INPUT FOR SEISMIC HAZARD ASSESSMENT USING VRANCEA SEISMIC SOURCE REGION

摘要

We use an extended and combined data base including historical and modern, qualitative and quantitative data, i.e., more than 25 events during the period 1790 to 1990 with epicentral/maximum intensities ranging from Ⅹ to Ⅴ degree (MSK scale), the variation interval of isoseismals ranging from Ⅸth to Ⅲrd degree. The data set was analysed using both the sum phasor techniques of Ridelek and Sacks (1984) for different magnitudes and depth intervals and the Stepp's method. For the assessment of seismic hazard we need a pattern of seismic source regions including an estimation for the maximum expected magnitude and the return period for the studied regions. Another necessary step in seismic hazard assessment is to develop macroseismic intensity attenuation relationships induced by the seismogenic zone, especially by Vrancea subcrustal earthquakes. The conceptual frame involves the use of appropriate fall off models, consideration of the randomness in the attenuation, taking into account the azimuthal variation of the isoseist shapes.