Site Effects on Seismic Waves at Santiaguito Volcano, Guatemala (2009)

Undergraduate: Jacob Anderson

Faculty Advisor: Jonathan Lees
Department: Geology

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Santiaguito is an active volcanic complex consisting of four dacitic domes, one of which is currently erupting. A five-day 2009 seismic study revealed that seismic waves undergo changes in frequency and amplitude between the active vent and deployed sensors. A station on top of an inactive dome recorded a narrower band of frequencies than the source signal and had unusually low amplitudes, while another station of equal distance from the vent on flat terrain recorded a frequency range and amplitude closer to that of the source. Further, it was found that events with an above-median source amplitude had strong low frequency (<.5 Hz) components, below the inactive dome's main recorded spectrum. These events also had the greatest amplitude loss between the source and the station. I propose that the dome has a natural spectrum at which it vibrates preferentially and resists vibration at other frequencies.