Investigating multiple fault rupture at the Salar del Carmen segment of the Atacama Fault System (northern Chile): Fault scarp morphology and knickpoint analysis

Oktawian Ewiak, Pia Victor, Onno Oncken

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

This study presents a new geomorphological approach to investigate the past activity and potential seismic hazard of upper crustal faults at the Salar del Carmen segment of the Atacama Fault System in the northern Chile forearc. Our contribution is based on the analysis of a large set of topographic profiles and allows extrapolating fault analysis from a few selected locations to distances of kilometers along strike of the fault. We detected subtle changes in the fault scarp geometry which may represent the number of paleoearthquakes experienced by the structure and extracted the cumulative and last incremental displacement along strike of the investigated scarps. We also tested the potential of knickpoints in channels crossing the fault scarps as markers for repeated fault rupture and proxies for seismic displacement. The number of paleoearthquakes derived from our analysis is 2-3, well in agreement with recent paleoseismological investigations, which suggest 2-3 earthquakes (Mw = 6.5-6.7) at the studied segments. Knickpoints record the number of events for about 55% of the analyzed profile pairs. Only few knickpoints represent the full seismic displacement, while most retain only a fraction of the displacement. The along-strike displacement distributions suggest fault growth from the center toward the tips and linkage of individual ruptures. Our approach also improves the estimation of paleomagnitudes in case of multiple fault rupture by allowing to quantify the last increment of displacement separately. Paleomagnitudes calculated from total segment length and the last increment of displacement (Mw = 6.5-7.1) are in agreement with paleoseismological results.
Original languageEnglish (US)
Pages (from-to)187-212
Number of pages26
JournalTectonics
Volume34
Issue number2
DOIs
StatePublished - 2015
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2021-10-15
Acknowledgements: This research (project VI 497/2-1) has been funded by Deutsche Forschungsgemeinschaft (DFG) within scope of the DFG bundle PAK 464. Additional funding for field work has been provided by GFZ Potsdam. We wish to thank Gabriel González (Universidad Católica del Norte, Antofagasta, Chile) for support during field campaigns and interesting discussions. We also thank Olaf Zielke (King Abdullah University of Science and Technology, Thuwal, Saudi Arabia) for interesting discussions on fault scarp evolution, and Manuela Dziggel (GFZ Potsdam) for help with figure design. Additional thanks go out to Tilman Bucher and Jörg Brauchle (German Aerospace Center DLR). Finally, we thank the Editors and the reviewers Steve DeLong and Felipe Aron for their numerous constructive comments, which helped to improve the manuscript.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.

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