We evaluate three identifiers of continental mantle earthquakes motivated by surface-wave normal-mode theory, the amplitude ratio of Sn to Lg, and the frequency content of Sn and of Lg, after wave propagation through continental crustal thinning. These methods are flexible and easy to apply, allowing for potential new discoveries of unusual continental mantle earthquakes, but they rely on guided waves whose propagation is dependent on the uniformity of their waveguides. For a range of Moho models, we perform 2.5D axisymmetric simulations that reach the conventional distance and frequency ranges of observational studies, and we compare results from four different source depths straddling the Moho. Using our synthetics and also six south-Tibet earthquakes recorded by an array in Bangladesh, we show that our Sn/Lg identifier is robust in the presence of crustal thinning on the continents, but the identifying frequency contents of Sn and Lg are easily obscured.