Seismic Velocity Measurement Method
Original Publication Date: 1985-Dec-01
Included in the Prior Art Database: 2005-Feb-19
A method is disclosed for continuous and precise measurement of seismic velocities for the purpose of earthquake prediction or oil, water or mineral exploration, and monitoring changes in mechanical properties of the earth's crust. A device that converts light into sound efficiently, such as a lance 1 (Fig. 1) is rammed into the ground at the location where the seismic velocity is to be measured. Lance 1 comprises a hollow cylinder, terminating in a cone 2, filled with a suitable light absorbing substance 3 having a high thermal expansion coefficient to insure efficient sound generation. The optical density of the absorbing substance at the excitation wave length is chosen such that a single pulse (or continuous pulses) from a laser 4 (Fig. 2) is absorbed throughout the length of the absorbing substance.