AGU Fall Meeting, San Francisco, USA, 14-18 December, 2009
C. Satriano, L. Elia, C. Martino, M. Lancieri, A. Zollo, G. Iannaccone
In the framework of earthquake early warning (EEW) experimentation in Southern Italy, we have developed an integrated software platform called PRESTo (PRobabilistic and Evolutionary early warning SysTem). PRESTo is a methodology for regional EEW applications, based on a fully probabilistic and evolutionary approach. This means that probability density functions of source parameters and ground shaking levels are computed , which make possible to evaluate the uncertainties, and to set an appropriate level of reliability of the issued warning. Moreover, the estimates of earthquake location, size and expected ground motion are continuously updated, as new data is available in real-time from the network. The earthquake location algorithm is based on an equal differential time formulation, and a probabilistic framework for describing the hypocenter solution. The algorithm, at each time step, relies on both the information from triggered arrivals and not-yet-triggered stations.
The magnitude estimation is based on a Bayesian approach, and exploits an empirical relationship that correlates the final event magnitude with the logarithm of the distance-corrected, peak ground displacement, measured over the first 2÷4 seconds of P- and S-signals. Finally, a ground motion prediction equation valid at regional scale is used to predict the peak velocities and accelerations at the target sites. The core infrastructure of the EEW system in Southern Italy is the high density, wide dynamic-range seismic network ISNet (Irpinia Seismic Network), deployed along the Apennine chain, which is frequently stricken by moderate to large magnitude damaging earthquakes. For earthquakes originating inside the ISNet seismic network, a first alarm can be issued within 4-6 seconds from the origin time, and a stable estimate with relatively small error on location (less than 5 km) and magnitude (about 0.5 magnitude units) is achieved within 10 seconds after the origin time. PRESTo can easily be configured, tailored and exported to other digital seismic networks worldwide. A simple integration with the network is granted by the widely available SeedLink communication protocol used for data acquisition. In this note we illustrate and discuss the method flexibility and exportability to different acquisition layouts through off-line simulations, using real data recorded by the Japanese K-Net and KiK-Net, and RAN, the Italian strong motion network operated by the Department of Civil Protection.