A HISTORY OF ROMANIAN SEISMOLOGY ( )

Transcription

1 Romanian Reports in Physics, Vol. 53, Nos. 3 8, P , 2001 EARTH PHYSICS A HISTORY OF ROMANIAN SEISMOLOGY ( ) FLORIN RĂDULESCU National Institute for Earth Physics, Bucharest-Măgurele (Received June 28, 2001) Abstract. The paper presents a short review on the Romanian seismological studies from the macroseismic observations initiated in 1892 by Ştefan C. Hepites to the surveys and scientific contributions of Mathei M. Drăghiceanu, Grigore Ştefănescu, Ioan G. Popescu, N. Al. Rădulescu, Gheorghe Demetrescu, Ion Atanasiu, Gheorghe Petrescu and Aurelian Iacovache. Also, it mentions the setting up of the first seismological station in Bucharest Filaret (1895) and the apparatus endowment of this important station and of next three stations in Timişoara (1904), Cluj and Cernăuţi (1911). Later, prof. Gh. Demetrescu founded other seismological stations: Focşani (1942), Bacău (1942), Câmpulung Muscel (1943), Iaşi (1951) and Vrâncioaia (1952). The collected data offered interesting information on the seismicity of the Romanian territory with active seismic foci in the Eastern Carpathians and its foredeep (Vrancea region), in the Romanian Plain, Banat and Transylvania. Key words: seismology, Romania, earthquakes, historical study. The beginning of the Romanian seismology was connected to the indefatigable activity of academician Ştefan C. Hepites [1, 2]. He was born in Brăila town on February 5/17, His father was the chemist Constantin Hepites and his mother, Smaranda, was born Dâmboviceanu. He attended the Matei Basarab gymnasium (Brăila) and the Military High School (Bucharest). Doctor in physical and mathematical sciences of the University of Brussels (1873) and engineer of the Polytechnical School (1875) from same town, Ştefan C. Hepites was appointed in 1884 as director of the Meteorological Institute, new founded at Herăstrău, Bucharest. In this position (held until 1908) he was permanently preoccupied with the endowment of recording equipments for earthquakes.the earliest instrumental concerns date from 1887 and two warning Brassart type seismoscopes were imported in 1889 from Italy. An apparatus was mounted in the director s cabinet and it was attached to two electric bells: one of them indicated the arrival of the first seismic waves and other one released a clock which marked the time interval from that moment. Ştefan Hepites organized since 1892 regular macroseismic observations in the national meteorological stations net (400 stations in 1901). To this effect he elaborated Specific instructions for the observation of the earthquakes and

2 294 Florin Rădulescu 2 questionnaires for the voluntary persons who gathered seismic observational data. This system initiated by Hepites was extremely useful and it permitted the elaboration of some earthquake lists since 1893 ( Register of Romanian earthquakes ) yearly published in the Annals of the Meteorological Institute of Romania. These observational data have also been published since 1894 in the Annals of the Romanian Academy (Debates, series II). Şt. Hepites published in 1893 (in Romanian and in French) the Register of earthquakes felt during the period [3]. It is an early work of a Romanian author in this direction. But, in 1882, Hepites published a paper on the earthquake of December 25, 1880 of Brăila [4]. Previously, we must mention the writings of some mediaeval chroniclers as Grigore Ureche and Ion Neculce from Moldavia and Radu Popescu and Constantin (Chesarie) Daponte from Wallachia, all describing the effects of these fearful natural phenomena. In Transylvania, we must specify the chronicles of Ostermayer and Thomas Tartler from Braşov, Hannes Hutter from Mediaş, Andreas Oltard and György Cserei from Aita Mare and Jakob Schnitzler s book from Sibiu [5]. Regarding the early papers on earthquakes, we must add the work of the French Alexis Perrey (1846) Mémoire sur les tremblements de terre dans le Bassin du Danube, including the earthquake felt in Transylvania and in the Romanian Principalities during d [5]. A. E. Bietz published in Sibiu M. Schuster s paper on the Transylvanian earthquake of October 3, 1880 (intensity in the epicentral area about 9 degrees, after [6] and 8 degrees after [7]). The Royal Geographical Society Bulletin published in 1882 the report of the German councillor Gustav Schüller on the earthquakes produced in Wallachia in He visited the Buzău and Râmnicu Sărat counties after the January 11/23, 1838 earthquake, where he found the damages and numerous cracks caused by the earthquake (some with great length, about 1700 m) through which mud and black water, combined with sand emerged to the surface. In the newspaper Românul of January 13/25, 1838 the effects of the earthquake in Bucharest were described. An official report of the police chief established the following victims and damages: 8 dead, 14 wounded, 36 demolished buildings and numerous damaged buildings (among which the Princely Palace, Khan and the Sf.Gheorghe Nou church) [8]. In 1895, Hepites mounted in the Filaret buildings a Guzzanti microseismoscope and a Tacchini pendulum. So, here at Filaret, the first Romanian seismological station was founded. In 1902 this station was endowed with two Bosch seismographs (horizontal mechanical pendulum). They were mounted by Ştefan Murat (Hepites son-in-law). The respective pendulum had a 10 kg mass and the mechanical recording was made on a reel covered with blacked paper. The reel was moved by a clock mechanism, with 15 mm/min rotation speed. An electric clock marked the minutes on the paper, with an amplification of the horizontal displacements of soil of 5, 10 and 15 times.

3 3 A history of Romanian seismology 295 These instruments with low performance continuously recorded the horizontal components of the seismic waves until 1908 and later in the time period having an important contribution to the progress of the Romanian seismological studies [9]. In a paper from 1902 Hepites analysed the earthquakes felt in Romania in 1901 and he specified an Agamemnon seismoscope in the endowment of the Filaret observatory. Since 1914 there were here also two Galitsin horizontal pendulums with high sensitivity (photogalvanometric recording), mounted just in May 1937 due to prof. Octav Onicescu s insistence and the financial support of the manufacturer Nicolae Malaxa [10]. In the yearly seismic papers published by Ştefan Hepites in the time interval he registered the following seismic parameters : time recording of the microseismic movement; arrival time of the maximum phase; maximum amplitude (in mm); total duration of the seismic movement. He also presented photocopies of the most important earthquakes. Hepites divided earthquakes into two categories: macroshocks, felt by human beings and microshocks, perceived by seismological devices [11]. In 1904 the Kingdom of Romania adhered to the International Association of Seismology and Şt. Hepites was appointed to the Permanent Commission of Seismology; in this position he participated in some international meetings (Rome, 1906 and Hague, 1907). In 1908, following a new organization of the Meteorological Institute, Ştefan Hepites was removed from the director s position. Further on he performed an intense scientific activity in the frame-work of the Romanian Academy, as the editor of the Scientific Bulletin (since 1913) and secretary of Scientific Section of the Academy (since 1919). In 1902 he was elected as a full member of the Romanian Academy. He died at Brăila, on September 18, 1922 [12]. The macroseismic observations performed in the meteorological stations net added a rich and valuable seismic material used by Şt. Hepites and Mathei M. Drăghiceanu, as well as by foreign scientists, as Montessus de Ballore, Emmanuel de Martonne and A. Sieberg [13, 14, 15, 16]. Thus, eng. Mathei Drăghiceanu published in 1896, in French, the paper Monograph of the earthquakes of Romania and neighbouring countries [17]. He mentioned the old strong earthquakes of October 14/26, 1802, January 11/23, 1838 and February 7/19 and March 14/26, The 1802 earthquake, named The Big Earthquake of God s Friday, is considered to be the strongest earthquake in Romania, with a magnitude of 7.7 after [7]. This seismic event produced great damages especially in Bucharest, where it demolished the Tower of Colţea and numerous churches. The earthquake was felt on a very large area, between the Ithaca Island, Istanbul, Warszaw, St. Petersburg and Moscow. Major damages were produced in Braşov, Iaşi and Cernăuţi.

4 296 Florin Rădulescu 4 Mathei Drăghiceanu ( ) graduated in 1871 from the National Upper Mining School in Paris. He came back to Romania in 1873 and he worked as an engineer at the Ocnele Mari salt mine and from 1874 (for only two years) as a Salt Mines Inspector. In 1880 he was assigned at the Direction of Studies and State Mines. In the next period he started his geological studies. In 1890 he published at the Vienna Geological Institute The Geological Map of Romania, the first geological and mining map of the country. The paper was highly appreciated by Eduard Suess and by other Austrian geologists [18]. Mathei Drăghiceanu and his wife witnessed the February 23, 1887 earthquake occurred on the Côte d Azur and they were very impressed by the effects on people and the environment; following this event Drăghiceanu became interested in the earthquakes study, scientific preoccupation for all his life. He also approached the difficult problem of earthquake prediction and he made interesting associations between the Romanian earthquakes and the geological structure, being the first Romanian geologist-seismologist. In a work dating from 1896 M. Drăghiceanu mentioned the prediction of the August 31, 1894 earthquake. He presumed a migration of the seismic activity along some lines of great dislocations (east-west oriented) of the Black Sea Caspian Sea Minor Asia area. In 1894, Drăghiceanu quoted some successive earthquakes localized along these ruptural zones and he predicted a strong Romanian earthquake after the one produced in Istanbul on July 10, 1894; this predicted seismic event occurred on August 31, This is considered to be the first Romanian earthquake prediction. Mathei Drăghiceanu paid special attention to the major faults along which the important tectonic forces may accumulate and the seismic foci may migrate. An example is the Cerna alignment, where the earthquakes migrated from Băile Herculane towards south. Drăghiceanu prolonged this tectonic line towards north, up to Geoagiu, from Transylvania and towards south, in the mountainous massif of Serbia. He indicated some important faults, connected with the seismic events, such as : The great fault of the Carpathians (Rm. Sărat-Buzău-Mizil-Urlaţi), the Danube fault, the Babolna-Bivolari-Călimăneşti, Câineni-Şuici-Cepari, Nămăeşti- Lotru and Bistriţa-Bumbeşti-Baia de Aramă fractures. In his paper from 1896 M. Drăghiceanu presented a map of Romania with the isoseismal lines of the earthquakes produced in 1892, 1893 and 1894 (situated in the south of Moldavia) and of the earthquakes of the Banat-Moldova Veche region in the time interval October 1, 1879 April 1, The seismic activity from this second region is concentrated along the Oraviţa-Moldova Nouă fault, with a persistent focus where in the time interval 53 small earthquakes occurred [19].

5 5 A history of Romanian seismology 297 When 93 years old, Mathei M. Drăghiceanu published his last work entitled Euro-Asia, tectonics-seismics (in French) which represented the first Romanian book of seismotectonics. In this book he made for Romania some correlations between the earthquakes foci and the tectonic lines of the Transylvanian Basin, Eastern Carpathians and Banat [20]. Mathei Drăghiceanu was an honour member of some scientific institutions, such as: the Romanian Academy, the Royal Society of Geography, the Geological Institute of Romania. His activity was recognized and he was awarded the rank of Great Officer of the Crown of Romania. He died at Câmpulung-Muscel on May 2, 1939, after a life dedicated to geology and seismology and to the modern development of Romania [18]. At the end of the 19th century, surprising remarks on the effects of earthquakes were made by geographer Matei F. Xenopol ( ), the nephew of historian A.D. Xenopol [21]. In February 1900 the Revue de Géographie in Paris published his paper L action plutonique en Orient. The paper comprises some data on the seismic events occurred all over the globe in the second half of the 19th century, especially in Wallachia and Serbia. He made interesting correlations between the volcanic eruptions and the earthquakes. Also, he mentioned the transformation of the relief forms because of the seismic motion. He analysed the effects of the earthquakes and the animal manifestation before and during of the seismic shocks. In May 1901 acad. Grigore Ştefănescu presented in the framework of the Scientific Section of the Romanian Academy the paper The earthquakes from Romania during 1391 years, from the year 455 to 1846 (in Romanian) [8]. In this work he consulted different Romanian historical documents, Perrey s memorial (1846), the Treasure of the Historical Monuments (Al. Papiu Ilarian), the Review for history and archaeology (Gr. Tocilescu), the manuscripts of historian C. Erbiceanu and geographer G. Lahovary. In his paper Grigore Ştefănescu made some hypotheses on the earthquakes causes, such as: water vapour and gas condensation from the underground cavities which produce an increase of the crustal strain; landslide of the underground layers in regions with a complicated geological structure. Another hypothesis regards the cause of the collapse earthquakes, local seismic shocks of low energy, in comparison with tectonic earthquakes (named by Ştefănescu general earthquakes ). The studies of Şt. Hepites, M. Drăghiceanu and Gr. Ştefănescu on the geographical distribution of the Romanian earthquakes were used by foreign scientists. In his book Wallachia (1902, in French), Em. de Martonne mentions the significance of the seismic region Galaţi-Buzău [14]. In his 1901 paper Montessus de Ballore referred to the seismic events occurred along the Black Sea coast [15]. Ion Atanasiu (1949) named pontic earthquakes, the seismic foci

6 298 Florin Rădulescu 6 situated in the sealine region of the Black Sea, from Mangalia to Cavarna-Balcic- Shabla (in Bulgaria). In the Shabla seismic area three strong events occurred: in the 1st century B.C., in 543 and on March 31, 1901 (M=7.4). The last shock had catastrophic effects in the epicentral area (intensity of 10 degrees) and it was followed by a long series of strong aftershocks (M= ) [6, 7]. The beginning of the 20th century marked the setting up of the Timişoara station (in 1904). It continuously worked until 1910, and with interruptions until 1914 [22]. This station was re-established in September 1, 1943 by prof. Ion Curea (having two horizontal mechanical pendulums of 540 kg) and after a interruption period (April 1, 1944 June 1, 1950) it worked until the present time [9]. The observation data from the Timişoara station were very useful for the local events studies (with epicenters at Periam, Parţa-Şag, Banloc) and earthquakes of the Southern Banat (Băile Herculane, Moldova Nouă). In 1919 the seismological stations of Cluj and Cernăuţi (identical to the Timişoara station) were created in Romania following the Peace Treaty, but they did not work for a long time after the end of the First World War [10]. Interesting instrumental information was supplied by the Bucharest-Filaret station about the strong earthquakes of the Vrancea region of February 6, 1904 (M=6.3), May 25, 1912 (M=6.4 and 5.8) and November 1, 1929 (M=5.8). Concerning the Vrancea earthquake of 1929 we mention that this strong shock was recorded by 51 stations distributed all over the globe and was investigated by the famous English seismologist Harold Jeffreys. This scientist estimated the depth of the seismic focus at 184 km. Further determinations supplied different values, but not far from that: 198 km [23] and 160 km [7]. In the same period it is worth mentioning Grozescu and Gheocălescu s paper [24] on the Făgăraş earthquakes series occurred in January-February, The main shock of January 14/26, 1916 had the magnitude of 6.4 and a focus depth of 21 km [7]. In the epicentral area the macroseismic intensities of 7-8 degrees (Rossi- Forel scale) after [23] and 8 degrees, MSK scale, after [7] were observed. The earthquake was felt in the Făgăraş and Vâlcii mountains, up to Curtea de Argeş- Jiblea to the south and Bistriţa-Năsăud to the north. In the next period, after the new organization of the Meteorological Institute in 1908 and its inclusion in the Astronomic Observatory, the seismological activity was considerably restrained. Only the short notes of the monthly meteorological bulletin indicated that this activity founded by Hepites continued. In 1920 the Central Meteorological Institute was separated by the Astronomic Observatory [12] and Enric Oteteleşanu became the director of the Institute. This small activity continued until January 1, 1935 when the Romanian Seismological Department was established under the direction of prof. dr. Gheorghe Demetrescu [25, 26].

7 7 A history of Romanian seismology 299 Gheorghe Demetrescu was born on January 22, 1885 and in 1907 he graduated from the Faculty of Sciences, section of mathematics. After a specialization at the Paris Observatory he came back to Romania and developed a prolific activity in connection with the organization of the Astronomic Observatory in Bucharest. In 1915 he obtained the title of doctor in mathematical sciences, with a doctoral thesis on the original method for computing the sun eclipses. In 1923 he was appointed professor of astronomy at the University of Cluj and in 1928 he returned to Bucharest as vice-director of the Astronomic Observatory. In 1943 he became director of the Observatory until 1963[27]. Starting with 1935 he reorganized the seismological activity by improving the instrumental endowing and setting up five new stations: Focşani (1942), Bacău (1942), Câmpulung Muscel (1943), Iaşi (1951) and Vrâncioaia (1952) all working till now. Thus, in seismic pendulums worked in the Bucharest Observatory manufactured through the persevering efforts of Gh. Demetrescu and M. Marcopol. The mechanic Mircea Marcopol built the horizontal and vertical pendulums with 540, 450 and 105 kg masses. Marcopol conceived and materialized an air damping system for the 540 kg mass pendulum. These apparatus had a times static amplification and they were equipped with a time recording device [25, 28]. In 1940 the Bucharest-Filaret station had the following instrumental endowing: two mechanical horizontal pendulums Mainka type of a 540 kg mass (installed on January 1, 1935); two horizontal Galitsin pendulums of a 7.2 kg mass and photogalvanometric recording (installed on 1937); a vertical Alfani pendulum of 27 kg mass and photo recording (installed on 1940). Gh. Demetrescu performed a didactic university activity at the Science Faculty of the University of Bucharest, where he taught general astronomy, stellary cinematics and dynamics and seismology courses. His seismology course included three main chapters: notions on the elasticity theory and the seismic waves theory; earthquakes study, discontinuity surfaces, seismicity; seismographs, seismic pendulums, galvanometer theory [29]. In the chapter concerning Earthquakes study he made references to Romania s seismicity, especially to the seismic focus of the Vrancea region. He also presented the computing methods of the epicenter coordinates and of the depth focus. In the time interval he published eight notes on seismology where he presented the problems of the seismic waves interpretation and the determination of the seismic foci coordinates. He studied the earthquakes of November 1, 1929, July 13, 1938, October 22, 1940 and November 10, Regarding the strong earthquake of November 10, 1940 (M=7.4) he elaborated the map of the macroseismic intensities for the Romanian and Bulgarian territories [30].

8 300 Florin Rădulescu 8 Prof. Gh. Demetrescu studies evidenced the deep earthquake focus beneath the Carpathian arc bend, in thevrancea region, a persistent and isolated focus comparable with the focus of the Hinducush Mts (Afghanistan) and Bucaramanga (Columbia). Another notable contribution of prof. Demetrescu was the determination of the crustal layers thickness computed on the basis of the converted waves (between P and S waves arrivals) generated by the Vrancea earthquakes. In 1954, together with Gh. Petrescu, he determined the intermediate layer depth in Wallachia and Moldavia [31]. The idea of this practical method was presented by Gh. Demetrescu at the first Meeting of Seismology of the Czechoslovak Science Academy, Liblice, May He determinated a thickness of km for the granitic layer and km of the basaltic layer for the region situated at km northeast from Bucharest. In 1955 Gh. Demetrescu was elected member of the Romanian Academy. For the fruitful long scientific activity he was awarded orders and medals recompensing the important contributions in the field of astronomy and seismology. The Cernăuţi station, endowed with one Mainka horizontal seismograph (with two components and 450 kg mass), one Wiechert vertical seismograph (80 kg mass) and one Conrad horizontal seismograph for the strong earthquakes recording, has been working since 1936 [32]. The activity of this seismological station is mainly due to professor Ioan G. Popescu, from the Faculty of Sciences in Cernăuţi (chair of cosmic physics), corresponding member of the Romanian Academy. Prof. Ioan G. Popescu performed a study on the earthquakes felt in Bukovina [33]. Among 700 macroseismic events localized in Romania (in the period), only 31 were felt in Bukovina and only 6 earthquakes occurred here, being connected to an important fault situated 20 km south of Cernăuţi. These local earthquakes (August 9, 1679, May 9, 1822, December 28 and 30, 1877, May 7, 1902 and January 20, 1903) had small depth foci and they were situated in the transition zone from the Moldavian Plateau to the East-European Platform. In another paper Ioan G. Popescu analyzed the earthquakes felt in Dobrogea, in the period [34]. He identified 170 observed shocks, only 117 having the epicenter in this region. Among these events, 11 occurred between Galaţi and Sulina, 3 along the Peceneaga-Camena fault, 17 south of the Durostor county and 86 epicenters were located in the south-eastern part of Dobrogea. The author divided Dobrogea in three seismic regions: the northern sector between the Danube Delta and the Peceneaga-Camena fault; the median sector between the Peceneaga-Camena (to the north) and the Rosova-Mangalia (to the south) lines; the southern sector, rich in seismic events.

9 9 A history of Romanian seismology 301 Between the two World Wars we must remark the paper of geographer N. Al. Rădulescu, professor at the Faculty of Sciences of the University of Bucharest, published in 1930, which contains the catalogue of the earthquakes occurred in Southern Moldavia in the time period [35]. In this work the author used information collected by V.A. Urechia, Gr. Ştefănescu, Şt. Hepites and M. Drăghiceanu, as well as the data included in the Annals of the Meteorological Institute ( ), the monthly Bulletin of the Meteorological Institute ( ), the monthly Bulletin of the Astronomic and Meteorological Observatory of Romania ( ) and the monthly Bulletin of the meteorological observations of Romania ( ). For the time interval, N.Al. Rădulescu elaborated a map of southern Moldavia containing the seismic foci and the earthquake frecquency. He distinguished the following important seismic areas: Galaţi, Focşani, Brăila, Tecuci and Rm. Sărat. The author made a correlation between tectonics and seismicity. He showed that the Zăbala-Focşani-Nămoloasa-Galaţi fault represents the line with the highest seismicity. He also mentioned the main seismic focus of the Bârlad-Avrămeşti region. In a previous paper, N.Al. Rădulescu analysed the earthquakes felt in the Oltenia region in the period [36]. He remarked the intense seismic activity in 1893, 1912, 1913 and Thus, in 1916 in the January 11 April 15 time interval earthquakes in series (term proposed by E. Oteteleşanu) were generated. Among these events he remarked the well-known earthquake of January 14/26, 1916 (M=6.4 after [7]) with epicenter in the Făgăraş Mts, having a large macroseismic area comprised between Vienna, Sofia and St.Petersburg. Prof. N.Al. Rădulescu proposed to introduce the term of seismic coefficient, characterizing the seismic activity of an epicentral area. This number represents the sum of the observed macroseismic intensities (on the Rossi-Forel scale) for the respective region. N.Al. Rădulescu calculated the seismic coefficients for Oltenia and obtained the following values: Turnu Severin 19; Tg.Jiu 17; Câineni, Vâlcea 11; Călimăneşti 7; Craiova, Caracal, Corabia 6; Rm.Vâlcea, Ocnele Mari 4; Govora, Tismana 3. The map of the seismic coefficients showed the local earthquakes generated at the border of the Mehedinţi plateau, in the Tg. Jiu depression, along the Olt pass (between Govora and Câineni) and in the southeastern sector of the Oltenia region. The author observed a high correlation between the dislocation lines and the seismic foci [36]. In the time period, the seismological activity knew difficult conditions [25]. However, the seismic Bulletin elaborated by the Observatory of Bucharest has been published monthly until the present. This highly specialized bulletin contributed to the scientific connection with more than 130 seismological stations from all over the world and permanent exchanges of scientific publications.

10 302 Florin Rădulescu 10 After the major earthquake of November 10, 1940 the Romanian specialists interest for these natural phenomena with catastrophic effects grew up. Worth mentioning are: I. Popescu-Voiteşti [37, 38], Th. Kräutner, I. Atanasiu [39] and Gh. Petrescu. Notable contributions on the seismicity of Romania had prof. Ion Atanasiu. In 1949 he published the paper Earthquakes and seismic sensitivity (in Romanian) where he analysed the effects of the earthquakes occurred on the Romanian territory and he made a summary characterization of the seismicity of this area [40]. Ion Atanasiu was born in Iaşi (1892) in geologist Sava Athanasiu s family. He attended the Faculty of Sciences (geological section) in Bucharest which he graduated in He worked at the Geological Institute of Romania (ascending all hierarchical steps up to the chief geologist s position in 1930) and at the Polytechnic School in Bucharest, where he taught oil and ore deposits geology. In 1929 he presented his doctoral thesis and in 1931 he was appointed professor at the chair of geology of the University of Iaşi (following prof. Ion Simionescu). He returned to Bucharest in 1940 occupying the position of prof. I. Popescu-Voiteşti who had retired. Ion Atanasiu made numerous geological studies in different areas of the country, such as: the Eastern Carpathians, the Carpathian flysch, the Carpathian Mio-Pliocene area, the Neogene region of the Transylvanian Basin, the Tertiary magmatic rocks of the Căliman-Harghita chain, being interested in the knowledge of the deep structure of the Romanian territory. He inferred the connection between the earthquakes and the tectonics of basement and he added a large observational material on earthquakes, contained in his paper of 1949 [40]. After his death (April 14, 1949) a monographic volume remained in manuscript and, due to Emilia Saulea, it was published in 1961 by the Publishing House of the Romanian Academy [41]. The book is a monograph on comparative macroseismology, based on rich observational data (more than 400 seismic events) which offers an interesting image of the earthquake surface effects and of the correlation elements with the geological structure. The author identified the main seismic foci, their mode of manifestation, the important seismic lines and he elaborated the first seismotectonic map of Romania. He classified the Romanian earthquakes in the following categories: Moldavian (with the epicenter situated at the Carpathian arc bend), Danubian (on the Vršac-Moldova Nouă line), Transylvanian (between the Mureş and Târnava Mare rivers) and Pontic (the Black Sea coastline) earthquakes. Concerning the Moldavian earthquakes I. Atanasiu mentions the maximum effects localized in the middle part of Moldavia (between the Siret and the Prut), in the subcarpathian hills from Wallachia and Dobrogea or in the eastern sector of the Romanian Plain. These features were also verified by the strong earthquake of March 4, 1977 which produced great damages in the subcarpathian region (Cislău, Vălenii de Munte) and in the southern areas of the Romanian Plain (Zimnicea, Turnu Măgurele) [42].

11 11 A history of Romanian seismology 303 I. Atanasiu classified the seismic events into two categories: polykinetic earthquakes (corresponding to the Făgăraş, Danubian and Pontic earthquakes), where the initial strong shock is followed by a long series of seismic motions (epicentral area well outlined, relatively small macroseismic area), and monokinetic earthquakes (corresponding to the Moldavian, Banat and Transylvanian earthquakes) represented by a principal shock followed by smaller shocks (diffuse epicenter, large macroseismic area). In the mentioned papers [40, 41]. I. Atanasiu elaborated the Map of seismic sensitivity of Romania, where he marked some seismic sensitivity lines, representing the maximum effects during the earthquake of 1940 (November 10) and other seismic events; he correlated these seismic lines with the main structural elements of the crystalline basement. Concerning the causes of the Vrancea earthquakes, I. Atanasiu supposed that the seismic motion may be generated by some changes in the physical state of the crustal or subcrustal material, the abrupt transitions determining a considerable volume change. This hypothesis was reconsidered in the last time by recent papers of Romanian and foreign researchers. A remarkable scientific activity was carried out by seismologist Gheorghe Petrescu in the framework of the Bucharest Observatory. We mention his studies on the Vrancea earthquakes of October 22, 1940 (M=6.2), August 23, 1942 (M=5.1) and April 28, 1943 (M=5.5), as well as the crustal earthquake of January 5, 1940 (M=4.5) occurred at Câmpulung Muscel [43, 44]. He was interested in the problem of the epicenter coordinates determination of the near earthquakes [45]. In 1959 he published at the Technical Publishing House the book The Earthquakes (in Romanian), the first Romanian synthesis on the knowledge of these ill-fated phenomena from our planet life [9]. Gh. Petrescu performed a didactic activity at the University of Bucharest. He elaborated together with acad. Gh. Demetrescu the Seismology and Seismometry course which was taught at the Faculty of Mathematics and Physics [46]. Concerning the seismological teaching we must mention prof. Aurelian Iacovache. He taught in the period the theoretical seismology notions and the elastic waves theory and, later on, the seismic prospecting course at the Technical Geology Faculty of the Mining Institute of Bucharest (until 1957) and at the Institute of Oil, Gas and Geology (since 1957). Prof. Iacovache together with Gh. Demetrescu studied the seismic foci the Vrancea region [47,48]. We must also mention Aurel Beleş papers on the effects of the earthquake of November 10, 1940 on the buildings of Bucharest. He emphasized the important role of the shallow layers on the observed seismic intensities and the influence of the water saturation of these layers [49, 50]. He made some recommendations for buildings resisting the earthquake forces.

12 304 Florin Rădulescu 12 In 1955 (May 14-16) an international meeting on seismological problems was organized in Bucharest. Romanian scientists (acad. S.Stoilov, acad. Gr. Moisil, acad. Gh. Demetrescu, Gh. Atanasiu, corresponding member of the Romanian Academy, prof. A. Iacovache) and seismologists from the Soviet Union (prof. E..F. Savarenski, prof. D.A. Harin) and Bulgaria (prof. I. Petkov) attended this important meeting. Here acad. Gh. Demetrescu mentioned the Romanian Seismological Department activity during 20 years ( ) and some aspects of the seismicity of Romania. He specified the seismic focus of Periam (Banat) and Câmpulung Muscel (depths of 8-10 km), Râmnicu Sărat and Mărăşeşti (depths km) and of course the persistent focus from the Vrancea region (depth of 150 km) [25]. Gh. Demetrescu also mentioned the studies carried out on the Vrancea earthquakes of October 22, 1940 and November 10, These works made possible the elaboration of the macroseismic maps of the country [51] and the Macroseismic intensities zones State Standard, an official obligatory document in the building activity. In the same time period an ample observational seismic, macroseismic and instrumental material was collected, permitting a general characterization of Romania s seismicity. These data were used for the elaboration of some earthquakes catalogues [6, 7]. After 1955 the Romanian seismological studies were developed, diversified and modernized, in agreement with the world scientific orientation. The Romanian researchers carried out studies on the earthquake generation mechanism, the geometric and dynamic parameters of the seismic foci (especially of the Vrancea region), the internal structure of the crust and upper mantle, the seismotectonics of Romania and of course the earthquake prediction problems. REFERENCES 1. L. Constantinescu, St.cerc. geol. geofiz. geogr., seria geofiz., 15, (1977). 2. A. Florinescu, Ştefan C. Hepites, , Ed.Academiei, 145 p., Şt. Hepites, An. Inst. Meteor. Rom.,VI, (1893). 4. Şt. Hepites, An. Acad. Rom. Desbaterile, seria II, III, (1882). 5. P. Cernovodeanu, P. Binder, Cavalerii apocalipsului-calamităţile naturale din trecutul României (până la 1800), Ed. Silex, Bucureşti, A. Florinesco, Catalogue des tremblements de terre ressentis sur le territoire de la R.P.R., Lit. Tip. Inv., Bucarest, 168 p., L. Constantinescu, V. I. Mârza, Rev. Roum. Géol. Géophys. Géogr., Sér. Géophys., 24, 2, (1980). 8. Gr. Ştefănescu, An. Acad. Rom., XXIV (1901). 9. Gh. Petrescu, Cutremurele de pământ, Ed. Tehnică, 320 p., G. Demetrescu, Natura, 7, 10 p., (1937). 11. V. Anestin, Cutremurele de pământ. Cutremurele din România, Bibl. Ştiinţa pentru toţi, nr.5, 81 p., 1916.

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