MULTICOMPONENT STRAIN SEISMOGRAPH.
Quarterly rept. no. 4, 1 Apr-30 Jun 66.
GEOTECH GARLAND TX
Pagination or Media Count:
Verification of the correct phase response of the variable capacitance transducer has permitted the running of several tests to investigate phase discrepancies in the vertical strain seismometer. An indicated 20 degree phase shift has led to planning of more tests to determine whether the magnetostrictive calibrator or the instrument itself is the contributing factor. During this quarter, modification of the horizontal strain seismograph housing and drilling of a new borehole with compliant casing were completed. All instruments have been returned to operation with the vertical strain seismometer operating in the new plastic-cased borehole. Preliminary strain measurements of Rayleigh waves from a limited number of earthquakes indicate that the plastic-cased borehole is yielding as much as a factor of 4 more strain than the steel-cased borehole. Routine recording of strain seismic data, interrupted by Retrofit I and II and the drilling of the new strain borehole, has been resumed. Strain data, recorded during the preceding quarter, has been processed to examine the similarity of recordings by the vertical strain and inertial seismographs. Three 200-second microseismic noise samples are also being processed digitally to compare spectra and phase measurements among the strain and inertial seismograph signals.