Sea quakes trigger release of methane

AFP-JIJI

Earthquakes can rip open sub-sea pockets of methane, a highly potent greenhouse gas, according to a study by German and Swiss scientists published on Sunday. Quake-caused methane should be added to the list of heat-trapping carbon emissions, although the scale of this contribution remains unclear, they said.

The evidence comes from cores of sediment drilled from the bed of the northern Arabian Sea during a research trip by marine scientists in 2007.

Methane hydrates — an ice-like form of methane and water — plus signs of water between sediment grains and concentrations of a mineral called barite suggested that methane had surged up through the seabed in recent decades.

“A major earthquake had occurred close by, in 1945,” said David Fischer from the University of Bremen. “Based on several indicators, we postulated that the earthquake led to a fracturing of the sediments, releasing the gas that had been trapped below the hydrates into the ocean.”

Over a likely period of decades, around 7.4 million cu. meters of methane belched to the surface, the authors calculate. This estimate is conservative, they stress.