Midlatitudinal manifestation of polar substorm and seismic energy realization in Vrancea
Heading:
| 1Bakhmutov, VG, 1Sedova, FI, 2Mozgovaya, TA 1S.I. Subbotin Institute of Geophysics of the National Academy of Sciences of Ukraine, Kyiv, Ukraine 2S.I. Subbotin Institute of Geophysics of the National Academy of Sciences of Ukraine, Kyiv, Ukraine |
| Kosm. nauka tehnol. 2006, 12 ;(1):057-063 |
| https://doi.org/10.15407/knit2006.01.057 |
| Publication Language: Russian |
Abstract: Using the concentrated seismicity zone of Vrancea as an example, it is shown that the main morphological sign in the geomagnetic variations spectrum before earthquakes is the near-midnight polar substorm when it is marked by the highest intensity and longest duration. The substorms manifest themselves both at a relative quietness and during storms. The main feature is an abrupt and notable increase of the H-component at mean and low latitudes. As the substorm manifestation is clearly related to the day and night time they may coincide with different phases of geomagnetic storm, which naturally affects the difference (gradient). It is the geomagnetic field difference that provides a trigger mechanism for seismic energy realization. We introduce the conception of the gradient «type» to which the earthquakes may be related. First of all, it is an isolated near-midnight polar substorm against a quiet background. The other types are associated with the version of the order of the midnight substorm with respect to the Dst-variation as well as the sudden commencement storm. On the example of the Vrancea earthquakes it is shown how the gradient type in the geomagnetic field changes the seismic characteristics.
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| Keywords: geomagnetic variations, morphological sign, seismicity zone |
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