G41A-01
Plate Boundary Observatory (PBO): A large Geodetic Network on the Pacific-North America Plate Boundary
The Plate Boundary Observatory is being installed along the Pacific-North America plate boundary and when
complete will add 875 new GPS sites and incorporate 209 existing GPS sites into the network.
The GPS phase data from all these sites and an additional 40 sites to tie to the North America plate are analyzed
by PBO analysis centers (ACs) at the New Mexico Institute of Mining and Technology (NMT) and at Central
Washington University (CWU). The results from the two ACs, which use different GPS data processing programs,
are combined into PBO GPS products by the Analysis Center Coordinator (ACC) at the Massachusetts Institute of
Technology. Three levels of analysis are performed on the data: a "rapid" analysis available with a 1-day latency;
a "final" analysis that uses IGS final orbit products and is available with a 6-13 day latency; and a "supplemental"
analysis that runs with 12-week latency and adds to the final analysis data from sites with late data retrieval.
Results from these analyses in the form of velocity estimates, time series, and Solution Independent Exchange
Format (SINEX) files that contain position and full covariance information are all available from
http:pboweb.unavco.org/gps_data. The median root-mean-square (RMS) scatter of the daily estimates from
currently about 800 stations in a North America fixed reference frame from the final analysis is 1.3 mm horizontal
position and 4.0 mm in vertical position. We discuss the results being obtained from the PBO analyses and the
methods used to process the GPS data from this network.
http:pboweb.unavco.org
G41A-02
The EarthScope Plate Boundary Observatory Distributed Data Management System
EarthScope is an ambitious multi-year project funded by the United States National Science Foundation to
explore the structure and dynamics of the North American continent using a wide range of geophysical methods.
The Plate Boundary Observatory (PBO), being built by UNAVCO, is the geodetic component of EarthScope, and
will comprise 880 continuous GPS stations, 103 borehole strainmeter stations, 28 tiltmeters, and five laser
strainmeters; in addition, PBO will manage data for 209 existing GPS stations and 11 GPS stations installed by
the USArray segment of EarthScope. As of February 2007, 561 of these stations have been installed.
PBO data flow is managed from the PBO Boulder Network Operations Center (NOC), located at UNAVCO
Headquarters. Automated systems at the NOC retrieve data from our stations at least daily, monitor the status of
the network and alert operators to problems, and pass data on for analysis, archiving, and distribution. Real-time
network status can be found at http:pboweb.unavco.org/soh_map.
PBO's analysis centers generate high-quality derived data products from PBO raw data. Two centers, at Central
Washington University and the New Mexico Institute of Mining and Technology, process raw GPS data to produce
initial PBO GPS products including network solutions and station position time series, andthese products are
combined by the Analysis Center Coordinator at MIT to produce the official PBO GPS products. Two analysis
centers, at UNAVCO's Socorro office and the University of California, San Diego, process data from the PBO
borehole and laser strainmeter networks and produce cleaned time series of shear, areal, and linear strain,
Earth tides, pore fluid pressure, and other parameters.
The UNAVCO Facility archives and distributes all PBO GPS data products and runs a secondary archive offsite; to
date, these centers hold more than 2.5 TB of PBO products. The IRIS Data Management Center and Northern
California Earthquake Data Center archive and distribute all PBO strainmeter data products, and IRIS archives all
PBO seismic data products; all told, more than 160 GB of strain and seismic data products are available from
these archives. These same two centers also archive other EarthScope seismic and strain data, which makes it
much simpler for users to access EarthScope products from a unified set of centers.
PBO and EarthScope data products may be accessed using a variety of tools. The PBO Web site
(http:pboweb.unavco.org) provides centralized access to PBO products stored in our distributed archives. For
example, GPS products may be accessed from http:pboweb.unavco.org/gps_data and strain data products from
http:pboweb.unavco.org/strain_data. In addition, the individual archives provide access to their holdings, both
for PBO and other networks, through a variety of discipline-specific tools.
The most exciting development still to come in providing access to EarthScope data products will be the creation
of the EarthScope Portal. This system will be based on Web services, operated by the EarthScope components,
that provide access to holdings at the EarthScope archives and are linked to a central Web portal. This system
will provide a unified system for discovery and access to EarthScope digital data products, and is planned to be
operational by October 2008.
http:pboweb.unavco.org
G41A-03
Low-latency high-rate GPS data from the EarthScope Plate Boundary Observatory
Real-time processing of high rate GPS data can give precise (e.g., 5-10 mm for data recorded once per second)
recordings of rapid volcanic and seismic deformation. GPS is also an inertial sensor that records ground
displacement with very high dynamic range, which allows the use of high rate GPS as a strong-motion
seismometer. Such processing applied to low-latency streams of high sample rate GPS provide an emerging
tool for earthquake, volcano, and tsunami geodesy and early warning.
UNAVCO, as part of the EarthScope Plate Boundary Observatory project, is developing a system to provide such
streams from some PBO and other UNAVCO-operated GPS stations, which we call UStream. UStream will be
based on the Ntrip standard, a widely used protocol for streaming GNSS data over the Internet. Remote GPS
stations will provide a stream of BINEX data at 1 sample/sec to an Ntrip server at UNAVCO's Boulder offices,
while at the same time recording data locally in the event of communications failure. Once in Boulder, the data
will be forked into three output streams: BINEX files stored at the UNAVCO archive and streams of data in BINEX
and RTCM format. These data will flow to an Ntrip broadcaster that will distribute data to Ntrip clients, which can
be anything from epoch-by-epoch processing systems to external data archiving systems. Data will flow through
this system with no artificial latency and will be freely available to the community for use in scientific research.
http:pboweb.unavco.org
G41A-04
Reloading Continuous GPS in Northwest Mexico
For more than 10 years we try to follow the steps of the Southern California Integrated GPS Network (SCIGN) and the Plate Boundary Observatory (PBO) in USA, this gives us the opportunity to be in position to contribute to develop a modern GPS Network in Mexico. During 1998 and 2001, three stations were deployed in Northwest Mexico in concert with the development of SCIGN: SPMX in north central Baja California state at the National Astronomical Observatory, UNAM in the Sierra San Pedro Martir; CORX in Isla Coronados Sur, offshore San Diego, Ca./Tijuana, Mexico and GUAX in Guadalupe island 150 miles offshore Baja California peninsula, which provide a unique site on the Pacific plate in the Northamerica/Pacific boundary zone in Las Californias. The former IGS station in CICESE, Ensenada, CICE installed in 1995, was replaced by CIC1 in 1999. In 2004 and 2005 with partial support from SCIGN and UNAVCO to University of Arizona a volunteer team from UNAVCO, Caltech, U.S. Geological Survey, Universidad de la Sierra at Moctezuma Sonora and CICESE built two new shallow-braced GPS sites in northwest Mexico. The first site USMX is located at east-central Sonora and the second YESX is located high in the Sierra Madre Occidental at Yecora near the southern border of Sonora and Chihuahua. All data is openly available at SOPAC and/or UNAVCO. The existing information has been valuable to resolve the "total" plate motion between the Pacific plate (GUAX) and the Northamerica plate (USMX and YESX) in the north- central Gulf of California. Since the last year we have the capability of GPS data processing using GAMIT/GLOBK, and after gain some practice with survey mode data processing we can convert us in a GPS processing center in Mexico. Currently only 2 sites are operational: CIC1 and USMX. With new energy we are ready to contribute to the establishment of a modern GPS network in Mexico for science, hazard monitoring and infrastructure.
G41A-05
Multi-spatial and temporal scale deformation of Japan from GEONET data
The Japan subduction zone represents a complex set of plate interfaces with significant trench-parallel variability in great earthquakes and transient deep slip events. Through analysis of the GEONET GPS data, the spatial and higher frequency temporal characteristics of plate coupling and transient slip events can be captured. We describe our analysis methods, the resultant velocities and time series, as well as progress to date on models of interseismic, transient and coseismic deformation. To quickly and routinely analyze the large volume of GPS data from GEONET, we have developed the GPS Network Processor (GNP). The GNP is based on the JPL- developed GIPSY-OASIS GPS analysis software. The GNP efficiently implements precise point positioning and bias fixing on a 1000 node cluster. We are currently working on using the GEONET time series to determine the degree and spatial extent of plate coupling along the subducting plates. We will be using strain maps and the Network Inversion Filter [Segall and Matthews, JGR, Vol. 102, 22391-22409, 1997] to look at transient deformation at different spatial and temporal scales. In addition, we have developed fault plane parameterizations that adapt the spatial complexity of the coseismic slip model to the distribution and signal to noise ratio of the data. This coseismic slip modeling will be applied to the 2003 Tokachi-Oki M8.1 earthquake. The Japanese subduction zones provide an excellent natural laboratory for studying transient motion and fault mechanics. By applying state- of-the art analysis and modeling techniques to the GEONET data, we get improved estimates of interseismic velocities, transient deformation, plate coupling, and coseismic slip, all of which are crucial for understanding subduction zone fault properties.
G41A-06
GPS Seismology and Earthquake Early Warning along the Southern San Andreas Fault System
We are in the process of upgrading CGPS stations in southern California to high-rate (1-10 Hz) real-time (latency
< 1 s) operations. Currently we have about 60 upgraded SCIGN and PBO stations that straddle the San
Andreas Fault System south of the Big Bend in southern California and cover the three major faults (San Andreas,
San Jacinto and Elsinore). Our next major upgrade will include 12 PBO stations in the Imperial Valley straddling
the Imperial and Cerro Prieto faults, the region of highest strain rate in southern California and the narrowest part
of the North America-Pacific plate boundary. South of the Big Bend, the zero velocity contour (the "boundary")
between the North America and Pacific plates does not follow the SAF segment, but rather is located just east of
the San Jacinto Fault (SJF) segment and then follows the Imperial and Cerro Prieto faults. The primary purpose of
the real-time network is to serve as an early warning system for a large earthquake along the southern San
Andreas Fault System by quickly measuring coseismic displacements, and also for GPS seismology to rapidly
measure the associated dynamic displacements. The network, called the California Real Time Network (CRTN),
also supplies data for real GPS surveys within the region and will provide rapid displacement waveforms to the
SCEC data archive at Caltech in the event of a medium to large earthquake. Although the real-time data flow is
currently at 1 Hz, the PBO stations have an internal buffer that records GPS data at a 10 Hz rate.
http:sopac.ucsd.edu/projects/realtime/
G41A-07
Deformation integrity monitoring for GNSS positioning services including local, regional and large scale hazard monitoring - the Karlsruhe approach and software(MONIKA)
GNSS-positioning services like SAPOS/ascos in Germany and many others in Europe, America and worldwide,
usually yield in a short time their interdisciplinary and country-wide use for precise geo-referencing, replacing
traditional low order geodetic networks. So it becomes necessary that possible changes of the reference stations'
coordinates are detected ad hoc. The GNSS-reference-station MONitoring by the KArlsruhe approach and
software (MONIKA) are designed for that task. The developments at Karlsruhe University of Applied Sciences in
cooperation with the State Survey of Baden-Württemberg are further motivated by a the official resolution
of the German state survey departments' association (Arbeitsgemeinschaft der Vermessungsverwaltungen
Deutschland (AdV)) 2006 on coordinate monitoring as a quality-control duty of the GNSS-positioning service
provider.
The presented approach can - besides the coordinate control of GNSS-positioning services - also be used to set
up any GNSS-service for the tasks of an area-wide geodynamical and natural disaster-prevention service.
The mathematical model of approach, which enables a multivariate and multi-epochal design approach, is
based on the GNSS-observations input of the RINEX-data of the GNSS service, followed by fully automatic
processing of baselines and/or session, and a near-online setting up of epoch-state vectors and their
covariance-matrices in a rigorous 3D network adjustment. In case of large scale and long-term monitoring
situations, geodynamical standard trends (datum-drift, plate-movements etc.) are accordingly considered and
included in the mathematical model of MONIKA. The coordinate-based deformation monitoring approach, as third
step of the stepwise adjustments, is based on the above epoch-state vectors, and - splitting off geodynamics
trends - hereby on a multivariate and multi-epochal congruency testing. So far, that no other information exists, all
points are assumed as being stable and congruent reference points. Stations, which a priori assumed as
moving - in that way local monitoring areas can be included- are to be monitored and analyzed in reference to the
stable reference points. In that way, a high sensitivity for the detection of GNSS station displacements, both for
assumed stable points, as well as for a priori moving points, can be achieved.
The results for the concept are shown at the example of a monitoring using the MONINKA-software in the 300 x
300 km area of the state of Baden-Württemberg, Germany.
http:www.goca.info
G41A-08
iGeoPS©, a Matlab tool for High Rate GPS data analysis: application to the Mt.Etna network
In these last years, an increasing interest in high rate GPS is clearly showed by the numbers of papers where this methodology is applied in seismology (Larson et al., 2003; Bock and Prawirodirdjo, 2004; Ji et al., 2004; Miyazaki et al., 2004; Elosegui et al., 2006.), in volcanology (Mattia et al., 2004), and in tsunami hazard evaluation (Blewitt et al., 2006). Sometime this technique is applied in "a posteriori", meaning that the data collected by the GPS stations are reprocessed and analysed, but the great potential of HRGPS is surely related to its application in the field of real time processing and to the big interest of the civil protection authorities in following dynamic processes related, for example, to the opening of a fracture field or to a dome extrusion during a volcanic eruption. Since 2002, the INGV (Istituto Nazionale di Geofisica e Vulcanologia) section of Catania (Italy) manage two real time high rate GPS networks in Stromboli and Etna volcanoes. In order to improve our capability to evaluate the volcanic risk and our knowledge of the deformative processes linked to magma movements at shallow depths, we developed a software tool finalised to the analysis of HRGPS data. This software tool, named iGeoPS©, runs in Matlab© framework and permits to analyze long series of HRGPS data sampled with any frequency. In particular, the tool can visualize raw data, statistically filter the raw data, sidereally filter the data, calculate power spectrum for specified windows (both in time and frequency content), display spectrograms of the signal, calculate statistics and RMS of the scatter of the data, and perform cross-correlation and trend analysis for different series. Moreover, iGeoPS© allows to do advanced non linear analysis such as fractal and chaotic analysis and integrates different non linear modelling techniques such as neural networks, fuzzy systems and wavelets. In this paper, after a brief introduction to the features of the developed tool, we summarize the main results related to the characteristics of the HRGPS signal and to the main volcanic events observed using this approach. Furthermore we show an analysis of data collected since 2003 on Mt.Etna where phenomena related to explosive activity, opening of fractures, tidal effects etc, clearly define the potential of this technique in volcano monitoring.