The resistivity structure of the North Alex Mud Volcano from marine CSEM measurements.

Hölz, Sebastian and Jegen, Marion (2011) The resistivity structure of the North Alex Mud Volcano from marine CSEM measurements. [Poster] In: 71. Jahrestagung der Deutschen Geophysikalischen Gesellschaft gemeinsam mit der Arbeitsgemeinschaft Extraterrestrische Forschung. , 21.02.- 24.02.2011, Köln . 71. Jahrestagung der Deutschen Geophysikalischen Gesellschaft gemeinsam mit der Arbeitsgemeinschaft Extraterrestrische Forschung und dem Fachverband Extraterrestrische Physik der Deutschen Physikalischen Gesellschaft : 21.–24. Februar 2011 in Köln. ; p. 40 .

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Abstract

Active mud volcanoes, where changing salinities of pore fluids, large temperature gradients and occurrences of free gas are frequently observed, potentially exhibit significant variability in their internal resistivity structure. In marine environments, these resistivity variations may be investigated using controlled source electromagnetic (CSEM) measurements. Within a RWE Dea funded investigation at the North Alex Mud Volcano (NAMV), we have developed a new high resolution CSEM system. The system consists of several autonomous electric dipole receivers and a lightweight electric dipole transmitter, which was mounted on a small remotely operated underwater vehicle (ROV). In an experiment carried out in November 2008, ten receivers were deployed over the surface of NAMV at a total of 16 receiver locations.
During three successful ROV dives, the transmitter was deployed at a total of 80 locations. Measured transients are interpreted using 1D inversions, where good data fits can be achieved by models containing 2-3 layers. Generally, models show low resistivities close to the ocean floor, indicative for penetrating salt water and/or high temperatures. Toward greater depths, increasing resistivities presumably are due to a combination of compaction of sediments (i.e. reduced pore space), an increased presence of fresh water and possible occurrences of free gas. The increase in resistivity may exceed a factor of 10 or more and layer interfaces are indicated down to depths of up to 100m. A combination of 1D models reveals lateral resistivity contrasts, which are well in agreement with structures evident in 3D seismics.

Document Type: Conference or Workshop Item (Poster)
Keywords: Meeresgeologie; Volcanology
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Open Access Journal?: Yes
Related URLs:
Date Deposited: 06 Jan 2012 11:52
Last Modified: 23 Feb 2012 05:53
URI: http://oceanrep.geomar.de/id/eprint/13300

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