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.
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Figure 1. Regional map showing the September 30, 2020 to October 3, 2020 Westmorland swarm (yellow dots) in the Imperial Valley south of the Salton Sea, near the California-Mexico border. The Imperial Valley is a part...Read more » -
Figure 2. Map of ground displacements for the 8 closest NOTA GPS/GNSS stations within ~20 km of the Westmorland swarm of September 30 - October 3, 2020 in the Imperial Valley south of the Salton Sea. The offsets were...Read more » -
Figure 3. Daily time series for GNSS stations near the Westmorland swarm from September 30 to October 3, 2020. Time series have been detrended and show offsets at P495, WMDG, and P506. A second, smaller sequence...Read more » -
Figure 4. Horizontal displacements from nearby real-time NOTA GNSS stations for the 01 Oct 2020 earthquake. Positions were generated within seconds of the data being recorded, blue dots show the predicted arrival times...Read more » -
Figure 5. Photo from February 2020 of old geothermal mud pots and mud volcanoes near Calipatria, CA, on the southern end of the Salton Sea, 15 miles north of Westmorland, CA. (Photo by Sean Malloy, UNAVCO)...Read more » -
Figure 6. Seismogeodetic station, WMDG, in the Imperial Valley installed and operated by the USGS Pasadena field office. This station consists of both seismic and geodetic instrumentation to aid in earthquake locations...Read more » -
Figure 7. Flow structure along the flank of one of the active mud volcanoes in December 2017. The mud was extruded in real-time in front of observers. (Photo by Chris Walls, UNAVCO)...Read more » -
Figure 8. Gurgling vent with mudflows of approximately 1meter/minute in December 2017. (Photo by Chris Walls, UNAVCO)...Read more » -
Figure 9. Alignment of mud volcano vents (December 2017). Note that the mud volcanoes are within the Salton Sea geothermal field and near station P507. This is also the proximity of a cluster of events that followed...Read more » -
Figure 10. Oblique aerial drone view of mud volcanoes in December 2017. (Photo by John Galetzka, UNAVCO (2017), NGS)....Read more »
GAGE Data and Support
- Please contact archive-gps
unavco.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.
Acknowledgements
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
- Regional map with GPS/GNSS stations (Figure 1)
- Map of ground displacements for NOTA GNSS (Figure 2)
- High-rate GNSS position time series (Figure 3)
- Real-time GNSS time series (Figure 4)
- Salton Sea Mud Volcanoes (Figure 5)
- USGS Seismogeodetic station, WMDG (Figure 6)
- Mud volcano flow structure (Figure 7)
- Gurgling mudflow vent (Figure 8)
- Mud volcano alignment (Figure 9)
- Aerial view mud-volcanoes (Figure 10)
Related Links
- UNAVCO Geophysical Event Response page
- USGS event page
- Nevada Geodetic Laboratory (UNR)
- Network of the Americas
- UNAVCO GPS Velocity Viewer
- UNAVCO Geophysical Event Response Data Explainer: Dynamic Strain
Map Center:
Lone Pine, California
Last modified: 2020-11-03 12:02:40 America/Denver
2021