Preliminary report on the landslide early warning on August 20, 2021, in Nangqian County, Qinghai Province, China

Nangqian is located on the southeastern Tibetan Plateau and stretches over a vast area from the southern Kunlun Mountains to the northern Tanggula Mountains. The county is the southern gate of Qinghai Province and is also a major pastoral region. Within the region, the terrain has high altitudes, deep gaping valleys and continuous tall mountains. Since August 10th, 2021, an increase in rainfall has been witnessed in the Baima Elin Monastery area of ​​Jiqu Township, Nangqian County, Yushu, Qinghai Province. The geological location is 96 ° 14′51.00 ″ longitude and 32 ° 00′42.12 ″ latitude, as shown in Fig. 1. On August 19th, the rainfall per hour reached 8 mm and totaled 100 mm for the day. In addition, a geological disaster early warning was given at 4:00 AM on August 20th.

Figure 1
figure 1

Aerial satellite image of the landslide (download using BIGEMAP GIS).

The landslide reached 25 m3, causing different scales of damage to the monk’s retreat and the wall of the great hall, but the landslide did not cause direct economic losses and casualties. The panorama of the landslide is shown in Fig. 2. After the landslide, at 11:00 AM on August 20, 2021, technicians of the Qinghai Coal Geo-engineering Co. LTD visited the site and investigated the landslide. The landslide is approximately 35 m long, 85 m wide, 4 m thick, 1.2 × 104 m3 in scale and 5.2 × 104 m3 in volume. At present, the landslide’s extensional crack along its back edge tends to widen and deepen. Heavy rainfall and earthquakes may cause local landslides or collapse disasters, which poses a threat to the monastery.

Figure 2
figure 2

Panorama of the landslide.

In contrast to the previous red bed soft rock landslide and collapsible loess landslide, this landslide is in a high-altitude area. Its geomorphic and geological conditions are affected by seasonal freeze – thaw cycles and rainfall, which have typical representative and regional characteristics. The Baimaolinsi landslide is directly affected by continuous rainfall. Through the successful early warning of landslides and by comparing other similar landslides in the study area, this paper summarizes the quantitative relationship between single-day rainfall, the relationship between continuous rainfall accumulation and location, and the occurrence of landslides, thereby providing a reference case. for landslide early warnings on the Qinghai-Tibetan Plateau.

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