Application of remote sensing and GIS for early warning of geological hazards in Vietnam
Institute of Geological Science, NCNST, Vien Dia Chat, Nghiado, Caugiay, Hanoi, Vietnam.
Satellite imagery has significantly contributed to the progress in Earth observation and geological mapping. It gives us also a very powerful tool for the prediction and warning of geological hazards. We focus on three applications in Vietnam: seismic hazard assessment, landslide hazard and coastal zone erosion. The most important application is the estimation of seismic risk. We use TM, SPOT, RADA and airborne images to determine active faultlength, their characteristics (normal, reverse or strike-slip, sliprate) and measure horizontal displacement accumulated during Holocene. Directional filter of SPOT and TM images in combination with Digital Elevation Modelling (DEM) from topographic data and RADA imagery provides evidence of active fault segments. The parameters are used to estimate the maximum credible earthquake magnitude. The result of satellite analysis is combined with other data of geomorphology, topographic DEM, earthquake epicentres, radon distribution, stress field, etc. in the Geographical Information System. It could be combined with the intermediate methods of earthquake prediction such as M8 for the precise location of great events.
The high resolution of SPOT panchromatic and airborne images is good for the observation of large landslides. We combine it with topographic DEM to reveal large landslide circles. The modelling of GIS allows to estimate the different level of landslide hazard in the region. With the very high resolution of satellite image in the near future (2 m) and RADA interferometry a precise early warning of this phenomenon might become possible.
Comparison of multi-temporal satellite imagery with various topographic maps could calculate the rate of erosion in the coastal zone. Coastal zone erosion is a general phenomenon in Vietnam. In some areas the rate of erosion is 5–10 cm/y. The coastal erosion is associated with the rise of sea water level.