Paleoseismology of the Mejillones Fault, northern Chile: Insights from cosmogenic 10Be and optically stimulated luminescence determinations

J. Cortes, Gabriel Gonzalez, S. A. Binnie, R. Robinson, S. P. H. T. Freeman, G. Vargas

Research output: Contribution to journalArticlepeer-review

33 Citations (Scopus)

Abstract

We have undertaken the first paleoseismological study on an upper plate fault in Chile. The selected structure was the Mejillones Fault, which is marked by a conspicuous fault-scarp. Using cosmogenic 10Be and OSL dating and detailed sedimentary logging of trenches, we have constrained the abandonment of two alluvial surfaces by fault activity at ca. 35 ka and ca. 14 ka. Based on stratigraphic observation we characterized the fault evolution in four intervals over the last ca. 35 ka. During the first three intervals the fault had a steady slip rate of 0.61 +/- 0.26 m/ka. The fourth interval is delineated by the last vertical fault slip and the accumulation of un-deformed hillslope deposits after ca. 3.3 ka and has a slip rate of 0.22 +/- 0.06 m/ka. The younger surface abandonment was caused by two Mw similar to 7 paleoearthquakes with a recurrence interval of 5.0 +/- 3.5 ka. The third interval is characterized by the interaction of hillslope deposits and aseismic slip and/or centimeter scale seismic slip events. At ca. 3.5 ka, a last large (Mw similar to 6.6) earthquake took place. The recurrence intervals of large (Mw > 8.5) subduction earthquakes do not appear to be the same as the recurrence intervals of the Mw similar to 7 events on the upper plate Mejillones Fault.

Original languageEnglish
Article numberTC2017
Number of pages21
JournalTectonics
Volume31
DOIs
Publication statusPublished - 26 Apr 2012

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