Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6439788 | Journal of Volcanology and Geothermal Research | 2015 | 10 Pages |
Abstract
We recorded high-frequency (>Â 10Â Hz) harmonic tremor with spectral gliding at Hekla Volcano in Iceland. Particle motion plots indicated a shallow tremor source. We observed up to two overtones beneath our Nyquist frequency of 50Â Hz and could resolve a source of closely spaced pulses of very short duration (0.03-0.1Â s) on zoomed seismograms. Volcanic tremor with fundamental frequencies above 5Â Hz, frequency gliding and/or repetitive sources similar to our observations were observed on different volcanoes around the world. However, this frequency content, duration and occurrence of volcano-related tremor was not observed in the last 35Â years of seismic observations at Hekla. Detailed analysis reveals that this tremor was related to helicopters passing the volcano. This study relates the GPS track of a helicopter with seismic recordings of the helicopter at various distances. We show the effect the distance, number of rotor blades and velocity of the helicopter has on the observed up and down glidings at up to 40Â km distance. We highlight similarities and differences between volcano-related and helicopter tremor in order to help avoid misinterpretations.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geochemistry and Petrology
Authors
Eva P.S. Eibl, Ivan Lokmer, Christopher J. Bean, Eggert Akerlie, KristÃn S. Vogfjörd,