Time, space and size distribution of earthquakes for Fagaras seismogenic region, Romania

The probabilistic seismic hazard assessment (PSHA) in dense-populated geographical regions and subsequently the design of the strategic objectives are primary based on the knowledge of the seismicity parameters of the seismogenic sources which can generate ground motion amplitudes above the minimum level considered risky at the specific site. The PSHA deals with a Poissonian earthquakes distribution in space and time. This assumption implies the necessity of a catalog containing only independent events. For Romanian territory, besides the major impact of the Vrancea seismic region, characterized by strong intermediate-depth earthquakes, another important seismic source of crustal earthquakes is the Fagaras region, located in the Southern Carpathians, which should be taken into consideration when assessing the seismic hazard. The seismic regime of the region shows significant clustering effects related to earthquake generation together with quarry blasts generation. In order to study the time, space and size clustering of the seismicity, first we propose a method to discriminate the quarry blasts in the existing catalog. Second, we focused our analysis on the earthquake sequence generated near the Sinaia town in 1993, consisting of fore shock and aftershock sequences associated to a main shock of magnitude Mw = 5.1. Fractal properties are investigated in the time, space and size distributions and their correlation. A few noticeable tendencies are outlined and discussed. (authors)