USGS Earthquake Hazards Program (EHP) GPS Use Case: Earthquake Early Warning (EEW) and Shake Alert
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USGS Earthquake Hazards Program (EHP) GPS Use Case: Earthquake Early Warning (EEW) and Shake Alert

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    GPS Adjacent Band Workshop VI RTCA Inc., Washington D.C., 30 March 2017. USGS GPS receiver ‘use case’ • Real-Time GPS for EEW -Continued: CRITICAL EFFECT – The GNSS component of the Shake Alert system augments the inertial sensors and is especially important for the largest earthquakes. The sensitive inertial sensors may go off scale, whereas GNSS data is expected to provide reliable ground motion recordings of displacement even in the largest events. – Real-time, uninterrupted GNSS signals are required, without interference, at all times because even a temporary black-out of data from one site could delay or thwart our early warning system (particularly if site is close to the epicenter of a major earthquake). – Radio Frequency Interference (RFI) could increase our “blind zone” and delay delivering or degrade the accuracy of our Shake Alert message to the public. – EEW (as well as Volcano, Landslide, and Tsunami early warning applications to come) requires the broadest spectrum so as to fully utilize the GNSS signals, including side bands, for getting the highest station position accuracy and precision possible in real-time. – The proposed RFI can potentially cause multiple critical sites to be useless for EEW during an event, especially if the RFI affected an entire region or sub-region of the real-time GPS network. – Depending on the stations affected by the interference/interruption, how many, how badly they are affected, their location relative to the events epicenter, and the magnitude of the event, GPS data could completely fail to contribute to the EEW Shake Alert system. – Any interference/interruption of the carrier phase measurements at a real-time GPS station has significant potential to degrade our ability to issue the most accurate and timely EEW alert, particularly concerning the largest earthquake events when the GPS data becomes most critical.
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    Presentation slides from GPS Adjacent Band Compatibility Assessment Workshop VI, March 30, 2017:
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