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Effect of Marine Reservoir Variations on the Temporal Correlation of Earthquake Evidence on the Central and Southern Hikurangi Subduction Zone

Description: 

A key question in New Zealand subduction zone hazard studies is if, or how often, the Hikurangi subduction zone ruptures both the central and southern parts of the subduction zone vs just southern section ruptures. To address this we rely on the temporal correlation of different types of earthquake and tsunami evidence from widely spaced sites. At several key sites the radiocarbon chronologies are constrained by terrestrial radiocarbon dates but at most, particularly marine terrace and paleotsunami sites, the chronology is dominated by marine radiocarbon ages. Calibration of the marine radiocarbon ages combines the marine calibration curve and a local marine reservoir offset (ΔR). Changes between versions of the global marine calibration curve (Marine20 vs Marine13 curves) have minimal impacts on modeled earthquake ages. However, over the past 3 years we have undertaken a study of marine reservoir variation around New Zealand and find regional differences in ΔR of up to 100 years. Focussing on the Hikurangi subduction zone, where marine reservoir measurements have increased from 14 to 45, we found an average ΔR for the whole margin is appropriate, rather than subdividing the margin as we have previously done. However, marine radiocarbon ages should not be acquired from two subduction paleoearthquake sites with limestone catchments or from molluscs from some particular environments. Overall it would be ideal to eliminate marine radiocarbon ages from the paleoearthquake chronologies as the uncertainties on individual ages are large but few alternative geochronology tools exist at many study sites. As we incorporate offshore turbidite ages from the central Hikurangi subduction zone into the margin-wide compilations of paleoseismology, understanding the offshore marine reservoir becomes increasingly important. The new marine reservoir values call for a re-evaluation of paleoearthquake temporal correlations, and examination of evidence for central and southern Hikurangi subduction zone ruptures.

Session: From Faults to Fjords: Earthquake Evidence in Terrestrial and Subaqueous Environments - I

Type: Oral

Date: 5/1/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Kate

Student Presenter: No

Invited Presentation: 

Authors