Magnitude and seismogenic fault determination of ground effects paleosismic-induced at Huoshan and Guzhen in Anhui province, China

In paleoseismic research, defining the age of an event is relatively straightforward, but pinpointing its magnitude with precision is challenging. This difficulty primarily arises because physical parameters, such as rupture area and displacement, which are intimately linked to the seismic moment, are hard to derive from paleoseismic studies. Our preceding study identified two earthquake sites in Huoshan and Guzhen, Anhui Province. While we qualitatively described the timing of these occurrences and the characteristics of sand veins, dislocations, and earthquake-induced cracks, we did not provide quantitative estimates of their magnitude or seismogenic faults. Consequently, these findings were insufficient for assessing regional seismic risks or determining the potential magnitude of specific faults. This study employs two empirical relationships: one between the farthest distribution distance based on liquefaction from earthquake-induced events and magnitude, and the other concerning the intensity-epicenter distance-magnitude relationship. Through these relationships, we analyze the sandy soil liquefaction and earthquake-induced cracks quantitatively. The analysis includes magnitude estimation and seismogenic fault evaluation for the sandy soil liquefaction and crack remnants of the Huoshan Daijiayuan earthquake, as well as the dislocation and crack remnants of the Guzhen Gaixia earthquake. The findings indicate that the Huoshan Daijiayuan site records two paleoseismic events. The first event transpired after 850 BC, and the second after 550 BC, with a gap of approximately 300 years between them; both had a seismic magnitude (M_S) of around 6.0. The likely seismogenic fault for the Huoshan Daijiayuan earthquake is the Luoerling-Tudiling fault. Meanwhile, the paleoseismic site in Guzhen Gaixia documents two seismic events occurring during 2350-2050 BC, both with a seismic magnitude (M_S) of approximately 6½. The Tancheng-Lujiang fault zone is likely the seismogenic fault associated with the Guzhen Gaixia earthquake site.