Helicopter vs. volcanic tremor: Characteristic features of seismic harmonic tremor on volcanoes
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|Title:||Helicopter vs. volcanic tremor: Characteristic features of seismic harmonic tremor on volcanoes||Authors:||Eibl, Eva P. S.; Lokmer, Ivan; Bean, Christopher J.; et al.||Permanent link:||http://hdl.handle.net/10197/7005||Date:||1-Oct-2015||Online since:||2017-10-01T01:00:20Z||Abstract:||We recorded high-frequency (> 10 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 50 Hz and could resolve a source of closely spaced pulses of very short duration (0.03-0.1 s) on zoomed seismograms. Volcanic tremor with fundamental frequencies above 5 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 35 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 40 km distance. We highlight similarities and differences between volcano-related and helicopter tremor in order to help avoid misinterpretations.||Funding Details:||European Commission - Seventh Framework Programme (FP7)||Type of material:||Journal Article||Publisher:||Elsevier||Journal:||Journal of Volcanology and Geothermal Research||Volume:||304||Start page:||108||End page:||117||Copyright (published version):||2015 Elsevier||Keywords:||Frequency gliding; Doppler shift; Harmonic tremor; Helicopter; Volcano||DOI:||10.1016/j.jvolgeores.2015.08.002||Language:||en||Status of Item:||Peer reviewed||This item is made available under a Creative Commons License:||https://creativecommons.org/licenses/by-nc-nd/3.0/ie/|
|Appears in Collections:||Earth Sciences Research Collection|
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