Study of Emergence Angle and Propagation Paths of Seismic Waves

Abstract

Travel-time curves are given for elastic waves through the earth in a region in which the velocity increases continuously with depth. These time-distance curves have been approximated by an equation of the form X=aT2+bT from which the velocity depth relation has been deduced. A new method for measurement of the emergence angle has been used and the values obtained agree reasonably well with those deduced from theoretical treatment of the time-distance curve. Formulas for the travel-time between any two points in the medium under consideration are derived. These formulas agree closely with two sets of direct measurements. In one of these the seismograph was placed at various distances directly beneath the explosion. In the second case it was placed at a fixed depth beneath the surface and the explosion was located on the surface at various distances. The approximate depth to bed rock is obtained from the time-distance curves by use of the formulas mentioned above.