REGION-TIME-MAGNITUDE ANALYSES OF EARTHQAUKE ACTIVITY IN THE ELBASANI GEOTERMAL ZONE, ALBANIA

A detailed analysis of the b-value within the Elbasani fault zone, Albania, were studied. From instrumental seismicity in this area have been located 1830 seismic events, with magnitude Ml>0.5 Richter. In the zone of Elbasani, hot mineral water (thermal waters) spot out from natural springs which have been known since the 19th century. The statistical properties of seismicity are analysed by using b-value known as Gutenberg-Richter law. The magnitude of completeness (Mc) value is determined as 2.6, and the bvalue is calculated as 1.03 ± 0.06, and it is determined that the region has a normal stress level. It is seen that the Mc-value varies from 1.6 to 2.9, the b-value changes between 0.9 and 1.3. The regions with the large b-values (> 1.0) are estimated in the eastern parts of the of Elbasani zone. However, the regions with the low b-values (< 1.0) are observed in the north, west and southwest of Elbasani zone. The regions with the small b-values correspond to great-magnitude events, whereas the other large values are related to smallmagnitude earthquakes. These results reveal that b-values for all regions are well represented by a b-value typically close to 1.0. There are clear decreasing trends in temporal changes of b-values before the occurrences of some strong main shocks. The lower b-value indicate that there is still moderate stress accumulation in the southwest area of the Llinxha-Kozan thermal water belt. The b-values smaller than 1.0 indicate potential future earthquake area. Following the strong events, there are remarkable decreases in b-value as a function of time. Changes in b-value with time varies in a large band between 0.6 and 1.4. Probabilities of earthquake activity in different magnitude sizes show comparatively great values changing from 50-100 % for earthquakes of 0.5 ≤ Ml≤ 4.5 and the values relatively lower than 90 % for the earthquakes of 5.0 ≤ Ml. The Elbasani zone has a complex geological structure with a significant number of geothermal water resources and some features of seismicity.