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Research Topic 3 (RP3) - Modelling Subduction Zones in South America

Participants

The South American region has a wide history of large and destructive earthquakes specially along the West Coast, where the largest earthquake recorded ever recorded (1960 Mw9.6, Valdivia, Chile) took place. The subduction along the Pacific coast of South America dominates the geodynamics of the whole South American continent, generating the vast majority of the earthquake activity in the region and some of the most powerful earthquakes ever reported (Concepción, 1835; Valdivia, 1960; Maule, 2010).

Methodology

Two research groups investigated subduction sources within the SARA project focusing on collecting information essential for the characterization of the subduction process and its inclusion into a Probabilistic Seismic Hazard Analysis (PSHA) input model. The first research group, led by scientists from Colombia(Universidad del Valle and Universidad Nacional de Colombia), prepared an extensive dataset of seismotectonic information relating to subduction earthquakes including historical and instrumental seismicity, catalogues of focal mechanisms (Salcedo-Hurtado et al.[2015a]), a critical review of segmentation models previously appearing in the scientific literature and proposed a zonation of the main subduction sources affecting South America (Salcedo-Hurtado et al.[2015b], see figures below)

 Zonation  S.16:  a) Histogram of events, b) Horizontal Velocity of STD, c) Cross section of seismicity
 S20:  a) Histogram of events, b) Horizontal Velocity of STD, c) Cross section of seismicity

The second research group focused specifically on the characterization of the South American subduction zones for PSHA. This was built around the work of a PhD student (UME School) within the GEM Secretariat developing reproducible, data-driven methodologies, for defining the subduction zone geometry, segmentation and earthquake activity rates which can be applied in other subduction regions throughout the world (see figures and table below).

Geometry definition Interface model In-slab model
 Interface geometry definitionIn-Slab geometry definition Interface segmented model In-slab segmented model

References

International Seismological Center (ISC). 2010. Online Bulletin. ISC Thatcham, UK. Vol. 4 Issue 1-6.

Salcedo Hurtado Elkin De J., Vargas C. A. and Triviño M. Report of the focal mechanism database. Topic 3: Modelling the subduction process along the western coast and creation of a source model to be used for hazard calculations. GEM SARA Internal Report, Fundacion Universidad del Valle, 2015a.

Salcedo Hurtado Elkin De J., Vargas C. A. and Triviño M. Modeling the subduction process along the western coast and creation of a source model to be used for hazard calculations. Topic 3: Modelling the subduction process along the western coast and creation of a source model to be used for hazard calculations. GEM Technical report, Fundacion Universidad del Valle, 2015b. Progress Report, March 2015b.

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