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| Titel |
Building an 18 000-year-long paleo-earthquake record from detailed deep-sea turbidite characterisation in Poverty Bay, New Zealand |
| VerfasserIn |
H. Pouderoux, G. Lamarche, J.-N. Proust |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 12, no. 6 ; Nr. 12, no. 6 (2012-06-27), S.2077-2101 |
| Datensatznummer |
250010936
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| Publikation (Nr.) |
 copernicus.org/nhess-12-2077-2012.pdf |
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| Zusammenfassung |
| Two ~20 m-long sedimentary cores collected in two neighbouring
mid-slope basins of the Paritu Turbidite System in Poverty Bay, east of New
Zealand, show a high concentration of turbidites (5 to 6 turbidites per
meter), interlaid with hemipelagites, tephras and a few debrites. Turbidites
occur as both stacked and single, and exhibit a range of facies from muddy
to sandy turbidites. The age of each turbidite is estimated using the
statistical approach developed in the OxCal software from an exceptionally
dense set of tephrochronology and radiocarbon ages (~1 age per meter).
The age, together with the facies and the petrophysical properties of the
sediment (density, magnetic susceptibility and P-wave velocity), allows the
correlation of turbidites across the continental slope (1400–2300 m water
depth). We identify 73 synchronous turbidites, named basin events, across
the two cores between 819 ± 191 and 17 729 ± 701 yr BP. Compositional,
foraminiferal and geochemical signatures of the turbidites are used to
characterise the source area of the sediment, the origin of the turbidity
currents, and their triggering mechanism. Sixty-seven basin events are
interpreted as originated from slope failures on the upper continental slope
in water depth ranging from 150 to 1200 m. Their earthquake trigger is
inferred from the heavily gullied morphology of the source area and the
water depth at which slope failures originated. We derive an earthquake mean
return time of ~230 yr, with a 90% probability range from 10 to
570 yr. The earthquake chronology indicates cycles of progressive
decrease of earthquake return times from ~400 yr to ~150 yr at 0–7 kyr, 8.2–13.5 kyr,
14.7–18 kyr. The two 1.2 kyr-long intervals
in between (7–8.2 kyr and 13.5–14.7 kyr) correspond to basin-wide
reorganisations with anomalous turbidite deposition (finer deposits and/or
non deposition) reflecting the emplacement of two large mass transport
deposits much more voluminous than the "classical" earthquake-triggered
turbidites. Our results show that the progressive characterisation of a
turbidite record from a single sedimentary system can provide a continuous
paleo-earthquake history in regions of short historical record and
incomplete onland paleo-earthquake evidences. The systematic description of
each turbidite enables us to infer the triggering mechanism. |
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