Millennium recurrence interval of morphogenic earthquakes on the Qingchuan fault, northeastern segment of the Longmen Shan Thrust Belt, China

Abstract:

In this study, I present new paleoseismic and topographic evidence for the Holocene faulting activity, including the recurrence interval of morphogenic earthquakes and the slip rate along the Qingchuan fault, the northern segment of the Longmen Shan Thrust Belt, central China, and discuss its tectonic implications for the zone at the eastern margin of the Tibetan Plateau. Field investigations, trench excavations, and radiocarbon dating results reveal that: (i) the Qingchuan fault is currently active as a seismogenic fault, along which six morphogenic earthquakes occurred in the past 6000 years; (ii) the most recent event prior to the 2008 Wenchuan earthquake took place in the period between AD 600 and 1400, which probably corresponds to the late Tang-Song (AD 800–1000) (M~8) earthquake that occurred in the central and southwestern segments of the LSTB; (iii) the penultimate paleoseismic event occurred in the period around 2000 yr BP, suggesting a millennium recurrence interval of morphogenic earthquakes in the late Holocene. The present results are comparable with those inferred in the central and southwestern segments of the LSTB within which the Wenchuan–magnitude earthquakes occurred in a millennium recurrence interval, that are in contrast with previous estimates of 2000-10,000 years for the recurrence interval of morphogenic earthquakes within the LSTB, and thereby necessitating substantial modifications to exiting seismic-hazard models for the densely populated region at the Sichuan region.

References:

1) Lin, A., Rao, G., and Yan, B., 2012. Field evidence of rupture of the Qingchuan Fault during the 2008 Mw7.9 Wenchuan earthquake, northeastern segment of the Longmen Shan Thrust Belt, China. Tectonophysics, 522-523, 243-252, doi:10.1016/j.tecto.2011.12.012

2) Lin, A., Rao, G., and Yan, B., 2014. Structural analysis of the right-lateral strike-slip Qingchuan fault, northeastern segment of the Longmen Shan thrust belt, central China. Journal of Structural Geology, 68, 227-244. doi:10.1016/j.jsg.2014.09.014