carbon budget
; earthquake event
; gas hydrate
; global change
; heterogeneity
; hydrocarbon
; marine sediment
; sediment chemistry
; sediment core
; seepage
; subduction zone
; Arabian Sea
; Indian Ocean
; Pakistan
英文摘要:
Methane, a potent greenhouse gas, is abundant in marine sediments. Submarine seepage of methane-dominated hydrocarbons is heterogeneous in space and time, and mechanisms that can trigger episodic seep events are poorly understood. For example, critical gas pressures have been predicted to develop beneath impermeable sediments that bear gas hydrates, making them susceptible to mechanical failure and gas release. Gas hydrates often occur in seismically active regions, but the role of earthquakes as triggers of hydrocarbon seepage through gas-hydrate-bearing sediments has been only superficially addressed. Here we present geochemical analyses of sediment cores retrieved from the convergent margin off Pakistan. We find that a substantial increase in the upward flux of gas occurred within a few decades of a M w 8.1 earthquake in 1945 - the strongest earthquake reported for the Arabian Sea. Our seismic reflection data suggest that co-seismic shaking fractured gas-hydrate-bearing sediments, creating pathways for the free gas to migrate from a shallow reservoir within the gas hydrate stability zone into the water column. We conservatively estimate that 3.26×10 8 mol of methane have been discharged from the seep site since the earthquake. We therefore suggest that hydrocarbon seepage triggered by earthquakes needs to be considered in local and global carbon budgets at active continental margins.
MARUM - Center for Marine Environmental Sciences, University of Bremen, Leobener Straße, D-28359 Bremen, Germany; Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, D-27570 Bremerhaven, Germany; Geological Institute, ETH Zürich, Sonneggstraße 5, CH-8092 Zürich, Switzerland
Recommended Citation:
Fischer D.,Mogollón J.M.,Strasser M.,et al. Subduction zone earthquake as potential trigger of submarine hydrocarbon seepage[J]. Nature Geoscience,2013-01-01,6(8)