S34A-01 INVITED
Real-time operation of the NSF EarthScope USArray Transportable Array
The Transportable Array (TA) component of USArray uses real-time telemetry to send data to the Array Network Facility (ANF) through a variety of satellite, mobile phone, wireless and wired communication links. The ANF is responsible for the timely delivery of metadata and waveform data to the IRIS DMC from the growing number of Transportable Array stations. The IRIS DMC makes these data available to the research community. The network has increased in size to 327 stations with 259 out of the 400 new TA sites installed (as of 28 February 2007). Starting in Fall 2007, equipment will start to roll from current stations to new locations to the east of the current footprint. Use of the Antelope software package has allowed the ANF to maintain and operate this extremely dynamic network configuration, facilitating the collection and transfer of data, the generation and merging of the metadata as well as the real-time monitoring of state of health of TA station data-loggers and their command and control. Four regional networks (ANZA, BDSN, SCSN, and UNR) as well as the USNSN contribute data to the Transportable Array in real-time. Although the real-time data flow to the IRIS DMC has been 93.4% over the last year, the ANF and the TA field teams have extended every effort and have managed to recover an additional 4.8% by recovering data from the local data storage device (Baler 14) at each station. Once the missing data is recovered, we then generate station-channel-day volume seed files, which are resent to the DMC to bring the total data recovery rate to 98.4%. The total network uptime is above 99%. Analyst review of automatic locations for the USArray network is being done at the ANF as part of the data quality monitoring strategy. All events are associated with the USGS and regional network bulletins. As of February 2007, around 13,000 weekly picks are being fully reviewed by analysts at the ANF and over 19,000 events have been recorded. We find a small percentage (about 10 %) of events that cannot be associated with existing bulletins. This information is used by the regional network operators to help them determine which TA stations may be beneficial to permanently add to their seismic networks. Operation of the USArray at the ANF has benefited by the real-time interface with the ORB and the Datascope database using PHP for display on the ANF website (http:anf.ucsd.edu) to provide station and system state-of- health information to field teams. Information available for all stations includes: location, maps, photographs, equipment deployed, communications, distribution of events recorded by each station, and displays of daily, weekly, and yearly state of health parameters as well as station noise spectra generated by the DMC.
S34A-02
Bolivian Seismic Network
One of the biggest challenges into the Seismic Network of Bolivia, composed of seven stations, is to connect all the differents characteristic of them. The Observatory San Calixto, network operator, is one of the few private seismic observatories in the world and for this reason is working only with agreement support or extern cooperation. This problem needs a promptly solution to obtain data system more convenient, in a real time, more effective and compatible with a future extension network. Now, we have differences in the equipment and transmission too. Two of our network stations, are part of the IMS (International System of Data), the information are transmitted by telemetry way from Primary Station PS6 (LPAZ) to OSC, and then by Vsat to IMS and by optic fiber to AFTAC. The auxiliary seismic station AS08 (SIV) sends information to DASE France by satellite way, and then DASE transmits to the IMS, and to the OSC by Internet. Similar situation is used for another station: MOC. The data of the other four stations are transmitted by telemetry to the OSC center, but here the difference with the other stations is that they are working with analogy system. This network does not cover all the Bolivian territory for a completed monitoring of the seismic activity of the country. For this reason it is very important for Bolivia to extend the network with installation of other stations and a project for the characteristic compatibility (formats specially) of this news stations with the actual stations and temporally stations. Temporally stations are mainly used to support the network and to obtain the evaluation of micro activity in some areas that have a possible seismic threat and because of the actual network distribution where the activity is unknown for us.
S34A-03
Adding seismic broadband analysis to characterize Andean backarc seismicity in Argentina
Characterization of the highly seismically active Andean backarc is crucial for assessment of earthquake hazards in western Argentina. Moderate-to-large crustal earthquakes have caused several deaths, damage and drastic economic consequences in Argentinean history. We have studied the Andean backarc crust between 30°S and 36°S using seismic broadband data available from a previous ("the CHARGE") IRIS-PASSCAL experiment. We collected more than 12 terabytes of continuous seismic data from 22 broadband instruments deployed across Chile and Argentina during 1.5 years. Using free software we modeled full regional broadband waveforms and obtained seismic moment tensor inversions of crustal earthquakes testing for the best focal depth for each event. We also mapped differences in the Andean backarc crustal structure and found a clear correlation with different types of crustal seismicity (i.e. focal depths, focal mechanisms, magnitudes and frequencies of occurrence) and previously mapped terrane boundaries. We now plan to use the same methodology to study other regions in Argentina using near-real time broadband data available from the national seismic (INPRES) network and global seismic networks operating in the region. We will re-design the national seismic network to optimize short-period and broadband seismic station coverage for different network purposes. This work is an international effort that involves researchers and students from universities and national government agencies with the goal of providing more information about earthquake hazards in western Argentina.
S34A-04
Monitoring on the Edge: The Need for New Regional Seismic Monitoring Technologies in the U.S. Pacific Northwest.
Regional seismic networks are relied upon to provide rapid information about a variety of ground motion hazards to stakeholders with diverse interests. This mission is increasingly complicated by the recognition of the importance of signals that are difficult for traditional seismic networks to monitor. Part of the strategy to meet these challenges should be a willingness to embrace non-traditional ground motion monitoring. In the Pacific Northwest region, for example, the recent discovery of episodic tremor and slip has made it important to understand the generation and propagation of what in previous times would have been dismissed as "background" microseism noise. Moreover, we are finding more frequent examples of earthquakes and tremor "triggered" by seismic waves from large regional or even teleseismic earthquakes. We have also found problems with broad-band seismic sensors that limit their use in accurately determining earthquake source parameters from even moderate-sized regional earthquakes. Great subduction zone earthquakes may be recorded on-scale only by accelerometers but recovering the displacement field quickly using data from these sensors (necessary to determine accurately the likelihood of tsunami generation) is tricky in the presence of the expected permanent ground tilts and rotations. Such diverse signals challenge the sensitivity, frequency response, dynamic range, and processing speed of regional seismic networks. We discuss how near-real-time data from high-sample-rate GPS monitoring, tilt-meters, borehole seismic arrays, small aperture surface seismic arrays, and infrasonic sensors may be used to extend the range of regional seismic network monitoring.