London: Surface processes such as erosion and sedimentation may trigger shallow earthquakes and favour the rupture of large deep quakes up to the surface, a new study has found.
Although plate tectonics was generally thought to be the only persistent mechanism able to influence fault activity, it appears that surface processes also increase stresses on active faults, such as those in Taiwan, one of the world's most seismic regions, researchers said.
Recent work has shown that Earth's surface can undergo major changes in just a few days, months or years, for instance during extreme events such as typhoons or high magnitude earthquakes.
Such events cause many landslides and an increase in sedimentary transport into rivers, as was the case in 2009 when typhoon Morakot struck Taiwan, leading to abrupt erosion of landscapes, researchers said.
Such rapid changes to the shape of Earth's surface alter the balance of forces at the site of deep active faults.
In Taiwan, where erosion and deformation rates are among the highest in the world, the researchers showed that erosion rates of the order of 0.1 to 20 millimetres per year can cause an increase of the order of 0.1 to 10 bar in stresses on faults located nearby.
Such forces are probably enough to trigger shallow earthquakes (less than five kilometres deep) or to favour the rupture of deep earthquakes up to the surface, especially if they are amplified by extreme erosion events caused by typhoons and high magnitude earthquakes.
Researchers from laboratories at Geosciences Rennes, Geosciences Montpellier and Institut de Physique du Globe de Paris, in collaboration with a scientist in Taiwan, have shown that plate tectonics is not the only persistent mechanism able to influence the activity of seismic faults, and that surface processes such as erosion and sedimentation can increase stresses on active faults sufficiently to cause shallow earthquakes.
Thanks to an analysis of the relationships between surface processes and active deformation of Earth in near real-time, the study provides new perspectives for understanding the mechanisms that trigger earthquakes.
The research was published in the journal Nature Communications.