The presented approximate formulas yield a critical value of anisotropy parameter sigma, for which an incipient off-axis SV-wave triplication occurs in transversely isotropic media. The formulas are simple but approximate the exact solution with a high accuracy. The best results are obtained using the third-order approximation, which yields accuracy at least 30 times higher than the formulas presented by Thomsen and Dellinger (2003). The formula works safely for parameters kappa=a33/a44>2 and 0.2>epsilon=(a11-a33)/2a33>-0.2, and yields critical values of sigma from 0.1 to 0.7. Outside this interval, it is recommended to use an exact solution.
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