Seismic hazard of the territory of Slovenia is estimated using a deterministic approach based on the computation of complete synthetic seismograms. The input data are the catalogues of earthquakes and fault plane solutions for Slovenia and surrounding regions. Structural models are defined based on available seismological and geophysical information, but are mainly constrained by surface-wave dispersion and 3-D tomographic modelling of the upper crust. Seismogenic zones are delineated considering geotectonic characteristics, fault plane solutions and distribution of earthquake hypocentres. Outside Slovenia seismogenic zones are extended up to distances from which they can considerably influence seismic hazard estimates.

Seismic Zoning of Slovenia Based on Deterministic Hazard Computations

The results of the second phase of a study devoted to the seismic risk assessment for the Friuli - Venezia Giulia region (NE Italy) are presented in terms of peak ground and spectral acceleration maps. A seismogenic zonation of regional relevance has been used, and a detailed separation between rock and soil is introduced for characterising the local response. The definition of the sub-areas where geological and seismological characteristics are constant was obtained by an appropriate processing using GIS software. The hazard results, calculated by the application of a standard probabilistic approach, refer to the 475-year return period; peak ground and spectral acceleration maps show the contribution of actual mean soil characteristics on the expected values.

Soil type dependent spectral seismic hazard in Friuli-Venezia Giulia (NE Italy)

Albania is situated in the Alpine-Mediterranean seismic belt and accommodates part of the deformation due to collision of the Adriatic microplate with the Eurasian plate. Albania has repeatedly been the site of historical earthquakes with considerable losses al even from moderate size events. The fact is attributed mainly to the poorquality of the construction in rural areas. During Albania's passing from an isolated and communist dictatorship to an open and democratic society in the beginning of 90's, a boom in the construction sector commenced which made imperative a modern seismic hazard assessment. In this work an evaluation of probabilistic seismic hazard in Albania is presented based on an updated seismicity catalogue.For this reason Albania has been subdivided in 8 seismogenic zones on the basis of seismotectonic criteria as well as on the spatial and temporal distribution of earthquake epicenters. The earthquake catalogue adopted contains 530 earthquakes with M ≥?4.5 for the time period A.D.58-2000. Values of Peak Ground Acceleration (PGA) for different probability levels of exceedance are obtained for a grid of 10 km × 10 km cells over the territory of Albania. Respective maps are also constructed.

Probabilistic Seismic Hazard assessment in Albania

A probabilistically based hazard map of Albania expressed in terms of PGA for 475 years of return period following the spatially smoothed seismicity approach proposed by Frankel (1995) and developed by Slovenian researchers (Lapajne et al. 1997), is presented.  Taking advantage of this development, an effort has been made to analyze the parameters of site-dependent acceleration response spectra parameters of the current seismic design code KTP-N.2-89 in Albania.

Seismic hazard assessment and site-dependent response spectra parameters of the current seismic design code in Albania

Probabilistic seismic hazard assessment in Albania

The preparation of the preliminary seismic hazard maps of the territory of Slovenia has been based on an expansion of the basic approach laid out by Cornell in 1968. Three seismic source models were prepared. Two of them are based mainly on the earthquake catalogue using the Poissonian probability model. A map of seismic energy release and a map of earthquake epicenter density are used to delineate seismic sources in these models. The geometry of the third model which is based on a rough estimate of seismotectonic setting is taken from the probabilistic seismic hazard analysis of a nuclear power plant in Slovenia. Published ground motion attenuation models based on strong motion records of recent strong earthquakes in Italy are used. Test maps for variable and uniform b-values are presented. The computer program, Seisrisk III, developed by the U.S. Geological Survey is used.

B. SŠket Motnikar

Papers

Preliminary seismic hazard maps of Slovenia