Landslides of the 1920 Haiyuan earthquake, northern China
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Yueren Xu I Jing Liu-Zeng I Mark B. Allen I Weiheng Zhang I Peng Du
Landslides of the 1920 Haiyuan earthquake, northern China
Abstract The great M ~ 8 1920 Haiyuan earthquake (HYEQ) was one of the largest and most deadly earthquakes in China in the last century, with ~ 234,000 deaths. The earthquake occurred within the Loess Plateau of northern China, where Quaternary loess deposits form a distinctive blanket across the landscape. Large regions of this loess cover experienced co-seismic landslides. Based on an analysis of the original disaster reports, field surveys, and satellite image interpretation, we have compiled the shaking effects of the earthquake, including the distribution of landslides, fatalities, and structural damage. Landslides triggered by the HYEQ (n > 7,000) are concentrated south of the Haiyuan fault, in a region that has both thick loess cover and long-term relief generated by the drainage network. This distribution is spatially separated from landslides triggered by other earthquakes. We find that in contrast to previous studies, the most important factor in the severe death toll of the HYEQ was the collapse of housing by ground shaking, including collapse of loess house-caves. Landslides were a secondary factor; although up to 32,000 deaths occurred in areas with intense landsliding. Based on the revised distribution pattern of landslides and damage (e.g., house collapses), we suggest that the isoseismal intensity IX line extends south of previous locations. We have also identified 126 dammed lakes created by co-seismic landslides, which form major modifications of this semi-arid landscape. The research methods in this paper, combining historical review, satellite image interpretation, and field validation of landslides, can be used as a reference for studies of other areas affected by historical earthquakes and coseismic landslides, elsewhere in the Loess Plateau and beyond. Keywords 1920 Haiyuan Earthquake . Landslide . Historical damage report . Loess Plateau Introduction Unlike earthquakes that occurred in recent times, historical earthquakes and co-seismic landslides are poorly understood. Recent earthquakes, such as the Wenchuan earthquake of Mw 7.9 on May 12 2008 in Sichuan Province, China, are rapidly studied (Xu et al. 2009), including the seismology, surface ruptures, landslides, and effects on the regional population (Yin et al. 2009; Huang and Li 2009). Information on historical earthquakes and their effects is based on records in non-scientific literature. Many of these documents did not follow scientific procedures and the contents were brief and short. This may lead to overestimation or underestimation of the real extent of the disaster (Cheng et al. 2017; Wen et al. 2008). Historical strong earthquakes need to be studied using modern technologies to assess previous understanding of earthquake rupture and ground shaking based on qualitative descriptions, because appropriate earthquake parameters have a significant impact on regional seismic hazard assessment (Liu-Zeng et al. 2
