AN EXPLANATION FOR THE HIGH ULTRASONIC VELOCITY IN INDIAN ROCKS*

It has been observed in the course of a detailed investigation that Indian granites exhibit high ultrasonic velocities in contrast to the specimens obtained from other countries. An attempt has been made in this paper to offer an explanation of this peculiar behaviour. Firstly, the initial internal pressure and initial velocity at the time of formation of rocks are calculated by using the experimental results for the changes in velocity with pressure in Indian, American, Japanese and Russian rocks. Besides this, standard curves have been computed using the above named parameters. Also, their possible influence on the high velocity values of Indian rocks, even under atmospheric conditions is studied. The effect of time of the formation of rocks at specific depths is also calculated in detail. As one of the results of this investigation, it comes out that under high pressure (deeper depths) it requires longer time to complete the processes of formation of rocks than under low pressure (shallow depths) and under high pressure a lot of stress energy can be stored i.e., the initial velocity becomes high when the rock is formed at great depths while at shallow depths a less stress energy can be stored and consequently less velocity values. Thus the combined effect of time and physical conditions at the time of formation of rock on the velocity in the rock at a given time is investigated. It can be seen here that the elastic behaviour of rocks with pressure will provide a clue to the possible petrogenetic history and also the approximate age of the rock.