Geostructural basis and geophysical investigations for the seismic hazard assessment and prediction in the Caucasus

Caputo, M. and Gamkrelidze, I. and Malvezzi, V. and Sgrigna, V. and Shengelaia, G. and Zilpimiani, D. (2000) Geostructural basis and geophysical investigations for the seismic hazard assessment and prediction in the Caucasus. Il nuovo cimento C, 23 C (2). pp. 191-216. ISSN 1826-9885

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This paper deals with neotectonics, seismic hazard, and earthquake prediction in the Caucasus, a very active region of the Alps-Himalaya collisional system. The aim is to propose the territory of Georgia as a test area for seismic hazard assessment and earthquake prediction in the Caucasus. The active northward advance of the Arabian Plate to the central Caucasian sector of the Mediterranean mobile belt on the neotectonic stage gives rise to specific structures of reoriented folds, longitudinal squeezing and strike-slip faults. In the most compressed sector of the Caucasus arises a whole system of deep faults of different direction and order. Important parameters of such active faults have been reported in a catalogue together with their numerical expression of trustworthiness and degree of importance for seismic hazard assessment. Precursor studies have also been carried out in the same area. The orientation of the maximum compressive stress axis (established from regional and detailed structural analyses), the recent kinematics of active faults (obtained from earthquake fault plane solutions), and results of direct measurements of the Earth's crust displacement (GPS technology) show on the whole a submeridional compression of the region and corroborate the opinion of continuing underthrusting of the Transcaucasian plate under the Greater Caucasus (continental subduction). In the plate situated east of the Tskhinvali-Kazbegi left lateral strike-slip fault, the compression has direction changed to NE. Neotectonic vertical movements, revealed on the basis of plantation surface analysis, include mainly the Greater Caucasus and the Adjara-Trialeti fold zone of the Lesser Caucasus. A seismotectonic map of the Caucasus showing active faults and epicentres of earthquakes occurred during the last century and the main historical events reveal the main patterns of seismicity in this region. Daily averaged tilt component data recently obtained at the Varzia tilt site in the southern Caucasus revealed intermediate-term creep-related ground tilts of preseismic origin which implement the above-mentioned structural investigation results. These tilts are also considered in the seismic hazard assessment since they were precursors of the Javakheti earthquake of December 16, 1990 (M = 4.7). An interpretation of such precursors includes tilt and strain fields slowly propagating from the preparation focal area to the measurement site. This propagating front activates oscillations of blocks which are regulated by the rheological properties of the fault materials.

Item Type: Article
Uncontrolled Keywords: Seismology; Earth's interior structure and properties
Subjects: 500 Scienze naturali e Matematica > 550 Scienze della Terra > 551 Geologia, Idrologia, Meteorologia
Depositing User: Marina Spanti
Date Deposited: 09 Mar 2020 14:48
Last Modified: 09 Mar 2020 14:48

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