A Penultimate Great Earthquake Revealed by In Situ Cosmogenic ¹⁰ Be Dating of the Bedrock Fault Surface on the Huashan Piedmont Fault (Central China)

Paleoearthquake studies on faults can help reconstruct the recurrence patterns of great earthquakes, furnishing critical scientific grounds for seismic hazard assessment and formulation of earthquake prevention and disaster mitigation strategies. The Huashan Piedmont Fault (HPF) is a prominent seismogenic normal fault located on the southern margin of the Weihe Basin, which has been active since the Late Quaternary. A strong earthquake, commonly quoted with a magnitude of 8.0–8.5, occurred on this fault in 1556 CE, which resulted in over 830,000 deaths and ranks as one of the deadliest earthquakes worldwide ever recorded. Despite extensive research, evidence for paleoearthquake on this fault remains limited owing to thick vegetation cover and human activities. Here, we assess paleoearthquake events on the fault using cosmic‐ray‐produced 10 Be from the Duyu bedrock fault surface, to determine paleoearthquake events on the fault. Our measurements reveal a pre‐1556 earthquake event, with an age of 3,092 ± 383 years and coseismic vertical displacement of 6 ± 0.5 m. This suggests a strong earthquake recurrence interval of 2,623 ± 383 years and Late Holocene vertical slip rates of 2.0–2.7 mm/yr for the HPF. In situ cosmogenic nuclide 10 Be exposure dating provides a novel approach for reconstructing the seismic history on normal faults, offering critical insights for seismic risk assessment in the densely populated Weihe Basin and regions worldwide with similar tectonic settings. These findings highlight the utility of this dating method in revealing seismic history on normal faults associated with great earthquakes.