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TOWARD A NEW GEOLOGIC AND GEOPHYSICAL MODEL FOR BUCHAREST, ROMANIA, BASED ON STANDARDIZED AND INTEROPERABLE DATABASES

Dragoş Tătaru, Ciugudean-Toma Viorica, Dragoş Toma-Danilă

Abstract

In the past decades, the necessity for detailed earthquake microzonation studies was recognized for Bucharest city first because significant damage occurred here during the last major earthquakes, as well as for other densely populated cities in Romania exposed to major seismic risk due to the intermediate-depth earthquakes occurring in Vrancea zone and local site effects. Numerous studies established different approaches incorporating non-linearity analyses, which generally did not consider groundwater level changes. For this purpose, notably, numerical models are most suitable. These models require a good knowledge of the local geological conditions (especially of the uppermost unconsolidated units), information about the geotechnical parameters of these units, and a hydrogeological model of the investigated area. These models required first the construction of a robust database which should contain all the information about geological strata in the area down to at least 100 m depth or more. The database should include geology or geometric data of the layers and other geophysical and geotechnical related details like the characteristic density and average seismic velocity for each layer, as well as the water table variation in the area. All of them have proved to be important in a scientific assessment of the local seismic hazard according to the modern procedures able to have an output in the city's local seismic hazard (microzonation). Most of this information can be obtained from geotechnical investigations and surveys that have already been carried out in the most densely populated areas. In the last 25 years, a lot of valuable information has been gathered by different research institutes, and only part of them was made available through publication. Other parts of the dataset will be acquired beginning now, according to new methods designed not to disturb the daily activity in the city and to respect the green spaces and general environment. The present study aims to establish a numeric database, organized from all this information in a GIS environment, capable of giving an appropriate image of the Bucharest surface and shallow geologic layers until 100 - 150 m depth. Due to the rapid changing of physical properties on the surface and in-depth, it is required that we have verified values in a grid of 100 m x 100 m and with an error of +/- 1 m depth. The geologic layers database, together with the database of the static and dynamic properties of the sedimentary rocks, that is already accomplished, will serve as valuable input for further studies aiming at a thorough quantification of local seismic hazard in Bucharest city.

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DOI resolver: doi.org/10.5593/sgem2022/1.1/s05.066

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