Application of remote sensing for major land geohazards

• Main Author: Lim, Benjamin Jie Min
• Other Authors: Leong Eng Choon
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Engineering::Civil engineering
• Online Access: https://hdl.handle.net/10356/143156
• Institution: Nanyang Technological University

In this thesis, the two largest forms of land geohazards were examined, namely, landslides and earthquakes. As they encompass large areas and can cause tremendous damage, remote-sensing methods are therefore of great value. For this research work, the overarching objective is to rely on readily available open-source satellite data alongside new and practical methods to characterize these land geohazards. The objectives are three-fold – 1) to establish a method to estimate landslide volume from two-dimensional imagery, 2) to assess the usefulness of landslide susceptibilities derived from low resolution open-source satellite images, and 3) to deploy an earthquake prediction system using ionospheric precursors. Firstly, a geometry model was proposed to quantify landslide depth using a varying cut-off plane, with the landslide failure surface being represented as an ellipsoid. This allows for the estimation of landslide volume with spatial information derived from satellite imagery. As compared to other techniques, the proposed approach is not only accurate and convenient to use, but it is also able to explain the theoretical basis behind the commonly observed landslide area-to-volume power law. Secondly, landslide triggering factors were examined on the basis of a short-term database due to the 25 April 2015 Nepal Mw 7.8 earthquake. While only larger landslides could be identified using low resolution open-source satellite images, it was found that the resulting landslide susceptibility map could adequately capture landslides detected using high resolution images. These results indicate that open-source satellite images are useful for timely landslide risk assessments and does not justify the need for costly but high resolution satellite images. Thirdly, a new method is proposed to confidently detect pre-earthquake total electron content (TEC) anomalies (PETA). This approach not only overcomes existing difficulties when identifying the effects of solar and geomagnetic activity on TEC, but can also be utilized in an earthquake prediction system. On top of findings related to the non-systematic spatial variations of TEC anomalies, a regional earthquake prediction system was explored and shows promise in approximating the epicentre within a 14 day period before an earthquake.