Jim -- I'm not sure what the magnitude of the expected strain is or how protected the area is from vandalism, but here's some suggestions: A frequently-used and very inexpensive method to measure horizontal strain across a fault is to drive stakes at A and B (one on each side of the fault, perhaps a meter on each side) and perhaps 5 meters apart along the fault: stake-A C-stake ========================================================fault stake-D B-stake Anchor a wire to one of the stakes and stretch it along to the other one, where it is attached by an extension spring. Measuring the length of the spring with a caliper, and compensating for change in the length of the wire due to thermal expansion, gives a measure of strain along the fault. A variation is to drive four stakes and to measure A-B, A-D, C-B, and D-C. This gives a vector of movement and also gives redundant measurements for checking. For more cost, a quartz fiber instead of the wire will improve temperature stability, and use of an LVDT instead of the calipers will improve measurement resolution and stability. And you can build a shelter over the apparatus to improve things even more. Regards, Karl Cunningham karlc@....... At 12:44 5/20/2000 -0700, you wrote: >Sean Thomas et al,.. > >A student at UNLV would like to measure movement across some fissures in >Las Vegas. The fissures are cracks in the soil (deep alluvium) about 10m >long in an area of mapped faulting. I was wondering if strain meters >would do the trick, the cheaper the better,and can you recommend or >suggest any methods or devices that would work? __________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>