VARIABLES AFFECTING IN SITU SEISMIC MEASUREMENTS

Variables which can affect the accuracy of in situ measurements of compression and shear wave velocities by the crosshole and downhole seismic methods are discussed. Requisite components in these methods for accurate field measurements are: mechanical sources which are strong, directional and repeatable shear wave generators; receivers with proper coupling, orientation and frequency response; recorders with accurate timing and proper frequency response; precise and consistent triggering systems; and well-trained personnel. Measurements of wave velocities are also affected by soil disturbance, borehole type and array, and data collection and analysis procedures. In general, the most significant errors result from improper triggering, borehole disturbance and casing effects, and the lack of borehole verticality measuremetns. Added together these variables can cause errors greater than 100 percent in measured wave velocities. A data collection procedure employing interval travel times with trigger and channel delays which minimizes these errors is presented. /Author/

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 919-939

Subject/Index Terms

Filing Info

  • Accession Number: 00179789
  • Record Type: Publication
  • Report/Paper Numbers: Proceeding
  • Files: TRIS
  • Created Date: Oct 12 1978 12:00AM