ARTICLE

Direct-S wave modes produced by vertical and horizontal vibrators

ENGIN ALKAN BOB HARDAGE
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Exploration Geophysics Laboratory, Bureau of Economic Geology, Austin, TX 78713-8924, U.S.A.,
JSE 2013, 22(2), 147–168;
Submitted: 7 August 2012 | Accepted: 15 February 2013 | Published: 1 May 2013
© 2013 by the Authors. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution -Noncommercial 4.0 International License (CC-by the license) ( https://creativecommons.org/licenses/by-nc/4.0/ )
Abstract

Alkan, E. and Hardage, B.A., 2013. Direct-S wave modes produced by vertical and horizontal vibrators. Journal of Seismic Exploration, 22: 147-168. Horizontal vibrators are considered to be the optimal source for generating direct-S modes, which are S modes produced directly at a source station, not by mode conversion at interfaces remote from a source station. We show some results of a field test in which we investigated direct-S modes produced by vertical-force seismic sources. The test data were acquired by positioning horizontal vibrators and various vertical-force sources (vertical vibrator, vertical impact, shot-hole explosive) at the same source stations and recording their downgoing illuminating wavefields with a vertical array of 3-component geophones. In this paper, we compare only direct-S modes produced by vertical vibrators and horizontal vibrators. We show that there are strong similarities between the direct-S modes produced by these two sources. This investigation has considerable economic value because if it can be established that direct-S modes produced by vertical-force sources can be substituted for direct-S modes produced by horizontal vibrators, a large number of direct-S sources become available that can be used in any environment where P-wave seismic data are acquired.

Keywords
direct-S
vertical force source
horizontal vibrator
vertical vibrator
P- and S-radiation
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Journal of Seismic Exploration, Electronic ISSN: 0963-0651 Print ISSN: 0963-0651, Published by AccScience Publishing