Abstract
This paper presents results of a seismic tomography experiment carried out on the accretionary margin off southwest Taiwan. In the experiment, a seismic air gun survey was recorded on an array of 30 ocean bottom seismometers (OBS) deployed in the study area. The locations of the OBSs were determined to high accuracy by an inversion based on the shot traveltimes. A three-dimensional tomographic inversion was then carried out to determine the velocity structure for the survey area. The inversion indicates a relatively high P wave velocity (Vp) beneath topographic ridges which represent a series of thrust-cored anticlines develop in the accretionary wedge. The bottom-simulating reflectors (BSR) closely follow the seafloor and lies at 325 ± 25 m within the well-constrained region. Mean velocities range from ~1.55 km/s at the seabed to ~1.95 km/s at the BSR. We model Vp using an equation based on a modification of Wood’s equation to estimate the gas hydrate saturation. The hydrate saturation varies from 5% at the top ~200 m below the seafloor to 25% of pore space close to the BSR in the survey area.
Similar content being viewed by others
References
Bünz S, Mienert J, Vanneste M, Andreassen K (2005) Gas hydrates at the Storegga slide: constraints from an analysis of multicomponent, wide-angle seismic data. Geophysics 70(5):B19–B34
Burbank DW, Verges J (1994) Reconstruction of topography and related depositional systems during active thrusting. J Geophys Res 99:20281–20297
Caine JS, Evans JP, Forster CB (1996) Fault zone architecture and permeability structure. Geology 24:1025–1028
Chand S, Minshull TA, Davide G, Carcione JM (2004) Elastic velocity models for gas-hydrate-bearing sediments—a comparison. Geophys J Int 159:573–590
Cheng WB, Lee CS, Liu CS, Schnurle P, Lin SS, Tsai HZ (2006) Velocity structure in marine sediments with gas hydrate reflectors in offshore SW Taiwan from wide-angle seismic tomography. Terr Atmos Ocean Sci 17:739–756
Dadson SJ, Hovius N, Chen H, Dade B, Hsieh ML, Willett SD, Hu JC, Horng MJ, Chen MC, Stark CP, Lague D, Lin JC (2003) Links between erosion, runoff variability and seismicity in the Taiwan orogen. Nature 426:648–651
Gei D, Carcione JM (2003) Acoustic properties of sediments saturated with gas hydrate, free gas and water. Geophys Prospect 51:141–157
Helgerud MB, Dvorkin J, Nur A, Sakai A, Collett T (1999) Elastic-wave velocity in marine sediments with gas hydrates: Effective medium modeling. Geophys Res Lett 26:2021–2024
Hobro JWD, Singh SC, Minshull TA (2003) Three-dimensional tomographic inversion of combined reflection and refraction seismic traveltime data. Geophys. J. Int. 152:79–93
Hobro JWD, Minshull TA, Singh SC, Chand S (2005) A three-dimensional seismic tomographic study of the gas hydrate stability zone, offshore Vancouver Island. J Geophys Res 110:B09102. doi:10.1029/2004JB003477
Hyndman RD, Davis EE (1992) A mechanism for the formation of methane hydrate and seafloor bottom-simulating reflectors by vertical fluid expulsion. J Geophys Res 97:7025–7041
Hyndman RD, Spence GD (1992) A seismic study of methane hydrate marine bottom simulating reflectors. J Geophys Res 97:6683–6698
Jakobsen M, Hudson JA, Minshull TA, Singh SC (2000) Elastic properties of hydrate-bearing sediments using effective medium theory. J Geophys Res 105:561–577
Jarrard RD (1997) Origins of porosity and velocity variations at Cascadia accretionary prism. Geophys Res Lett 24:325–328
Jiang WT, Chen JC, Huang BJ, Chen CJ, Lee YT, Huang PR, Lung CC, Huang SW (2006) Mineralogy and physical properties of cored sediments from the gas hydrate potential area of offshore southwestern Taiwan. Terr Atmos Ocean Sci 17:981–1007
Katzman R, Holbrook W, Paull C (1994) Combined vertical incidence and wide-angle seismic study of a gas hydrate zone, Blake Ridge. J Geophys Res 99:17975–17995
Korenaga J, Holbrook WS, Singh SC, Minshull TA (1997) Natural gas hydrate on the southeast U.S. margin: constraints from full waveform and traveltime inversions of wide-angle seismic data. J Geophys Res 102:15345–15365
Kumar D, Sen MK, Bangs NL (2007) Gas hydrate concentration and characteristics within Hydrate Ridge inferred from multicomponent seismic reflection data. J Geophys Res 112:B12306. doi:10.1029/2007JB004993
Kumar D, Dash R, Dewangan P (2009) Methods of gas hydrate concentration estimation with field examples. Geohorizons December:76–86
Lee MW, Dillon WP, Hutchinson DR (1992) Estimating the amount of gas hydrate in marine sediments in the Blake Ridge area, southeastern Atlantic margin. U.S. Geological Survey Open-File Report, pp 92–275, 24 p
Lee MW, Hutchinson DR, Collet TS, Dillon WP (1996) Seismic velocities for hydrate-bearing sediments using weighted equation. J Geophys Res 101: 20, 347–320, 359
Lin AT, Watts AB, Hesselbo SP (2003) Cenozoic stratigraphy and subsidence history of the South China Sea margin in the Taiwan region. Basin Res 15(4):453–478
Lin AT, Liu CS, Lin CC, Schnurle P, Chen GY, Liao WZ, Teng LS, Chuang HR, Wu MS (2008) Tectonic features associated with the overriding of an accretionary wedge on top of a rifted continental margin: An example from Taiwan. Mar Geol 255:186–203. doi:10.1016/j.margeo.2008.10.002
Liu CS, Schnurle P, Wang Y, Chung SH, Chen SC, Hsiuan TH (2006) Distribution and characters of gas hydrate offshore of southwestern Taiwan. Terr Atmos Ocean Sci 17:615–644
Mason EA, Malinauskas AP, Evans RB III (1967) Flow and diffusion of gases in porous media. J Chem Phys 46(8):3199–3216
Mienert J, Posewang J (1999) Evidence of shallow- and deep-water gas hydrate destablilizations in North Atlantic polar continental margin sediments. Geo-Marine Lett 19:143–149
Moore GF, Shipley TH, Stoffa PL, Karig DE, Taira A, Kuramoto S, Tokuyama H, Suyehiro K (1990) Structure of the Nankai Trough accretionary zone from multichannel seismic reflection data. J Geophys Res 95:8753–8765
Netzeband GL, Hubscher CP, Gajewski D, Grobys JWG, Bialas J (2005) Seismic velocities from the Yaquina forearc basin off Peru: evidence for free gas within the gas hydrate stability zone. Int J Earth Sci 94:420–432
Pecher IA, Minshull TA, Singh SC, von Huene R (1996) Velocity structure of a bottom simulating reflector offshore Peru: Results from full waveform inversion. Earth Planet Sci Lett 139:459–2469
Pecher IA, Rnerco CR, von Huen R, Minshull TA, Singh SC (1998) The nature and distribution of bottom simulating reflectors at the Costa Rican convergent margin. Geophys J Int 133:219–229
Sclater JG, Christie PAF (1980) Continental stretching: an explanation of the post-mid-Cretaceous subsidence of the central North Sea basin. J Geophys Res 85:3711–3739
Shipboard Scientific Party (2002) Leg 195 summary. In: Salisbury MH, Shinohara M, Richter C et al (eds) Proc. ODP, Init. Repts., 195, pp 1–63
Shipley TH, Houston MH, Buffler RT, Shaub FJ, McMillen KJ, Ladd JW, Worzel JL (1979) Seismic reflection evidence for the widespread occurrence of possible gas hydrate horizons on continental slopes and rises. Am Assoc Petrol Geol Bull 63:2204–2213
Sloan ED (1998) Physical/chemical properties of gas hydrates and applications to world margin stability and climate change. In: Henriet JP, Mienert J (eds) Gas hydrates: relevance to world margin stability and climate change. Geol Soc Spec Pub 137. London, pp 31–50
Tinivella U, Accaino F (2000) Compressional velocity structure and Poisson’s ratio in marine sediments with gas hydrate and free gas by inversion of reflected and refracted seismic data (South Shetland Islands, Antarctica). Mar Geol 164:13–27
West M (2001) The deep structure of axial volcano, Ph.D. dissertation. University of Columbia, New York
White RS (1977) Gas hydrate layers trapping free-gas in the gulf of oman. Earth Planet Sci Lett 42:114–120
Yen JY, Lundberg N (2006) Sediment compositions in offshore Southern Taiwan and their relations to the source rocks in modern arc-continent collision zone. Mar Geol 225:247–263
Acknowledgments
We are grateful to the scientists and the technologists participating in the cruise during MCS and OBS date acquisition. We thank Liang, J. W. for assistance in the processing of OBS data. This research was supported by the Central Geological Survey, Ministry of Economic Affairs Under grant 98-5226904000-04-02 and partly by the national Science Council, Taiwan under Grant NSC 98-2116-M-228-001.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Cheng, WB., Lin, S.S., Wang, T.K. et al. Velocity structure and gas hydrate saturation estimation on active margin off SW Taiwan inferred from seismic tomography. Mar Geophys Res 31, 77–87 (2010). https://doi.org/10.1007/s11001-010-9090-0
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11001-010-9090-0