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UNAVCO 1996 Annual Report

B.4 Support of Continuously Operating GPS Stations

The establishment of high quality continuous GPS measurement stations is a critical component of the current GPS data collection methodology, especially for data accuracy and reliability. The UNAVCO Boulder Facility has participated in establishing GPS networks around the world in support of NSF and NASA initiatives including direct support to stations that are part of the International GPS Service for Geodynamics (IGS) network. UNAVCO's experience in establishing network and site requirements for continuous station implementations includes collaborator negotiation, site reconnaissance, system configuration, data communications testing and implementation, equipment procurement and fabrication, installation and on-site training, network engineering and configuration management. This type of support by the Facility continues to grow with well over thirty NSF stations supported in the field and technical consulting support provided to another twenty. Table 3 in the main report shows continuous station implementations supported by UNAVCO on behalf of NSF investigators in FY97. Activities in support of these stations are summarized below.

Basin and Range Project (EAR-Continental Dynamics, Instrumentation and Facilities)

The Active Tectonics of Diffuse Intracontinental Deformation (see associated Science Snapshot) grant of Brian Wernicke and Jim Davis will study diffuse intraplate deformation along the 41o parallel in the Basin and Range province, which has been a locus of diffuse plate margin deformation for at least 500 Ma[9]. The Basin and Range province is about 800 km wide and comprises 25-30 evenly-spaced, major Quaternary fault zones, but historic seismic strain release is restricted to three belts each approximately 100 km wide. Previous geodetic work shows that the Basin and Range is expanding at approximately 9-13mm/yr, corresponding to an average of about 0.3mm/yr across each range block. The results of this study will, for the first time, constrain the scale and degree of heterogeneity of strain accumulation across a wide orogenic belt.

A network of 18 permanent Basin and Range GPS stations has been installed over the last two years. The installation was phased in with nine sites installed in July 1996 and nine installed in winter 1997. At the time of this report, five UNAVCO staff have provided field support for four reconnaissance, three installation, and five maintenance trips. UNAVCO's primary role has been data communications testing during field reconnaissance, system design, consultation on data communications, GPS systems installation, training and technology transfer to Caltech and Harvard-Smithsonian, and maintenance and trouble-shooting support. The system design, reconnaissance and Phase I installation support by UNAVCO were discussed in detail in the FY96 annual report.

The Phase II installation was finished in FY97 with UNAVCO installing the final station infrastructure and supporting the University of Nevada, Reno staff in integrating the GPS data communications for four sites into their seismic microwave link. Maintenance is an ongoing process and is a shared responsibility between UNAVCO and the investigators. UNAVCO staff traveled to the field in FY97 primarily to trouble-shoot and repair communications and electronic problems, including repairing or replacing equipment damaged by lightning strikes. Data are downloaded nightly at Harvard-Smithsonian using UNAVCO developed downloading scripts. The data are processed at Harvard-Smithsonian and submitted to the Boulder Facility for long term archiving.

Tien Shan - China (EAR - Continental Dynamics, Instrumentation and Facilities)

The Tien Shan-China project has been funded to carry out a four year investigation of the deep structure and kinematics of deformation of the Tien Shan, the largest and most active intracontinental range in the world. The objective is to understand the dynamic processes responsible for intracontinental mountain building. To achieve this objective, the investigators plan to use GPS geodesy to determine present-day relative movements of 120 benchmarks in Kazakhstan, Kyrgyzstan and western China.

The Tien Shan project requested Facility support for the installation of four continuous stations, one each in Kyrgyzstan and Kazakhstan and two in China in 1997. George Liu, UNAVCO field engineer, provided logistical support and technical consultation on the design and installation of infrastructure for the continuous permanent stations in Kyrgyzstan, Kazakhstan and the Xinjiang province of China. George supported the project from May until July when the Kyrgyzstan and Kazakhstan stations were installed and UNAVCO received notification that China would at present not grant clearance for the Xinjiang installations. Support for the China installations will be re-scheduled once the clearance is obtained.

Pacific Northwest Geodetic Array (PANGA) (EAR - Geophysics, Instrumentation and Facilities)

PANGA is a network of permanent stations in Washington, Oregon, and British Columbia under the auspices of Central Washington University (CWU) and the University of Washington. Equipment for 11 stations of the network was purchased under the NSF ARI award in 1996. Approximately ten other stations are being operated or planned by other universities or agencies in the region including the Coast Guard, Oregon State University, Renasselear Polytechnic Institute, Hanford Nuclear Reservation and the USGS. The principal investigator for the NSF-funded portion of the PANGA project is Meghan Miller (CWU) with co-investigators Charles Rubin (CWU) and Tony Qamar (University of Washington). The goal of the network is to provide geodetic monitoring for integrated geologic studies that support the geophysical models needed to resolve the kinematics and dynamics of deformation in the Pacific Northwest. The Pacific Northwest is located between two migrating triple junctions, and deforms in response to complex North America, Juan de Fuca, and Pacific boundary interactions, as well as the migrating triple junctions and plate driving forces. The network will characterize the crustal deformation within the continental crust of the overriding plate of the Cascadia subduction zone and help to characterize the seismic risk in eastern Washington and Oregon, where crustal earthquakes are common and historically exceed Mw = 7.

In 1997, three permanent GPS stations were installed within PANGA, two in Washington and one in Oregon. UNAVCO engineer, Oivind Ruud, supported project planning and in-field operations. Preceding deployment, Oivind reviewed the statement of work for the monument installation, which was contracted to a private company, and provided technical consultation on data communication and support hardware. Oivind spent three weeks in the field during the monument installations, installing the GPS receivers, phone communication equipment, and other support infrastructure such as lightning surge protection, antenna mounts and protective conduit. During the period of field support, Oivind also installed and tested the remote download and data management capability required to get the data to CWU. Dan Johnson, a CWU support staff, was trained on the use of the UNAVCO Local Automated Process for Downloading of Global Sites (LAPDOGS) software installed on CWU's download SUN Sparc-10. The UNAVCO Boulder Archive has been identified as the primary off-site archive backup and will work with CWU on installing the Local Data Manager (LDM) software for easy data transfer to the UNAVCO Archive.

Active Seismic Zones of Interior Alaska (EAR - Geophysics)

Jeff Freymueller's active seismic zones of interior Alaska project will combine GPS measurements with a study of seismicity to measure and compare geodetic and seismic strain rates over the NE trending left-lateral seismic zones of the area. These first quantitative measurements of the strain rates for the Denali and Tintina faults will quantify the block rotation model for a new tectonic model of the region, along with providing new information regarding the seismic hazards of interior Alaska.

In August 1997, UNAVCO field engineer Karl Feaux installed one station for this project using a University of Alaska ARI receiver (Figure B-2). Karl supported site reconnaissance, basic infrastructure design and installation, monumenting, receiver and communications installation, and data download and management software installation. Data were collected at four potential sites as part of the site selection process and Karl ran the site data through the UNAVCO quality control program, selected a site with the best data quality and worked with the Alaska technical staff to install the station on a very compressed time schedule. All of the potential sites required remote installation able to withstand severe temperature extremes and installation of extended power and communications lines. In October, UNAVCO staff will work closely with the Alaska staff to upgrade data communications to allow remote download to the University of Alaska. Once the data download is operational, LDM software will be installed to allow for easy data transfer to the UNAVCO Archive.

Figure B-2. Interior Alaska Permanent Station Installation.

Southern California Integrated GPS Network (SCIGN) (EAR - Instrumentation and Facilities)

In August 1997, the Facility received a request for six months of field engineering support to assist with the reconnaissance and permitting of the 200+ station SCIGN network. UNAVCO has agreed to three months of a field engineer, George Liu, to support this work. George will support site reconnaissance and permitting and provide technical assistance as required at Scripps and the USGS Pasadena office beginning in early September. A more complete discussion of this collaboration will be included in the 1998 annual report.

[9] Burchfiel, B.C., Cowan, D.S., and Davis, G., 1992, Tectonic overview of the cordilleran orogen in the western United States. In Buchfiel, B.C., Lipman, P.W., and Zoback, M.L., (eds), The Cordilleran Orogen: Conterminous U.S., Boulder, Colorado.

1997 Annual Report - 27 OCT 1997


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