Abstract
Abstract. Manifestations of disturbances in the lower ionosphere caused by a complex series of earthquakes (the strong earthquakes with M = 7.3 and M = 9 – known as M9 Tohoku EQ – and the subsequent aftershocks) that occurred near the Japanese island of Honshu have been considered with the use of monitoring measurements of the amplitude of lightning electromagnetic signals (atmospherics) received at Yakutsk. Some data of one-point lightning location systems have been compared with the data of the WWLLN network. The analysis of hourly values variation of the atmospheric amplitude passing over the earthquake epicenters shows that during the initial period (the strong earthquakes on 9 March and 11 March) a typical pattern of variations was observed. It was manifested in the increased amplitude after both earthquakes. There were also possible precursors in the form of the increase in amplitude 12–14 days before the events. Though the focuses of these earthquakes were very close to each other, the registration of both precursors may indicate that both of the lithospheric processes developed to a certain extent independently. During all the days of the atmospheric amplitude enhancement the quasi-periodic variation trains were recorded. Together with the delay of earthquake effects relative to the time of the events, they may testify in favor of transferring the energy of lithospheric processes into the lower ionosphere by means of atmospheric gravity waves.
Highlights
The search for earthquake (EQ) precursors is carried out in many directions, but no method of confident prediction for these catastrophic natural phenomena has been found yet
The analysis of variations of hourly amplitude values of the atmospherics passing above the area of EQ epicenters near the Japanese islands in March 2011 shows that during the strong EQs on 9 and March a typical pattern of variations, which we associate with seismic events, was observed days before them (Mullayarov et al, 2007, 2011)
It is known that atmospheric amplitudes are distributed according to the log-normal law, i.e. the amplitude dependence of the number of atmospherics can be approximated by an exponential dependence (Remezov, 1985)
Summary
The search for earthquake (EQ) precursors is carried out in many directions, but no method of confident prediction for these catastrophic natural phenomena has been found yet The reason for this is that each EQ is a unique event. In our opinion, a short-term EQ prediction is possible only with a set of methods used simultaneously These methods include monitoring of disturbances in the lower ionosphere caused by seismic processes that precede the EQs. Due to small values of the electron concentration, it is difficult to register the disturbances in the lower ionosphere (D-layer) with ionosondes, the disturbances of the sporadic layers in the E-region are found in connection with the forthcoming EQ (Liperovsky et al, 2005; Liperovskaya et al, 2006). The complexity of lithospheric events was to be manifested in the complex sequence of disturbances in the lower ionosphere, so the effect it produced
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