Movements of the fault of the Lake of Cavazzo in connection with the local rainfalls

P. CALOI, M. MIGANI

Abstract


Undeniable witnesses are given for t h e existence of micromovements
of the fault of the Lake of Cavazzo (Tolmezzo) in connection
with local rainfalls. They are recorded as vertical rotations by the clinographic
stations incorporated into ENEL's power station of Somplago which
lias been blast out of the rock on t h e Western edge of the large fault of the
lake. The fault in itself, which extends probably down to the confluence
of the Jlelo torrent with the Tagliamento River at about 10 kins South
of the Station, lies in the NW quadrant of the vast alluvium area of the
Tagliamento extending between Venzone, Gemona and Osoppo. The rotation
of the vertical toward SSE may be attributed to the weight increase of
the alluvium due to rainfalls. In fact, the deviation proves to be proportional
to rainfalls: the heavier are the latter, the larger is the former. This
suggests the idea that below the bed of the Tagliamento River there must
be a large underground flood which is alimented by leakage of rainwater.
I t should be considered in this respect t h a t during t h e Summer when rainfalls
are scarce, t h e vertical is subjected to a slow opposite movement at Somplago,
as if it were under the influence of a corresponding slow lightening of the
SSE area.
The micromovements of the two ledges of the fault may exert a
"release" effect on the fault area such as to prevent sizeable accumulations
of elastic tensions in the surrounding medium. As a matter of fact, the
Somplago area has never been in the epicentre of destructive earthquakes as
far as recorded history goes back, notwithstanding the high seismic character
of Carnia.

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References


DOI: https://doi.org/10.4401/ag-5098
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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X