Some Contributions of the Neo-Deterministic Seismic Hazard Assessment Approach to Earthquake Risk Assessment for the City of Sofia

Abstract

This paper describes the outcome of the advanced seismic hazard and seismic risk estimates recently performed for the city of Sofia, based on the state-of-the-art of knowledge for this site. Some major results of the neo-deterministic, scenario-based, seismic hazard assessment approach (NDSHA) to the earthquake hazard assessment for the city of Sofia are considered. Further validations of the recently constructed synthetic strong motion database, containing site and seismic source-specific ground motion time histories are performed and discussed. Displacement and acceleration response spectra are considered. The elastic displacement response spectra and displacement demand are discussed with regard to earthquake magnitude, seismic source-to-site distance, seismic source mechanism, and local geological site conditions. The elastic response design spectrum from the standard pseudo-acceleration, versus natural period, T n , format, converted to a capacity diagram in S a -S d format is discussed in the perspective of the Eurocode 8 provisions. A brief overview of the engineering applications of the seismic demand obtained making use of the NDSHA is supplied. Some applications of the outcome of NDSHA procedure for engineering purposes are shown. The obtained database of ground shaking waveforms and time-histories, computed for city of Sofia is used to: (1) extract maximum particle velocities; (2) calculate the space distribution of the horizontal strain factor Log 10 e; (3) estimate liquefaction susceptibility in terms of standard penetration test, N values, and initial over burden stress; (4) estimate damage index distribution; and (5) map the distribution of the expected pipe breaks and red-tagged buildings for given scenario earthquakes, etc. The theoretically obtained database, based on the simultaneous treatment of the data from many disciplines, contains data fully suitable for practical use. The proper use of this database can lead to a significant seismic vulnerability reduction and thus contributes to earthquake preparedness.

Seismic Damage Assessment of Unreinforced Masonry Structures After The Abruzzo 2009 Earthquake: The Case Study of the Historical Centers of L'Aquila and Castelvecchio Subequo

“…These observations point out one of the basic limits of PSHA estimates, particularly severe as far as building codes are concerned; that is the overly dependency of ground shaking on earthquakes recurrence (i.e., on the probability threshold selected for the maps). In view of the mentioned PSHA limits, NDSHA represents an innovative, but already well consolidated, scenario-based approach to seismic hazard assessment, providing realistic time histories from which it is possible to retrieve peak values for ground displacement, velocity and design acceleration in correspondence to earthquake scenarios (e.g., Parvez et al, 2010;Paskaleva et al 2010). NDSHA permits the integration of the available information provided by the most updated seismological, geological, geophysical and geotechnical databases for the site of interest.…”