Derived gravity field of the seismogenic upper crust of SE Germany and West Bohemia and its comparison with seismicity |
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Authors: | J ?vancara J Haví? W Conrad |
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Institution: | (1) Institute of Physics of the Earth, Masaryk University, Brno, Czech Republic;(2) Haydn Str. 8/912, Leipzig, Germany |
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Abstract: | The gravity field of the seismogenic upper crust was derived from the Bouguer gravity map by applying the Butterworth high-pass
filter in the wave-number domain. The cutoff wavelength of the filter was 110 km, to pass the gravity signals of structures
within the 18 km thick seismogenic layer. The derived residual gravity map reveals potential stress concentrating structures,
which may cause seismicity provided they lie within the existing zones of weakness. Furthermore we derived a shaded relief
map of the horizontal gravity gradient, which highlighted the tectonic lines accompanied by density contrast. The directional
analysis of this map shows three dominant strike directions. The most prominent one is “the Hercynian” NW-SE strike direction
represented by the Franconian Line, the Gera-Jáchymov Fault Zone and the Elbe Zone. The second dominant strike is the Rhenisch
NNE-SSW trending represented by the Upper Rhine Graben Zone, Rheinsberg-Heldburg Line and several Proterozoic volcanic belts
in the Teplá-Barrandien Unit. The third pronounced trending of the ENE-WSW direction is represented by the Erzgebirge and
Eger Graben gravity low. The N-S trending Rostock-Leipzig-Regensburg Zone (Pritzwalk-Naab Lineament) is not distinctly reflected
in the derived gravity maps, although many fault segments have a meridian direction.
The relative reactivation potential of some pre-existing fault systems identified in the gravity map was studied with respect
to the wide range of the recent stress configuration determined in the West Bohemia/Vogtland region. The resulting diagrams
show that the steep NNW-SSE to N-S faults (represented by some segments of the Mariánské Lázně Fault Zone) are oriented favourably
for reactivation. On the contrary, the orientation of the ENE-WSW faults limiting the Eger Graben (Litoměřice Fault, etc.)
is unfavourable for reactivation for all dip values. |
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Keywords: | Bouguer gravity seismicity reduced stress tensor fault reactivation potential Mariánské Lázně Fault Zone Gera-Jáchymov Fault Zone Eger Graben Rostock-Leipzig-Regensburg Zone |
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