Earthquake-induced methane migration through the gas hydrate stability zone in the subduction regime offshore Pakistan


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david.fischer [ at ] awi.de

Abstract

Although gas hydrates often occur in seismically active regions, the role of earthquakes as triggers of hydrocarbon seepage through gas hydrate-bearing sediments has been only super�cially addressed. The Makran continental margin o�shore Pakistan hosts hydrocarbon-laden sediments and gas hydrates and is prone to vigorous seismicity. The area was visited in the frame of RV METEOR expedition M 74/3 in 2007 (Bohrmann et al. 2008). Here we present geochemical evidence for a substantial increase in upward gas �ux inducing methane emission into the water column and gas hydrate formation in the sediment, a phenomenon which occurred within a few decades of the strongest earthquake ever reported for the entire Arabian Sea. We propose a causal relation and present re�ection seismic data supporting our hypothesis that co-seismic ground shaking induced mechanical fracturing of gas hydrate-bearing sediments creating pathways for free gas to migrate from a shallow reservoir within the gas hydrate stability zone into the water column. Our �ndings lead to conclude that hydrocarbon seepage triggered by earthquakes might play a role for carbon budgets at other seismically active continental margins. The newly identi�ed process presented here can help interpret data from similar sites.



Item Type
Conference (Poster)
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Not peer-reviewed
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Published
Event Details
Gordon Research Conferences - Natural gas hydrate systems, 01 Jan 2014 - 01 Jan 1970, Galveston, Texas, USA.
Eprint ID
35566
Cite as
Fischer, D. , Mogollon, J. M. , Strasser, M. , Pape, T. , Bohrmann, G. , Fekete, N. , Spiess, V. and Kasten, S. (2014): Earthquake-induced methane migration through the gas hydrate stability zone in the subduction regime offshore Pakistan , Gordon Research Conferences - Natural gas hydrate systems, Galveston, Texas, USA, 2014 - unspecified .


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