Near-Field Strong Ground Motions from GPS-Derived Velocities for 2020 Intermountain Western United States Earthquakes

In early 2020, four moderate sized earthquakes occurred in the Intermountain region of the western United States, two M 6.5 events in Challis, Idaho, and Monte Cristo Range, Nevada; an M 5.7 in Magna, Utah, within the Salt Lake City metropolitan area; and an M 5.8 in the Owens Valley of California. Although the Magna and Owens Valley earthquakes were well recorded in the near field with an array of seismic instrumentation, the Challis and Monte Cristo events were not densely recorded. All of the events, however, have reasonable coverage with high rate Global Positioning System (GPS) stations in the near field. Here, I report on strong-motion observations recorded at 19 regional GPS stations at 5 Hz. I compare these observations with seismic recordings where available and ShakeMap estimations of peak ground velocity to find good agreement with a natural-log residual of +/- 0.5. Furthermore, I compute the correlation between collocated stations and show a strong positive correlation > 0.65. This study highlights the utility of high-rate GPS velocity observations to strong-motion seismology.

Automated summary

In early 2020, four moderate sized earthquakes occurred in the western United States. High-rate GPS velocity observations were found to provide good agreement with seismic recordings and ShakeMap estimations of peak ground velocity. The study highlights the utility of high-rate GPS velocity observations to strong-motion seismology.