PRESTo - PRobabilistic and Evolutionary early warning SysTem

PRESTo is a free and open source software platform for Earthquake Early Warning (EEW).

It integrates recent algorithms for real-time, rapid earthquake location, magnitude estimation and damage assessment, into an easily configurable and portable package. PRESTo is designed to process the real-time ground motion recorded by the stations of a seismic network and it is currently under active experimentation in Southern Italy on the Irpinia Seismic Network (ISNet)(external link) (Satriano, Elia et al. [1]).

PRESTo continually processes real-time streams of three-component acceleration data for P-waves arrival detection. These data are normally streamed in real-time from the stations using a SeisComP(external link) server via the SeedLink(external link) protocol, but they can also be read from files (in SAC(external link) format), in order to provide a simulation mode whereby waveforms of past events can be played back into the system. While a (real or simulated) event is occurring, the software promptly performs event detection and provides location and magnitude estimates as well as shaking predictions at target sites.

The earthquake location is obtained by an evolutionary, real-time probabilistic approach based on an equal differential time formulation. At each time step, the algorithm uses information from both triggered and not-yet-triggered stations. Magnitude estimation exploits empirical relationships that correlate this parameter to the filtered peak displacement (Pd) measured over the first 2-4 s of P- and S-waves signal. Finally, peak ground-motion parameters at remote sites can be estimated through ground motion prediction equations once location and magnitude are available.

Alarm messages containing the evolutionary estimates of source and target parameters, sent over the internet, can thus reach vulnerable infrastructures at a distance before the destructive waves, enabling the initiation of automatic safety procedures.

This regional approach to Early Warning is integrated with an on-site, threshold-based method for the definition of independent local alert levels at each station. The dominant period τc and the peak displacement in a short time window after the first P-arrival time, Pd, are simultaneously measured at each station, independently from the rest of the seismic network. These two parameters are compared with threshold values that define a decisional table with four alert levels, correlated to the expected on-site damage as well as the damage at a distance. The alert level can be used to initiate safety measures at each site independently of the regional processing.
At the same time, at the regional scale the local alert levels, as they become available, can be combined with the estimated source parameters to define the extent of the Potential Damage Zone (PDZ), i.e. the area in which the highest intensity levels are expected.

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