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The UNAVCO data response to the M7.1 Puebla event includes high-rate GPS/GNSS data from TLALOCNET and COCONet stations and borehole strain data from the EarthScope Plate Boundary Observatory. As of September 21, we are still updating this page with new information. TLALOCNET is a partnership between UNAVCO and UNAM-Geofisica (at the National Autonomous University of Mexico) and data are being obtained with both UNAVCO and UNAM resources.

https://www.unavco.org/highlights/2017/puebla.html

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The August 21, 2017 Total Eclipse and the Ionosphere

UNAVCO collected 5-Hz GPS data from stations within the PBO network that were in the path of 90% totality. Demián Gómez, a postdoc at Ohio State with Mike Bevis, has taken the 15-second RINEX files inside the totality path and calculated the Total Electron Content (TEC) at each station-satellite pair for each epoch recorded during the day of the eclipse. These calculations result in TEC observations at the ionospheric piercing points (IPP), the intersection of the station-satellite line-of-sight (LOS) and the peak electron density of the ionospheric F layer at a height of ~300 km. Using the estimated TEC at each IPP, he produced a video showing the TEC change during the passage of the umbra and penumbra of the eclipse over North America over a period of one hour. The video shows that as the moon’s shadow passes and the sunlight is blocked, the TEC drops due to the recombination of the ionized particles.

The ionosphere is part of the upper atmosphere and is ionized by solar and cosmic radiation. Ultraviolet light, X-rays, and high-energy radiation strip electrons from atoms, creating an ionized environment. The sun is the largest contributor of ionizing radiation, so the atmosphere is strongly ionized during the daytime. At night cosmic rays from distant sources such as supernovae, black holes, etc. ionize the atmosphere more weakly. The ionosphere is dispersive, so that radio waves (such as from GPS satellites) traveling through will have a phase velocity dependent on their frequencies. The phase difference between the two GPS carrier frequencies is used to estimate the TEC along the column of atmosphere of the LOS between a station-satellite pair, characterized by the number of electrons per square meter in that column. This technique is exploited by researchers to study ionospheric structure and disturbances, as in the case of the 2017 total eclipse.

#TotalEclipse2017 #PBO #IonosphereGPS

Eclipse highlight at UNAVCO:
https://www.unavco.org/highlights/2017/eclipse2017.html

The ionosphere and total electron content:
http://www.swpc.noaa.gov/phenomena/ionosphere
http://www.swpc.noaa.gov/phenomena/total-electron-content
https://scied.ucar.edu/ionosphere

Sample papers:
Virtual array beamforming of GPS TEC observations of coseismic ionospheric disturbances near the Geomagnetic South Pole triggered by teleseismic megathrusts
http://onlinelibrary.wiley.com/doi/10.1002/2015JA021725/full

A new technique for mapping of total electron content
using GPS network in Japan
https://www.jstage.jst.go.jp/article/eps1998/54/1/54_1_63/_pdf

A global mapping technique for GPS-derived
ionospheric total electron content measurements
http://onlinelibrary.wiley.com/doi/10.1029/97RS02707/pdf

Application of ionospheric tomography to real-time
GPS carrier-phase ambiguities resolution, at scales of
400-1000 km and with high geomagnetic activity
http://onlinelibrary.wiley.com/doi/10.1029/1999GL011239/pdf

Spatial information used to plot the umbra and penumbra:
https://svs.gsfc.nasa.gov/4518

Shapefile reference
Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 8.0.0.0.0

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The UNAVCO data response to the M8.1 Chiapas event includes high-rate GPS/GNSS data from TLALOCNET and COCONet stations and borehole strain data from the Plate Boundary Observatory. As of Sept. 11, we are still updating this page with new information.

https://www.unavco.org/highlights/2017/chiapas.html

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UNAVCO downloaded data from 279 EarthScope Plate Boundary GNSS stations, including 38 in the path of totality, for the duration of the 2017 Great American Eclipse. The data are now available via our data archive.

https://www.unavco.org/highlights/2017/eclipse2017.html

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Learn about the hydrologic surface loading data products now available through UNAVCO, and hit us up with questions. UNAVCO uses estimates of surface water mass from global and national land data assimilation systems (GLDAS and NLDAS, respectively) to model the expected displacement from these loads at GAGE-processed PBO stations.

https://www.unavco.org/highlights/2017/hydrodata.html

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P029: Landslides in the Rockies

P029 is located in west-central Colorado, just south of the Black Canyon of the Gunnison National Park, near the town of Cimarron. The station is notable for having a horizontal velocity of 3.6 mm/yr to the southwest, in contrast to neighboring stations with horizontal motions of 1 mm/yr or less (Figure 1). The station is within the Rocky Mountains, which are considered part of stable North America and not expected to have significant motion in the NAM08 reference frame.

Except for a bad antenna between 2008 and 2010, the station has been in relatively good health, as shown by the UNR QA parameters (Figure 2) and the multipath (MP) and signal-to-noise ratio (SNR) (Figure 3) plots. However, the time series is clearly nonlinear (Figure 4).

The cause of this nonlinear time series is fairly obvious. The local topography is hummocky (Figure 5), suggesting that the site was built on a landslide. And indeed the Colorado Landslide Inventory shows that this is the case (Figure 6). P029 is located in the Black Canyon of the Gunnison and Vicinity Quadrangle, and the station sits on the geologic unit that the map describes as “landslides, mudflows, and debris flows.”

The nonlinearity of the P029 time series suggests that the landslide is active. Presumably the slide flows when there is precipitation or snowmelt. The area does receive a few inches of rain per year, according to nearby weather stations, so an unusually snowy winter or large storm in the summer could contribute to landslide flow. The southwest motion of the station suggests that the slide originated from the cliffs of the mesa to the north. Oddly enough, the station is going up in the vertical component. Perhaps this part of the landside is being pushed up by the horizontal motion from the north. In any case, the landslide flow is likely to be complex and cannot be constrained by a single GPS station.

Station Home Page:
http://www.unavco.org/instrumentation/networks/status/pbo/overview/P029

Quality parameters at UNAVCO
ftp://data-out.unavco.org/pub/products/unr_qa/

Guide to UNR QA files
ftp://gneiss.nbmg.unr.edu/qa/QA.pdf

Colorado Landslide Inventory
http://coloradogeologicalsurvey.org/geologic-hazards/landslides/colorado-landslide-inventory/

USGS Black Canyon of the Gunnison and Vicinity Geologic Map
https://ngmdb.usgs.gov/Prodesc/proddesc_9369.htm

Field trip guide showcasing landslides to the east of Cimarron
http://www.gly.uga.edu/railsback/VFT/VFTCimarron.html

#GPSStations #PBO #P029 #nonlinearGPS #landslideGPS

PhotoPhotoPhotoPhotoPhoto
7/7/17
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UNAVCO's data response to the May 12, 2017 M6.2 earthquakes near Acajutla, El Salvador includes high-rate GPS/GNSS data from COCONet stations within ~500 km of the epicenter.

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UNAVCO's data response to the May 1, 2016 M6.2 earthquakes near Skagway, Alaska includes high-rate GPS/GNSS data from EarthScope Plate Boundary Observatory stations within ~200 km of the epicenter and a fully processed 1-sps borehole strainmeter data set.

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UNAVCO is creating a whole series of data access videos to get newcomers started on accessing our free data. Experienced users may also learn about new datasets or new ways to access familiar data. Here is a video on accessing terrestrial laser scanning (TLS) data:

https://www.youtube.com/watch?v=Wa7SN9sjAjU&feature=youtu.be

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Join us at SSA next week. 11 co-authored presentations, including an Ignite talk. Plus, we have a booth this year. See you there?

http://www.unavco.org/highlights/2017/ssa.html
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