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Researchers testing a satellite-based early warning system developed for earthquakes that’s being developed for the U.S. West Coast, determined the system performed well, upon reviewing data collected from three large earthquakes that occurred in Chile between 2010 and 2015. Reported in the journal Seismological Research Letters, the findings suggest this system could provide early warnings of tremors and tsunamis for coastal communities in the future. Known as G-FAST, the early warning system utilizes ground motion data measured by Global Navigation Satellite Systems (GNSS), which estimate the magnitude and epicenters for these events, namely quakes that register 8 or higher on the Richter Scale.

Often occurring at subduction tectonic plate boundaries, where one plate thrusts beneath another, these are the usual cases for earthquakes off the coasts of the U.S. Pacific Northwest and Chile. Data collected from over 150 GNSS stations in Chile enabled researchers to test G-FAST’s performance against three large megathrust earthquakes that occurred in Chile—2010 Maule (8.8), 2014 Iquique (8.2), and the 2015 Illapel earthquakes (8.3). G-FAST provided magnitude estimated between 40 and 60 seconds after the origin times of each event. This helped provide magnitude estimates within 0.3 units of the known magnitudes.

The system also produced estimated of the epicenter and fault slip for each event, and agreed with the actual measurements, which were available 60 to 90 seconds after each origin time. Researchers were surprised at G-Speed’s converging speed to the correct answers, and how accurately they could characterize all three quakes. Most early warning systems measure seismic wave properties to quickly characterize an earthquake. These systems, however, can’t collect enough information for determining the extent an earthquake will grow and as a result, could prompt researchers to underestimate the event’s magnitude.

This issue can be avoided using satellite-based systems like G-FAST. While it’s difficult to test these particular types of early warning systems since earthquakes registering a magnitude of 8 or more are considerably rare, researchers decided to focus on Chilean earthquakes because any quakes that registered 8 or higher wererecorded with precise and consistent accuracy on the GNSS network.

Researchers were able to better categorize the system’s strengths and weaknesses as a result. The tests conducted in Chile will help immensely in further developing G-FAST for its intended use along the Pacific Coast, where researchers have been working to include the system in a prototype earthquake early warning system called ShakeAlert. This system is currently being tested in California, Oregon, and Washington state.

The Chilean quakes are only about half of magnitude 8 events in the recorded catalog of earthquakes used to test G-FAST and other geodetic algorithms to be included in ShakeAlert. Circling back to the rarity of earthquakes that are magnitude 8 or higher, at least ten of these events occurred along the Chilean coast in the past century.

One of these events was the 1960 Valdivia Earthquake, which registered a 9.5 on the Richter Scale, and is the largest quake recorded by instruments to date. Researchers say the hazard due to these large events is well recognized and understood, and enabled the scientists to determine a return period of 80-130 years for magnitude 8 or higher earthquakes in any region of Chile.

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