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Prototype documentation


Seismic rotation, curl of the seismic wavefield, represents a new observable which started beeing studied and analyzed namely in the past decade (Igel et al., 2012). Measurements of rotational ground motions are becoming relevant in a wide range of fields as it is documented also in two special issues devoted to advances in rotational seismology (Bull. Seis. Soc. Am, Vol 99, No. 2B, 2009, and J. Seismol, Vol 16, No. 4, 2012).

Rotaphone is a short-period mechanical sensor system designed to measure spatial ground motion gradients; it consists of geophones arranged in parallel pairs. The spatial gradients are used to evaluate seismic rotational componets, i.e., components of curl of the ground velocity. It is based on the patent CZ 301217 “Rotational Seismic Sensor System, Seismic Measuring Set Containing That System, and Seismic Survey Method” Published in Věstník Úřadu průmyslového vlastnictví in 2009 No. 49/2009, B6, p. 5, G 01V 1/143

Basic features:

  • Sensor system consisting of highly sensitive low-frequency geophones mounted in parallel pairs to a rigid frame anchored to the ground
  • Separation distance between geophones in a pair << lambda (a single-point measurement)
  • Collocated rotations and translations from one instrument (with the same instrumental charakteristics)
  • Each rotational component is determined from multiple geophone pairs, which allows us to perform in-situ calibration of individual geophones (simultaneously with each measurement)