Geotech Blastcorder I don't recognize this specific instrument, but most likely it's designed to record vibrations from dynamite blasts. There is a standard that says a particle velocity of 2-inches/second is the threshold for creating damage to structures. Whenever people use explosives for one reason or another, such occasions are followed by damage claims from the neighbors, even for cracks full of dirt and cobwebs that have obviously been there for years. To try and introduce some logic into the legal process, the blasters will set out instruments to record the actual vibrations around the area of the explosions (also works for pile driving or even big trucks). The vibration records are used in the lawsuits. The instrument consists of a 3-axis set of geophones (seismometers to you earthquake fans), some amplification, an automatic triggering device, and a means to record the maximum velocity (such as a strip chart recorder). Judging by the knobs, this one looks like an antique. Modern versions of this instrument are fully solid state (using digital memory to store the information) stand-alone devices that connect to a PC for much more complete analysis of the data. Normally, the systems contain a vertical and two horizontal 4.5-Hz geophones, which one of the PSN group might like to salvage as a sensor for local events. The strip chart might be usable if working and if you can still get paper for it, as would the fiberglass carrying case. In other words, buy it for the parts but don't pay too much. Doug Crice __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>