Local Terrain Relief: An Important Factor Influencing the Generation of Large Earthquake-Triggered Landslides

Abstract

Compared with ordinary scale landslides, landslides with a large scale of volume or plane area like deep-seated landslides and rock avalanches can cause more serious damages. The study of the factors controlling large earthquake-induced landslides by the 2008 Ms8.0 Wenchuan Earthquake demonstrated that this kind of large and deep slope failures could be specifically tied to some particular geologic settings after analyzing their distribution characteristics. Also, its big earthquake magnitude was an important factor. However, observations show some exceptions. For example, the 3 August 2014 Ludian, Yinnan, China Mw6.1 (Ms6.5) earthquake, though of a moderate intensity, has caused lots of landslides. Among them, there are 18 large landslides (landslide with plane area ≥50,000 m2) and the biggest one is the Honshiyan landslide, which created a 120 m high, 1.0 × 107 m3 dam. The damage caused by this earthquake surpassed some events of M = 7 or greater due to the serious landslides disaster. Base on the distribution features of coseismic landslides caused by the Ludian earthquake, this paper analyses the statistics relationship between the local terrain relief condition and large landslides occurrences in the seismic area. It is shown that the areas with high local relief are prone to generate the large landslides. To further address this issue, 2D limit equilibrium simulation is employed. The scaling relation between the landslide amount and topographic relief has been analyzed. The results demonstrate that under the other same conditions, the scale of seismically induced landslides increases with growing local terrain relief. Thus local terrain relief or the elevation difference is an important factor influencing on the amount of coseismic landslides in mountainous regions.