Geodetic and Geophysical Effects Associated with Seismic and Volcanic Hazards

Abstract

At present, one of the priorities of research should be to study all the aspects correlated with natural hazards, in particular those of geological origin, in an endeavour to reduce the vulnerability associated with them and therefore improve the quality of life, especially if our society at least purports to be a welfare society. Two of the natural hazards of geological origin that cause the greatest impact and pose the biggest risk to society are volcanic and seismic activity (e.g., [ISDR, 2002]; [EM-DAT, 2003]). Consequently, any advances in ascertaining the different physical processes linked to the several stages associated to these phenomena are highly important and clearly apply in day-to-day monitoring techniques. The final implication of any method capable of detecting and even predicting natural hazard precursory phenomena is that it could help to prevent the damage to people and property that such events might produce. Achieving this goal, which obviously has clear economic advantages, involves ascertaining every possible aspect of precursory phenomena (zone dependency, estimated size, etc.). The experimental and theoretical aspects of this task are highly complex, and must be combined if the best possible research results are to be attained. Volcanic and seismic hazards are very hard to predict, and though in recent years significant progress has been made with current monitoring systems, much remains to be done before such phenomena can be detected accurately (e.g., [RUNDLE et al. 2000]; [SIGURDSSON et al. 2000]; [STEIN et al. 2000]; [MATSU’URA et al. 2002a],[b]; [ONU; 2003]; [SPARKS, 2003]; [USGS, 2003]). Both kind of phenomena produce effects before, during, and after the activity, and even between events. On the basis of this fact and the high levels of precision attainable, many geophysical and geodetic techniques have proven to be necessary and powerful tools in the monitoring of volcanic and seismic activity. Applying such techniques to routine monitoring of active zones inevitably involves data processing and subsequent final interpretation of observed records. The advent of new techniques, such as the space-based geodetic techniques SAR Interferometry (InSAR) and continuous GPS, or the use of continuous gases measurements, has provided very powerful sources of information for gaining in-depth knowledge of these phenomena, and at a reasonable cost. However, more sophisticated and realistic mathematical models, as well as modern techniques for solving the inverse problem, are required to understand the new and more complex records.