Seismicity and Cultural Monuments of Georgia

Abstract

There are two main connections between seismicity and the state of cultural monuments in earthquake prone countries.

The first one is connected with using both historical chronicles and results of revision of monuments for parameterization of ancient earthquakes, namely, for reconstruction of date, location of epicenter, definition of hypocenter depth, macroseismic effect and intensity. This approach has been extensively used by Georgian seismologists for quantification of ancient event; recently the effects of 1088 Tmogvi, 1263 Samtskhe, 1350 Lechkhumi-Svaneti earthquakes of magnitudes close or equal to 7 have been investigated.

The second approach consists in assessment of destructive effects of recent earthquakes on cultural monuments and elaboration of cost-effective methods of their reconstruction and conservation which could guarantee their resistance to possible future seismic events. This implies involvement of seismologists, civil engineers, geologists, archaeologists and material scientists.

Racha 1991 earthquake (M∽7) damaged numerous architectural monuments of Middle Ages. The level of damage varied from zero to the full destruction (Mravaldzali). It is interesting to note that in some cases the monuments, founded on bedrock were more damaged than these founded on soft soils.

The monuments, damaged by Racha earthquake, are now partially or fully reconstructed. The reconstruction of the brilliant example of Georgian medieval architecture & — XI-th century Nikortsminda cathedral & — was performed in an original way: the shifted cupola of the church of 6 m diameter was lifted by a big inflating balloon, turned and fixed in the correct position. The materials, related to damage (III degree) and reconstruction of Oni synagogue (XIX-th century) with cupola-shaped roof are presented.