LISS Data to IRIS DMC
The USGS Albuquerque Seismological Laboratory (ASL) has processed digital seismic data for the distribution to scientists since 1972. We have provided GSN data to the IRIS DMC since 1988.
The processing of GSN data at the ASL Data Collection Center (DCC) has been primarily focused on the tape based data. We at the DCC receive a station tape with whatever latency is involved (usually 1 t o 8 weeks). We then QC the data and re-format the QC’d data into station-days and ship the final volume to the DMC. The data that we receive from LISS telemetry (see
www.liss.org http://earthquake.usgs.gov/monitoring/operations/) has been added ad-hoc to fill gaps in the tape data.
The latency to when the DMC gets each stations data is dependent on how long it takes for ASL to receive, via normal mail, the station tape. Some stations, like our local ANMO station, have no problems getting the station tape to the DCC and we generally have the data from ANMO to the DMC within one week of the tape being written. Some stations, like SPA in the Antarctic, have a limited ability to send station tapes, and the latency before we receive these tapes can be up to a year.
We are currently receiving LISS telemetry data from just about three quarters of the GSN stations that we process at the ASL DCC. We now have the software in place to begin the process of shipping data to the DMC with a single day of latency for the stations that transmit telemetry data. These data will be fully QC’d. When the station tapes arrive for these stations, we will then systematically fill gaps in the LISS data with the tape data. This represents a fundamental change in the order of business at the DCC. This change should be effective by the time this newsletter is published.
Other LISS News
The USGS computer network (GEONET) has over the summer undergone major changes. These changes have been the result of court orders, and have been implemented very quickly. A part of the changes has been to disallow DNS services to servers other than at the GEONET gateways. We had always provided our own liss.org name servers, and this change left some LISS users high and dry for up to a week as local ISP caches of DNS lookups were renewed. Our apologies go out to all who were inconvenienced.
The GTSN stations are in the process of being upgraded to SHI AIM248 digitizers. These new dataloggers export data as CD1 ‘alpha streams’. We have installed ‘alpha forward’ software at the ASL DCC and will soon make available these data as LISS miniSEED.
by Harold Bolton (Albuquerque Seismic Lab)