Carmen Ortanza Cioflan

Seismic Loss Estimates for Scenarios of the 1940 Vrancea Earthquake

One of the strongest earthquake in Romania was the Vrancea earthquake on 10 November 1940, with moment magnitude 7.7 and depth of 150 km. This event caused significant losses over a wide territory, up to Iasi and Craiova cities. The number of casualties in Romania was around 593 dead and 1271 injured and 65,000 homes were destroyed. A major questions nowadays is: “What could the consequences of a similar earthquake be?”. Through this paper we try to provide insights, by relying on the newly implemented System for Estimating the Seismic Damage in Romania (SeisDaRo), operated by National Institute for Earth Physics (NIEP). This system uses the Improved-Displacement Capacity Analytical Method implemented in the SELENA Software for expressing building loss probabilities. The building database (at city or commune level) is classified into 48 types (depending on construction material, height and age), each with a specific capacity and fragility curve. For this paper we also compute casualty estimates. In the absence of real seismic recordings from the 1940 earthquake we obtained hazard parameters through different ground motion prediction equations (developed by Sokolov, Marmureanu or Vacareanu) specific for the Vrancea intermediate-depth source. Also we test the possibility of using data converted from intensity to acceleration. The damage estimates are represented on relevant maps. Our results show that an earthquake like the one on 1940 could lead to significant damage in our times.

Conceptual Framework for the Seismic Risk Evaluation of Transportation Networks in Romania

The assessment of seismic risk for transportation networks is a difficult task, due to its complexity, hard to get detailed data, lack of methods with low uncertainties and difficulty of defining inter-relations. Through this paper we identify viable ways of analysing the seismic risk of transportation networks in Romania, considering the availability and characteristics of specific data, the possibilities of adapting external knowledge and recently developed methodologies. Until now there was no coherent and complex approach in Romania for this task, referring to the bigger picture. Therefore, we propose an integrative framework that incorporates GIS capabilities (like the ones provided by the ArcGIS Network Analyst Toolbox) and test it for Bucharest. This framework can provide answer to important questions, like “which are the critical segments of networks” or “what could the implications of connectivity loss be?” in case of an earthquake. The approach relies on using fragility functions for critical structures like bridges and tunnels, on empirical formulas for estimating damage level, traffic flow characteristics or connectivity analysis. Results are depicted through multiple performance indicators.

Scenarios for Local Seismic Effects of Tulcea (Romania) Crustal Earthquakes—Preliminary Approach of the Seismic Risk Characterization for Tulcea City

This paper is a multidisciplinary presentation of the seismogenic area situated in the North-Dobrogea Orogen (Tulcea). This zone is characterized by significant crustal seismic activity, with crustal earthquakes of magnitude Ms ≥ 5.0 on the Richter scale. Geological and geophysical data for the area are presented. The seismicity of the region is presented by making use of the latest catalogues, exemplified with maps and a 3D figure. Focal mechanisms with their parameters for several earthquakes are analyzed together with the observation data (provided by different seismological stations). A brief presentation of the main geological features, which are characteristic of the tectonic units that build up the North-Dobrogean Orogene, outlines the diverse petrographic constitution of the various structural levels. In order to discuss the local seismic site effects two scenarios are considered, both of which take into account the characteristics of the seismogenic area. The first one considers the city exposed to an earthquake (superficial) from the E Vrancea zone and the second one considers the city exposed to a seismic event with magnitude Mw = 5.1 from Sf. Gheorghe fault. The earthquake epicentres are located in very active seismic areas. The important features taken into account are the nonlinear behavior of the upper soil strata, the effect of the bedrock elasticity, and different shear modulus and damping of the linear-equivalent-type system. Additionally, several local amplification functions are presented.

Historical Earthquakes: New Intensity Data Points Using Complementary Data from Churches and Monasteries

The Vrancea seismogenic zone denotes a peculiar source of seismic hazard which represents a major concern in Europe, especially to Romania and neighbouring regions from Bulgaria, Serbia and Republic of Moldova. The strong seismic events that can occur in this area can generate the most destructive effects in Romania and may affect high-risk manmade structures such as nuclear power plants, chemical plants, large dams and pipelines located within a wide area including the Northern zone from the Republic of Bulgaria and the SW of the Moldavia Republic. A major part of the information for determining the design basis earthquakes consists of a complete set of historical earthquake data. Therefore, it is necessary that the available historical records to be collected, extending as far back in time as possible. Most of these historical records will be of descriptive nature, including such information as the number of houses damaged or destroyed, the behaviour of population etc. But from such information a measure of the intensity scale value of each earthquake in modern macroseismic intensity scale values may be determined. During the past project “Bridging the gap between seismology and earthquake engineering: from the seismicity of Romania towards a refined implementation of seismic action EN1998-1 in earthquake resistant design of buildings (BIGSEES)”, the authors developed the macroseismic intensity map of Romania by using newly compiled information about the damages experienced by 115 churches and monasteries after 10 strong earthquakes (Mw > 6.9) occurred in Vrancea zone starting with XVth century.

Main Characteristics of November 10, 1940 Strong Vrancea Earthquake in Seismological and Physics of Earthquake Terms

Vrancea earthquake on November 10th, 1940 (MW = 7.7; MGR = 7.5; h = 150 km; E = 1.122 × 1023 ergs, Imax = IX½) represents the first large earthquake in the last century and was preceded by other earthquakes as: October 22, 1940 (MW = 6.5) and November 8, 1940 (MW = 5.9). If recorded, it would be given the opportunity to get basic data for seismic hazard assessment and useful conclusions for seismic design of structures to strong earthquakes. Unfortunately, no seismic ground motion was recorded and, as a consequence, no improvements of the Romanian design building code were made after this earthquake. The earthquake of November 10, 1940 confirms the existence of deep earthquakes in Vrancea area, deeper than Moho discontinuity in the lower lithosphere, and this theory was developed for the first time by H. Jeffreys in 1935. Focsani city and several municipalities (Cotesti, Panciu etc.) were almost destroyed and the houses not taller than one floor, were completely damaged. More than 45 churches and monasteries were damages, destroyed or demolished. New data regarding damages at monasteries have been synthesized and analyzed, the resulting intensities are completing the known macroseismic field and data may be used to construct the isoseismic map of the maximum possible Vrancea earthquake.

Bridging the Gap Between Nonlinear Seismology as Reality and Earthquake Engineering

In seismic hazard evaluation and risk mitigation, there are many random and epistemic uncertainties. On the another hand, the researches in this area as part of knowledge are with rest, that is, the results are with interpretable questions with open answers. The knowledge cannot be exhausted by results. The authors developed in last time the concept of “Nonlinear Seismology – The Seismology of the XXI Century” (Marmureanu et al. Nonlinear seismology-the seismology of XXI century. In: Modern seismology perspectives, vol 105. Springer, New York, pp 49–70, 2005).

Steps in Seismic Risk Mapping for Romania Capital City

Bucharest, capital of Romania, is one of the most seismically vulnerable cities in Europe. The earthquakes affecting the city have their origin in the Vrancea intermediate-depth source. In the last century, major earthquakes (November 10, 1940, Mw = 7.7; March 4, 1977, Mw = 7.4; August 30, 1986, Mw = 7.1; May 30, 1990, Mw = 6.9) produced significant effects for this area. This study’s objective is to highlight the seismic risk of Bucharest nowadays by estimating the possible building and human losses, for relevant scenarios—based on real data and neodeterministic approach. The building loss estimates were obtained through the Improved Displacement Coefficient Analytical Method. In order to provide a balanced input that can also reflect different damage states in the risk analysis, for the hazard data we used real data from seismic stations for August 30, 1986 and May 30, 1990 earthquakes and microzonation map for the maximum possible earthquake that can be produced in Vrancea intermediate-depth source (\(\mathrm{{M}}_\mathrm{{w}}\) = 7.8 and depth 150 km). The spectral content was used for peak ground acceleration (PGA) and spectral acceleration at 0.3 and 1 seconds. For the vulnerability assessment, data obtained from the “Danube Cross-Border system for Earthquakes Alert” (DACEA) Project and a database with classification of the buildings in 1999 were used. The analysis is performed at sector level (6 in total). We computed the probability of damage for the buildings and human casualties in terms of different injury types with SELENA Software.

The Resonance of the Surface Waves. The H/V Ratio in the Metropolitan Area of Bucharest

The purpose of this work is to evaluate the natural period of oscillation T0 for soils in Bucharest city area. We will start by examine the elastic waves excited at the surface of an isotropic body by an oscillatory, localized force (Rayleigh waves). We define the “H/V”‐ratio as the ratio of the intensity of the in‐plane waves (horizontal waves) to the intensity of the perpendicular‐to‐the‐plane waves (vertical waves). It is shown that this ratio exhibits a resonance at a frequency which is close to the frequency of the transverse waves. It may serve to determine Poisons ratio of the body. We consider the ratio H/V of the horizontal to the vertical component of the Fourier spectrum for the seismic events recorded at 34 locations during the period October 2003 to August 2004. The method gives reliable data regarding the fundamental frequencies for soil deposits and the results of this experiment allows us to improve the known distribution of T0—regularly calculated with the approximate formula T = 4h/vs. ...

The Dependence of Q with Seismic-induced Strains and Frequencies for Surface Layers from Resonant Columns

Abstract—The gross effect of internal friction is summarized by the dimensionless quantity Q, defined in various ways. If a volume of soil is cycled in stress at a frequency ω, physically, the Q factor is equal to the ratio of energy dissipated per cycle to the total energy Q−1 = δE/(2πE). The authors used Hardin and Drnevich resonant columns to determine the damping capacity of cylindrical specimens from surface soil layers during torsional and longitudinal vibrations. The energy dissipated by the system is a measure of the damping capacity of the soil. The damping will be defined by the shear damping ratio for the soil D, analogous to the critical viscous damping ratio for a single degree of freedom c/c0. Values of damping determined in these resonant columns will correspond to the area of the hysteresis loop stress strain relation divided by 4π times the elastic strain energy stored in the specimen at maximum strain. Consequently, we can express D in the form of quality factor Q, that is Q=1/(2D), where Q is defined in terms of the fractional loss of energy per cycle of oscillation and D is a nonlinear function ω and γ. The nonlinear dependence of Q with seismic induced strains and frequencies for large deformations has an important influence on the propagation of the seismic waves in the hazard and microzonation studies.