Japan Geoscience Union Meeting 2019

Presentation information

[J] Poster

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

[S-CG60] Investigation of inputs to subduction zones: Influence of tectonic processes on the incoming plate

Mon. May 27, 2019 3:30 PM - 5:00 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Makoto Yamano(Earthquake Research Institute, the University of Tokyo), Tomoaki Morishita(School of Geoscience and Civil Engineering, College of Science and Technology, Kanazawa University), Gou Fujie(Japan Agency for Marine-Earth Science and Technology)

[SCG60-P02] The variation of seismic attributes about incoming oceanic crust in Nankai Trough using multi-channel seismic reflection data

*Mikiya Yamashita1, Seiichi Miura1, Ayako Nakanishi1, Jin-Oh Park2, Shuichi Kodaira1 (1.Japan Agency for Marine-Earth Science and Technology, 2.Department of Ocean Floor Geoscience, Atmosphere and Ocean Research Institute, The University of Tokyo)

The physical properties of seismic reflection profiles include many geological information with tectonic setting. Nankai Trough is one of the best places to reveal the characteristics about plate boundary of subducting oceanic plate for understanding the large disaster earthquake because there are many exploration data. Japan Agency for Marine-Earth Science and Technology carried out high-resolution multi-channel seismic reflection (MCS) survey in Shikoku Basin along the Nankai Trough by using R/V Kaiyo with high-resolution portable system in 2012 and 2014. To reveal the characteristics of the subducting oceanic plate is important to evaluate the property of plate boundary for understanding the large disaster earthquake. We evaluate not only structure of MCS profiles, but also the variations of reflection strength about the top of oceanic crust of incoming plate.

MCS profiles of lines KY12-4 and SB01 were obtained along the Nankai Trough. These data were valuable for case study by comparison about physical properties from seismic attribute of top of oceanic crust. In order to extract the physical properties from the reflector of top of oceanic crust, we apply seismic attributes analysis for these data. Seismic attributes are measured from seismic data that can be analyzed in order to enhance information that might be well understanding in a traditional seismic image (Tarner et al. 1979). The seismic envelope attributes often use the reflection strength of the reflector (e.g. Tsuji et al. 2007). The envelope of seismic attributes means the envelope of seismic signal. These attributes are good for looking at packages of amplitudes. We select the second derivative of single envelope as reflection strength of top of oceanic crust. Although calculated seismic attributes of reflection strength indicate the high intensities in the central part of Shikoku Basin, the west and east part of Shikoku Basin where is initial stage of spreading of Shikoku Basin have the small intensities. This suggests that the reflection strength of top of oceanic crust is affected by the created condition of oceanic crust. We also discuss about the relationship between the reflection strength of top of oceanic crust and the thickness of sediments of Shikoku Basin.
This study is part of 'Research project for compound disaster mitigation on the great earthquakes and tsunamis around the Nankai trough region' funded by Ministry of Education, Culture, Sports, Science and Technology, Japan.