Imaging seismic velocities for hydrate-bearing sediments using converted waves near Yuan-An Ridge, off southwest Taiwan
Journal
Journal of Asian Earth Sciences
Journal Volume
92
Pages
215-223
Date Issued
2014
Author(s)
Abstract
Data from P-waves and from S-waves generated by P-S conversion on reflection from airgun shots recorded along four lines of ocean bottom seismometers were used to construct 2-D velocity sections near the Yuan-An Ridge, off southwest Taiwan. The locations of the ocean bottom seismometers were determined to high accuracy by an inversion based on the shot traveltimes. Traveltime inversion and forward modeling of multicomponent wide-angle seismic data result in detailed P-wave (Vp) and S-wave (Vs) velocities of hydrate-bearing sediment layers. The inversion indicates a relatively high P-wave velocity beneath topographic ridges which represent a series of thrust-cored anticlines develop in the accretionary wedge. S-wave velocities of the sediments over the entire section, down to 400m below seafloor, range from 320 to 570ms-1. We suggested the lateral variation in Vp/Vs profiles in the hydrate-affected zones may be related to the migration conduit of gas-rich fluid and a characteristic of hydrate content. We model Vp using equations based on a modification of Wood's equation to estimate the gas hydrate saturation. The hydrate saturation varies from 5% at the top ~200m below the seafloor to 10-15% of pore space close to the bottom simulating reflector (BSR) in the survey area. © 2013 Elsevier Ltd.
SDGs
Type
journal article