Earthquake risk assessment for Romania

2000

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 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.

EGUGA, 2014

Bucharest, capital of Romania (with 1678000 inhabitants in 2011), is one of the most exposed big cities in Europe to seismic damage. The major earthquakes affecting the city have their origin in the Vrancea region. The Vrancea intermediate-depth source generates, statistically, 2-3 shocks with moment magnitude >7.0 per century. Although the focal distance is greater than 170 km, the historical records (from the 1838, 1894, 1908, 1940 and 1977 events) reveal severe effects in the Bucharest area, e.g. intensities IX (MSK) for the case of 1940 event. During the 1977 earthquake, 1420 people were killed and 33 large buildings collapsed. The nowadays building stock is vulnerable both due to construction (material, age) and soil conditions (high amplification, generated within the weak consolidated Quaternary deposits, their thickness is varying 250-500m throughout the city). A number of 373 old buildings, out of 2563, evaluated by experts are more likely to experience severe damage/collapse in the next major earthquake. The total number of residential buildings, in 2011, was 113900. In order to guide the mitigation measures, different studies tried to estimate the seismic risk of Bucharest, in terms of buildings, population or economic damage probability. Unfortunately, most of them were based on incomplete sets of data, whether regarding the hazard or the building stock in detail. However, during the DACEA Project, the National Institute for Earth Physics, together with the Technical University of Civil Engineering Bucharest and NORSAR Institute managed to compile a database for buildings in southern Romania (according to the 1999 census), with 48 associated capacity and fragility curves. Until now, the developed real-time estimation system was not implemented for Bucharest. This paper presents more than an adaptation of this system to Bucharest; first, we analyze the previous seismic risk studies, from a SWOT perspective. This reveals that most of the studies don't use a very local-dependent hazard. Also, for major earthquakes, nonlinear effects need to be considered. This problem is treated accordingly, by using recent microzonation studies, together with real data recorded at 4 events with Mw≥6. Different ground motion prediction equations are also analyzed, and improvement of them is investigated. For the buildings and population damage assessment, two open-source software are used and compared: SELENA and ELER. The damage probability for buildings is obtained through capacity-spectrum based methods. The spectral content is used for spectral acceleration at 0.2, 0.3 and 1 seconds. As the level of analysis (6 sectors for all the city) has not the best resolution with respect to the Bucharest hazard scenarios defined, we propose a procedure on how to divide the data into smaller units, taking into consideration the construction code (4 periods) and material. This approach relies on free data available from real estate agencies web-sites. The study provides an insight view on the seismic risk analysis for Bucharest and an improvement of the realtime emergency system. Most important, the system is also evaluated through real data and relevant scenarios. State-of-the art GIS maps are also presented, both for seismic hazard and risk.

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...

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

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.

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.

Journal of Seismology, 2012

On March 4, 1977, an earthquake with a moment magnitude M w 7.4 at a hypocentral depth of 94 km hit the Vrancea region (Romania). In Bucharest alone, the earthquake caused severe damage to 33,000 buildings while 1,424 people were killed. Under the umbrella of the SAFER project, the city of Bucharest, being one of the larger European cities at risk, was chosen as a test bed for the estimation of damage and connected losses in case of a future large magnitude earthquake in the Vrancea area. For the conduct of these purely deterministic damage and loss computations, the open-source software SELENA is applied. In order to represent a large event in the Vrancea region, a set of deterministic scenarios were defined by combining ranges of focal parameters, i.e., magnitude, focal depth, and epicentral location. Ground motion values are computed by consideration of different ground motion prediction equations that are believed to represent earthquake attenuation effects in the region. Variations in damage and loss estimates are investigated through considering different sets of building vulnerability curves (provided by HAZUS-MH and various European authors) to characterize the damaging behavior of prevalent building typologies in the city of Bucharest.