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Seismicity within the volcano is not well understood, but most is likely of volcanic origin. Both high- and low-frequency events are located at shallow depth and occur at a rate of almost two dozen per month. The low-frequency events are usually poorly recorded, and most are probably seismic signals generated by glacier movement. The shallow high-frequency events are usually well recorded and fall in the magnitude range -0.5 to 3.0. Epicenters appear to align in a NE-SW trend across the summit, and three available fault-plane solutions agree in general with this trend. Because of the difficulty in determining accurate hypocenter depths within the mountain, interpretation of this alignment as representing a fault zone or potential zone of weakness is premature. Moran et al. (1995) showed that the allignment is likely an artifact due both to poor station distribution before 1989 as well as to use of an inappropriate velocity model. Thus additional seismic velocity structure studies are needed.