Thirty Years From the Romania Earthquake of March 4, 1977

download Thirty Years From the Romania Earthquake of March 4, 1977

of 41

  • date post

    02-Apr-2015
  • Category

    Documents

  • view

    89
  • download

    1

Embed Size (px)

Transcript of Thirty Years From the Romania Earthquake of March 4, 1977

T hirty Years from the Romania Earthquake of March 4, 1977 Bucharest, Romania 1-3 March 2007

A VIEW ON THE EXPERIENCE, IMPACT AND IMPLICATIONS OF THE 4 MARCH 1977 EARTHQUAKE, AFTER THIRTY YEARS

Horea SANDI1, Emil Sever GEORGESCU2, ioan Sorin BORCIA2

ABSTRACT An attempt at summarizing the experience, impact and implications of the destructive earthquake of 1977.03.04 is presented. This is related to the knowledge acquired, to the main contributions of foreign experts participating in the making and discussion of postearthquake surveys, to the implications for the regulatory basis of structural design, to a critical view on the earthquake risk reduction activities developed to date and on the development of a comprehensive risk reduction strategy, to some actions that are complementary to classical engineering earthquake protection activities. The presentation relies essentially on the experience and activities of a group having worked for a long time in the frame of INCERC - Bucharest.

1. INTRODUCTION Three decades elapsed from the occurrence of the earthquake of 1977, the most destructive seismic event having affected Romania during historical times. The MGR = 7.2, Mw = 7.5 Vrancea earthquake having occurred in Romania on 1977.03.04 represented a major event, generating a severe economic and social impact, but also a strong favourable scientific impact. An attempt of developing a summary view at this moment is, of course, enrightened. Some early scientific and technical publications on this subject, devoted to the aspects relevant to the engineers, namely the papers (Cimigiu, 1977) and (Sandi & al., 1978), as well as the comprehensive monograph (Blan & al., 1982) must be mentioned. It must be also mentioned that ICCPDC (the former Central Institute for Research, Design and Guidance in Civil Engineering) organized a comprehensive collection of data, aimed for internal use. The publication by seismologists of numerous papers on the subject of the earthquake must be mentioned too. The data and developments presented in this paper, which is concerned essentially with aspects that are relevant to engineers, are due essentially to the group of INCERC Bucharest in the frame of which the authors were active for a long time. The activities dealt with may be considered to a high extent as a part of the activities of research in the field of structural safety and earthquake engineering performed in INCERC Bucharest, presented in (Sandi, 2006). ________________________________________________________________________ __1 2

M., Acadeny of Technical Sciences of Romania. E-mail: sandi@geodin.ro INCERC (National Building Research Institute), Bucharest.

1

E-mail: ssever@incerc2004.ro, isborcia@incerc2004.ro.

Of course, the view presented cannot be complete. Some complementary developments that are relevant for the field dealt with can be seen in other contributions to this symposium, like (Georgescu & Pomonis, 2007) and (Vlad, 2007). It may be stated that the most significant effects of this dramatic event were related to: - the social and economic impact; - the lessons of the earthquake, from the viewpoint of various socio - professional groups The bulk of this presentation is related to topics of interest for engineers, with the remark that the most extended part of it is devoted to topics of engineering seismology. 2. 2.1. A BRIEF SUMMARY VIEW Some References to the Economic and Social Impact

An official view on the impact of the 1977 earthquake was released by Romanian authorities at the end of 1977. Some main data are as follows (Blan & al., 1982): - 1570 lives lost, as identified, and more than 11300 persons injured, out of which about 90% in Bucharest; - 32900 housing units destroyed or heavily damaged; - 35000 families remained homeless; - heavy damage or destruction for numerous buildings of the educational, medical and commercial networks recorded; - important damage having affected 763 units of the basic networks of industry, construction and transportation; - additionally, numerous cases of heavy damage or destruction for agricultural buildings, mechanical workshops, silos, hothouses etc., involving numerous cases of loss of animals. 9 As a summary estimate, the losses exceeded US$ 2 10 . This estimate is subject to some comments in Section 8. The size of the impact, as shown before, was generally confirmed, with some slight modifications, in the World Bank Report (World Bank, 1978). Some further data may be seen in (Georgescu & Pomonis, 2007). Nevertheless, some reservations on these estimates are presented further on. It is widely accepted that the socio psychological impact was very heavy and had serious consequences, even long term ones, but quantifications in this direction are a shaky task. 2.2. A Short View on the Scientific and Technical Impact of the Earthquake

Two destructive Vrancea earthquakes have affected Romania during the 20th century,.on 1940.11.10 (MGR = 7.4, Mw = 7.7) and on 1977.03.04 (MGR = 7.2, Mw = 7.5) respectively (note that the most severe historical earthquake occurred on 1802.10.26, with an estimated magnitude MGR = 7.5 7.7). Such events represent in principle a major source of learning in order to improve the system of earthquake protection measures. It must be noticed nevertheless that, while in 1940 the professional community that should have been involved in earthquake protection was poorly prepared to learn from the earthquake, the situation was totally different in 1977, when a lot of competence had been accumulated in this field. This scientifically favourable situation was due to the joint action of several factors, increasingly at hand during the second half of the 20th century: specific training of engineers in the frame of civil engineering faculties, existence of quite strong research centers,

2

existence of a certain regulatory basis of wide use in practice, strong practical activities in the frame of design institutes, that helped to develop a national school of practicioners of good quality. It may be stated that the most significant and explicit scientific and technical lessons provided by this event concerned: - data concerning the seismic conditions of Romania; - data concerning the earthquake performance of structures of various categories. One should add, to these ones, data of various natures about the economic and social impact, which are out of the reach of this paper. The data concerning the seismic conditions of Romania referred mainly to: - a memento on the high frequency of recurrence of strong, perhaps destructive, Vrancea earthquakes, leading to a wide scale revival of the interest for the characteristics of high magnitude recurrence; - a memento on the long distance radiation of high intensities, as well as a stimulation of the interest for the analysis of the specific features of attenuation; - gathering of direct instrumental data about the features of ground motion acceleration, which made it possible to put to evidence especially the rather nonusual spectral features of ground motion due to Vrancea earthquakes. These data were considerably extended subsequently to the strong Vrancea earthquakes of 1986 and 1990, when a rich instrumental information was obtained. The most extended part of this paper, in Section 6, is devoted to a discussion of the seismic conditions related to the [VSZ] (Vrancea seismogenic zone) activity. The data concerning the eartthquake performance of structures referred mainly to: - a wealth of case studies, developed as a rule in an individual frame and insufficiently summarized to date; - studies of statistical nature, of two sub-categories: - studies based on visual observation only; - studies based on engineering analyses. Some references to these studies are presented in Section 7, besides some methodological developments. 2.3. Some References to Actions Undertaken in the Short Run

As in case of any destructive earthquake occurring in a country with a decent level of development, the occurrence of this disastrous event led to the mobilization of consderable resources in view of coping with the new situation created. One should mention here primarilly: - emergency actions of rescue of persons trapped under debris; - emergency actions to prevent further collapses of buildings or other structures heavily damaged; - measures to clean up places with debris; - measures for emergency rehabilitation of communication and transport ways; - measures for emergency rehabilitation of the functional capacity of medical units; - measures for providing shelter to people rendered homeless; - organization of groups of engineers asked to summarize the situation created and to yield a first view on the proportions of damage and risk, in order to provide the necessary premisses for systematic emergency action; - some emergency actions aimed at correcting obvious shortcomings of the regulatory basis put to evidence by the earthquake experience (zonation of the territory, microzonation, dynamic factor of design code);

3

-

organization of activities of scientific interest; cooperative actions with foreign experts having visited Romania at the times.

In case one thinks of engineering activities, one should mention the concern for preventing further collapses, that was conducted on an individual basis. There existed no widespread regulations or recommendations on the ways of selecting rehabilitation and strengthening solutions. So, one could witness a considerable variety of solutions, able to strengthen more or less efficiently the damaged structures tackled. Given the philosophy of drastic limitation of expenditure of the holders of political power of the time, the General Inspection of Construction (IGSC), together with the Central Institute for Research, Design and Guidance (ICCPDC) issued