A magnitude 8.1 earthquake in the mid-twentieth century could have triggered the release of large amounts of methane - a potent greenhouse gas - from the Arabian sea floor, reports a study published online this week in Nature Geoscience. If quake-triggered release of methane is a common occurrence, it could contribute significantly to the global carbon budget.
David Fischer and colleagues use seismic and geochemical data to image and analyse seafloor sediments off Pakistan. They find that the strongest earthquake recorded for the Arabian Sea, which occurred in 1945, probably fractured sediments that held stores of fragile gas hydrates. The researchers estimate that significant amounts of methane may have escaped into the ocean in the decades following the earthquake. Gas hydrates are common in many seismically active regions, and earthquakes could therefore provide an important natural trigger for their release.