Remote sensing’s contribution to earthquake risk assessment and mitigation

Abstract

The dramatic increase of human population in areas exposed to seismic hazard (especially in developing countries) is leading to a large increase in earthquake risk. Remote sensing products can certainly contribute to following the rapid expansion of urban environments and the dynamics of risk evolution in areas of interest. In particular, remote sensing can contribute to the different portions of the risk assessment chain, including hazard and site effects evaluation. The contribution of remote sensing to mapping physical vulnerability and exposure is therefore very promising when coupled with advanced statistical approaches, as well as the possibility of rapid damage estimation in the immediate postdisaster stage, and the monitoring of the longer term recovery phase. However, while the positive results are very often shared with the rest of the interdisciplinary community involved in this field with a great deal of enthusiasm, I personally very often miss a deeper discussion on the drawbacks of the adopted procedure, including costs, the feasibility of analysing large areas over short time periods, the lack of data (or risk of missing data in the case of emergency) due to bad weather conditions, etc. This leads to the possibility of using these methods at a reasonable cost in nearly real time. InSar data have been exploited for some time in providing information about earthquake source processes, as well as being combined with seismological observations in joint inversions to better constrain source parameters. However, most of the used models are still too simple and, in my experience, I often miss a deeper analysis of the robustness and reliability of the solutions. As an engineering seismologist, I take a great interest in those results that show fairly good correlation between areas affected by subsidence and the surface geology. However, such results should not be used, as has been attempted, for a correlation with damages, forgetting the simple fact that it is not the site effects that determine damages, but the actual ground motion, which is the result of the seismic source process, wave propagation and, finally, site effects and the physical vulnerability of the built environment. Nevertheless, the reasonable correlation observed between subsidence and surface geology might be used for optimizing site effect studies by identifying areas that require a more thorough investigation since such areas are likely to be underlain by