Helicopter vs. volcanic tremor: Characteristic features of seismic harmonic tremor on volcanoes
Helicopter vs. volcanic tremor: Characteristic features of seismic harmonic tremor on volcanoes
复制标题
DOI：
10.1016/j.jvolgeores.2015.08.002
复制
发表时间：
2015-10-01
影响因子：
2.9
通讯作者：
Vogfjord, Kristin S.
中科院分区：
文献类型：
--
作者：
Eibl, Eva P. S.;Lokmer, Ivan;Vogfjord, Kristin S.
我们在冰岛的Hekla火山记录到了频谱滑动的高频(>；10赫兹)谐波震动。质点运动曲线图表明震源较浅。我们在50赫兹的奈奎斯特频率下观察到了多达两个泛音，并可以在放大的地震记录上分辨出非常短持续时间(0.03-0.1Nyquist)的近距离脉冲源。在世界各地的不同火山上都观察到了基频在5赫兹以上的火山震动、频率滑动和/或与我们观察到的类似的重复源。然而，在赫克拉最近35年的地震观测中，没有观察到与火山有关的震动的频率、内容、持续时间和发生情况。详细分析表明，这次震动与直升机飞过火山有关。这项研究将直升机的GPS轨迹与直升机在不同距离的地震记录联系起来。我们展示了直升机的距离、旋翼数目和速度对在40公里距离内观测到的上下滑行的影响。我们强调与火山有关的震动和直升机震动之间的异同，以帮助避免误解。(C)2015爱思唯尔B.V.保留所有权利。
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. (C) 2015 Elsevier B.V. All rights reserved.