G22A-01
California Real Time Network: Test bed for earthquake early warning systems
More than 80 CGPS stations in southern California have been upgraded to a 1 Hz sample rate, including
stations from the SCIGN and PBO networks. The upgraded stations comprise the California Real Time
Network and provide continuous 1 Hz (upgradable to 10-20 Hz at some stations) GPS displacement
waveforms and troposphere delay estimates with a latency of less than 1 s. With funding from NASA, CRTN
provides a test bed for developing advanced in situ-based observation systems within a modern data portal
environment, which can be extended seamlessly to the entire PBO region and to other plate boundaries. We
describe a prototype early warning system for earthquakes using CRTN, which is also being deployed at other
plate boundaries. We demonstrate the elements of an earthquake early warning system by analyzing the 2003
Mw 8.3 Tokachi-Oki thrust earthquake off Hokkaido Island detected by the dense Japan national real-time
CGPS network. The network has an approximately 20-km spacing with 1156 stations streaming 1 Hz data to a
central facility. A Delaunay triangulation of the network is created every second and the 1 Hz displacements
within triangular element are converted to principal components of strain to detect the event. The large spatial
extent allows us to compute displacement waveforms relative to a station well away from the affected region
through a real-time network adjustment algorithm. We then compute the earthquake hypocenter through a grid
search and L2-norm minimization. The final earthquake source model is computed using the total
displacement waveforms, the earthquake hypocenter and the predetermined fault structure in the inversion
program Defnode. We finish by showing the method in action for the November, 2008 ShakeOut earthquake
scenario using CRTN. We show that more accurate earthquake source parameters can be obtained by utilizing
higher rate GPS up to 10-20 Hz.
http://sopac.ucsd.edu/projects/realtime/
G22A-02
Current and Future Real-time Data Requirements for Space Weather Applications
The US-Total Electron Content (USTEC) model is a GPS data assimilation model for ionospheric specification over the continental US (CONUS). The model ingests GPS data from the CORS (primary data stream), the real time IGS (RTIGS), and the GPS/MET (meteorological applications of the GPS) networks. Currently, there are about 80 CORS, 30 GPS/MET and 15 IGS stations ingested into the model. These data are characterized by a near-real time rates and very low latencies, of the order of a minute and a half for the CORS networks and just over 5 minutes for RTIGS data. Due to the processing time of the data assimilation scheme, the final products are published with about 13 minutes delay, and are updated every 15 minutes. Our future plans involve the development of multi-regional and global capabilities of the model, as well as increasing of the number of stations ingested from the three networks, and the assimilation of new data, such as FAA-WAAS and COSMIC radio occultation satellite data. To accomplish the aforementioned goals we are also considering the assimilation of data from regional networks (e.g. IHY-Africa, South America, Asia, EUREF, etc.) and from new platforms (e.g. ocean buoys).
G22A-03
Real Time Data From the Plate Boundary Observatory Continuous GPS Network
EarthScope's Plate Boundary Observatory (PBO) runs a network of 1,100 continuous GPS stations in North
America and has the potential to be a major provider of real-time GPS data for scientific research, hazard
monitoring and survey control. PBO is planning to implement real time data flow for its three volcanic
subnetworks (at Mt. Saint Helens and Alaksa's Akutan and Unimak Islands) to maximize the return of
scientifically important data to detect the onset of eruptive activity. GPS sites with collocated instruments for
meteorological measurement are also targeted for both GPS and met data streaming in the near future. On a
larger scale, the USGS and a handful of academic institutions are doing research on integrating GPS into
earthquake early warning (EEW) networks. The implementation of GPS-based EEW will involve real time
streaming from GPS sites on major faults and in areas of high seismic hazard, and PBO is partnering with the
USGS to help develop the first implementation of this early warning capability. Finally, planning is underway to
develop open statewide real time networks to serve surveying communities and the general public, and PBO is
positioned to be a key data provider for these efforts.
PBO has been operating a pilot program to provide real-time GPS streams to the public from 75+ stations from
the Salton Sea to Alaska. PBO's streaming data is provided exclusively via the NTrip
protocol, from servers located at UNAVCO headquarters in Boulder, CO. The formats supported are BINEX
and RTCM 2.3 at 1 second sampling, with RTCM 3.0 to be added in the near future. Access to PBO data
streams is currently unrestricted and users are free to rebroadcast these streams provided they do not charge
for these services. Our experience with this program indicates that we are technically capable of streaming
low-latency, real time GPS data from most of our network using existing telemetry, although PBO's IT
infrastructure would have to be upgraded to support an expansion of the current system.
http://pboweb.unavco.org/?pageid=107
G22A-04
PBO Integrated Real-Time Observing Sites at Volcanic Sites
The Plate Boundary Observatory, an element of NSF's EarthScope program, has six integrated observatories in
Yellowstone and four on Mt St Helens. These observatories consist of some combination of borehole
strainmeters, borehole seismometers, GPS, tiltmeters, pore pressure, thermal measurements and
meteorological data. Data from all these instruments have highly variable data rates and formats, all
synchronized to GPS time which can cause significant congestion of precious communication resources. PBO
has been experimenting with integrating these data streams to both maximize efficiency and minimize latency
through the use of software that combines the streams, like Antelope, and VPN technologies.
http://pboweb.unavco.org
G22A-05
Bringing High Rate, Low Latency Data From Unimak Island, Alaska
The Plate Boundary Observatory (PBO), part of the NSF-funded EarthScope project, completed the installation of a fourteen GPS stations, eight tiltmeters, one webcam, and one digital broadband seismometer on Unimak Island, Alaska in August, 2008. PBO collaborated with the USGS, who provided engineering support for this project. Combined with the USGS operated seismic network, the Unimak Island network is a state of the art scientific network. The primary data communications goal of the project was to design and implement a robust data communications network capable of downloading 15-sec daily GPS files and to test the streaming of 1- Hz GPS data at a select set of GPS stations on Unimak Island. As part of the permitting agreement with the landowner, PBO co-located the GPS stations with existing USGS seismic stations. The high-speed radio link deployed allowed the USGS to test the feasibility of broadband seismometer installations on Unimak Island. This collaboration with the USGS was another successful joint operation between PBO and the USGS. The technical and logistical challenges involved in the project as well as some preliminary results of the data communications system will be presented. These challenges include complicated logistics, bad weather, complex network geometries with multiple radio repeaters, long distance RF transmission over water, hardware bandwidth limitations, power limitations, space limitations, as well as working in bear country on an incredibly remote and active volcano.