Landslides and mega-thrust earthquakes at convergent margins - trigger-bang, or trigger-trigger-trigger ... bang? The case of the Maule earthquake, Chile
Presented by Dr. David VöLKER on 23 Sep 2013 from 17:15 to 19:15
Type: Poster presentation
Session: Poster session
Earthquakes trigger landslides, if there are accumulations of instable slope sediments and the slope is sufficiently steep. It is a simple as that. Is it? Obviously it is not.... On 27 February 2010, the Central Chilean Maule Region was ruptured by a megathrust earthquake of magnitude (Mw) 8.8. This 6th largest ever instrumentally recorded earthquake occurred after a phase of relative seismic quiescence since 1835. The hypocenter of the main shock was located ~10 km offshore. Close to the epicenter, the earthquake produced horizontal ground acceleration of up to 6ms−2 and maximum slip was between 10 and 20 m. In spite of a multitude of morphological features of past mass movement events the youngest of which are some ky old, no new slides of a size > ~ 4 km2 were detected as a consequence of the earthquake. On the other hand, a recent microslide was reported and dated to some months after the main shock. We hypothesize that frequent shaking of the active continental margin with megathrust earthquake recurrence of 100-200 years rather shifts the size spectrum of mass wasting events towards smaller events. We also established a rough size-frequency relation for mass wasting events which holds for Central Chile and Central America. This relation allows to make reasonable assumptions on the temporal frequency of events of different size scale. A major result is that it should take a time span that exceeds the seismic cycle by far to create a landslide voluminous enough to be considered tsunamogenic.
Location: GEOMAR East shore
Address: Wischhofstr. 1-3 / D-24148 Kiel