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Data Event Response to the July 19, 2018 M 6.0 Earthquake 92km WSW of Chernabura Island, Alaska

UNAVCO has downloaded high-rate 1-sps (1 Hz) GPS/GNSS data from Plate Boundary Observatory stations within ~200 km of the epicenter for a 6-hour time window around the event (± 3 hours).

https://www.unavco.org/highlights/2018/chernabura.html

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On September 7, 2017, a magnitude 8.2 earthquake occurred offshore southern Mexico, causing damage and strong shaking as far away as Mexico City. A network of GPS stations throughout the country and in Central America recorded ground motion caused by the earthquake. In this image, we're showing the real-time horizontal motions.

See more of these data with our new visualization of the Chiapas Earthquake: https://youtu.be/hpQ2Wu8ZIIs

#unavco #geoscience #geodesy #gps #data #visualization #video #chiapas #earthquake #mexico #tlalocnet #coconet

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P312: Relentless Vegetation Growth in the Rainforests of The Pacific Northwest

P312 is located just to the northeast of Fort Bragg, CA, in the Northern Coast Ranges of California in a clearing that is traditionally used as a landing or staging point for felled timber (Figure 1). Although the station moves consistently to the northwest with its nearest neighbors (Figure 2), its time series has been nonlinear since ~2013, compounded with increased noise and offsets (Figure 3).

A check of the maintenance logs reveals a history of events and vegetation growth that explain the time series. A UNAVCO field engineer visited P312 on March 19, 2015 and observed a failing antenna and vegetation overgrowth by an unidentified bush and some pampas grass (Figure 1). The vegetation was pruned back on that visit and the antenna was replaced a month later on April 29. The antenna failure is corroborated by the Signal-to-Noise Ratio (SNR) (Figure 4), which deteriorated rapidly starting in 2014 in a pattern characteristic of antenna failure. The noisiness of the time series did not improve, however, possibly because the pampas grass and shrub quickly grew back. The SNR improved after the antenna was replaced, but the scaled formal error for processed positions and other quality parameters continued deteriorating (Figure 5), indicating ongoing problems with vegetation.

When an engineer returned in January 2017, the station was once again overgrown. Furthermore, someone had stolen the fence around station and bears had entered the enclosure and ripped off the solar panel junction boxes, leading to loss of power and a station outage at the end of 2016. The engineer soldered the chewed-upon cables and restarted station operation, but had to return in April 2016 with materials to rebuild the enclosure fencing.

The most striking plant in the station photos is the pampas grass (Figure 1). Native to South America, pampas grass was introduced to North America as an ornamental plant. Although it prefers warmer climates, it is hardy, drought-tolerant, fast-growing, and prolific. Pampass grass flourishes in the Coastal area of the Pacific Northwest and is now a noxious weed and an invasive species. The distinctive fronds can reach heights of over 2 meters and the leaves are inflammable and have a micro saw-tooth pattern that can easily slice through clothing and skin. Removal of large specimens requires either a backhoe or an herbicide to kill the root system, and neither method is practical or advisable at the station’s remote location at this time. Additionally, the use of herbicides requires special permits due to the sensitive nature of the ecosystem.

A further problem is the encroaching forest (Figure 1). As station photos over time show, the trees around the station are getting taller and the clearing is gradually filling in. The sky view at the station will continue to worsen over time, degrading the satellite signals that reach the antenna. The multipath will continue to increase, as the satellite signals bounce off the plants before reaching the GPS antenna and contributing to poor position solution quality and increased time series noise.

It is uncertain whether the excess vegetation will be cleared soon. The UNAVCO field engineer is in contact with the landowner for permission clear shrubbery and grass, and maybe cut back some trees. Until this work can be performed, users should take care when analyzing the P312 time series.

On a final note, there is a spike in the horizontal components of the time series (Figure 3) and the errors in the quality parameters (Figure 5) in the fall of 2016, just before bears disable the power. The spikes denote a rapid deterioration of station quality with a slight improvement before power failed. This pattern is consistent with a sudden growth of vegetation that dies back in wintertime, when the weather turns cold, except that the photograph from January 2017 (Figure 1) shows luxuriant plant growth around the antenna, so wintertime dieback seems unlikely. Perhaps the shrubbery is deciduous? Unless the field engineers can visit multiple times at different seasons, the mystery is unlikely to be resolved. Of course, if it is vegetation-related, then the proposed large-scale clearing around the GPS station will take care of the mystery as well.

#GPSStations #PBO #P312 #nonlinearGPS #vegetationGPS

Station Home Page:
http://www.unavco.org/instrumentation/networks/status/pbo/overview/P312

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

Pampas grass
https://www.hgtv.com/outdoors/flowers-and-plants/planting-pampas-grass
https://www.wildlife.ca.gov/Conservation/Plants/Dont-Plant-Me/Pampas-Grass
PhotoPhotoPhotoPhotoPhoto
5/29/18
5 Photos - View album

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Data Event Response to the April 5, 2018 M5.3 Earthquake 29km SW of Santa Cruz Is. (E end), California

UNAVCO has downloaded high-rate GPS/GNSS and borehole strainmeter data for the event.

https://www.unavco.org/highlights/2018/santacruz.html

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NASA’s Space Geodesy Project (SGP) was initiated in order to develop and maintain a global network of next-generation space geodetic observing instruments. UNAVCO’s contribution to the SGP involves engineering support for the construction of GNSS infrastructure at selected core sites. In September 2017, UNAVCO completed the installation of four new deep drilled braced GNSS monuments (DDBM) and one short drilled braced GNSS monument (SDBM) at the McDonald Observatory near Fort Davis, Texas.

https://www.unavco.org/highlights/2018/sgp.html

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Data Event Response to the February 25, 2018 M 7.5 Earthquake 81km SW of Porgera, Papua New Guinea

UNAVCO has produced a fully processed 1-sps borehole strainmeter (BSM) dataset spanning the time period of this event, available from the PBO borehole strainmeter event response page.

https://www.unavco.org/highlights/2018/papua.html

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The NASA Jet Propulsion Laboratory (JPL) operates a global network of over 60 permanent GNSS stations called the Global Geodetic Network (GGN). UNAVCO offers support to the GGN by providing data flow monitoring, troubleshooting, station installation and maintenance, and engineering services to help improve the capabilities and performance of station infrastructure.

https://www.unavco.org/highlights/2018/GGNupdates.html

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UNAVCO downloaded high-rate 1-sps (1 Hz) and 5-sps (5 Hz) GPS/GNSS data from 18 stations and 1-sps (1 Hz) data only from an additional three stations in response to the M7.5 earthquake 44km E of Great Swan Island, Honduras, on 2017-01-10 (Figure 2). Stations downloaded include 14 COCONet stations and additional stations operated by OVSICORI, within 1000 km of the earthquake's epicenter. Date were downloaded for a ±3-hour period around the event (7 hours total, from 23:00 - 05:59 UTC). These data are available from the UNAVCO high rate data page. Note: Six of these stations stream data in real time: TGMX, UNPM, CN23, CN30, CN12, and SSIA; to request access to these and other RT-GPS stations operated by UNAVCO please send an email request to rtgpsunavco.org.

UNAVCO has also produced a fully processed 1-sps borehole strainmeter (BSM) dataset spanning the time period of this event, available from the PBO borehole strainmeter event response page.


https://www.unavco.org/highlights/2018/honduras.html

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Data Event Response to the January 4, 2017 M4.4 Earthquake 2km SE of Berkeley, California

UNAVCO is downloading high-rate 5-sps (5 Hz) GPS/GNSS data from 18 Plate Boundary Observatory stations within or close to a 50-mile radius around the epicenter for a 3-day period around the event (day of event ± 1 day).

UNAVCO has also produced a fully processed 1-sps borehole strainmeter (BSM) dataset spanning the duration of the quake, available from the PBO borehole strainmeter event response page.

All data are free and open access. More at:
https://www.unavco.org/highlights/2018/berkeley.html

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Title: PBO Borehole Strainmeters: 2017 Episodic Tremor and Slip Event for Southern Vancouver Island, BC, Canada through Olympia, WA, USA

Authors: Elizabeth Van Boskirk, Kathleen Hodgkinson, Michael Gottlieb, Wade Johnson, David Henderson, David Mencin, and Glen S Mattioli

Date: Tuesday, 12 December 2017, 13:40 - 18:00

Location: New Orleans Ernest N. Morial Convention Center - Poster Hall
T23F-0682

Abstract:
The Plate Boundary Observatory's (PBO) borehole strainmeters along the Cascadia Subduction Zone (CSZ) record the development and migration of Episodic Tremor and Slip (ETS). Along the southern Vancouver Island to Olympia, WA portion of the CSZ ETS events seem to repeat every ~14 months. ETS events are non-volcanic tremor swarms that occur over periods of weeks, often migrating along segments of the subduction zone and can release the energy equivalent to a M7 or greater earthquake. Each ETS event is different; initial propagation location, ETS movement, duration, and direction all vary. Constraints provided by strainmeter observations of ETS events illuminate strain release patterns along the subducting slab interface and may help resolve questions regarding the location of the locked zone of the slab and what role ETS events play in the CSZ earthquake cycle.

The 2017 CSZ ETS began in early February continuing through early April. Beginning in the northern Olympic Peninsula, near Port Angeles, it migrated south towards Olympia over the course of a week. After a two week pause it resumed under the Straits of Juan de Fuca and propagated northwest under Vancouver Island. There are 15 PBO borehole strainmeters along this segment, and ETS strain observations correlate with seismic and GPS measurements. The PBO borehole strainmeters are sensitive even over great distances from the ETS epicenters, and observe compression or extension relative to the ETS migration.

Openly available PBO borehole strainmeter data used by the community has made significant contributions to understanding the ETS process, including the determination that ETS slip is tidally modulated. Data are publically available through UNAVCO and IRIS, which provide links to online tutorials and scripts. There are 32 strainmeters covering the CSZ from southern Vancouver Island, Canada to northern California, USA, and data spans back to 2005. Each site has a Gladwin tensor borehole strainmeter, a Malin three-component geophone, and some sites also have co-located PBO GPS and/or pore pressure sensors.

www.unavco.org

www.unavco.org/data/strain-seismic/bsm-data/bsm-data.html

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