Abstract
The relative importance of magnitude and depth of an earthquake (EQ) in the generation of seismo-ionospheric perturbations at middle latitudes is investigated by using the EQs near the propagation path from the Japanese LF transmitter, JJY (at Fukushima) to a receiving station at Petropavsk-Kamchatsky (PTK) in Russia during a three-year period of 2005-2007. It is then found that the depth (down to 100km) is an extremely unimportant factor as compared with the magnitude in inducing seismo-ionospheric perturbations at middle latitudes. This result for sea EQs in the Izu-Bonin and Kurile-Kamchatka arcs is found to be in sharp contrast with our previous result for Japanese EQs mainly of the fault-type. We try to interpret this difference in the context of the lithosphere-atmosphere-ionosphere coupling mechanism.
Highlights
There have been found different kinds of electromagnetic precursors of earthquakes (EQs), and the presence of those seismo-electromagnetic precursors is recently considered to be an irrefutable fact, though the physics of these phenomena remains poorly understood. (e.g., Molchanov and Hayakawa (2008) [1], Hayakawa (Ed.) (2009, 2012) [2,3], Uyeda et al (2009) [4], and Hayakawa and Hobara (2010) [5])
The regression equation for each scatter plot is not so meaningful. This means that the EQ D seems to be not so important as compared with M in inducing the seismoionospheric perturbation at middle latitudes in this paper
Based on the data analysis for three years (2005-2007) for the propagation path of JJY-PTK, we have investigated the relative importance of M and D in generating the seismo-ionospheric perturbations for sea EQs in the Kurile-Kamchatka region
Summary
There have been found different kinds of electromagnetic precursors of earthquakes (EQs), and the presence of those seismo-electromagnetic precursors is recently considered to be an irrefutable fact, though the physics of these phenomena remains poorly understood. (e.g., Molchanov and Hayakawa (2008) [1], Hayakawa (Ed.) (2009, 2012) [2,3], Uyeda et al (2009) [4], and Hayakawa and Hobara (2010) [5]). The first type is the direct effects such as electromagnetic radiation from the lithosphere in a wide frequency range, while the second is the indirect effect such as seismoatmospheric and ionospheric perturbations as detected by means of propagation anomalies of transmitter signals in different frequency ranges. Liu (2009) [8] has presented the result on the statistical correlation of the foF2 in the upper ionosphere with EQs. This paper deals with the lower ionospheric perturbations detected by subionospheric VLF/LF propagation anomalies. Yakawa et al (2010) [6] have found that a significant correlation is established for an EQ with significant magnitude (M) ˃ 5.5 [9,10] and shallow depth (D) (D less than 40 - 50 km) These results are based on the observation in and around Japan (that is, mainly inland (or fault-type) EQs). We discuss this difference in the context of the lithosphere-ionosphere coupling mechanism
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