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Data Event Response to the September 30 to October 3, 2020, Westmorland, California, Earthquake Swarm

Written by Kathleen Hodgkinson, Christine Puskas, & Shelley Olds
Originally posted 02 November 2020

Event Summary

A magnitude 4.9 earthquake occurred at 00:31:27 UTC (16:31:27 local) on October 1, 2020, 4 km North East of Westmorland, California as part of an earthquake swarm from September 30, 2020 to October 3, 2020. For more information, see the USGS Earthquake Hazards Program event page.

The event occured within the Network of the Americas (NOTA) footprint. NOTA is a core component of the NSF Geodetic Facility for the Advancement of Geoscience (GAGE), operated by UNAVCO.

GAGE Response

NOTA GPS/GNSS Real Time Data Solutions
8 GPS/GNSS stations were operating in real-time within ~20 km of the epicenter, i.e., they were continuously streaming high rate (1-sps / 1 Hz) data to UNAVCO. Figure 1 shows a regional map; Figure 2 shows the nearby GPS/GNSS stations and ground displacements. Typical latencies for real-time stations, the time lapse between and observation being recorded on the receiver and it arriving in Boulder are less than 1 second. Positions are calculated and redistributed within 1 second of arriving in Boulder.

NOTA GPS/GNSS High-Rate Data for Post Processing
Using final clock and orbit solution it may be possible to detect dynamic signals and coseismic offsets that are not visible in the real-time position time series. UNAVCO has downloaded high-rate 1- and 5-sps (1 and 5 Hz) data from GPS/GNSS stations close to the epicenter, P495, P507 and CRRS. These data are available in RINEX format from the UNAVCO high-rate data ftp site.

GAGE GPS/GNSS Displacement Estimates
The GAGE AC (MIT) inspects the NOTA GPS/GNSS daily positions for significant offsets when they have two to three days of post-event data. Offsets for this event have been posted to the UNAVCO Data Products event page in file cwu_201001_0032_eq58_coseis_rapid.evt.

NOTA Borehole Strainmeter Data
UNAVCO produced a fully processed 1-sps borehole strainmeter (BSM) dataset for NOTA strainmeters in southern California this event. This dataset can be downloaded from the UNAVCO Geophysical Event Data page, or directly via the 20201001_Westmorland folder.

Note: Figures and findings are preliminary and subject to revision.

GAGE Data and Support

  • Please contact archive-gpsunavco.org for information on data availability.
  • To request access to these and other RT-GPS stations operated by UNAVCO please send an email request to rtgpsunavco.org.
  • For information on past event responses, see the UNAVCO Geophysical Event Response page.


These data are provided by the GAGE Facility, operated by UNAVCO, Inc., with support from the National Science Foundation and the National Aeronautics and Space Administration under NSF Cooperative Agreement EAR-1724794. The Network of the Americas (NOTA) is a core component of the NSF GAGE Facility. To acknowledge use of these data please follow the acknowledgment guidelines.

High-resolution Figures

Related Links

Map Center:
Lone Pine, California


Last modified: 2020-11-03  12:02:40  America/Denver