Megathrust earthquakes and submarine landslides

The question whether each megathrust earthquake necessarily and instantaneously triggers submarine mass-movement has been intensively discussed in the wake of the giant earthquakes that occurred over the last decade. Whereas the 2011 Tohoku-Oki earthquake (Japan) caused failure of parts of the lowermost continental slope, no similar evidence was found after the 2010 Maule earthquake (Central Chile).

G&G Marie Curie Research Fellow Jacob Geersen has been involved in analysing the size-frequency relationship of submarine landslides on the Middle America (MA) and the Central Chile (CC) margin and estimate the approximate recurrence rates for slides of a given size. Although forearc tectonics differ substantially (subduction erosion off MA versus frontal accretion off CC) the size-frequency relationship of submarine landslides for both margins is remarkably similar. Considering a recurrence interval between 100-1000 years for megathrust earthquakes our results indicate that it takes at least 20 to 200 plate boundary earthquakes to set off a medium sized (>10 km²) or larger slide.

Read the paper here.