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 magnitude
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 initiation
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 existing
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 station
deployments.

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