Earthquake Early Warning in Peru

20 Jan

With the delivery of 106 seismic sensors Gaiacode's Sigma Accelerometers are at the core of a new earthquake early warning system in Peru. This Peruvian Seismic Alert System (SASPe) is currently being built along the country's coast and on the two offshore islands of San Lorenzo and Hormigas. Peru will be one of the first countries in South America to operate such an alert system. It is similar to the earthquake early warning networks operating in Japan and Mexico. SASPe is a project of national scope and is executed by the National Institute of Civil Defense (INDECI) and the Geophysical Institute of Peru (IGP).

High Seismic Hazard

With its location on the western edge of South America, the seismic hazard in Peru is very high. Under this nation, the Nazca lithosperic plate dives under the South American plate. This subduction zone generates the volcanic chains of the Andes and numerous dangerous earthquakes of the megthrust type. During the last 80 years alone, at least seven catastrophic earthquakes with magnitudes of 8.0 or larger have occurred under Peru and offshore of this nation. The new seismic alert system is desgined to give up to several dozen seconds of warning to the large part of Peru's population which lives in the seismic hazard zone.

 

building a station

                                             Building a SASPe station on Peru's coast (Photo: IGP)

Each of the 106 early warning station consists of a Gaiacode Sigma accelerometer, a digitizer, a small palm-sized computer and an autonomous power system. The computer is programmed with Artificial Intelligence (AI) based algorithms to detect, locate and estimate the magnitude of the earthquake. The algorithm decides if the earthquake exceeds a critical magnitude level (usually M>6)  and issues a warning signal that is immediately transmitted to INDECI for dissemination. The stations are spaced along Peru's coast with an average distance of approximately 30 kilometers. The first stations of the SASPe network were in installed in July 2020 and the plan is to have the complete system ready for initial tests and a public rollout in the summer of 2022. 

 

Difference in travel times

SASPe and other earthquake early warning systems make use of the characteristic velocities of the different types of seismic waves. On average, the less dangerous primary P waves travel almost twice as fast as the more destructive S waves. When a seismic station close to the epicenter registers a P wave with an amplitude above a certain threshold, it will send a warning to the central site at INDECI which in turn will automatically send out an alert. As a first stage of the public warning, the alert will trigger acoustic sirens to warn the population of the imminent danger of the expected arrival of the stronger S waves. Depending on the distance to the epicentral location, this warning time can be up to several dozen seconds, enough time to seek shelter or turn off  hazardous equipment.

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References

  • Ref 1 USHER, M.J., BURCH, R.F. and GURALP, C.M., “Wide-band Feedback Seismometers”, 1979. Physics of the Earth and Planetary Interiors, 18: 38-50.
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  • Ref 5 GURALP C.M. United States Patent Application Number: 4,280.206 March 1979. SEISMOMETERS.
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  • Ref 7 GURALP C.M. UK Patent Application No. 1900719.4; Title: Infrasound Detector [M&S-IRN.FID4315516]