How erosion can change seismicity

Better understanding of the triggering of earthquakes by tectonics and external processes

A better understanding of earthquake triggering through tectonics and external processes is crucial for better seismic risk assessment, particularly in densely populated areas such as Taiwan’s west coast. It is this region that a team of researchers has chosen to study to show that a single event of intense erosion can temporarily alter the seismicity of an active mountain range. The event in question: Typhoon Morakot (8 August 2009) which dumped 3 metres of rain in 3 days, causing many landslides and one of the strongest erosion episodes ever recorded. The volume of eroded rock is estimated close to 1.2 km3 and corresponds to 17 cm of erosion on a surface equivalent to that of a French department.

Through careful statistical analysis, the researchers found an increase in the number of low-magnitude and shallow earthquakes during the 2.5 years following the typhoon. The increase occurs only in the area where there is a significant mass loss due to landslides. They explain this change in seismicity by an increase in crustal stresses at low depth (15 km), linked to surface erosion.


Steer Sci. Rep. 2020 >>> For more information, see on INSU's website