Terrawatch: how sea level changes can trigger earthquakes | Earthquakes

Terrawatch

Study of seismic activity in southern Turkey shows even small fluctuations can have a big impact

Most earthquake faults require a huge input of energy to make them shift but occasionally a tiny shove is enough. Recent data from the Armutlu peninsula, on the southern shore of the Sea of Marmara, Turkey, show the small stress changes associated with sea level fluctuations are enough to trigger quakes up to magnitude 4.5.

Scientists monitored seismic activity and sea level change in the region for six months and found the likelihood of earthquakes on the peninsula increased significantly when the sea level was rising. The effect was amplified during the winter, when the variations in sea level were greater.

Patricia Martínez-Garzón, the lead author of the paper in Geophysical Research Letters, said: “The sea level changes in the Sea of Marmara are small – up to 0.8 metres – so the fact that these small changes result in earthquakes indicates that these faults only need a small kick to rupture.”

The Armutlu fault is a small branch of the main North Anatolian Fault and is easy to monitor because it lies on land. But the big question is whether the main branch of the North Anatolian Fault, which runs underwater just 12 miles (20km) from Istanbul, could also be triggered by sea level changes. This major fault last ruptured in 1766 and is believed to be due a magnitude-7 quake or greater.