In the interval method, travel times are measured between two receivers row (Figure 1) placed at different depths, thus allowing for better quality measurements (speed intervals).
Figure 1 - Diagram of down hole using interval method
When you have only one receiver, that is assuming that the pairs do not match a single impulse, the rate determined values are defined in the pseudo-range, allowing only an apparent better definition of the velocity profile. The obtained measurements make possible to calculate the correct time using 1.0 formula and the speed range of P and S waves, with the graph (Figure 6), with the following formula:
Figure 2 - Profile of seismic velocity with range method
With the calculated speed range is possible to calculate the density, the Poisson's ratio, the shear deformation modulus, the oedometric modulus, Young's modulus, the bulk modulus for each interval, with the formulas above. But the method has its limitations:
a) does not take into consideration the speed of the overlying strata;
b) is not applicable if t2cor < t1cor
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