Velocity Structure in Marine Sediments with Gas Hydrate Reflectors in Offshore SW Taiwan, from OBS Data Tomography

Cheng, Win-Bin; Lee, Chao-Shing; Liu, Char‐Shine; Schnürle, Philippe; Lin, Shih Chang; Tsai, Hong-Ruai

doi:10.3319/tao.2006.17.4.739(gh)

Cited by 16 publications

(11 citation statements)

References 41 publications

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“…Compilation and analyses of geophysical and geological data have been carried out to establish the regional geophysical characters, geological structures, and sedimentary patterns of both the accretionary wedge province and the passive China continental slope regions of the investigation area. Special geophysical investigation techniques, such as 2.5-D (or pseudo 3-D) seismic surveys, ocean bottom seismometers (Cheng et al 2006;, heat flow measurements (Shyu et al 2006), deep-tow magnetic survey, etc., have been conducted. Regional sedimentary deposition processes (Yu and Huang 2006) and structural patterns have been proposed.…”

Section: Cgs Gas Hydrate Investigation Programmentioning

confidence: 99%

“…These datasets were collected using the high-resolution MCS system described above but with 400-to 250-m line spacing. OBSs were deployed along key profiles during each of the 3 2.5-D MCS surveys to provide velocity constrains (e.g., Cheng et al 2006), and to derive S-wave velocity information . Further analyses of these 2-D MCS/OBS experiments will be published later.…”

Section: Seismic Investigationmentioning

confidence: 99%

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Distribution and Characters of Gas Hydrate Offshore of Southwestern Taiwan

Liu¹,

Schnürle²,

Wang³

et al. 2006

Terr. Atmos. Ocean. Sci.

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149

108

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ABSTRACT1 Institute of Oceanography, National Taiwan University, Taipei, Taiwan, ROC 2 Central Geologic Survey, Taipei, Taiwan, ROC 3 Exploration Department, Chinese Petroleum Company, Miaoli, Taiwan, ROC * Corresponding author address: Prof. Char-Shine Liu, Institute of Oceanography, National Taiwan University, Taipei, Taiwan, ROC; E-mail: csliu@ntu.edu.tw Bottom simulating reflector (BSR) is a key indicator for the presence of gas hydrate beneath the sea floor. Widely distributed BSRs have been observed in the area offshore of southwestern Taiwan where the active accretionary complex meets with the passive China continental margin. In order to better understand the distribution and characters of the gas hydrate in the region, closely spaced (1.86-km line spacing) multichannel seismic reflection surveys have been conducted in recent years under the support of the Central Geological Survey, ROC. Over 10000 km of multichannel seismic reflection profiles have been collected that cover an area of about 10000 km 2 offshore of southwestern Taiwan. BSRs can be identified along 50% of the seismic profiles that we collected. A newly compiled BSR distribution map suggests that gas hydrates are distributed both in the passive margin of the China continental slope as well as in the submarine Taiwan accretionary wedge, from water depths of 500 to over 3000 m. Gas hydrates are most concentrated underneath anticlinal ridges in the accretionary wedge, and underneath the slope ridges of the passive continental margin that were formed due to sedimentary processes. Active fluid activities are evident from various features observed on seismic reflection and chirp sonar profiles, such as mud volcanoes, gas plumes and gas charged shallow sedimentary layers. Fluid migration model has been established from a set of pseudo 3D seismic reflection data. The predicted locations of high fluid Terr. Atmos. Ocean. Sci., Vol. 17, No. 4, December 2006 616 flux correlate well with those interpreted from geochemical analyses that show very high methane concentrations and very shallow sulfate-methane interfaces (SMI). This demonstrates the importance of structural control over gas hydrate emplacement. From the observed gas hydrate distribution and characters, the area offshore of southwestern Taiwan provides an ideal place to study and compare the formation and migration of gas hydrates under different tectonic settings.

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Section: Cgs Gas Hydrate Investigation Programmentioning

confidence: 99%

Section: Seismic Investigationmentioning

confidence: 99%

Distribution and Characters of Gas Hydrate Offshore of Southwestern Taiwan

Liu¹,

Schnürle²,

Wang³

et al. 2006

Terr. Atmos. Ocean. Sci.

Self Cite

149

108

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“…After erosion, the sub-seafloor temperature gradient redistributes and results in the hydrate/gas phase boundary moving downward. The results obtained in this study show that tectonic control is an important factor in determining bottomsimulating reflector (BSR) distributions offshore of southwestern Taiwan 121 .…”

Section: Research In Taiwanmentioning

confidence: 73%

Gas Hydrates Research Programs: An International Review

Gabitto¹,

Barrufet²

2009

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Gas hydrates sediments have the potential of providing a huge amount of natural gas for human use. Hydrate sediments have been found in many different regions where the required temperature and pressure conditions have been satisfied. Resource exploitation is related to the safe dissociation of the gas hydrate sediments. Basic depressurization techniques and thermal stimulation processes have been tried in pilot efforts to exploit the resource.There is a growing interest in gas hydrates all over the world due to the inevitable decline of oil and gas reserves. Many different countries are interested in this valuable resource. Unsurprisingly, developed countries with limited energy resources have taken the lead in worldwide gas hydrates research and exploration.The goal of this research project is to collect information in order to record and evaluate the relative strengths and goals of the different gas hydrates programs throughout the world. A thorough literature search about gas hydrates research activities has been conducted. The main participants in the research effort have been identified and summaries of their past and present activities reported. An evaluation section discussing present and future research activities has also been included.

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“…Schnürle et al (2006) utilized three independent methods to determine the acoustic and shear-wave velocities of the sediments and investigate the gas hydrate content through rock physic modeling. Cheng et al (2006) found westward thrusting high velocity wedges along several east-west OBS profiles and suggested them as a series of thrust faults. Schnürle et al (2011) estimated fluid and gas migration path and intensity for the southern part of the Yuan-An ridge and found that the maximum fluid and gas transport across BSR should occur below the crest of anticlines.…”

Section: Resultsmentioning

confidence: 95%

Imaging P- and S-wave velocity structures in hydrate bearing sediments along an OBS profile across the Yuan-An Ridge, off southwest Taiwan

Cheng

Liang

et al. 2018

Terr. Atmos. Ocean. Sci.

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In order to improve our understanding of the marine slope instability of hydratebearing sediments in the offshore southwestern Taiwan, P-and S-waves seismic data generated by P-S conversion on reflection from airgun shots recorded from a multicomponent Ocean Bottom Seismometer (OBS) survey were used to construct twodimensional velocity model. The investigated profile lies above a structural high of the Yuan-An ridge, proposed as a high priority drilling site for gas hydrate investigations off southwest Taiwan. The locations of the OBSs were determined with high accuracy by an inversion based on the shot traveltimes. Traveltime inversion and forward modeling of seismic data result in general trends P-and S-wave velocities of sediments. Generally, P-and S-wave velocities are high beneath topographic ridges which might represent a series of thrust-cored anticlines develop in the accretionary wedge. P-wave velocities of the sea floor are about ~1.58 km s -1 , increasing to the bottom simulating reflectors (BSR), reaching values of about ~2 km s -1 . Below it, a low velocity layer (1.62 -1.74 km s -1 ) is observed, which indicates the presence free gas in the sedimentary layer. S-wave velocities of the sediments over the entire section range from 0.3 to ~0.6 km s -1 . Significant lateral velocity variations were found beneath the eastern flank of the Yuan-An ridge, probably represents thrust faults that extend from seafloor to hydrate-bearing layer. We suggest that the BSR has been disturbed by the thrust faults and further rupture of the fault could potentially trigger failures in the study area.

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Velocity Structure in Marine Sediments with Gas Hydrate Reflectors in Offshore SW Taiwan, from OBS Data Tomography

Cited by 16 publications

References 41 publications

Distribution and Characters of Gas Hydrate Offshore of Southwestern Taiwan

Distribution and Characters of Gas Hydrate Offshore of Southwestern Taiwan

Gas Hydrates Research Programs: An International Review

Imaging P- and S-wave velocity structures in hydrate bearing sediments along an OBS profile across the Yuan-An Ridge, off southwest Taiwan

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