Performances of the Italian Seismic Network, 1985-2002: the hidden thing

Abstract

Seismic data users and people managing a seismic network take a great interest in the potentiality of the data,

with the difference that the former look at stability, the latter at improvements. This work measures the performances

of the Italian Telemetered Seismic Network in the years 1985-2002 by defining basic significant parameters

and studying their evolution during those years. Then, we deal with the geological methods used to characterise

or to plan seismic station deployments in a few cases. Last, we define the gain of the network as the percentage

of well-located earthquakes with respect to the total recorded earthquakes. By analysing the distribution

of non-located («missed») earthquakes, we suggest possible actions to take to increase the gain. Results show

that completeness magnitude is 2.4 in the average over the analysed period, and it can be as low as 2.2 when we

consider non-located earthquakes as well. Parameters such as the minimum recording distance and the RMS of

the location decrease with time, reflecting improvements in the location quality. Methods for geologic and seismological

characterisation of a possible station site also proved effective. Finally, we represent the number of

missed earthquakes at each station, showing that nine stations control more than 50% of all missed earthquakes,

and suggesting areas in Italy where the network might easily be improved.