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Seismic imaging and velocity structure around the JFAST drill site in the Japan Trench: low Vp, high Vp/Vs in the transparent frontal prism

Seismic imaging and velocity structure around the JFAST drill site in the Japan Trench: low Vp, high Vp/Vs in the transparent frontal prism
Seismic imaging and velocity structure around the JFAST drill site in the Japan Trench: low Vp, high Vp/Vs in the transparent frontal prism


Seismic image and velocity models were obtained from a newly conducted seismic survey around the Integrated Ocean Drilling Program (IODP) Japan Trench Fast Drilling Project (JFAST) drill site in the Japan Trench. Pre-stack depth migration (PSDM) analysis was applied to the multichannel seismic reflection data to produce an accurate depth seismic profile together with a P wave velocity model along a line that crosses the JFAST site location. The seismic profile images the subduction zone at a regional scale. The frontal prism where the drill site is located corresponds to a typically seismically transparent (or chaotic) zone with several landward-dipping semi-continuous reflections. The boundary between the Cretaceous backstop and the frontal prism is marked by a prominent landward-dipping reflection. The P wave velocity model derived from the PSDM analysis shows low velocity in the frontal prism and velocity reversal across the backstop interface. The PSDM velocity model around the drill site is similar to the P wave velocity model calculated from the ocean bottom seismograph (OBS) data and agrees with the P wave velocities measured from the core experiments. The average Vp/Vs in the hanging wall sediments around the drill site, as derived from OBS data, is significantly larger than that obtained from core sample measurements.
Japan Trench, Seismic image, P and S wave velocities, JFAST
1343-8832
121
Nakamura, Yasuyuki
831cfb7d-1dfb-4147-be84-69cbd8f7825a
Kodaira, Shuichi
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Cook, Becky J.
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Jeppson, Tamara
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Kasaya, Takafumi
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Yamamoto, Yojiro
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Hashimoto, Yoshitaka
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Yamaguchi, Mika
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Obana, Koichiro
c303e2d8-7fd5-40fc-abb7-0421ef4a1c48
Fujie, Gou
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Nakamura, Yasuyuki
831cfb7d-1dfb-4147-be84-69cbd8f7825a
Kodaira, Shuichi
98fd4032-ee7d-43a9-b90d-438d3b60d24c
Cook, Becky J.
c114ede4-47e6-450b-a754-71097473245e
Jeppson, Tamara
2f4a3446-645a-43d8-897f-90f4af932d2e
Kasaya, Takafumi
4265ca88-e083-4e97-834e-49f914283b39
Yamamoto, Yojiro
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Hashimoto, Yoshitaka
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Yamaguchi, Mika
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Obana, Koichiro
c303e2d8-7fd5-40fc-abb7-0421ef4a1c48
Fujie, Gou
0fdd617c-ef4e-4cb1-a673-20922d904032

Nakamura, Yasuyuki, Kodaira, Shuichi, Cook, Becky J., Jeppson, Tamara, Kasaya, Takafumi, Yamamoto, Yojiro, Hashimoto, Yoshitaka, Yamaguchi, Mika, Obana, Koichiro and Fujie, Gou (2014) Seismic imaging and velocity structure around the JFAST drill site in the Japan Trench: low Vp, high Vp/Vs in the transparent frontal prism. Earth Planets and Space, 66 (1), 121. (doi:10.1186/1880-5981-66-121).

Record type: Article

Abstract



Seismic image and velocity models were obtained from a newly conducted seismic survey around the Integrated Ocean Drilling Program (IODP) Japan Trench Fast Drilling Project (JFAST) drill site in the Japan Trench. Pre-stack depth migration (PSDM) analysis was applied to the multichannel seismic reflection data to produce an accurate depth seismic profile together with a P wave velocity model along a line that crosses the JFAST site location. The seismic profile images the subduction zone at a regional scale. The frontal prism where the drill site is located corresponds to a typically seismically transparent (or chaotic) zone with several landward-dipping semi-continuous reflections. The boundary between the Cretaceous backstop and the frontal prism is marked by a prominent landward-dipping reflection. The P wave velocity model derived from the PSDM analysis shows low velocity in the frontal prism and velocity reversal across the backstop interface. The PSDM velocity model around the drill site is similar to the P wave velocity model calculated from the ocean bottom seismograph (OBS) data and agrees with the P wave velocities measured from the core experiments. The average Vp/Vs in the hanging wall sediments around the drill site, as derived from OBS data, is significantly larger than that obtained from core sample measurements.

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More information

Published date: 2014
Keywords: Japan Trench, Seismic image, P and S wave velocities, JFAST
Organisations: Geology & Geophysics

Identifiers

Local EPrints ID: 371798
URI: http://eprints.soton.ac.uk/id/eprint/371798
ISSN: 1343-8832
PURE UUID: 01e00ef2-1356-472f-9472-c5933c515894

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Date deposited: 14 Nov 2014 15:07
Last modified: 14 Mar 2024 18:27

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Contributors

Author: Yasuyuki Nakamura
Author: Shuichi Kodaira
Author: Becky J. Cook
Author: Tamara Jeppson
Author: Takafumi Kasaya
Author: Yojiro Yamamoto
Author: Yoshitaka Hashimoto
Author: Mika Yamaguchi
Author: Koichiro Obana
Author: Gou Fujie

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