Modification of the ionosphere before the strong earthquake of january 13, 2007 with magnitude <i>М</i> = 8.1: An integrated approach

A study was carried out of vertical sounding data collected by two ground-based vertical ionosondes Wakkanai and Kokubunji, situated within the preparation zone of an earthquake with a magnitude of M = 8.1, which occurred on January 13, 2007 at 04:23:21 UT east of Simushir Island and was the second of a sequence of two strong (M >8) earthquakes on November 15, 2006 and January 13, 2007, which were unique events in the seismic history of the Middle Kuril Islands. A comprehensive analysis of ionospheric data showed that 13-14 hours before this earthquake, specific anomalies in the E- and F-regions of the ionosphere were simultaneously observed over both ionospheric stations, which, with a high degree of probability, were its short-term ionospheric precursors. It is shown that additional consideration when analyzing ionospheric data of the behavior of the Barbier δ-parameter, constructed on their basis, significantly increases the correctness of identification of detected ionospheric earthquake precursors in complex situations.