Application of Digital Coordinate Transformation to a New Posthole Broadband Seismometer

Abstract

Most seismological instruments recording ground motion use three sensors oriented north, east, and upward. In this cardinal configuration horizontal and vertical sensors differ in their construction because of the gravitational acceleration affecting the vertical sensor. In order to solve this inconsistence, we have developed a new posthole broadband seismometer with Galperin’s configuration. In this arrangement three identical sensors are also positioned orthogonally to each other but are tilted at the same angle to the vertical axis. We have presented the nominal coordinate transformations used to derive the differential output signals X, Y, Z from the cube-corner-oriented sensor output signals U, V, W, including four types of corrections: orthogonal correction, sensitivity correction, tilt correction and orientation correction. In addition, the hardware circuit for the coordinate transformation matrix is also described in details.