HR: 1340h
AN: V13B-1351    [Abstracts]
TI: 3D Investigation of gas Hydrates and Free gas Saturation of a mud Volcano in the Black Sea With High Resolution Wide Angle Seismic Methods
AU: Krabbenhoeft, A
EM: akrabbenhoeft@ifm-geomar.de
AF: IFM-GEOMAR, Leibniz-Institut fuer Meereswissenschaften, Wischhofstr. 1-3 24148 Kiel, Kiel, 24148, Germany
AU: * Bialas, J
EM: jbialas@ifm-geomar.de
AF: IFM-GEOMAR, Leibniz-Institut fuer Meereswissenschaften, Wischhofstr. 1-3 24148 Kiel, Kiel, 24148, Germany
AU: Netzeband, G
EM: gnetzeband@ifm-geomar.de
AF: IFM-GEOMAR, Leibniz-Institut fuer Meereswissenschaften, Wischhofstr. 1-3 24148 Kiel, Kiel, 24148, Germany
AU: Zillmer, M
EM: mzillmer@ifm-geomar.de
AF: IFM-GEOMAR, Leibniz-Institut fuer Meereswissenschaften, Wischhofstr. 1-3 24148 Kiel, Kiel, 24148, Germany
AU: Papenberg, C
EM: cpapenberg@ifm-geomar.de
AF: IFM-GEOMAR, Leibniz-Institut fuer Meereswissenschaften, Wischhofstr. 1-3 24148 Kiel, Kiel, 24148, Germany
AB: Geoscientific investigations were performed as a part of the MARGASCH project with the aim to quantify the distribution of gas hydrates and relate them to fluid migration zones in sediments. The research area lies in the Sorokin Trough, Black Sea, south-east of the Crimea peninsula. It is affected by compressional tectonics, leading to diapiric compressional structures in the sediments where fluids and gas migrate to the seafloor. This study focuses on a 3D-grid, 7km x 2.5km, of high resolution seismic measurements. 14 Ocean Bottom Instruments (OBH/S) recorded the seismic signals generated by two 1.7l GI-guns at a shooting rate of 10s. A 2.5D Kirchhoff depth-migration applied to the OBH/S time sections (common receiver gathers) gives a spatial image of the subseafloor, where reflectors extend to a max. depth of 1000m and 400m distance to the receiver at the seafloor. Superimposing all OBH/S sections along one transect gives the depth image of the entire profile. The resulting image shows strong lateral variations in the reflection patterns: parallel layering to a max. depth of 1000m bsf occurs in the peripheral regions of this 3D-grid. The central part is characterized by blanking and fault zones dipping in the south-eastward direction. The traveltime inversion and its correlation with all seismic migrated sections results in a 3D-grid of seismic velocities and structures of the subseafloor. The two methods are complementary. The fluid-migration paths are indicated by reduced seismic velocities in the inversion models and extend to tens of meters. They are mainly found in the north-western part of the 3D-grid and originate from deeper sources, which are beyond the resolution of this seismic dataset. Lateral migration of gas is indicated by reduced velocities within certain sediment layers. This is especially found in the uppermost layer, with values of about 1.45km/s. A gas-hydrate bearing layer is imaged at a depth of about 300m bsf, implied by higher P-wave velocities than the ones in the layers above and below. The thickness of this layer is varying throughout the imaged research area at about 50-100m.
UR: http://www.ifm-geomar.de
DE: 0930 Oceanic structures
DE: 0935 Seismic methods (3025, 7294)
DE: 8045 Role of fluids
DE: 8426 Mud volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting