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

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• Elkin De Jesús Salcedo Hurtado - Universidad del Valle, Cali, Colombia (Coordinator)
• Carlos Alberto Vargas Jiménez - Universidad Nacional de Colombia, Bogotá, Colombia
• Marily Triviño Abella - Universidad Nacional de Colombia, Bogotá, Colombia
• Luis Rodriguez - UME School, Pavia, Italy
• Julio Garcia - GEM Hazard Team, GEM Foundation, Pavia, Italy

The South American region has a wide history of large and destructive earthquakes specially along the West Coast, where the largest earthquake 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).

Two research groups investigated subduction sources within the SARA project focusing on collecting essential information 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 related to subduction earthquakes including historical and instrumental seismicity and catalogues of focal mechanisms (Salcedo-Hurtado et al.[2015a]). In addition, a critical review of segmentation models previously appearing in the scientific literature was made and the group proposed a zonation of the main subduction sources affecting South America (Salcedo-Hurtado et al.[2015b], see figures below).

The second research group focused specifically on the characterization of the South American subduction zones for PSHA. This characterization was built around the work of a PhD student (UME School) within the GEM Secretariat developing reproducible, data-driven methodologies, in order to define 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
	Characterisation of the sources and segmentation

A first model for the subduction earthquake sources based on seismological and geophysical information was created, combining large fault sources for modelling the subduction interface and 3D volumes of ruptures describing the spatial distribution of in-slab seismicity.

• International Seismological Center (ISC). 2010. Online Bulletin. ISC Thatcham, UK. Vol. 4 Issue 1-6.
  
• Rodriguez-Abreu L. E. Characterization of subduction source models for probabilistic seismic hazard analysis (PSHA). Thesis Submitted in Partial Fulfilment of the Requirements for the Degree of Doctor of Philosophy in Engineering Seismology, UME-School, Pavia, Italy, 2016.
  
• 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.

The SARA Subduction Zoning DATA-SET can be downloaded at the link provided below - Please read the license and disclaimer attached.

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