A borehole logging device for obtaining shear wave velocities in formations adjacent the borehole, a device which utilizes a closely controlled, relatively low frequency torsional shear wave. The system includes an elongated housing for suspension within the borehole, said housing including a shear wave...http://www.google.com/patents/US4394754?utm_source=gb-gplus-sharePatent US4394754 - Apparatus for low frequency torsional shear wave logging
