 4:45 PM

[SCG59-11] Estimation of thick crustal distribution of the Ontong Java Plateau

*Seiichi Miura1, Gou Fujie1, Taro Shirai1, Naoto Noguchi1, Eiichiro Araki1, Millard F. Coffin2, Simon A. Kawagle3, Ronald T. Verave4 (1.Japan Agency for Marine-Earth Science and Technology, 2.University of Tasmania, Australia, 3.University of Papua New Guinea, Papua New Guinea, 4.Mineral Resource Authority, Papua New Guinea)

Keywords:LIPs, OJP, MCS, OBS, crust, Moho

The Ontong Java Plateau (OJP), which is the largest oceanic plateau on Earth, has an area of 1.86 x 106 km2 (Coffin and Eldholm, 1994), five times Japan’s area. Scientific drilling on the OJP has shown that ages of basement basalts below sediments are approximately 120 million years (Ma) (e.g. Shipboard Scientific Party, 2001), suggesting that formation of the OJP was geologically brief. No formation mechanism yet proposed explains all observations. Crustal structure is important for understanding the formation mechanism of oceanic plateaus, and geophysical experiments have been conducted on the OJP since the 1960s. However, only a few experiments addressed the whole crust, i.e., everything above the Moho (e.g. Furumoto et al., 1976, Gladczenko et al., 1997). The Moho depth of the southernmost OJP colliding with the Solomon Islands is about 35 km (Miura et al., 2004). However, the Moho depth of the central OJP has not been determined confidently because of discrepancies in results among different survey methods. In 2010, we conducted a seismic experiment on the central OJP using a large volume airgun array, 100 ocean bottom seismometers (OBS), and a 6 km multi-channel seismic (MCS) streamer cable (Miura et al., 2011). We analyzed the OBS data using a forward modelling approach (Miura et al., 2013), a traveltime inversion approach (Fujie et al., 2013) using first arrival and Moho reflection phases (PmP) with the uncertainty outlined by Korenaga (2011), and a finite-difference amplitude method (Larsen and Grieger, 1998) for reflection phases (Miura et al., 2014, 2015). From these analyses, the Moho depth of the central OJP exceeds 40-km below sea level. To estimate the distribution of the Moho depth or crustal thickness of the OJP outside of the 2010 survey area, we will analyze wide-angle data collected in 1998 by scientists aboard RV Hakuho-maru (Araki et al., 1998) and previous results (e.g. Furumoto et al., 1976, Gladczenko et al., 1997) to calculate crustal volume and formation rate. These will contribute to resolving the mechanism(s) by which OJP formed and to assessing the environmental impact of formation.