Abstract
Abstract. Electromagnetic phenomena, especially those in the Very Low Frequency/Low Frequency (VLF/LF) bands are promising for short-term earthquake prediction. Seismo-ionospheric perturbations cause a variety of changes in different receiver-transmitter VLF/LF signal paths. Therefore, independent and simultaneous observations at different points thus in different VLF/LF signal propagation paths are necessary to better predict the earthquake. Most of the previous research on VLF data have been based on one path or limited number of paths which examined perturbations in the time domain and less attention has been paid to estimate the location of the earthquake. In the present research, using wavelet analysis, the temporal variations of seismo-ionospheric perturbations and the approximate time of earthquake are predicted. Clear disturbances are observed two weeks before the Kumamoto earthquake happened in Japan in 2016. The novelty of this study is to present an approach called Intersection-Union method to predict earthquake location. Based on the geometry of a VLF/LF network, the Intersection-Union method was introduced to estimate the earthquake epicenter. This method is based on the overlay of earthquake occurrence probable areas. With simultaneous use of different propagation paths by the Intersection-Union method, an area with a radius of about 300 km was determined as the probable location of the earthquake epicenter. The accuracy of the proposed method is 300 km compared with 1000 km accuracy of other earthquake location prediction scenarios.
Highlights
Earthquake is one of the most important natural hazards that has always caused great human and financial damages
As Japan is located in the seismic belt of the world, an integrated network of transmitters and receivers of Very Low Frequency/Low Frequency (VLF/LF) waves has been established throughout the country
Since the VLF/LF method consists of an integrated measurement, it is possible to correlate many pre-earthquake effects to the ionosphere of any earthquakes happening within the sensitive area of the transmitter-receiver great circle
Summary
Earthquake is one of the most important natural hazards that has always caused great human and financial damages. Since the VLF/LF method consists of an integrated measurement, it is possible to correlate many pre-earthquake effects to the ionosphere of any earthquakes happening within the sensitive area of the transmitter-receiver great circle. This is the main advantage of VLF/LF method (Hayakawa, 2016). The main advantage of an integrated VLF measurement is that the observed signal is sensitive to all earthquakes near the propagation path between the transmitter and receiver which facilitates data collection on VLF anomalies (Hayakawa et al, 2018). Due to lack of comprehensive reports on VLF/LF data and methods for earthquake prediction from spatial perspective, despite a number of research on the use of geospatial information systems (GIS) in earthquake prediction with various methods, we believe that the present study is among the first researches in using GIS to assist earthquake prediction through VLF/LF signals and data along with its accuracy assessment
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