A geophysical multi-parametric analysis of hydrothermal activity at Dallol, Ethiopia

During December 2003, three seismic stations were installed close to the hornitos of the hydrothermal system at Dallol, complemented by radiometer and infrasonic measurements. A combined geophysical data set was collected for about three days. During this period thermal, seismic and acoustic records indicate the presence of two regimes characterized by a different energy distribution in frequency. Few volcano-tectonic events appear superimposed to the continuous hydrothermal tremor. The continuous data indicate variable shallow processes most likely related with variations in temperature and degassing processes within the shallow geothermal system. This alternation of low and high regimes shows significant similarities with other volcanic systems of different nature, although at Dallol the transition is more evident in the thermal than in the seismic and acoustic data.