Physical Sciences and Mathematics Commons^™

Use Of Principal Component Analysis To Determine Down-Hole Tool Orientation And Enhance Sh-Waves, Paul Michaels

CGISS Publications and Presentations

A common problem in down-hole shear wave surveys is the determination of the tool rotation relative to the seismic source polarization direction. This paper reports an algorithm which has been developed to solve for this angle in the horizontal plane. The method employs Principal Component Analysis (PCA) to determine the angle from the large motion of the SH-wave (not first motion). Once the angle is known, the horizontal component data may be rotated so that one component is aligned with the source polarization, and the other orthogonal to it.

Significant findings include the following. First, subtraction of oppositely polarized source …

Use Of Engineering Geophysics To Investigate A Site For A Bridge Foundation, Paul Michaels

CGISS Publications and Presentations

The Idaho Transportation Department (ITD) commissioned a geophysical study to aid in the design of a replacement for an existing concrete span bridge. Because the river current was too swift to place geophones in the river, the solution was to shoot p-wave profiles in a reciprocal geometry (phones on land, shots in the river). In addition to the refraction work, a down-hole seismic profile was acquired to calibrate the surface data. Geotechnical boreholes drilled on the north and south river banks detected a laterally varying soil profile. The south-bank hole encountered 9.1 m of granular overburden, followed by 8.5 m …