Short Note The Potential for Earthquake Early Warning in Italy Using ElarmS

The new Italian National Seismic Network (INSN) is a dense network of broadband stations deployed for monitoring Italian seismicity. The network consists of 250 stations with a typical station spacing of ∼40 km. Earthquake early warning is the rapid detection of an event in progress, assessment of the hazard it poses, and transmission of a warning ahead of any significant ground motion. We explore the potential for using the INSN real-time network for the purpose of earthquake early warning. We run the ElarmS early warning methodology off-line using a data set of more than 200 events with magnitudes between 2.5 and 6.0. A scaling relation for magnitude determination from the dominant period of the first seconds of signal following the P onset is developed from the data set. The standard deviation in the magnitude estimates using this approach is 0.4 magnitude units, and all event mag- nitude estimates are within 0:75 magnitude units of the true magnitude. Given the existing distribution of seismic stations it takes an average of 10 sec after event in- itiation before the P wave has been detected at four stations. If we require a detection at four stations before issuing the first alert, then the blind zone, within which no warning would be available, has a radius of ∼37 km. The ElarmS methodology can provide a warning earlier than this but with a greater uncertainty. An assessment of past damaging earthquakes across Italy shows that applying ElarmS with the ex- isting seismic network could provide warning to population centers in repeats of past events. For example, in a repeat of the 1980 Irpinia earthquake Naples could receive an ∼15-sec warning. The variations in the size of the blind zone and warning times for different regions can be used as a guide to selecting strategic locations for future sta- tion deployments.