Paleoearthquake History Along the Southern Segment of the Daliangshan Fault Zone in the Southeastern Tibetan Plateau

Abstract

Assessing the seismic hazard of a fault is usually based on its record of strong earthquakes. Earthquake records with long periods of quiescence for active faults can lead to underestimates of seismic hazards, such as for the Longmenshan fault zone which produced the unanticipated 2008 Mw 7.9 Wenchuan earthquake. The Daliangshan fault zone has a low slip rate and has not produced any strong earthquakes in history. As a result, little is known about its paleoearthquake history, including the behavior of any strong earthquakes it might produce and the seismic hazards posed by the Daliangshan fault zone. To solve this problem, we excavated four trenches across the Jiaojihe and Butuo faults along the southern segment of the Daliangshan fault zone. The paleoseismic investigations revealed six paleoearthquakes on the Jiaojihe fault in ~20,000 years and determined another seven rupturing events on the Butuo fault in ~42,000 years. The strong earthquake history of the Jiaojihe fault has evidence of temporal clustering, while the Butuo fault exhibits a relatively periodic recurrence pattern with intervals of 1,710–2,460 years. Based on its surface rupture length and the magnitude of observed displacement, the southern segment of the Daliangshan fault zone is capable of producing M > 6.5 earthquakes. Furthermore, based on their respective slip rates and the elapsed times since the most recent events along the Jiaojihe and Butuo faults, they have accumulated seismic energy equivalent to M ~ 7.6, suggesting they pose a significant seismic hazard to the southeastern Tibetan Plateau.

Multi-fault rupture behavior of the 1786 M 73/4 Kangding earthquake on the eastern margin of the Tibetan Plateau

“…Since the late Pleistocene, the Gongyihai fault has been a weakly active fault according to the most recent geological and geomorphological surveys. High-precision geomorphological observations and satellite interpretation indicate that the late Quaternary left-strike rate of the Shimian fault is 1.5-3.3 mm/a, which is consistent with the fault's relatively intense late Quaternary activity (Sun et al, 2015). Although the DLSF lacks historical earthquake records, palaeoearthquake research has shown evidence of intense seismic activity, indicating that earthquakes of M 7 or above have occurred and will occur in the future (Gao et al, 2016;Sun et al, 2019;Feng et al, 2021).…”

Heterogeneous Interseismic Coupling Along the Xianshuihe‐Xiaojiang Fault System, Eastern Tibet

“…We do not include the sub‐block for two reasons. First, compared with the Anninghe and Zemuhe faults, the Daliangshan fault is significantly less seismically active (e.g., Sun et al., 2019). Second, if the Daliangshan fault is included in block model, despite the RMS value of GPS velocity residuals decreases from 1.60 mm/a to 1.52 mm/a, this decrease is found to be statistically not significant given the increased number of free parameters.…”

Combining InSAR Technology to Uncover the Deformation Factors and Mechanisms of Landslides in the Baihetan Hydropower Station Reservoir Area

“…This will aid in exposing the concealed risk factors embedded within the deformation processes. Observations from GPS data, as well as plate tectonic models, denote that the southeastern periphery of the Tibetan Plateau, which encapsulates the research area, is a hotbed of tectonic activity [45,48]. This incessant orogenic activity is underscored by a complex deformation regime featuring both vertical and horizontal strain partitioning.…”

“…These fault segments are relatively independent and have not yet fully connected. The DF fault has remained active during the Holocene epoch, with it being associated with surface-rupturing earthquakes [48,49]. The left-lateral slip rate at the southern end of the Daliangshan Fault near the dam area of Baihetan is 4.3 ± 0.1 mm/yr, and the horizontal shortening rate is 4.2 ± 0.7 mm/yr [45].…”