SCIGN Steering Committee chair: Tom Herring

SCIGN is an array of Global Positioning System (GPS) stations distributed throughout southern California with emphasis on the greater Los Angeles metropolitan region.

• SCIGN web site

  For information about the Southern California Integrated GPS Network: station information, photos and maps, the SCIGN data policy, archives, administration, and other related links.

• SCIGN Unveiling Event

  SCIGN celebrated completion on July 6, 2001. For photos and full transcripts of the event, see the SCEC Instanet on-line article.

2004 Annual Report

SCEC has served as the managing organization of SCIGN since 1996. The network was completed in 2001 and we have been actively pursuing a long-term strategy for the maintenance of the SCIGN network and the archiving and availability of the data for basic and applied research applications. In 2004, a long-term strategy was developed by SCEC/SCIGN in collaboration with UNAVCO/PBO and other western US geodetic networks.

The plan will include the transfer of maintenance of 125 SCIGN stations to UNAVCO/PBO by 2007. The USGS will continue to maintain 95 stations in the array from its Pasadena office. The remaining 30+ stations will be maintained by UCSD through funding provided by the California Spatial Reference Center (CSRC) and by local county surveying agencies in Orange, Riverside, and San Diego counties.

SOPAC (Scrips Orbit and Permanent Array Center at UCSD) provides ongoing infrastructure support for geodetic studies of crustal deformation in southern California under the umbrella of SCIGN. They have responsibility for archiving SCIGN GPS data and data products, parallel responsibility (with JPL) for generating daily position time series, and responsibility for maintaining 20% of SCIGN sites (the other 80% maintained by the USGS). We highlight 2004 highlights in the areas of archive, web applications and cyberinfrastructure, fieldwork, and data gathering and analysis at SOPAC.

Archive

• Retrieval of data from the SOPAC archive, including SCIGN data, continued to increase. In 2003, about 20M files were transferred by ftp (about 90% of the transfers were RINEX files). Of these, more than 3M were SCIGN data files. Up to the end of October, more than 18.2M files have been retrieved in 2004. In 2003, we identified about 2300 unique host addresses and 52 client domains retrieving SCIGN data. More extensive statistics can be found on the SOPAC homepage.
• Archived on-line 1 Hz raw receiver data (and instantaneous positions) from 40 SCIGN stations (see ftp/http://garner.ucsd.edu/pub/highrate/). In terms of storage requirements this is equivalent to 1200 sites at a 30 s sampling rate. Real-time data streams through TCP/IP are available for all stations except the 13-station Parkfield network, which does not have a fast Internet link. Latency of the data streams is a fraction of a second on a wired connection and 1-2 s for cellular modem connections used by surveyors and others for network RTK.
• Connected a redundant 1GB fiber link between SOPAC’s computer room and SIO's network switch. The SCIGN archive is now only three hops from the Internet and has two separate gigabit wide area connections to the outside world, providing redundancy and increased bandwidth.

Web Applications and Cyberinfrastructure

• SOPAC developed an XML for Geodesy webpage and completed the schema definition for site log metadata.
• Initiated participation in the five-year NASA REASoN project “GPS Products for the Solid Earth Sciences.” SOPAC’s primary responsibilities are to design, develop, and implement the SCIGN cyberinfrastructure, including redesign of the SCIGN web page, and participate in the production of higher-level data products.
• Improved the design and utility of the SOPAC Online Map Interface (SOMI). We added a query and export feature and a velocity toolbox to display velocity vectors in various reference frames.
• Created a new Java based application to view coordinate time series. The oldest time series now span nearly 14 years.
• Enhanced the SECTOR application for determining epoch ITRF coordinates.

Field Work

• Upgraded SCIGN stations in four southern California counties (Imperial, Orange, Riverside and San Diego) and the Parkfield Network to real-time (<1 sec latency) high-rate (1 Hz) operations to support traditional geodetic, as well as seismic applications (see next section). There are now 40 upgraded stations with the distribution as follows: Parkfield Network (14), Imperial County (5), Orange County (10), Riverside County (8), San Diego County (3), and all remaining SCIGN sites in the four counties are in the active upgrade queue (. In the Parkfield network and Orange County we’ve installed a dedicated radio communications network. In Imperial, Riverside, and San Diego Counties we are using UCSD’s HPWREN communications backbone and ROADNet infrastructure, and the backbone of the three counties and the Metropolitan Water District of Southern California (MWD). See a map of upgraded stations.

Data Gathering and Analysis

• Computed, analyzed (and archived) instantaneous relative positions (Bock et al., 2000) for 40 SCIGN stations.
• Recorded teleseismic waves from the 3 November 2002 Mw 7.9 Denali fault earthquake with 1 Hz data from the Orange County Real Time Network (Bock et al., 2004). Our experience with the Denali fault earthquake confirmed the detection of seismic waves by Nikolaidis et al. [2001] based on 30 s SCIGN data collected during the 1999 Hector Mine earthquake.
• Recorded the 22 December 2003 Mw 6.5 San Simeon earthquake with 1 Hz data from the Parkfield network. The closest site to the earthquake was CRBT (35 km away). These data were used to detect seismic motion and model fault slip (Hardebeck et al., 2004; Ji et al., 2004).
• Characterized the errors in instantaneous positions and the sensitivity to the detection of fault slip and seismic displacements (Langbein and Bock, 2004). Characterized signal and noise in daily coordinate time series (Williams et al., 2004).
• Recorded 1 Hz data for the 28 September 2004 Mw 6.0 Parkfield earthquake. Published a global plate motion model (Prawirodirdjo and Bock, 2004) and updated this model once per month.

SCIGN Network Coordinator Report

Real Time

SCIGN is currently upgrading stations to real time high rate data collection in partnership with county and city agencies. The Los Angeles City Surveyor, the Port of Los Angeles and Metropolitan Water District have agreed to fund upgrades of 9 SCIGN stations to support real time data streaming back to the US Geological Survey office. Their contribution will be used to purchase hardware for SCIGN stations and to fund continued development of SCIGN real time software. Also, the US Geological Survey will leverage these contracts to upgrade several other stations in SCIGN in the Los Angeles basin and surrounding areas.

Site Status

The extremely durable building procedures used in SCIGN have given the stations extreme longevity and little troubles with much of the equipment. Failures in equipment boxes and other metallic parts have been most notable in sites in the Channel Islands. Also, the Ashtech Z12 receivers currently used in SCIGN are againg and we have noticed an increase rate of receiver failures. We have sent all of our receivers for repair by the manufacturer before the official end-of-life date for the equipment. From this point on, none of the Z12 receivers will be repairable.

Most of the problems with the stations have centered around communication issues such as phone lines or radio problems. We have been aggressive in trying to remove phone line telemetry within SCIGN and work with our stations hosts to use existing ethernet telemetry or to install more reliable radio telemetry. The majority of the SCIGN stations have little to no problems and the majority of the stations with problems we are able to repair quickly and completely.