To which level did the 2010 M 8.8 Maule earthquake fill the pre-existing seismic gap?

There is a long-standing debate whether or not the 2010 M 8.8 Maule earthquake filled a pre-existing seismic gap in which no large earthquake occurred for about 200 yr. Utilizing the inversion approach of Wang et al. that considers elastic strain accumulation and strain release during the earthquake cycle and includes the fault-coupling state as prior information in coseismic slip modelling, we investigate the inter- and coseismic slip balance for the 2010 M 8.8 Maule earthquake. The coseismic slip model is obtained as the product of three components: the interseismic backslip rate, the strain accumulation time, and the fraction of coseismically released slip potency (the product of slip and slip area) that may either fully or partially release the local strain. We construct slip models using the Slab1.0 fault geometry, and constrain the strain accumulation time for the 2010 Maule earthquake based on historical large earthquakes in the region. The results demonstrate that two slip clusters (north and south of the hypocentre) are required to model the geodetically measured coseismic displacements. The slip patch south of the hypocentre is located in a strongly coupled zone, and possibly released the local strain completely. The slip area north of the hypocentre overlaps with the interseismically creeping zone in which strain buildup may be low. The northern slip patch released higher slip potency than accumulated since the last mega-event in 1751, suggesting a possible dynamic overshoot during coseismic rupture (under the assumption that the last major earthquake has reset the regional strain). Alternatively, the last big event may not have fully released the strain in this region. Our study reveals that the Maule earthquake, combing its coseismic and post-seismic slip over 1.3 yr, released ~67-72 per cent of the local strain. Remaining strain is concentrated mainly south of the hypocentre, with potency equivalent to an M 8.4 event considering strain accumulation for 259 yr (since 1751).