Albuquerque Seismological Laboratory
Using the Internet to Distribute
Live Seismic Data from the
Global Seismographic Network
WOODWARD, Robert L., USGS, GD, Albuquerque Seismological Laboratory, Bldg. 10002, Kirtland AFB-E, Albuquerque, NM, 87115-5000; HALBERT, Scott, Allied Signal Technical Services Corporation, Albuquerque Seismological Laboratory, Bldg. 10002, Kirtland AFB-E, Albuquerque, NM, 87115-5000
We have developed a mechanism for distributing digital seismic data, in near-real-time, via the Internet. The seismic data are collected by USGS stations of the Global Seismographic Network at sites around the world. Data from these seismographic stations are used for a variety of purposes, such as earthquake reporting, tsunami warning, and nuclear monitoring. The data distribution mechanism, which we call the Live Internet Seismic Server (LISS), can support any number of simultaneous client connections. Each client connects to the LISS via the Internet and receives copies of the digital seismic waveform data which the server receives from the seismographic stations. Typical broadband seismic data records (at 20 Hz sampling) at the GSN stations contain about 30 s of data. As each record is filled it is sent, typically via the Internet, to the LISS server running at the USGS Albuquerque Seismological Laboratory. When a data record is received from a station, the LISS duplicates the record and sends copies to each client that is connected to the LISS. Latency of data obtained from the LISS is typically less than 30 seconds.
LISS's can be run in a chain, such that one LISS is a client to another LISS. In this way LISS's can be placed at different locations on the Internet to provide redundant paths for accessing the data. At present, auxiliary LISS's are running in Moscow and Beijing and these are forwarding data to the LISS at Albuquerque.
In our present version of the LISS the communication is essentially one way. That is, a client connects to the server and starts receiving data records. The client obtains data from different stations by connecting to different ports on the server. In the next generation LISS we hope to implement a simple command language, such that the client can query the server and customize the selection of data the client wishes to receive.
Data from 24 stations around the world are presently available via the LISS. In addition to distributing these data, the most recent 24 hours of data from each station are plotted in a manner resembling the popular drum style recording (helicorder) mechanism which is widely familiar to the public. These plots are updated every thirty minutes and are accessible via the WWW. These data plots, as well as more information on the LISS, can be obtained via the WWW at the URL: http://aslwww.cr.usgs.gov/Seismic_Data/liss.htm