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Earthquakes and Seismic Hazard in Southern New Caledonia, Southwest Pacific

journal contribution
posted on 2024-03-24, 22:35 authored by Shao-Jinn ChinShao-Jinn Chin, Rupert SutherlandRupert Sutherland, Martha SavageMartha Savage, John TownendJohn Townend, Julien Collot, Pelletier Bernard, Olivier Monge, Finnigan Illsley-KempFinnigan Illsley-Kemp
We use 12 temporary and 9 permanent broadband seismometers that were operating for ~400 days from October 2018 to November 2019 to generate the first published earthquake catalogue and local magnitude function for southern New Caledonia. Local earthquakes were mostly shallower than 20 km. Hypocentres in the nearby subduction zone are < 30 km deep west of the trench and deepen to > 100 km eastward. Our local magnitude estimates M_L for 107 earthquakes in the ~250 km away New Hebrides-Vanuatu subduction zone are consistently 1.1 units smaller than M_w and mb over a range of M_w from 4.5 to 7.5, as determined by the USGS. Our catalogue has 460 earthquakes with M_w≥3.7 in the subduction zone and the largest event in southern New Caledonia has M_L 3.8. Seismicity rates in southern New Caledonia are low, but M_L > 5 earthquakes are 2.7 times more frequent than elsewhere in the northern Australian plate. The probability of an M_L > 5 event in 50 years is 0.6 in southern New Caledonia. Seismic shaking hazard in southern New Caledonia is dominated by local shallow moderate-magnitude earthquakes, rather than large-magnitude subduction events. The predicted peak ground acceleration (PGA) for Nouméa at 10% probability of exceedance in 50 years is 0.08 g. Residual analysis of ground accelerations demonstrates that the exceedance probability of PGA for Nouméa from subduction earthquakes is currently overestimated and that new regionally-specific ground motion prediction equations are needed. Our results highlight the inadequacy of current ground motion prediction equations in subduction zone footwall settings and the need for additional studies of this type of setting.

Funding

Analyses des donnees recoltees par le reseau sismologique du massif du sud (NSC06a) | Funder: DIMENC/SGNC

History

Preferred citation

Chin, S. -J., Sutherland, R., Savage, M., Townend, J., Collot, J., Bernard, P., Monge, O. & Illsley-Kemp, F. (2022). Earthquakes and Seismic Hazard in Southern New Caledonia, Southwest Pacific. Journal of Geophysical Research: Solid Earth, 127(12). https://doi.org/10.1029/2022JB024207

Journal title

Journal of Geophysical Research: Solid Earth

Volume

127

Issue

12

Publication date

2022-12-01

Publisher

Wiley-Blackwell

Publication status

Submitted

Contribution type

Article

Online publication date

2022-12-08

ISSN

2169-9313

eISSN

2169-9356

Article number

ARTN e2022JB024207

Language

en

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