Cuantificarea actiunii seismice

H. SANDI (Project Director & Editor),
F. APTIKAEV, I. S. BORCIA, O. ERTELEVA, V. ALCAZ

Quantification of Seismic Action on Structures

(studies related to a project sponsored by NATO,
in the frame of the Program "Science for Peace")
AGIR Publishing House, Bucharest, Romania, 2010, pp 224

            The concept of intensity of the seismic ground motion, born already a long time ago, in order to evaluate the severity of seismic ground motion during one earthquake, at a certain geographic point (or upon a limited geographic area, for which this severity is believed to be about the same), is widely popular. On the other hand, the ways in which this concept is understood may differ considerably. Perhaps one could state that there exists a scale of the levels of understanding of this concept. If so, we have at one end laypersons and, unfortunately, not seldom, some mass media agents, who even do not make a difference between the concepts like that of ground motion intensity and of earthquake magnitude. At the other end we have the professionals, who would like to adapt this concept in a way to make it as suitable as possible to the requirements of their activities. This volume pertains definitely to the latter orientation.

            This volume relies on two main sources. On one hand, we have the long term and fruitful activities of the Russian school of seismology, for which the group of the Institute of Physics of the Earth of Moscow played a dominant scientific role, that contributed considerably to the gradual improvement of knowledge and achievements related to the traditional concept of seismic intensity. On the other hand, we have the activities of a group, pertaining initially to INCERC (National Building Research Institute) Bucharest, generated by the impact of the destructive Vrancea earthquake of 1977.03.04 and by the task of carrying out an in depth post – earthquake survey.

An immediate incentive to organize cooperative activities on this theme was due to a meeting held in Moscow in 2004 under the auspices of the NATO Programme Security through Science (NATO – Russia Joint Scientific and Technological Cooperation), on the theme "Disaster Forecast and Prevention", in which the author participated. I was encouraged by the organizer of the meeting, Dr. Frederick Krimgold Director, Center for Disaster Risk Management, Virginia Tech., to apply to the NATO Office of Brussels, in his capacity of scientist of a NATO member country, for support required by the development of a project in this field. Soon thereafter, during a meeting held in Bucharest, hosted by Prof. Dorel Zugravescu, Corresponding Member of the Romanian Academy, Director of the Institute of Geodynamics, Academician Alexandr Gliko, Director of the Institute of Physics of the Earth, Moscow, agreed to set up a joint project aimed to contribute to developments in the domain of quantification of seismic intensity. He nominated Prof. Felix Aptikaev, who was leading research activities in this field, as a counterpart on behalf of his institute. During subsequent contacts, it was agreed to invite the Institute of Geology and Seismology of Chisinau, Moldova (Director and counterpart: Dr. Vasile Alcaz), to join the project. The application forwarded to the NATO Office was accepted and NATO provided the Collaborative Linkage Grant No. 981619 for the Project

QUANTIFICATION OF EARTHQUAKE ACTION ON STRUCTURES.

The cooperative activities in this frame lasted from 2005 to 2008. They included meetings in Bucharest, Chisinau and Moscow and led to the drafting of some joint papers. The main participants in these activities were the authors of this volume. Finally, the NATO Office agreed to provide support for the publication of the volume.

           The volume includes following papers (the papers P.1 to P.8 reproduced from previous publications; the papers P.9 to P.12 newly drafted):

P.1. Sandi, H. & Floricel, I. 1998: "Some alternative instrumental measures of ground motion severity". Proc. 11-th European Conf. on Earthquake Engineering, Paris.P.2. Aptikaev F. 2005: "Instrumental seismic intensity scale". Proc. Symposium on the 40-th anniversary of IZIIS, Skopje.

P.3. Aptikaev F. (editor), 2006: "Project of Russian Seismic Intensity Scale RIS-04". Proc. First European Conf. on Earthquake Engineering and Seismology. Geneva, Switzerland, (Paper No. 1291).

P.4. Sandi, H., 2006: "Bridging a gap between seismologists and engineers: possible restructuring of the intensity scale(s)" Proc. First European Conf. on Earthquake Engineering and Seismology. Geneva, Switzerland, (Paper No. 571).

P.5. Sandi, H., Aptikaev, F., Alcaz, V., Borcia, I. S., Drumea, A., Erteleva, O., Roman, A, 2006: "A NATO project on deriving improved (instrumental) criteria for seismic intensity assessment" Proc. First European Conf. on Earthquake Engineering and Seismology. Geneva, Switzerland, (Paper No. 581).

P.6. Sandi, H. & Borcia, I. S., 2006: "Damage spectra and intensity spectra for recent Vrancea earthquakes" Proc. First European Conf. on Earthquake Engineering and Seismology. Geneva, Switzerland, (Paper No. 574).

P.7. Aptikaev F.F., Mokrushina N.G., Erteleva O.O, 2008: "The Mercalli Family of Seismic Intensity Scale". Journal of Volcanology and Seismology, 2008, vol. 2, № 3, pp.210-213. Pleiades Publ., Ltd.

P.8. Aptikaev F., Borcia I. S., Erteleva, O., Sandi H., Alcaz V., 2008: "Development of instrumental criteria for intensity estimate. Some studies performed in the frame of a NATO project. Proc. 14-th World Conf. on Earthquake Engineering, Beijing, China (Paper No. 02-0042).

P.9. Borcia, I. S., Sandi, H.: "Techniques and results of processing of macroseismic and instrumental information for sample events, in relation to the calibration of instrumental criteria".

P.10. Alcaz, V, Borcia, I. S., Sandi, H.: Some data and results concerning ground motion in Moldova during recent strong earthquakes of 1986 and 1990.

P.11. Borcia, I. S., Sandi, H., Aptikaev, F., Erteleva, O., Alcaz V.: Some statistical results related to the correlation of macroseismic estimates with instrumental estimates of seismic intensity.

P.12. Sandi, H., Borcia, I. S.: A major reason to fundamentally revise the traditional concept of macroseismic intensity: to avoid possible zonation mistakes. An illustrative case.

Horea SANDI (director de proiect si editor),
Felix APTIKAEV, Ioan Sorin BORCIA, Olga ERTELEVA, Vasile ALCAZ

Cuantificarea actiunii seismice asupra structurilor

Editura AGIR, Bucuresti, 2010, 224 pag.

            Volumul, editat in limba engleza, prezinta o serie de lucrari aferente unui proiect de cercetare dezvoltat sub egida NATO, in cadrul programului "Science for Peace", componenta colaborarii NATO – Rusia. In timpul unei conferinte de specialitate desfasurate la Moscova in cadrul acestei colaborari in vara 2004, argumentarea primului autor privind oportunitatea unui astfel de proiect a fost acceptata, incurajandu-se inaintarea catre Oficiul NATO a unei propuneri in acest sens. Propunerea, inaintata in urma obtinerii acordului conducerilor Institutului de Geodinamica al Academiei Romane (prof. Dorel Zugravescu, membru corespondent al Academiei Romane) si Institutului de Fizica Pamantului al Academiei Ruse de Stiinte (acad. Alexandr Gliko) in timpul unei intalniri de lucru desfasurate la Bucuresti in toamna anului 2004, a fost acceptata la Oficiul din Bruxelles. Coordonarea si gestiunea proiectului au revenit colectivului din Romania, datorita apartenentei tarii noastre la NATO. La propunerea primului autor, a fost cooptat pentru participare la proiect Institutul de Geologie si Seismologie al Academiei de Stiinte a Republicii Moldova. Proiectul s-a desfasurat in perioada 2005 – 2008.

            Lucrarile prezentate in volum sunt dedicate necesitatii de modernizare a conceptului de intensitate a miscarii seismice a terenului (la un anumit amplasament) si corespund unei priviri critice asupra conceptului traditional de intensitate macroseismica, asa cum a fost el reflectat de cele mai recente scari de intensitati adoptate oficial de Comisia Seismologica Europeana: scara MSK-64 (standardizata si in tara noastra prin STAS 3684-71 si modernizata ulterior sub forma MSK-77) si cea mai recenta scara, EMS-98. Aceste lucrari au doua surse principale:

-     pe de o parte, activitatea de durata desfasurata de partenerii din Moscova, dedicata teoriei scarilor de intensitate si unor analize statistice extinse privind imbunatatirea criteriilor instrumentale de estimare a intensitatii seismice;

-     pe de alta parte, activitatea sustinuta de interpretare a experientei cutremurelor vrancene puternice din 1977 (cel mai important), 1986 si 1990, care a evidentiat necesitatea de considerare aprofundata a caracteristicilor miscarii terenului (in primul rand, a compozitiei spectrale a acesteia) si a condus la dezvoltari analitice ample, soldate cu propunerea unui sistem complex, flexibil, de cuantificare a intensitatii seismice.

Lucrarile legate de proiect au fost determinate de o privire critica asupra scarilor de intensitati de factura traditionala, care a condus la doua constatari principale:

-     pe de o parte, absenta totala a unor criterii instrumentale de estimare a intensitatii seismice in scara EMS-98, care in prezent reprezinta un document oficial al Comisiei Seismologice Europene (desi in comentariile atasate textului de baza se recunoaste explicit ca o inregistrare corecta caracterizeaza complet miscarea terenului);

-     pe de alta parte, lipsa totala, in cadrul scarilor de factura traditionala, a preocuparii pentru compozitia spectrala a miscarii terenului, care constituie o caracteristica de interes fundamental pentru activitatile ingineresti de protectie antiseismica.

 Volumul cuprinde, dupa un cuvant introductiv al directorului de proiect, 12 lucrari de specialitate, dintre care primele 8 au fost publicate anterior (4 dintre acestea in timpul desfasurarii proiectului, cu referiri directe la acesta), iar ultimele 4 sunt noi. Drept rezultate principale prezentate, sunt de semnalat:

-     rezultatele analizei statistice efectuate de partenerii rusi, care au condus la modificarea ratiilor progresiilor geometrice ale criteriilor instrumentale corepunzatoare parametrilor cinematici considerati de catre scara MSK, de la ratia unica, fixa, 2, la ratii diferentiate, de aproximativ 2,5 pentru acceleratiile de varf, 3,0 pentru vitezele de varf si 4,8 pentru deplasarile de varf, fapt care reflecta tendinta statistica bine cunoscuta de crestere a perioadei dominante a miscarii terenului odata cu cresterea intensitatii seismice;

-     propunerea, de catre partenerii romani, a unui sistem complex de estimare a intensitatii seismice pe baza datelor instrumentale, care conduce la definitii alternative si compatibile pentru intensitatea globala, intensitatea corespunzatoare unei anumite frecvente de oscilatie si intensitatea mediata pe o anumita banda spectrala si, de asemenea, prezinta o buna corelare cu estimarile macroseismce de factura traditionala (atat timp cat cele din urma nu sunt distorsionate de lipsurile tehnicii traditionale de interpretare a datelor de observatie furnizate de anchetele post-seism).

Printre rezultatele demne de a fi semnalate se mai mentioneaza in primul rand:

-     proiectul unei noi scari ruse de intensitati seismice;

-     prezentarea unei cantitati deosebit de mari de rezultate de interes ale prelucrarilor de date instrumentale, referitoare la spectre de raspuns, intensitati globale si spectre (discrete) de intensitati;

-     elemente de analiza comparativa a miscarilor seismice generate de cutremurele vrancene puternice recente in puncte de observatie instrumentala din Romania si din Republica Moldova;

-     o analiza critica a cauzelor care au condus la greseli de zonare seismica in tara noastra, datorita lipsei de discernamant a scarilor traditionale MCS si MSK pentru implicatiile compozitiei spectrale a miscarii seismice a terenului, in timpul interpretarii datelor de ancheta obtinute in urma cutremurelor distrugatoare dn 1940 si 1977. 

In concluzie, este sustinuta necesitatea elaborarii unei scari radical restructurate de intensitati seismice, de catre o grupa de lucru formata din seismologi si ingineri, care sa fie organizata sub egida comuna a Comisiei Seismologice Europene si a Asociatiei Europene de Inginerie Seismica, asigurandu-se conditii pentru ca pozitia inginerilor sa aiba o pondere egala cu aceea a seismologilor.