We show that shear modes in a neutron star crust are quite sensitive to the existence of non-uniform nuclear structures, the so-called "pasta." Due to the existence of the pasta phase, the frequencies of shear modes are reduced and the dependence on fundamental frequency is different from that on overtones. Since the torsional shear frequencies depend strongly on the structure of the pasta phase, one can probe the pasta structure in the crust from observations of stellar oscillations. This is difficult to do with other types of observations. In addition, by considering the effect of the pasta phase, we show the that it is possible to explain the observed frequencies in SGR 1806-20 using only crust torsional shear modes.
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