Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

236 PATA Days 2024 C O N C L U S I O N S Trench and preliminary OSL age constraints suggest at least three surface-rupturing earthquakes have occurred on the Jindabyne Thrust since ~40 ka, with the most recent event occurring within the early to mid-Holocene. A surface rupture of the Hill Top Fault occurred between 24 – 20 ka. The earthquake chronology will be further refined through additional OSL analyses to reduce and quantify the uncertainties in available dates, and through integration of these data with cosmogenic radionuclide dating. This will allow for more confident correlation between events identified in the different trenches on the Jindabyne Thrust, and also refine fault slip rates. This study has demonstrated multiple large (~MW ≥ 7) surface-rupturing earthquakes on the Jindabyne Thrust since ~ 40 ka and presents the first evidence of a Holocene-age paleoearthquake in Australia. This study has also shown that strike-slip surface-rupturing R E F E R E N C E S Allen, T. I ., Griffin, J. D., Clark, D. J., Cummins, P. R., Ghasemi, H., and Ebrahimi, R. (2023). The 2023 National Seismic Hazard Assessment for Australia; Model Overview, Geoscience Australia, Record 2023/53, eCat 148969, Canberra, Australia, 10.26186/148969. Clark, D., Leonard, M., Griffin, J., Stirling, M. W., and Volti, T. (2016). Incorporating fault sources into the Australian National Seismic Hazard Assessment (NSHA) 2018, Australian Earthquake Engineering Society 2016 Conference, Nov 25-27, Melbourne, Vic. Clark, D., McPherson, A., Pillans, B., White, D., and Macfarlane, D. (2017). Potential geologic sources of seismic hazard in Australia’s south-eastern highlands: what do we know?, Australian Earthquake Engineering Society 2017 Conference, Nov 24-26. Canberra, ACT. Clark, D. J. (2023). The 2023 National Seismic Hazard Assessment for Australia; Notes on fault- source parametrisation for the Fault Source Model, Geoscience Australia, Record 2023/54, eCat 149143, Canberra, Australia. Geoscience Australia. (2024). Neotectonic Features Database, Retrieved November, 2023, from https: //neotectonics.ga.gov.au/. Leonard, M. (2014). Self-consistent earthquake fault-scaling relations: Update and extension to stable continental strike-slip faults, Bulletin of the Seismological Society of America, Vol 104, No 6, pp 2953-2965, DOI : 10.1785/0120140087. McCalpin, J. (2009).Paleoseismology, Burlington, MA, Academic Press, pp. Rajabi, M., Tingay, M., Heidbach, O., Hillis, R. R., and Reynolds, S. D. (2017). The present-day stress field of Australia, Earth-Science Reviews, Vol 168, No February, pp 165-189, DOI : 10.1016/j . earscirev.2017.04.003. Stirling, M., Fitzgerald, M., Shaw, B., and Ross, C. (2023). New Magnitude–Area Scaling Relations for the New Zealand National Seismic Hazard Model 2022, Bulletin of the Seismological Society of America, Vol 114, No 1, pp 137- 149, DOI : 10.1785/0120230114. Thingbaijam, K. K. S., Mai, P. M., and Goda, K. (2017). New empirical earthquake source- scaling laws, Bulletin of the Seismological Society of America, Vol 107, No 5, pp 2225- 2246, DOI : 10.1785/0120170017. Yang, H., Quigley, M., and King, T. (2021). Surface slip distributions and geometric complexity of intraplate reverse-faulting earthquakes, GSA Bulletin, Vol 133, No 9- 10, pp 1909-1929, DOI : 10.1130/b35809.1. earthquakes occur in the southeast highlands in the current stress regime, presenting the first evidence of such events from the Hill Top Fault. These results provide updates to the national Neotectonic Features Database (Geoscience Australia, 2024) and valuable insights for national seismic hazard products (Allen et al., 2023) and site-specific studies required for nearby dam infrastructure. A number of other faults in the southeast highlands show similar geomorphic expression to the Jindabyne Thrust. These faults form part of a deforming system contributing to ongoing generation of relief in the southeast highlands. It may therefore be expected that these faults have broadly similar earthquake activity rates to those presented here. Analogous studies on other faults will allow the hazard posed to infrastructure in the region to be more accurately quantified.