Fast Holocene slip and localized strain along the Liqui\xf1e-Ofqui strike-slip fault system, Chile

Luis Astudillo-Sotomayor,Andrés Tassara,Daniel Melnick,Manfred R Strecker,Joaquín Cortés-Aranda,Julius Jara-Muñoz

doi:10.1038/s41598-021-85036-5

Abstract

In active tectonic settings dominated by strike-slip kinematics, slip partitioning across subparallel faults is a common feature; therefore, assessing the degree of partitioning and strain localization is paramount for seismic hazard assessments. Here, we estimate a slip rate of 18.8 ± 2.0 mm/year over the past 9.0 ± 0.1 ka for a single strand of the Liquiñe-Ofqui Fault System, which straddles the Main Cordillera in Southern Chile. This Holocene rate accounts for ~ 82% of the trench-parallel component of oblique plate convergence and is similar to million-year estimates integrated over the entire fault system. Our results imply that strain localizes on a single fault at millennial time scale but over longer time scales strain localization is not sustained. The fast millennial slip rate in the absence of historical Mw > 6.5 earthquakes along the Liquiñe-Ofqui Fault System implies either a component of aseismic slip or Mw ~ 7 earthquakes involving multi-trace ruptures and > 150-year repeat times. Our results have implications for the understanding of strike-slip fault system dynamics within volcanic arcs and seismic hazard assessments.

Highlights

In active tectonic settings dominated by strike-slip kinematics, slip partitioning across subparallel faults is a common feature; assessing the degree of partitioning and strain localization is paramount for seismic hazard assessments
The Surface Classification Model (SCM) is based on a combination of slope and terrain roughness that allows masking flat and smooth areas from the DTM29
Details on the acquisition and processing of terrestrial laser scanner data as well as Digital Terrain Model (DTM) and SCM generation may be found in the Methods section and Supplementary Materials

Summary

Introduction

In active tectonic settings dominated by strike-slip kinematics, slip partitioning across subparallel faults is a common feature; assessing the degree of partitioning and strain localization is paramount for seismic hazard assessments. We associate these structures affecting bedrock and fluvial conglomerates with a NNE-striking dextral fault parallel to the deflected river channel (Fig. 3).

Results

Conclusion