Depth-dependent geometry of margin-parallel strike-slip faults within oblique subduction zones

Nicole Stephanie Catalán Ormeño,Rodolfo Araya,Klaus Bataille,Andrés Tassara

doi:10.5027/andgeov44n1-a05

Nicole Stephanie Catalán Ormeño, Rodolfo Araya + Show 2 more

Open Access

https://doi.org/10.5027/andgeov44n1-a05

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Journal: Andean geology	Publication Date: Jan 31, 2017
Citations: 3	License type: cc-by

Affiliation: University of Concepción

Abstract

Based on the principle that faults develop where shear stress is maximum, we determine the depth-dependent geometry of margin-parallel strike-slip faults within oblique subduction zones. Using an elastic half-space model for the south Chile subduction zone, we show that the geometry of a margin-parallel strike-slip fault as the Liquiñe-Ofqui Fault Zone (LOFZ), is vertical near the free surface and curved downwards, until reaching the subducting slab. This geometry is compatible with the observations of reflectors on seismic data obtained from wide angle refraction studies in southern Chile. GPS measurements also support this curved geometry. We suggest that this curved pattern should occur on all margin-parallel strike-slip faults within oblique subduction zones worldwide.

Highlights

In oblique subduction zones, margin-parallel strike-slip faults accommodate part of the trenchparallel component of convergence
Using an elastic half-space model for the south Chile subduction zone, we show that the geometry of a margin-parallel strike-slip fault as the Liquiñe-Ofqui Fault Zone (LOFZ), is vertical near the free surface and curved downwards, until reaching the subducting slab
The family of planes of maximum margin-parallel shear stress obtained by modeling the oblique subduction of the Nazca plate beneath South America in southern Chile, is shown in f igure 3

Summary

Introduction

Margin-parallel strike-slip faults accommodate part of the trenchparallel component of convergence. The presence of this type of faults, together with factors such as the obliquity angle (angle between the convergence vector and the normal to the plate boundary), the age of the subducting plate, the nature of the overriding plate and ridge subduction would control the degree of convergence partition (Fitch, 1972; Jarrard, 1986; Beck, 1991; McCaffrey, 1992, 1996; Nelson et al, 1994; Tikoff and Teyssier, 1994). The Liquiñe-Ofqui Fault Zone (LOFZ) runs parallel to the Nazca-South America plate boundary between ~38°-48° S, aligned with the active Southern Volcanic Zone (Fig. 1).

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