From New Scientist
CAN you put a freeze on earthquakes? It seems so, according to a computer model showing that earthquakes happen less often in areas covered by ice caps. Trouble is, quakes come back with a vengeance when the ice melts.
Andrea Hampel at Ruhr University in Bochum, Germany, and colleagues wondered why Scandinavia experienced a surge in tectonic activity around 9000 years ago, whereas few earthquakes occur there today. They realised that the earthquake flurry coincided with the melting of the Fennoscandian ice sheet, which blanketed the area in the last ice age.
To discover why, they devised a model to test how geological faults respond when buried beneath several hundred metres of ice. They found that the vertical stress placed on the Earth’s crust by a heavy ice sheet can suppress many types of fault from slipping and causing a quake.
Though the faults are pinned down for a time, stresses in the crust continue to build, so when the ice melts, earthquakes occur more strongly and more frequently (Earth and Planetary Science Letters, DOI: 10.1016/j.epsl.2008.02.017). This has already been been observed in Alaska, says Hampel. She warns that Greenland and Antarctica could experience more earthquakes as their ice sheets disappear.