Low friction along the high slip patch of the 2011 Mw 9.0 Tohoku-Oki earthquake required from the wedge structure and extensional splay faults
Résumé
We analyze the mechanical properties needed to
account for the large shallow slip during the 2011
Tohoku-Oki earthquake and the activation of landward
normal faulting within the forearc. We show that the
morphology and internal structure of the forearc follows
closely the prediction of the critical Coulomb wedge in
horizontal compression, implying a high internal pore
pressure ratio ( = 0.7 + 0.14/ – 0.48) and a low effective
basal friction (eff
b = 0.14 + 0.18/ – 0.04). We then show
that the activation of the normal fault requires a lower
effective basal friction beneath the outer wedge than beneath
the inner wedge (outer 0.015), possibly due to transient
dynamic weakening associated to the seismic rupture.
Forearc normal faults could be considered as evidence
for very efficient dynamic weakening along the megathrust
and typify megathrust with high tsunamigenic potential.
Domaines
Tectonique
Origine : Fichiers produits par l'(les) auteur(s)
Loading...