Zusammenfassung
The magnitude-8.8 Maule (Chile) earthquake of 27 February 2010 ruptured
a segment of the Andean subduction zone megathrust that has been
suspected to be of high seismic potential. It is the largest earthquake
to rupture a mature seismic gap in a subduction zone that has been
monitored with a dense space-geodetic network before the event. This
provides an image of the pre-seismically locked state of the plate
interface of unprecedentedly high resolution, allowing for an assessment
of the spatial correlation of interseismic locking with coseismic
slip. Pre-seismic locking might be used to anticipate future ruptures
in many seismic gaps, given the fundamental assumption that locking
and slip are similar. This hypothesis, however, could not be tested
without the occurrence of the first gap-filling earthquake. Here
we show evidence that the 2010 Maule earthquake slip distribution
correlates closely with the patchwork of interseismic locking distribution
as derived by inversion of global positioning system (GPS) observations
during the previous decade. The earthquake nucleated in a region
of high locking gradient and released most of the stresses accumulated
in the area since the last major event in 1835. Two regions of high
seismic slip (asperities) appeared to be nearly fully locked before
the earthquake. Between these asperities, the rupture bridged a zone
that was creeping interseismically with consistently low coseismic
slip. The rupture stopped in areas that were highly locked before
the earthquake but where pre-stress had been significantly reduced
by overlapping twentieth-century earthquakes. Our work suggests that
coseismic slip heterogeneity at the scale of single asperities should
indicate the seismic potential of future great earthquakes, which
thus might be anticipated by geodetic observations.
Nutzer