About The Wave Origin of The Horizontal Stresses Field In Fennoscandia.
Abstract
The analysis of display of the sources of earthquakes in time and space on the territory of Fennoscandia is held. The intraplate seismicity of the studied territory is conditioned, in general by strong horizontal pressing from the side of the North Atlantic spreading zone. The initial information for the analysis the catalog of the earthquakes of the Northern Europe for a period of 1900-1997 years was used. The material was introduced as temporary series of the originating of underground shocks along the profiles by latitude () and longitude () with a pitch of 1 month. The analysis was carried out separately for two areas. The first area is situated closer to spreading zone. It includes the Scandinavian caledonids and the region of the whereabouts of branching faults in a zone of junction of a continental part of Fennoscandia with Barents and Norwegian seas. The second area are introduced by the Fennoscandian shield. For the first of them the temporary series of 250 earthquakes with ? =3.5 - 5,4 and h=0-70 km by latitude () and longitude () are plotted. For the second area the temporary series of 1400 earthquakes with ? =1-5,4 and h=0-40 km are plotted. For these series the spectral - temporary analysis is held and the STA-diagrams are plotted. The analysis of the STA-diagrams reveals steady, precisely expressed 20-years' rhythm of the seismicity display on all studied territory. There are also observed another rhythms of more high-frequency, but less long (10-, 7-, 4-, 2-years). For weak earthquakes are characteristic 1,5-; 1-; 0,9-; 0,5-year's rhythms. The received results allow us to draw a conclusion that the field of horizontal stresses of Fennoscandia has wave nature. It gives rise to the deformation waves that are moving from Mid-Atlantic ridge to the South-East to Fennoscandia with the approximate velocity by 60 kms per year. This circumstance causes rhythmic character of the display of seismicity. It is remarkable, that in the studied territory the trails of the earthquakes (seismoscarps and landslides) are extended in rows by the North-East direction and parallel of the fronts of driving deformation' waves.
- Publication:
-
EGS General Assembly Conference Abstracts
- Pub Date:
- 2002
- Bibcode:
- 2002EGSGA..27.1229Y