Morphometric parameters and outlines of 62 landslides off central Chile

The comparison of bathymetric datasets compiled before and after the Mw = 8.8 Maule Earthquake of the 27 February 2010 offshore Central Chile proves that no new submarine landslides on a size scale detectable with hull-mounted bathymetric echosounders (features of a horizontal size of > 1 km) formed as a direct consequence of the ground shaking. Gravity coring around a pre-existing slide feature offshore Concepción (BioBio Slide), however, documents that (1) a number of events occurred as retrogressive failures of the BioBio Slide wall, the youngest of which is 700?1000 years old, and that (2) a very recent small scale slide structure resulted from non-destructive imbricate stacking of a thin sediment layer. Pore water geochemical data show that this event post-dates the Maule Earthquake, suggesting that it was triggered by one of the numerous aftershocks. The absence of larger failures and the presence of a small slide let us propose that in contrast to apparent logic, frequent violent earthquakes at convergent margins do not necessarily pose a particular tsunami risk by landslides. The frequent shaking might even limit the slide volume and therefore their tsunami hazard, as instead of rare and large slides, frequent smaller slides are induced.