Mid-term correlation of CO2 and seismic energy release from a volcanic system

The cogenetic relationship between seismic activity and geochemical processes is confirmed on a theoretical basis, but is still lacking of empirical verifications through the direct comparison of suitable time series showing the behaviour of natural systems. The main problems in comparing time series of different parameters are the needing of: a) processing any time series in order to filter, or to highlight, the different components; b) to select source areas and time span that can be suitable for following the evolution of a complex phenomenon through few measurable parameters. Here are shown the results of a comparison between time series of CO2 flux from soil measured at Vulcano Porto and the seismic energy release associated to local events. In particular the concept of concurrent modification of some selected geochemical and geophysical parameters describing the activity of a volcanic system has been here reviewed through the comparison between extensive parameters. On the base of the presented data, the preliminary results are: - different flows of energy transferred from the active source to the surface can be sometimes comparable; - the integration of specific interpretations from different disciplinary approaches allow to reduce some undetermined variable of any system. CO2 flux from soil is the expression of a natural phenomenon common to any volcanic area. In many systems soil gas emissions cannot be neglected for the balance of energy discharged in a continuous mode, through the advective transfer of fluids. This is one if the reasons why a discrete time series of CO2 flux measured in the Vulcano Porto area has been acquired homogeneusly since 1989. In a time span of about 4 years no relationship seems evident with the time variation of seismic energy released by "fluid driven shocks" concentrated at rather shallow depth (400-1000 m) beneath La Fossa cone, while the seismic energy release associated to a class of events, interpreted as effect of rock failure processes, showed the same increase of CO2 flux from soil. The localization of focal depth of these small earthquakes would give the reference depth for the source of excess carbon dioxide released by soil gas emissions. On the other hand the time relationship between the 2 different phenomena could allow to extrapolate the energy stored between seismic events related to the common energy source, to follow the mid-term variations of volcano-tectonic activity