Study of the movement behaviour of the Pos Selim landslide from land survey data

Abstract

A study of survey data plans in different years for the Pos Selim landslide in Malaysia has been carried out to provide supplementary data on the movement of the landslide. The objectives of the study were to determine and portray on plan the displacement vectors in the parts of the landslide where no such data exist, and interpret the data to advance understanding of the movement behaviour of the landslide. Data has been obtained from previous studies and measuring new displacement vectors by observing and recording the coordinates of the different locations of prominent features in the as-built plan in 2003, orthophoto in 2005, and shaded relief models in 2005 and 2010 of the landslide. The data is presented here in the form of dip contour plots, velocity contour plots, longitudinal velocity profiles and longitudinal landslide surface profiles. Apparent displacement vectors are also measured at points outside the landslide which are notionally stationary to check for the uncertainty associated with measurements of new displacement vectors. The data has been interpreted based on the correlation of contour patterns with the observed geological features and changes in contour patterns in different periods of time. The patterns of the longitudinal profiles have also been discussed. It is concluded that the supplementary data could help to connect the north-west part of the landslide to the central part in velocity contour plots. The velocity and dip patterns could be correlated with the effect of the presence of physical constraints. Zones of rapid dip changes are found not controlled by geological faults and an apparent downhill shift of the zones from 2003-5 to 2005-10 is noticed.