Ground-Deformation Methods and Results

Abstract

A comprehensive volcano-monitoring program should include techniques to measure surface deformations in order to contribute to a complete characterization of volcanic behavior. Conventional modern geodetic techniques provide useful tools for the capture of discrete or continuous ground-deformation data. Baseline data volcano deformation observed during repose periods are fundamental for distinguishing “abnormal” volcanic behavior, or an increase of activity. Magma movements or hydrothermal pressurization effects generally occur within the volcano some time before an eruption takes place. Once an eruption begins, the volcano-monitoring program should include direct observations of the volcanic activity, in addition to the ongoing volcano-monitoring techniques. The interpretation of ground-deformation data should focus on the movement — in time and space — of magma and (or) hydrothermal pressurization sources within he volcanic system. Modeling of the ground-deformation data can provide important information on the subsurface configuration (size, pressure, shape, and depth) of the volcano’s magma reservoir and its associated hydrothermal system. Very few successful predictions of volcanic activity are known, primarily because of the lack of adequate monitoring at most of the world’s active volcanoes but also because some of the more precise, advanced techniques of monitoring them are relatively recent. Hawaii and Japan were the first places to use ground-deformation studies in monitoring active volcanoes early in this century. The techniques have improved greatly since then, but much more must be done to monitor dangerous volcanoes all over the world.