Albuquerque Seismological Laboratory
Martin Marietta GSN systems
Table C contains only stations using Martin Marietta data loggers.
In August of 1986 the fledgling IRIS sent out a request for proposal which included broadband digital data acquisition systems for the planned Global Seismic Network (GSN). Several early installations (termed IRIS1) were installed. These were non-standardized instruments with each being somewhat different from the previous.
In the fall of 1989 an agreement for 10 standardized instruments was made with the Martin Marietta Corporation of Glen Burnie, Maryland. Their first instrument became operational in March of 1991 with installations continuing until March of 1993. Though most of these instruments have been phased out, some of the original 1991 installations are still operational. Martin Marietta lost the bid to Quanterra for the next phase (IRIS2) of the GSN.
The error in the FIR delay calculation appears to have passed on from the Martin-Marietta instruments to the Quanterra systems. While the filter cascade at the highest sample rates is different from the Quanterra Q680 systems, the relative variation of the time tags between the lower sample rate channels is exactly the same as in the Quanterra systems.