EARTHQUAKE INDUCED LANDSLIDE HAZARD ZONATION

Abstract

Landslide is very catastrophic natural hazard in the Himalayan region. There are highly destructive effects on environment, wealth, life, and landscape due to landslide. These effects make it necessary to study the landslide and development of landslide hazard zonation map. Sikkim is considered for this study. This area is very prone to landslide due to steep slope and geological conditions. Landslide hazard zonation has conducted for Sikkim region in this study. Further as Sikkim is situated in the lesser Himalaya, seismically induced landslide are also common in this region. Hence earthquake induced landslide hazard zonation is conducted for the study region Sikkim. The landslide hazard zonation is carried out using different causative factors. Probabilistic seismic hazard has been carried out to evaluate variation of seismicity in this region. Peak ground acceleration (PGA) is considered as an indicator of severity of earthquake shaking for landslide. For probabilistic seismic hazard analysis Earthquake catalogue for the region is obtained from USGS. These catalogues were homogenized and de-clustered to compile an appropriate seismicity database. The compiled catalogue includes earthquake of magnitude Mw>=3.5 for period between 1934 and 2015. For getting earthquake parameters like Mc , a, b value and λm by ZMAP software which is based on MATLAB software is used. For probabilistic seismic hazard analysis CRISIS software is used. For this analysis different earthquake sources like faults, thrusts, lineaments etc. are considered. By processing these data in CRISIS 2012 PGA values for Sikkim region are obtained. These PGA values are used in earthquake induced landslide hazard zonation. ARCGIS 10.2.2 has been used for preparation of landslide hazard zonation map of the study region. Different maps like lithology, slope etc. are obtained from geological survey of India (GSI) and ISRO website www.bhuvan.nrsc.gov.in. These maps are processed to generate hazard map in ARCGIS. The final map of the landslide hazard represents the different categories of hazard namely very low hazard (VLH), low hazard (LH), moderate hazard (MH), high hazard (HH) and very high hazard (VHH) which represent the relative degree of susceptibility to landslide occurrence. This landslide hazard zonation map is very useful for future planning of construction, landslide hazard mitigation etc.