Where giant earthquakes may come

W. Marzocchi (1) , L. Sandri (2) , Arnauld Heuret (3) , F. Funiciello (4)

1 INGV - Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Roma
2 INGV - Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Bologna
3 Géosciences Montpellier
4 ROMA TRE - Università degli Studi Roma Tre = Roma Tre University

Giant earthquakes (Mw≥8.5) usually occur on the boundary between subducting and overriding plates of converging margins, but it is not yet clear which (if any) subduction zones are more prone to produce such a kind of events. Here we show that subduction zones may have different capabilities to produce giant earthquakes. We analyze the frequency-magnitude distribution of the interplate earthquakes at subduction zones that occurred during 1976–2007 and calculate the propensity (defined as the average annual rate) of giant events for about half of the subduction zones. We find that the b value of interplate earthquakes is significantly different among the subduction zones, and out-of-sample giant earthquakes (before 1976 and after 2007) have occurred preferentially in high-propensity areas. Besides the importance for seismic hazard assessment and risk mitigation, our results seem to indicate that a higher seismicity rate does not necessarily imply a higher likelihood to generate giant earthquakes, and the way in which the stress is released at a subduction interface does not change significantly after the occurrence of such events.

Domaines: Tectonique

W. Marzocchi, L. Sandri, Arnauld Heuret, F. Funiciello. Where giant earthquakes may come. Journal of Geophysical Research, 2016, 121 (10), pp.7322-7336. ⟨10.1002/2016JB013054⟩. ⟨hal-01467738⟩