Geomagnetic effect of the Albanian earthquake on November 26, 2019

Abstract

Background. The main cause of geomagnetic disturbances is known to be space sources, processes acting in the solar wind and in the interplanetary medium, as well as falling large celestial bodies. Earthquakes also give rise to geomagnetic effects. In accordance with the systems paradigm, the Earth–atmosphere–ionosphere–magnetosphere system comprises the single system where direct and reverse, positive and negative coupling take place. The mechanism of the earthquake effect on the magnetic field is poorly understood. A rock cracking, a fluctuating movement of fluids in pores, a corona discharge of the high-voltage static charge, etc., are thought to be the processes that give rise to the geomagnetic effect. In the course of earthquakes, seismic, acoustic, atmospheric gravity, and magnetohydrodynamic waves are generated, which provide for coupling between the subsystems in the Earth–atmosphere–ionosphere–magnetosphere system. Purpose of Work. The paper describes the possible response in the level of the geomagnetic field to the earthquake of 26 November 2019 that took place in Albania. Techniques and Methodology. The measurements were taken with the fluxmeter magnetometer at the V. N. Karazin Kharkiv National University Magnetometer Observatory. It delivers 0.5 – 500 pT sensistivity in the 1–1000 s period range over a quite large frequency band of 0.001 to 1 Hz. To study the quasi-periodic processes in detail, the systems spectral analysis of the temporal dependences of the horizontal (H, D) geomagnetic field components has been employed. It includes the short-time Fourier transform, the Fourier transform in a sliding window with a width adjusted to be equal to a fixed number of harmonic periods, and wavelet transform, simultaneously. The wavelet transform employs the Morlet wavelet as a basis function. Results. The quasi-periodic variations in the level of the geomagnetic field observed to appear with a 6 min lag and to last for 70–80 min could be due to the earthquake. These disturbances could be transferred by the magnetohydrodynamic waves. The quasi-periodic variations that were observed to appear with a 97–106 min lag and to last for about 130–140 min were most likely due to the earthquake. They were transferred by the atmospheric gravity waves with a period of 7–14 min. A relative disturbance in the electron density in the atmospheric gravity wave field was observed to be approximately 5.3%. The results obtained from observations of Albanian and Turkish earthquakes show agreement. Conclusions: The magnetic variations in the 1–1000 s period range that were observed to occur before and during the earthquake have been studied.