To increase the speed and efficiency of shallow seismic SH-wave data recording and to decrease acquisition costs, we have designed, constructed, and tested a new velocity tool that detects horizontal movements better than standard horizontal geophones. A comparative evaluation of significant characteristics and field performances of this new detector was conducted through laboratory and field tests on two sets of receivers: one consisting of 24 prototypes of the new detector and the other consisting of 24 standard horizontal geophones. Laboratory measurements revealed similar behaviors of impedance curves and geophone responses for the two types of detectors, but the impedance amplitudes and the frequency-response amplitudes of the new detector were twice those of the standard geophones. However, comparison of the horizontal-to-vertical (response) ratios, proved that the new detector better discriminates (6 dB on average) between the horizontal and vertical excitements. Field data proved that the energy, the maximum amplitude in the trace, and the maximum reflected amplitude were always higher in the data recorded with the new detector, although only half the source energy was used. The extra cost and weight of the new detector should be outweighed by its advantages, such as higher sensitivity to horizontal motions, better energy efficiency, and greater cost effectiveness. When a wavefield can be interpreted as SH-waves, SH-wave records can be acquired without the traditional drawbacks such as acquiring two records in each shot position, preprocessing of each record, and the final trace-to-trace subtraction needed to produce a pure SH-wave record.
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|Titolo:||Comparison of standard horizontal geophones and newly designed horizontal detectors|
|Data di pubblicazione:||2001|
|Tipologia:||1.1 Articolo in rivista|