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Segmentation of megathrust . . . (2009)
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@MISC{Melnick09segmentationof,
author = {Daniel Melnick and Bodo Bookhagen and Manfred R. Strecker and Helmut P. Echtler},
title = {Segmentation of megathrust . . . },
year = {2009}
}
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Abstract
This work explores the control of fore-arc structure on segmentation of megathrust earthquake ruptures using coastal geomorphic markers. The Arauco-Nahuelbuta region at the south-central Chile margin constitutes an anomalous fore-arc sector in terms of topography, geology, and exhumation, located within the overlap between the Concepción and Valdivia megathrust segments. This boundary, however, is only based on 500 years of historical records. We integrate deformed marine terraces dated by cosmogenic nuclides, syntectonic sediments, published fission track data, seismic reflection profiles, and microseismicity to analyze this earthquake boundary over 10 2 –10 6 years. Rapid exhumation of Nahuelbuta’s dome-like core started at 4 ± 1.2 Ma, coeval with inversion of the adjacent Arauco basin resulting in emergence of the Arauco peninsula. Here, similarities between topography, spatiotemporal trends in fission track ages, Pliocene-Pleistocene growth strata, and folded marine terraces suggest that margin-parallel shortening has dominated since Pliocene time. This shortening likely results from translation of a fore-arc sliver or microplate, decoupled from South America by an intra-arc strike-slip fault. Microplate collision against a buttress leads to
Keyphrases
marine terrace historical record megathrust earthquake rupture seismic reflection profile pliocene time likely result coastal geomorphic marker anomalous fore-arc sector south-central chile margin cosmogenic nuclides adjacent arauco basin fission track age fission track data intra-arc strike-slip fault fore-arc structure margin-parallel shortening south america arauco-nahuelbuta region microplate collision spatiotemporal trend syntectonic sediment rapid exhumation valdivia megathrust segment fore-arc sliver arauco peninsula pliocene-pleistocene growth stratum earthquake boundary nahuelbuta dome-like core
