Subduction and interplate seismicity: new insights from statistical analysis of natural data and analog-numerical modeling
Abstract
Subduction zones are the site of the largest and most dangerous seismic events occurring on the Earth. The interface of converging plates is comprised of major fault zones where most of the total seismic moment is released due to the global seismicity. Despite first order similarities between convergent margins, the statistical distribution of interplate seismic activity on different subduction zones is considerably diverse: some regions are characterized by the occurrence of megathrust earthquakes while others show only minor seismic activity, with moderate-sized events. Determining the causes of this variability is challenging. While essential features characterizing the behavior of the subduction thrust faults are known, it is still difficult to merge them in a single, comprehensive picture. This is mainly related to the lack of direct observables (i.e. subduction thrust faults are not readily accessible developing in the deeper crust, in the offshore domain) and to a short (i.e. limited to the last century) instrumental seismic record. Here we present the main results of an interdisciplinary study realized in the framework of the ESF (European Science Foundation) - EURYI project 'Convergent margins and seismogenesis: defining the risk of great earthquakes by using statistical data and modeling'. This project aims to improve the current understanding of the physics of subduction zone thrust fault earthquakes, analyzing and gathering a) a wide range of geometric, kinematic and seismological data on current subduction zones and related statistical analysis and b) results of innovative laboratory and numerical models. In particular, our results allow us to identify many interesting features characterizing interplate earthquakes, for example; 1) the key role played by the velocity of subduction in defining both the geometry and the mechanical behavior of the subduction thrust fault; 2) the competing role played by size and distribution of protrusions of the plate interface (which determine frictional contact properties of the subduction thrust fault and hence affect its seismogenic behavior; 3) that events with Mw ≥8.5 preferentially occur in the vicinity of slab edges, where the upper plate is continental and the back-arc strain is neutral. Trench fill ticker than 1 km seems to have only a secondary effect; 4) the existence of different frequency-magnitude distributions across the trenches. This multidisciplinary research has a two-fold outcome. From a scientific point of view, it improves our current knowledge on the thrust fault earthquakes along subduction zones, highlighting the influencing factors. From a social point of view, our results contribute to improve the interplate earthquake forecasting capability.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.T21D..03F
- Keywords:
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- 7240 SEISMOLOGY / Subduction zones;
- 8163 TECTONOPHYSICS / Rheology and friction of fault zones;
- 8170 TECTONOPHYSICS / Subduction zone processes