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
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 glidingDoppler shiftHarmonic tremorHelicopterVolcano
DOI: 10.1016/j.jvolgeores.2015.08.002
Language: en
Status of Item: Peer reviewed
Appears in Collections:Earth Sciences Research Collection

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