Control of asperities size and spacing on seismic behavior of subduction megathrusts

Fabio Corbi (1) , Francesca Funiciello (2) , Silvia Brizzi (2) , Serge Lallemand (1) , Matthias Rosenau (3)

1 Géosciences Montpellier
2 ROMA TRE - Università degli Studi Roma Tre = Roma Tre University
3 GFZ - German Research Centre for Geosciences - Helmholtz-Centre Potsdam

The majority of the largest subduction megathrust earthquakes share the common characteristic of rupturing more than one asperity along strike of the margin. Understanding the factors that control coseismic failure of multiple asperities, and thus maximum magnitude, is central for seismic hazard assessment. To investigate the role of asperities size and spacing on maximum magnitude, seismicity rate, and percentage of synchronized ruptures, we use analog models simulating along-strike rupture behavior of megathrust earthquakes. We found negative correlations between the barrier-to-asperity length ratio Db/Da and maximum magnitude and seismicity rate. Db/Da also controls the process of asperities synchronization along the megathrust. A permanent barrier behavior is observed for Db/Da > 0.5. Comparing our experimental results to the Nankai Trough historical seismicity, we propose that the distribution of megathrust frictional heterogeneities likely explains the diversity of earthquakes which occurred there.

Mots clés: Asperities; megathrust earthquakes; analog modelling

Domaines: Tectonique; Milieux et Changements globaux

Fabio Corbi, Francesca Funiciello, Silvia Brizzi, Serge Lallemand, Matthias Rosenau. Control of asperities size and spacing on seismic behavior of subduction megathrusts. Geophysical Research Letters, 2017, 44 (16), pp.8227-8235. ⟨10.1002/2017GL074182⟩. ⟨hal-01685546⟩