Reference : Tectonic vs. shallow origin of geodetically inferred ground movements: an NE Ardenne ...
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Tectonic vs. shallow origin of geodetically inferred ground movements: an NE Ardenne (Belgium) case
Demoulin, Alain mailto [Université de Liège - ULiège > Département de géographie > Unité de géographie physique et quaternaire (UGPQ) >]
Vliegen, Bernard [> > > >]
Charlier, Robert mailto [Université de Liège - ULiège > Département Argenco : Secteur GEO3 > Géomécanique et géologie de l'ingénieur >]
Earth and Planetary Science Letters
Elsevier Science Bv
Yes (verified by ORBi)
[en] crustal ; movement ; leveling ; loading ; Western Europe ; holocene
[en] In order to get a better insight into the temporal pattern of height change variations in a moderately seismic intraplate area, a 1 km long section has been weekly leveled from April, 21, 1997 to January, 12, 1998 in NE Ardenne (Belgium). As this section is located very close to a small reservoir of 25 X 10(6) m(3), it also allowed the influence of lake level variations on the nearby ground motion to be studied. The measured height difference variations show a maximum amplitude of 3.45 mm, with weekly values not exceeding 1 mm. A two-dimensional (2D) finite element modeling confirms that waterload variations in the lake are the primary cause of movement of the section, inducing maximum ground subsidence of about 2 cm and seasonal tilting of 3-4 mu rads within a range of 2-3 km. We also show that a fault passively alters the spatial distribution of the waterload-dependent movements. The removal of this component from the observed ground motion leaves oscillating residual displacements characterized by an amplitude of 1-1.5 mm and a 'period' of about 2 months. We demonstrate that these displacements are independent of rainfall and probably of groundwater fluctuation too. Although most of the residual motions take place on the fault straddled by the leveling section, no credible mechanism can be found to ascribe these motions to a tectonic process. (C) 2000 Elsevier Science B,V. All rights reserved.

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