Understanding historical earthquakes by mapping coseismic landslides in the Loess Plateau, northwest China

Abstract

Locating the epicenters and quantifying the magnitudes of historical earthquakes are important, yet difficult, tasks. These tasks often entail estimating seismic intensities based on written documentation, which suffers from biases and uncertainties that are difficult to evaluate. However, past strong earthquakes may trigger numerous landslides that remain in the landscape to the present day, whose number and distribution are correlated with the magnitude and location of the earthquakes. Thus, mapping historical coseismic landslides may provide a useful tool for re-evaluating the magnitudes of historical earthquakes. We use remote sensing images to map landslides in the southern Loess Plateau, China. We suggested that c. 5000 preserved landslides are related to the 734 CE Tianshui earthquake. These landslides are densely distributed along a c. 70-km-long section of the West Qinling Fault. Based on the assumption that the length of the zone in which substantial landslides occurred is equal to the fault rupture length, we estimated a M w of 7.2 for the 734 CE Tianshui event, which is similar to previous estimates (M w = 6.8-7.5). We confirmed that the 1920 CE Haiyuan, 1718 CE Tongwei, and 1654 CE Lixian earthquakes did not contribute to the historical landslides observed in the study area by combination of the mapping and Chinese related literature. We estimated an M w of 7.0 for the 1654 CE Lixian earthquake, which is lower than previous estimates (M w = 8.0). We suggest that coseismic landslide of medium and large sizes with areas > 10 4 m 2 can be used as a criterion to locating and quantifying historical earthquakes, thereby reducing uncertainties in the estimated magnitudes of historical earthquakes that lack instrument records.

Insight into the Characteristics and Triggers of Loess Landslides during the 2013 Heavy Rainfall Event in the Tianshui Area, China

“…For instance, Xu et al [57] emphasized that visual interpretation based on high-resolution images can identify subtle morphological indicators of landslides, especially in complex terrains. Similarly, Xu et al [58] highlighted the superiority of interpreting ancient landslides based on visual interpretation.…”

Comprehensive Study on the 143 A.D. West Gangu Earthquake in the West Qinling Area, Northeastern Margin of Tibetan Plateau

“…It is composed of four secondary faults (Guomatan fault segment S1, Zhangxian fault segment S2, Wushan fault segment S3, and Tianshui-Baoji fault segment S4, from west to east of the WQLF in Figure 1) and has exhibited a slip rate of approximately 2-3 mm/a [17][18][19]. Along the WQLF, a series of typical left-lateral gullies and terraces, fault passes, and ridge dislocations were formed, and multiple significant earthquakes have occurred in history, such as the Longxi M 7 earthquake in 47 B.C., Gangu M 6½ earthquake in 128 A.D. (magnitude classification standard used for historical earthquakes, which uses fractions such as ¼, ½, and ¾ to designate non-integer historical earthquake magnitudes, with an error margin of 1/4), Tianshui M 7 earthquake in 734 A.D., Gangu-Wushan M 6½ earthquake in 1765, and Kangle M 6¾ earthquake in 1936 [10,[20][21][22][23], indicating that the fault has exhibited strong activity throughout the late Holocene. Li et al [24] revealed that the recurrence interval of seismic events on the Zhangxian segment of the WQLF is approximately 2000 years according to paleoseismic trenches.…”

Deformation Mechanism of the Zhoujiashan Landslide Under the Combined Effect of Rainfall and Earthquakes in Tianshui, Northwestern China

“…Tectonically, it belongs to the middle-north section of a north-south strong seismic tectonic zone, which contains many late-Quaternary active fracture zones and intense tectonic activity (Lei et al, 2006). According to records, many earthquakes have occurred in Tianshui and its surrounding areas; such events include an M8.0 earthquake, with its epicenter in Tianshui in 1654, and an M7.5 earthquake, with its epicenter in Tongwei in 1718 (Xie et al, 2017;Xu et al,2022). Earthquakes often induce landslide geological disasters and form disaster chains, resulting in a large number of casualties (Yin et al, 2009;Li et al, 2015;sun et al, 2017).…”