Crustal thickness and mantle wedge structure from receiver functions in the Chilean Maule region at 35°S

A temporary passive seismic network of 21 broad-band stations was deployed in Central Chile between 35°S to 36°S. The network recorded data prior to the magnitude Mw = 8.8 2010 Maule earthquake at a latitude of the major slip and surface deformation. The experiment was conducted to survey crustal and mantle structures and to assess the state of hydration of the mantle wedge. We present results of a teleseismic P receiver function study, supporting a continental Moho at approx. 38 km depth. Phase conversion at this boundary could be observed continuously from the intersection of the subducting slab with the continental Moho towards the Andes. The character of receiver functions indicated little evidence for infiltration of water from the subducting plate into the overlying mantle wedge, suggesting that only a small amount of water is released from the subducting plate. Aftershocks of the Maule earthquake and post-seismic slip reached depths of 50 km and hence slip spread down-dip of the continental Moho in the post-seismic phase. Co-seismic rupture, however, occurred updip of the continental Moho. Spare aftershock seismicity is observed at the intersection of the continental Moho with the subducting slab.

► The continental Moho intersects the subducting slab at approx. 38 km depth. ► Cont. Moho acts as barrier for the great Maule earthquake with co-seismic slip updip. ► Largest post-seismic slip occured downdip the continental Moho. ► Spare aftershock seismicity at the intersection of continental Moho and downgoing slab. ► Receiver function analysis supports a low grade of mantle wedge serpentinisation.