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Jointing of the Earth’s Crust in the Garm Region Based on Statistics of Source Mechanisms of Weak Earthquakesстатья
- Авторы: Lukk A.A., Leonova V.G.
- Журнал: Izvestiya, Earth Physics
- Том: 14
- Номер: 8
- Год издания: 1978
- Первая страница: 564
- Последняя страница: 671
- Аннотация: The form and temporal stability of the distribution of dynamic parameters is analyzed for sources of small earthquakes (M > 1.5) observed in the Garm region for nine years. The spatial orientation of the principal stress axes at the earthquake sources is shown to have strong anisotropy. This suggests that deformation of the Earth's crust in this region occurs primarily along certain fault systems. Three prevailing directions are observed in the strike of the fault plane (0°, 50°, and 90°) with dip mainly in the 55-85° range. A formal method is used for the unambiguous choice of the fault plane. Since earthquake sources with 0° and 90° strikes of the fault planes have a greater spatial distribution, it is assumed that this "seismic jointing" determines the general structure of fracturing in the upper 5-10 km of the crust in the Garm region, up to the level of microfissures, and may lead to anisotropy of the medium's elastic properties. This jointing must comprise a dynamic system since considerable temporal variations are observed in the number of "fissures" with a 90° strike per unit volume ("closing" and "opening" of fissures). These variations may cause changes in the effective elastic moduli of the medium (especially the M modulus) due to variations in the force of friction betweenthe sides of the fissures, which may lead to the observed variations in velocity of the elastic waves during their propagation across the fissure system [1].
- Добавил в систему: Лукк Альберт Артурович