HR: 0830h
AN: OS51C-0878    [PDF]
TI: Combined Studies of ODP log Data and Seismic Reflection Data at Southern Hydrate Ridge
AU: * Papenberg, C A
EM: cpapenberg@geomar.de
AF: GEOMAR Research Center, Wischhofstrasse 1-3, Kiel, 24118 Germany
AU: Petersen, J
EM: jpetersen@geomar.de
AF: GEOMAR Research Center, Wischhofstrasse 1-3, Kiel, 24118 Germany
AU: Klaeschen, D
EM: dklaeschen@geomar.de
AF: GEOMAR Research Center, Wischhofstrasse 1-3, Kiel, 24118 Germany
AB: In August 2002 Ocean Drilling Program (ODP) Leg 204 (Hydrate Ridge) provided essential borehole data to complement recent seismic studies at Hydrate Ridge to correlate amplitude analysis investigations and to constrain previous results. Seismic data was acquired during cruise SO-150 in September 2000 on the German RV SONNE, aiming at qualitative and quantitative estimates of free gas and gas hydrates within the sediments across Hydrate Ridge. Hydrate Ridge is part of the accretionary complex and is characterized by the presence of extensive gas hydrates, causing a prominent Bottom Simulating Reflector (BSR) in marine seismic records. Several seismic in- and crosslines were shot across the ridge to map the spatial distribution of the BSR. Wide angle reflection data of narrowly spaced Ocean Bottom Seismometers (OBS) allow frequency dependent amplitude variations with offset (AVO) investigations. Seismic reflection data, recorded simultaneously with a single channel surface and deep tow streamer completed the data set. The usage of different sources during acquisition provided additional information of the frequency response of the BSR signature. This data set was used to study the complex seismic behaviour of such gas hydrate environments in detail. The borehole data, collected during ODP Leg 204, now improve recent seismic investigations and support previous results. Within the COLIBRI project log information (Vp, Vs and density) was used for forward modeling to combine seismic investigations with new borehole data. The P wave velocity model of a traveltime inversion and AVO analysis of the seismic OBS sections suggest rather low quantities of gas hydrate or at least the lack of massive hydrate zones. Shear wave phases, identified in the seismic OBS sections, refer to slow S wave velocities in the upper sediment layers above the BSR, which support a model with small amounts of hydrate or patchy hydrate zones within the upper sediments.
DE: 0910 Data processing
DE: 0935 Seismic methods (3025)
DE: 3025 Marine seismics (0935)
DE: 5102 Acoustic properties
DE: 9350 North America
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting