10Be-Based indentification of Paleoearthquake event on the Huashan Piedmont Fault

Over the past few decades, reconstructing paleoseismic sequences using in situ cosmogenic ³⁶Cl exposure ages has proven effective in numerous countries and regions, greatly enhancing our quantitative understanding of active faults (Akçar et al., 2012; Benedetti et al., 2002; Goodall et al., 2021; Mitchell et al., 2001; Mouslopoulou et al., 2014). However, in China, where normal fault bedrock exposures are typically rich in quartz, ¹⁰Be is the optimal nuclide for dating fault scarps, offering a better fit to the local geological context than ³⁶Cl. Despite this, only a handful of  ¹⁰Be studies have reconstructed earthquake slip histories for large events (M>7) using the relationship between exposure ages and height on cumulative scarps (Lunina et al., 2020; Shen et al., 2016).
This study investigates the bedrock fault scarp at Duyu, situated along the Huashan Piedmont Fault (HPF)—the source of the AD 1556 M 8½ earthquake—using ¹⁰Be concentration profiling to identify paleoearthquake events. Our analysis confirms a strong earthquake occurred prior to the 1556 event, dated to 3092 ± 383 years ago. This finding bridges a significant gap in the paleoseismic record for this interval, which was previously undetected by traditional trenching methods. The HPF exhibits a quasi-periodic recurrence pattern with an estimated interval of 2623 ± 383 years. During the late Holocene, the fault maintained a vertical slip rate of 2.0 to 2.7 mm/yr, with individual events generating coseismic vertical displacements of 6 ± 0.5 m. These results demonstrate the value of in situ¹⁰Be exposure dating as a robust method for reconstructing the seismic histories of normal faults in tectonically similar regions globally.