If the amplitude for the case is anomalously low compared to the untroublesome and cases, this could indicate the energy is missing the receiver and thus the traveltime measurement should be regarded with suspicion. Unfortunately amplitude variations in such experiments can be caused in many ways, so this is not a reliable indicator.
Another cross check is possible because some of the elastic constants are overdetermined. In particular, (as we already saw) the key elastic constant C13 can be found from either the qP or qSV traveltime measurements; assuming the velocity measurements at and can be trusted, we can compare the values of C13 calculated from each of the two measurements independently as a check. There should not be a problem with both values of C13 erring in the same direction due to side-slip effects. Since the phase-velocity arrival time is the earliest possible, a ``partial miss'' must always result in a delay, resulting in a velocity measurement that is too low. The effect of such a mismeasurement on the calculated value of C13 depends on the wavetype; a too-slow qP phase-velocity results in finding a C13 (and ) that is too low, while a too-slow qSV phase-velocity measurement results in a C13 (and ) that is too high.
Probably the best way to estimate whether there might be significant side-slip problems, though, is to use the (possibly inaccurate) measured elastic constants to model the problem. Analytically, the side-slip velocity is simply .In the case of qP and qSV waves in transverse isotropy the total side-slip at can be expressed directly in terms of the core height H and the measured phase velocities:
Conveniently, these equations appear to be rather insensitive to the precise value used for the phase velocity; for our example could be varied by with only a 1mm resulting change in the calculated qP sideslip. (The denominator does start to blow up if , but hopefully this fact alone would already have suggested there just might be a problem!) If equations (7) or (8) indicate the total sideslip is greater than about half the transducer width for a given wavetype, extra care should be taken when interpreting the corresponding measurement as a phase velocity.