engleski

PRELIMINARY RESULTS AND DIFFERENT GEODYNAMIC OBSERVING TECHNIQUES USED AT THE OBSERVATORY HVAR (CROATIA)

Many phenomena that are happening on the surface and in the lithosphere, whose consequences (Earthquakes) are of great importance for us, are mostly in direct connection with geodynamics. Although for a correct and general understanding of geodynamics an interdisciplinary approach is essential, among different joined professions, methods and ways of measurements, GPS undisputedly ensures the most important exact information. GPS enables the determination of position and height of discrete points over very long periods with high accuracy and precision, and therefore the parameters of really movements can be distinguished from noise and measurement errors. A combination of data from different origins will enable us to get better crust behaviour models in future and get better information of earthquake origins which could be used for disaster prevention. Croatia lies in a region, which is seismotectonically very active. The main reasons for that are the Adriatic microplate movements towards the Dinarides, with its different specific densities of rock masses in the crust. Several active zones in the Adriatic sea but also along the Adriatic coast are known which in the past experienced strong earthquakes with damages in cities like Dubrovnik, Makarska, Rijeka, Ston, and others. In our research project it is planned to install several different measuring instruments in the middle of the Adriatic sea at the Observatory of the Geodetic Faculty Zagreb on the island Hvar. Besides exact real-time high rate GPS position measurements, geodynamics should be continuously monitored by other measuring instruments and methods. Among that the most important are continuous determination of gravity change, local deformation measurements by tilt-meters and extensometers, geophysical measurements of shallow and deep strata, and all along with detailed geological interpretation. Conclusions about dynamics, tectonics, faults and seismic of the Adriatic offshore will be enabled by long-time monitoring and comparison with dynamics parameters of existing permanent GPS points on our and the Italian coast and the inner land. The measurements will help to interpret the dynamics of faults and fractures of the Adriatic plate, which is according to several investigations fractured on many places. The result of such estimated dynamics of these fractals are often contradictory so the right answer would probably be that the Adriatic plate is so intensely fractured that movements of these parts in different directions are possible. Based on long-period continuous monitoring data of position, height and acceleration on the GPS point Hvar and through compilation with other data, conclusions about dynamics of the central part of the Adriatic plate could be obtained. To get information about earthquake precursors (if they occur), real-time high rate GPS, on-line tilt meter measurements and gravity change measurements will be compared and analysed together.

Earthquakes; earth chrust; geodynamics; GPS; tilt-meter; extensometer; gravity meter

nije evidentirano