A Virtual Simulator As A Tool For Testing The Performance Of The ISNet Early Warning Infrastructure.

The ISNet (Irpinia Seismic Network) consists of 29 six-components seismic stations deployed in a 100×70 km2 area in Southern Italy, containing the fault system that generated the 1980, M=6.9, Irpinia earthquake. The seismic stations, equipped with both accelerometers and seismometers, are able to follow both the strong and the weak motion. The computation is distributed along the network, with local control centers collecting data-streams from the single stations and performing a redundant computation of the early warning parameters (picking, location, magnitude and hazard integral). The decision is finally sent to the network control center, which is located far-away from the network itself. The performance of the infrastructure therefore depends on the latency of the information in the acquisition and in the transmission, on the computation time and on the failures of the system. We build up a virtual simulator to analyze off-line both the lead-time of the whole infrastructure and the influence of the failures of the system on the final decision. We use the simulator as a platform to test and optimize the algorithms for the computation of the early warning parameters, to investigate the optimum topology for the existing network, to asses weaknesses of the present infrastructure and define interventions plans to make the alarm decision robust. The simulator is a flow chart, in which the single blocks (acquisition, transmission, computation and decision) are either mathematical operators based on empirically estimated physical quantities or code lines running on the same platform. We evaluate the performances of the network on a synthetic database of records simulating the 1980, Irpinia earthquake and a set of real data from an earthquake of magnitude 3.0.