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A 2300-year paleoearthquake record of the Southern Alpine Fault and Fiordland subduction zone, New Zealand, based on stacked turbidites

Philip M. Barnes, Helen C. Bostock, Helen L. Neil, Lorna J. Strachan and Matthew Gosling
A 2300-year paleoearthquake record of the Southern Alpine Fault and Fiordland subduction zone, New Zealand, based on stacked turbidites
Bulletin of the Seismological Society of America (August 2013) 103 (4): 2424-2446

Abstract

Turbidites from three sedimentary basins <10 km offshore of Fiordland, New Zealand, provide a 2300 yr submarine record of large magnitude paleoearthquakes associated primarily with the Alpine fault and the Fiordland subduction zone. Sedimentary cores comprise proximal sand-silt turbidites, which are stacked with no intervening hemipelagite. Radiocarbon dating of foraminifera constrains the sediment source ages, not direct event ages. Despite reworking, however, the dates are largely in chronological order. Upper slope source regions of the turbidity currents have been largely evacuated during triggering events and replenished by shelf-to-upper-slope sediment transport between events. Age models for the turbidites are constructed via an unconventional application of the OxCal Sequence program. The mean recurrence interval of turbidites decreases southward from approximately 190 yr in George basin, approximately 160 yr in Looking Glass basin, to approximately 150 yr (and possibly as low as 100) in Secretary basin, and the respective coefficients of variability increase from 0.30 to 0.60-0.99. These data imply that turbidites are more frequent and less periodic in the south. Consideration of potential turbidity-current triggering mechanisms, including sediment transport during extreme storm events, indicates that large magnitude earthquakes are the most likely trigger. The paleoearthquake records include turbidites emplaced during two recent interplate thrust earthquakes, as evidenced by excess Formula data, and probably the A.D. 1826 Fiordland earthquake and the well-dated A.D. 1717 Alpine fault earthquake. The recurrence intervals are shorter than recently published recurrence data from the Alpine fault on land, reflecting mixed fault-source earthquake records and potentially increased Alpine fault segmentation offshore.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 103
Serial Issue: 4
Title: A 2300-year paleoearthquake record of the Southern Alpine Fault and Fiordland subduction zone, New Zealand, based on stacked turbidites
Affiliation: National Institute of Water and Atmospheric Research, Wellington, New Zealand
Pages: 2424-2446
Published: 201308
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 100
Accession Number: 2013-069338
Categories: Quaternary geology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Supplemental information/data is available in the online version of this article
Illustration Description: illus. incl. strat. cols., 3 tables, geol. sketch maps
S45°34'60" - S45°30'00", E166°40'00" - E166°45'00"
Secondary Affiliation: University of Auckland, NZL, New Zealand
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201341
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