Istituto Nazionale di Geofisica, Roma, Italy

n the frame of the geochemical monitoring of seismicity mainly aimed at deepening the relationships between active seismotectonics and fluid geochemistry, i.e. earthquake prediction, a 222 Rn study was accomplished. It is addressed to inter-calibrate in diverse tectonic settings different methods to measure radon in groundwater: Alpha Scintillation Method using Lucas Cells (ASM-LCC) and Gamma Spectrometry Method (GSM), adopting both the Charcoal Trap Method (CTM) by Active Charcoals Canisters (ACC) and the Beaker Marinelli (BM) sampling devices. The intercalibration occurred on the field as well as in the laboratory, to finally select the best-fitting to gather radon information in each situation. Three Italian areas were selected to verify radon behavior and background concentration in different seismotectonical, geo-structural and lithological settings: ancient metamorphosed rocks – quiescent faults (Eastern Alps), carbonate foreland – active faults (Gargano) and quiescent volcanic structure overlapping a carbonate basement – swarm seismic activity (Colli Albani). The high radon concentration variability and the factors affecting radon behavior in groundwater (i.e. carrier gases presence, convection along fault systems, lithology influence, etc.) strongly constrain the measurement method to be adopted. The results point out apparently that the ASM-LCC method may be useful for expeditious and quick response of groundwater radon concentration during geochemical surveys aimed at grossly detecting the presence of tectonic structures, the deepening of circulation or the peculiar geological features linked to the presence of U-Th minerals. This method is not reliable for accurate measurements, while the GSM methods showed low standard deviation (higher precision with respect ASM-LCC) and accurate radon measurements. Finally, a customized DINCE Standard Radiactive Source (DSRS) was set up, and first used for the efficient estimation of the ING available Lucas Cells. A calibration factor for each ING Lucas Cell was defined and the most critical aspects of the ASM-LCC method revised.

A new 222Rn monitoring prototype has been designed, assembled and tested at the Istituto Nazionale di Geofisica (ING) specifically addressed to seismic surveillance tasks, exploiting environmental monitoring, etc. It operates with an a scintillation technique (photomultiplier + Lucas Cell) coupled with a water input system, that lets continuous dehumidified gas flow, stripped from groundwater under monitoring. Several laboratory tests have been carried out to check the stability and versatility of the system; moreover statistical tests have been accomplished on several data sets obtained with an 241Am radioactive standard source, to check stability of the photomultiplier. A customised water flow system has been developed to perform both the highest efficiency and lowest influence of external noise parameters. This new prototype is very cheap and will be integrated within the new multiparametric geochemical monitoring system GMS II, that is currently being developed at ING, specifically designed for geochemical surveillance of seismic events.

The digital preservation of the unique seismological heritage consisting of historical seismograms and earthquake bulletins, and of related documentation (e.g., observatory logbooks, station books, etc.), is critically important in order to avoid deterioration and loss over time [Kanamori, 1988]. Dissemination of this seismological material in digital form is of equal importance, to allow reanalysis of past earthquakes using modern techniques and the reevaluation of seismic hazard. This is of particular interest for those areas where little or no earthquake activity has occurred since the last signifi cant historical earthquake.

This article describes the ARGO Satellite Seismic Network (ARGO SSN) as a reliable system for monitoring, collection, visualisation and analysis of seismic and geophysical low-frequency data, The satellite digital telemetry system is composed of peripheral geophysical stations, a centraI communications node (master sta- tion) located in CentraI Italy, and a data collection and processing centre located at ING (Istituto Nazionale di Geofisica), Rome. The task of the peripheral stations is to digitalise and send via satellite the geophysical data collected by the various sensors to the master station. The master station receives the data and forwards them via satellite to the ING in Rome; it also performs alI the monitoring functions of satellite communications. At the data collection and processing centre of ING, the data are received and analysed in real time, the seismic events are identified and recorded, the low-frequency geophysical data are stored. In addition, the generaI sta- tus of the satellite network and of each peripheral station connected, is monitored. The procedure for analysjs of acquired seismic signals allows the automatic calculation of local magnitude and duration magnitude The communication and data exchange between the seismic networks of Greece, Spain and Italy is the fruit of a recent development in the field of technology of satellite transmission of ARGO SSN (project of European Community "Southern Europe Network for Analysis of Seismic Data" )