The primary application is in slope stability.
Numerous examples can be found in the Slope Stability Verification Manual in the Verification section of the Online Help.
While the seismic load option is primarily for slope stability applications, the following comments from Evert Hoek regarding seismic loading of tunnels may be of interest:
There are indeed ways of estimating seismic effects on tunnels and probably the best known US author on this is C.H. Dowding (Dowding, C.H., and Rozen, A., ‘Damage to Rock Tunnels from Earthquake Shaking’, Journal of Geotechnical Engineering Division, ASCE, Vol. 104, No. GT2, Febr. 1978.)
A quick search online should result in a few case histories of tunnel problems related to earthquakes.