Study of seismic Propagation Paths and Regional Traveltimes in the California-Nevada Region
Semiannual progress rept. 30 Dec 1960-31 May 1961
GEOLOGICAL SURVEY DENVER CO
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The Crustal Studies Group investigated new seismic equipment for long-range seismic refraction profiling, shot-point to recorder communications, and timing. INSTRUMENTATION The seismic refraction system features a reel-to-reel magnetic tape recorder and a photographic oscillograph for recording seismic waves. The 8 seismic-amplifier outputs are displayed on the oscillograph at 2 levels of amplification separated by 15 db. The communications system consists of 3 HF allocations in the 3- to 8-mc range, for radiotelephone and shot-instant signaling when propagation conditions are good, and LF 180 kc for transmitting shot-time instants. SEISMIC FIELD OPERATIONS The adaptability of the seismic refraction system was shown in recording long-offset shots. GRAVITY STUDIES Studies are under way in the Southern Rocky Mountains, Colo., Sierra Valley, Calif. , Snake River Plain, Idaho, and Yellowstone Plateau. THEORETICAL STUDIES A digital computer is being used to calculate the frequency content of seismic waves. Studies were started into surface wave dispersion for Love and Rayleigh waves by using a digital computer program for calculating dispersion curves for reasonable models of crust mantle systems, where crust is defined as including all layers, from the surface down, lying above the layer having compressional wave velocity of about 8.1 km per sec.