Paleoseismic study on active normal faults in the southeastern Weihe Graben, central China

• Four faulting events are identified in the past 4000 years in the SE Weihe Graben.
• The most recent fault event is correlated to the 1556 M ∼ 8.5 Huaxian earthquake.
• Average vertical slip rate is estimated to be 1.7–2.1 mm/yr in the late Holocene.
• Active faults have the potential trigger large earthquakes of M > 7 in the future.

Field investigations and trench excavations can provide direct and indirect geological evidence for the occurrence of paleo-earthquakes. In this study, we present geological and topographical evidence for the occurrence of great paleo-earthquakes produced by active normal faults in the southeastern Weihe Graben, central China. Field and trench observations, in combination with radiocarbon ages, reveal that: (i) four surface-faulting events occurred in the past 4000 years with an average recurrence interval of ∼1000 years, which is in contrast with the previously estimated interval of ∼2000–2900 years; (ii) the most recent fault event is correlated to the 1556 M ∼ 8.5 Huaxian earthquake; (iii) an alluvial terrace riser that formed at ∼5300 yr B.P. has been vertically offset by 9–11 m, indicating an average vertical slip rate of 1.7–2.1 mm/yr in the late Holocene. Our results confirm that normal faults in the southeastern Weihe Graben have been active in the late Holocene as source seismogenic faults, and that these faults have the potential to trigger large earthquakes of M > 7 in the future. Therefore, it is important to urgently reevaluate the seismic potential and seismic hazard in the densely populated Weihe Graben region.