[Media Release] Research at the University of Electro-Communications suggests how to identify anomalies due to geomagnetic storms in low frequency signals, which may help distinguish them from seismic activity.
January 28, 2016
A potential for earthquake prediction may lie in detecting anomalies in the propagation of very low frequency (VLF: 3-30 kHz) radio signals, as they are greatly affected by ionospheric disturbances that may originate from seismic activity. However there are several other possible causes for VLF anomalies, including terrestrial and space weather, many of which are little understood. In their latest work the UEC researchers help to shed light on how to distinguish VLF anomalies caused by geomagnetic storms that have no relation to seismic activity.
The UEC researchers, Kenshin Tatsuta and Yasuhide Hobara, in collaboration with S. Pal, also associated with the Indian Centre for Space Physics and M. Balikhin at the University of Sheffield in UK, analysed data from 16–21 independent VLF and low-frequency transmitter-receiver paths at different latitudes over 27 months. The transmitter-receiver paths ran at high-latitude (east to west), mid-latitude (east to west) and north to south. They considered statistical parameters including the average signal amplitude and variability of the signal amplitude, and compared changes in the VLF propagation characteristics with data of geomagnetic storm indicators.
The comparisons indicated that VLF propagation is far more likely to exhibit anomalies caused by geomagnetic storms at high latitude than those at mid latitude or north-south transmitter-receiver paths, where anomalies originating from other events are more commonly observed. Paths over land rather than water may be also better for revealing anomalies with seismic origins due to the difference in conductivity.
The UEC team concludes, “Although it is still uncertain that only VLF data can be used to assess the probability of future seismic activities, the characteristics of VLF signals can form a part of the set of parameters that will allow us to provide a warning of possible hazards.”
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