COMPILING INVENTORY OF LANDSLIDES TRIGGERED BY MINXIAN-ZHANGXIAN EARTHQUAKE OF JULY 22, 2013 AND THEIR SPATIAL DISTRIBUTION ANALYSIS

On July 22, 2013,an earthquake of MS 6.6 occurred at the border area between Minxian and Zhangxian Counties, Gansu Province. The earthquake triggered many landslides of various types. The mainly types are small-scale falls, slides, and topples that occurred on loess scarps. There were also some deep-seated landslides, large-scale soil avalanches, and soil lateral spreads. In this paper, an inventory of landslides triggered by the earthquake is compiled based on partial field investigations and visual interpretation of high-resolution satellite images. Subsequently landslides spatial distribution analysis is also developed. It is indicated that the earthquake at least triggered 2330 landslides. Correlations of landslides with topographic, geological, and earthquake factors are developed on GIS platform. It is shown that the landslides were less affected by topographic factors but were more controlled by strata and lithology. Among of the 2330 landslides, 1401 landslides, occupied 60.13% of the total number with a maximum value of landslide number density of 22.78 landslides/km2,were occurred in areas of underlying bedrock of conglomerate and sandstone of Lower Permian strata of Paleogene(Eb). Correlation of PGA with landslides number density was obscure. Most of the landslides were concentrated in an elongated region, with 14km length and 5km width, parallel with seismogenic fault. A total of 1864 landslides, occupied 80% of the total landslide number, were occurred in the region. This indicates the landslides triggered by the earthquake were occurred close together. The event-based inventory of earthquake-triggered regional landslides in this article is an essential and core data for subsequent studies on earthquake-triggered landslides. Spatial distribution analysis of the landslides can provide scientific references for follow-up landslides and debris flow mitigation in earthquake struck area.