Abstract
According to historical earthquake records, the Luhuo segment of the Xianshuihe fault has produced two large earthquakes: the 1816 M7.5 earthquake and the 1973 M7.6 earthquake. The surface ruptures caused by these events remain well preserved. This study focused on the rupture behavior of the Luhuo segment. Based on field investigations, trench excavations and analysis of historical earthquakes, we identified six seismic events that occurred within the past 3000 years, which are dated at 769 BC, 318–545AD, 677–833AD, 1008–1444 AD, 1816 AD and 1973 AD. The recurrence intervals of these events, from oldest to youngest, are approximately 1200, 324, 471, 590 and 157 years. Thus, the recurrence behavior of the fault segment appears inconsistent with time- or slip-predictable models, whereas, the revealed seismic sequence appears consistent with clustering and abnormal accelerating stress release behavior. The fault strike-slip rate during the period of anomalous stress release is approximately 2-3 times faster than the average rate of 8.4 mm/a. Moreover, the Luhuo segment has experienced ongoing high levels of seismic activity over the past 3000 years, and the entire Xianshuihe fault currently shows a high degree of seismic activity. Therefore, we suggest there was a long period of earthquake quiescence prior to 3000 years ago, which might have balanced the high activity and accelerating stress release of current earthquakes.
Highlights
Knowledge of the rupture behavior of large seismic events is critical to understanding the spatiotemporal variations of strain loading and release on active faults
We cannot rule out the possibility of paleoearthquake omissions during such a long recurrence interval, we suggest that there was a long lull in earthquake activity during this period, which might balance the high level of activity and abnormal accelerating stress release of current earthquakes
We only obtain the recurrence behavior of the Luhuo segment in past 3000 years and suggest there was a long lull in earthquake activity prior to this period, which might balance the high level of activity and abnormal accelerating stress release of current earthquakes
Summary
Knowledge of the rupture behavior of large seismic events is critical to understanding the spatiotemporal variations of strain loading and release on active faults. Y3: This unit is a sedimentary deposit environment of sag pond in the middle of the trench, which is composed of gray-black loam and fine sand. The upper section (U1b) of the unit is mainly composed of fine sand, containing some brown sand belts rich in organic material This unit, on the western wall of the fault zone in TC3, consists of alternating layers of fine sand and coarse sand with different colors. On the eastern wall of TC3, subunit U1b, which can be regarded as a marker for this event and contains some thin sand layers rich in organic material, was obviously displaced and deformed and it is unconformably overlain by sedimentary unit U2 (Figure 12). The radiocarbon calibrated dating and stratigraphic constraints for the events are 318–545 AD, 677–833 AD, 907–1622 AD and 1973 AD
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
