Seismic risk and loss assessment for Bucharest, Romania

Romanian Journal of Physics

The seismic recordings from certain types of buildings in urban areas during moderate earthquakes from Vrancea-intermediate depth focal region are processed and analysed. One of the most important element in hazard evaluation at national level is the seismic recording network which has been upgraded in the last years up to over 20 strong motion accelerometers in Bucharest and 135 in Romania with easy data handling (accelerations easy to transform in displacements). The general behaviour of reinforced concrete buildings in Bucharest Metropolis during destructive seismic events from Vrancea-intermediate depth focal region is briefly described. The analysis of the elastic response spectra is made for four buildings subjected to the two recent earthquakes with magnitude higher than 4.8, of October 28, 2018 and January 31, 2020 from Vranceaintermediate depth seismic zone. The information consisting in maximum level of the pseudo-acceleration to which the buildings were subjected may be used to detect and quantify any exceedance of the code spectra of interest in near real-time. The recorded earthquakes data are transmitted in real time to the National Data Centre. The goal is to develop and implement modern techniques and tools able to estimate the effect of earthquakes on the built environment in the shortest time possible after a major earthquake.

2000

The paper describes procedures and actions adopted for assessment and reduction of seismic risk in Romania. The study is based on following information: (i) Design provisions for earthquake resistance of structures during 6 generations of seismic codes (1941 1998); (ii) Probabilistic hazard assessment in the influence area of subcrustal (60÷170 km) Vrancea source in Eastern Europe; (iii) Classification of model buildings of the Romanian building stock (iv) Vulnerability curves for typical RC and masonry model buildings and (vi) Expertise reports for the most damaged by earthquakes buildings in Bucharest. Using FEMA/HAZUS methodology (1997), the paper presents Guidelines for selection of the damage function for building structures in Romania, based on building age and seismic zonation map valid during construction of the building. Two Governmental countermeasures documents aiming at providing safety to strong earthquakes for the building stock of Romania are presented: Order No.6173/...

2007

This paper is intended to present some studies undertaken in order to develop a seismic vulnerability estimation system to fit the needs of development of earthquake scenarios and of development of an integrated disaster risk management system for Romania. Methodological aspects are dealt with, in connection with the criteria of categorization of buildings, with the definition of parameters used for characterizing vulnerability, with the setting up of an inventory of buildings and with the calibration of parameters characterizing vulnerability. Action was initiated along the coordinates referred to in connection with the methodological aspects mentioned above. The approach was made, as far as possible, specific to the conditions of Romania. Some data on results obtained to date are presented.

Proceedings of: 15th World Conference on Earthquake Engineering, 2012

The project aims to identify and quantify urban phenomena for the development of a fast analysis instrument that would allow spatial visual representation of the environmental vulnerabilities in Bucharest, from the perspective of the seismic risk as a multi-hazard generator. The final product of this project is a complete data base including urban environment parameters. It offers also a variety of analysis procedures validated statistically and ecologically in order to identify the hazard and vulnerability situations in different scenarios of seismic risks, which will be available for the local authorities in an easy to use web interface. In the same time, in order to sustain Bucharest's strategy for seismic risk reduction, the project structured and diversified the information communicated to the population through different types of contextually adapted messages, based on the identification of the psychosocial circumstances and pattern indexes in the process of coping to the seismic risk.

Earthquake Spectra, 2009

We propose a method to calculate damage and human losses for cities in the developing world by averaging over an entire city, or its administrative districts. Bucharest, Romania, serves as an example. First, we modeled this city as located at a single coordinate point. We transformed the census information on building types, ages and height into EMS-98 vulnerability classes and distribute the population into them. We assumed a seismic load of MSK Intensity= 8 (M7.4 1977 Vrancea earthquake). Validating our model by comparison with casualties reported in 1977, we find differences of 20% to 30%. We reduced these errors to about 4%, by adjusting the distribution of building types into vulnerability classes, based on their performance in the 1977 earthquake. Calibrations of this type will be necessary for most developing countries. In a second step, we modeled Bucharest with six districts, in which the distribution of people into building types and the average soil conditions are known. This is our preferred model. We also calculated the soil properties that would be estimated from topography, if microzonation would not be available. The agreement was satisfactory. We propose this method to model important cities in earthquake prone areas of the developing world.

Soil Dynamics and Earthquake Engineering, 2004

The paper presents recent achievements in evaluations of site-dependent seismic hazard in Romania and the capital city of Bucharest caused by the Vrancea focal zone (SE-Carpathians). The zone is characterized by a high rate of occurrence of large earthquakes in a narrow focal volume at depths 60-170 km. The database that was used for the hazard evaluation includes parameters of seismicity, ground-motion source scaling and attenuation models (Fourier amplitude spectra), and site-dependent spectral amplification functions. Ground-motion characteristics were evaluated on the basis of several hundred records from more than 120 small magnitude (M 3.5-5) earthquakes occurred in 1996-2001 and a few tens of acceleration records obtained during four large (M 7.4, 7.2, 6.9 and 6.3) earthquakes. The data provide a basis for probabilistic seismic hazard assessment in terms of peak ground acceleration, peak spectral acceleration and MSK intensity using Fourier amplitude spectra for various exceedance probabilities or average return periods. It has been shown that the influence of geological factors plays very important role in distribution of earthquake ground-motion parameters along the territory of Romania. q

Natural Hazards, 2017

This paper focuses on the investigation of seismic risk for residential buildings situated in Bucharest, the capital city of Romania. With a population of nearly 2 million inhabitants and a residential building stock of more than 130,000 units, Bucharest represents a city with one of the highest seismic risks in Europe. The seismic risk is evaluated taking into consideration only the Vrancea intermediate-depth seismic source which exhibits a dominant influence on the seismic hazard in southern and eastern Romania (including Bucharest, as well). The analyses are conducted based on a Monte Carlo earthquake catalogue which covers a time span of 50,000 years and includes more than 13,000 seismic events with magnitudes M W C 6.0. In addition, in order to account for the ground-motion variability throughout Bucharest, a recently developed spatial correlation model is applied. Thus, the influence of the ground-motion correlation on the damage estimates for Bucharest is evaluated, as well. The seismic risk estimates obtained for various earthquake scenarios show a significant variability of the results obtained and offer valuable information for the decisionmakers from public institutions dealing with the risk management.

Scientific Papers Series E Land Reclamation Earth Observation Surveying Environment Engineering, 2012

Increased vulnerability of human society to natural hazards is not so much due to a change in the way phenomena manifest, but also to anthropogenic causes, which require more than ever, a pertinent analysis of risk factors and constant involvement of specialists in all fields activity in reducing the negative effects they may cause to people, to the infrastructure or to environmental factors. Safety of structures is one of the main performance requirements for buildings. Expressed in a quality-like manner, this requirement must be completed with quantitative factors.

Pure and Applied Geophysics PAGEOPH, 1991

In this paper we apply a probabilistic methodology to map specific seismic hazard induced by the Vrancea Seismogenic Zone, which represents the uttermost earthquake danger to Romania as well as its surroundings. The procedure is especially suitable for the estimation of seismic hazard at an individual site, and seismic hazard maps can be created by applying it repeatedly to grid points covering larger areas. It allows the use of earthquake catalogues with incompletely reported historical and complete instrumental parts. When applying the methodology, special attention was given to the effect of hypocentral depth and the variation of attenuation according to azimuth. Hazard maps specifying a 10% chance of exceedance of the given peak ground acceleration value for an exposure time of 50 years were prepared for three different characteristic depths of earthquakes in the Vrancea area. These maps represent a new realistic contribution to the mitigation of the earthquake risk caused by the Vrancea Seismogenic Zone in terms of: (1) input data (consistent, reliable, and the most complete earthquake catalogue), (2) appropriate and specific attenuation relationships (considering both azimuthal and depth effects); and (3) a new and versatile methodology.

2000

The seismic hazard of Romania is estimated in terms of peak-ground motion valuesdisplacement, velocity, design ground acceleration (DGA) -computing complete synthetic seismograms, which are considered to be representative of the different seismogenic and structural zones of the country. The deterministic method addresses issues largely neglected in probabilistic hazard analysis, e.g., how crustal properties affect attenuation, since the ground motion parameters are not derived from overly simplified attenuation ''functions,'' but rather from synthetic time histories. The synthesis of the hazard is divided into two parts, one that of shallow-focus earthquakes, and the other, that of intermediate-focus events of the Vrancea region.

Engineering Failure Analysis, 2019

Romania is an eastern European country, with two major seismic zones, Vrancea and Banat. Timisoara is the most important city located in the Banat seismic area, characterized by shallow earthquakes. The city with its many architectural values was declared the European Capital of Culture for 2021. Obviously, an important number of activities that will take part in 2021 will be held in the historical zones of Timisoara, which are also expected to be the most visited ones. In order to assure both the safety of Timisoara's citizens and of the tourists is very important to acknowledge the seismic vulnerability of the buildings of these historical areas. This article presents a study in which there was investigated the seismic vulnerability of 25 buildings from two historic areas, Fabric and Iosefin which were classified according to their geometrical and structural characteristics. There was determined the seismic vulnerability for different scenarios depending on the EMS-98 macroseismic intensity for each identified typology, considered with the representative geometrical and the structural configurations for the zone. The vulnerabilities were obtained using the quick vulnerability assessment methodology, i.e.: the Vulnerability Index Method and the mechanical methodology based on the pushover analysis obtained with the Tremuri software. For the first time in Timisoara, there were shaped both the vulnerability and fragility curves of the buildings under analysis. This study also proposes a new methodology which also takes into consideration the influence of the cultural value in the process of assessing the seismic vulnerability. It is based on the original vulnerability form of the Vulnerability Index Method and on the correlation law between all these methods and it represents the first step of a larger seismic vulnerability assessment for the Timisoara city.

2018

The 1977.03.04 Vrancea earthquake had a strong impa ct, from the view points of the losses inflicted to s ciety, as well as for the subsequent efforts aimed at redu cing seismic risk. The paper is aimed mainly at pre senting a brief review of the efforts coordinated by the stat e nd, then, of the scientific efforts of INCERC (B uilding Research Institute) – Bucharest to develop some sci entific tools and apply them by means of the provis i n of the regulatory base of design, given the political context of the epoch. The most significant scientif ic efforts, referred to in the paper, were aimed at developing: The methods of estimate of ground motion intensity from instrumental information made available during earthquakes, The methods of assessing the influence of local geo o ical conditions upon local features of seismic ground motions, The methods of analyzing the features of radiation / attenuation of the seismic waves. The most significant results of using the methodolo gical dev...

The Bulletin of the Polytechnic Institute of Jassy, Construction. Architecture Section, 2014

This paper presents an overview of the resilience concepts, being focused on the seismic resilience linked to the North-Eastern region of Romania. This research theme is studied in varied and distinct disciplines, and in the engineering field is one of the most important issues because seismic resilience must be achieved in order to have a safety built environment. Earthquakes produced in the Vrancea region affect a large part of Romania, but few studies have particularized the general framework of Vrancea earthquakes’ effect on the Iasi county, Iasi municipality within N-E Romania context. In this manner, this paper analyses the situation of the Iasi County related to the resilience against natural disaster, like earthquakes, and the actual state of the road network. For a right analysis, it is important to understand the resilience definitions, the way of quantifying it, the possible natural hazards that could affect the area and to identify the critical components in case of emer...

NATO Science for Peace and Security Series C: Environmental Security, 2009

Within the NATO Science for Peace (SfP) Project 981882 "Site-effect analyses for the earthquake-endangered metropolis Bucharest, Romania" we obtain a unique, homogeneous dataset of seismic, soil-mechanic and elasto-dynamic parameters. Eight 50 m deep boreholes are drilled in the metropolitan area of Bucharest in order to obtain cores for dynamic tests and vertical seismic profiles for an updated microzonation map related to earthquake wave amplification. The boreholes are placed near former or existing seismic station sites to allow a direct comparison and calibration of the borehole data with actual seismological measurements. A database is assembled which contains P-and S-wave velocities, density, geotechnical parameters measured at rock samples and geological descriptions for each sedimentary layer. Using SHAKE2000 in a first step, we compute the spectral acceleration response and transfer functions obtained from the in situ measurements. The acceleration response spectra correspond to the shear-wave amplifications due to the sedimentary layers from 50 m depth (maximum depth) up to the surface. Bucharest, the capital of Romania, with more than 2 million inhabitants, is considered, after Istanbul, the second-most earthquake-endangered metropolis in Europe. It is identified as a natural disaster hotspot by a recent global study of the World Bank and the Columbia University (Dilley et al., 2005). Four major earthquakes with moment-magnitudes between 6.9 and 7.7 hit Bucharest in the last 65 years. The most recent destructive earthquake of 4 March 1977, with a moment magnitude of 7.4, caused about 1.500 casualties in the capital alone. All disastrous earthquakes are generated within a small epicentral area-the Vrancea region-about 150 km northeast of Bucharest. Thick unconsolidated sedimentary layers in the area of Bucharest amplify the arriving seismic shear waves causing severe destruction. Thus, disaster prevention and mitigation of earthquake effects is an issue of highest priority for Bucharest. In Bucharest there are only a few sites, which were investigated with geophysical and geotechnical methods, to relate the local geology with seismic wave propagation properties (especially amplitude amplification). Therefore, the main purpose of NATO SfP Project 981882 is to obtain a unique, homogeneous dataset of soil-mechanic and elasto-dynamic parameters of the subsurface of Bucharest from 8 new boreholes to systematically model the so-called seismic site responses.

Natural Hazards and Earth System Science, 2005

A seismic hazard map proposed as part of a new building code for Romania is presented here on basis of the recommendations in EUROCODE 8. Seismic source zones within an area of about 200 km around Romania were constructed considering seismicity, neotectonics and geological development. The probabilistic seismic hazard assessment in terms of intensities is performed following Cornell (1968) with the program EQRISK (see Mc Guire, 1976), modified by us for use of intensities. To cope with the irregular isoseismals of the Vrancea intermediate depth earthquakes a factor is introduced to the attenuation law (Kövesligethy, 1907). Using detailed macroseismic maps of three earthquakes is calculated by fitting the attenuation law to observed intensities, i.e. to local ground conditions. Strong local variation of is avoided by a gridding of 0.5 • in longitude and 0.25 • in latitude. The contribution of the Vrancea intermediate depth zone to the seismic hazard at each grid point is computed with the corresponding representative. A seismogenic depth of 120 km is assumed. The final seismic hazard is the combination of both contributions, of zones with crustal earthquakes and of the Vrancea intermediate depth earthquakes zone. Calculations are done for a recurrence period of 95, 475 and 10 000 years. All maps show the dominating effects of the intermediate depth earthquakes in the Vrancea zone, also for the capital Bucharest.