Assessing vulnerability of elevated cities to earthquake induced landslides based on landslide mobility

Abstract

Earthquake induced landslides in seismically active steep terrain pose a threat to human lives. Urban settlements in such terrain are exposed to widespread destruction due to these sudden slope movements. Predicting slope failures using Newmark algorithm has been a traditional way of estimating landslide distribution in the aftermath of a strong shallow focus earthquake. Mobility of the slope as represented by the equivalent coefficient of friction is a strong indicator of the destruction caused by the landslides. In this work we evaluate the vulnerability of urban settlements to earthquake induced landslides using a relation developed for mobility of rock slides caused by earthquakes. Seven landslide sites that were identified by field survey after the devastating earthquake of magnitude Mw 6.9 in the Indian state of Sikkim, were used as a case study to assess the mobility and predicted displacement. Results suggest that larger landslides have a higher mobility and are more destructive than smaller rockslides. Landslide with a friction coefficient value of 0.8403 was responsible for severely damaging and blocking the highway. A preliminary model that correlated volume and Newmark’s displacement is obtained from the data in this study however, this model needs to be validated with a larger dataset for better accuracy. We propose that the mobility of landslides can be used to assess the vulnerability of urban settlements to earthquake induced landslides in steep terrain. Software that predicts the ground motion and generate reliable strong motion data can be integrated with automated disaster warning system in smart cities.