Limited overlap between the seismic gap and coseismic slip of the great 2010 Chile earthquake

The M(w) 8.8 mega-thrust earthquake and tsunami that occurred on 27 February 2010 offshore the Maule region, Chile, was not unexpected. A clearly identified seismic gap(1-13) existed in an area where tectonic loading has been accumulating since the great 1835 earthquake1(4). Here we jointly invert tsunami and geodetic data to derive a robust model for the coseismic slip distribution and induced coseismic stress changes. We compare these with past earthquakes and the preseismic locking distribution(13), to assess if the Maule earthquake has filled the seismic gap. We find that the main slip patch is located to the north of the gap, overlapping the rupture zone of the M(w) 8.0 earthquake that occurred in 1928, with a secondary concentration of slip to the south. The seismic gap was only partially filled and a zone of high preseismic locking remains unbroken, inconsistent with the assumption that distributions of seismic rupture might be correlated with preseismic locking. Moreover, we conclude that increased stress on the unbroken patch may in turn have increased the probability of another major to great earthquake there in the near future.