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  • 6/9/2011

Earthquake in Persia

part 1



Sources and state of current knowledge. Based on numerous but fragmentary observations of earthquakes over a long period of time, it is only since the middle of the 20th century that there has been an attempt at systematic study of seismic activity in Persia and that macroseismic data collected at international stations have been refined in relation to the Persian situation, through the establishment of a network of local seismological stations, in Tehran (1337./1958); Shiraz (1338./1959); Safidrud (1341./1962); Tabriz, Mash'had, and Kermanshah (1343-44./1964-65); Bushehr (1354./1975); Isfahan (1355./1976); and Sava (1356./1977), each the center of a constellation of substations. After early, incomplete, and imperfect attempts at cataloguing earthquakes in Persia (A. T. Wilson), the first comprehensive seismotectonic map of the country was published; it was limited to north central Persia and was drawn to a scale of 1:1 million (Tchalenko et al.). It was soon followed by a map of the entire country, drawn to a scale of 1:2.5 million, with supplementary maps of the epicenters of destructive earthquakes in the period 1318-96=1279-1355./1900-76, of the principal faults in the country, and of earthquakes recorded since the 4th century B.C.E., all drawn to a scale of 1:5 million (Berberian). The historical study was taken up again in a fundamental work by N. N. Ambraseys and Charles Melville (1982), who drew upon a much broader range of documentary sources; their work is a model of its kind, encompassing not only a general study, but also reconstructed maps of the areas of destruction connected with a number of major historical earthquakes. More recently these data have been integrated into a much less detailed synthesis and then into a general seismic map of the entire Near and Middle East (Schler and Bauer; Schler). Nevertheless, it must be admitted that our knowledge of past earthquakes is still insufficient, owing particularly to the extreme unevenness of the documentation for different regions; indeed, for many sparsely populated desert areas it is almost entirely absent, both from textual sources and from the archeological record. The broad outlines of seismotectonics have thus been established, but they cannot yet be filled in without some hesitation and approximation.

General features of the seismological geology of Persia. The main relevant feature is the great Zagros fault line, where the Arabian and central Iranian plates overlap.

 In this zone, 1,600 km long and on average 250 km wide, seismic activity is extreme. Historical data suggest that there has been continuous seismic activity, with occasional local tremors, but chiefly a large number of mild earthquakes bearing little relation to tectonic fractures in the region or to visible traces of recurrence; nor can they be linked with major faults. In certain parts of the Zagros nomadic tribes report that the earth trembles more or less regularly every year, setting off notable rock slides. At Bandar-e Abbas in 1031/1622, besides a major earthquake on 28 Du’l-qada/4 October, there were six or seven minor tremors, but the residents reported to a European traveler that there was usually an average of only one earthquake a year (Della Valle, III, p. 590). Altogether, however, this zone seems to have been relatively free from major earthquakes, and, despite continual deformation of the earth’s crust, most episodes have had no serious seismic consequences. Throughout its history Shiraz has experienced numerous tremors in which varying numbers of buildings have collapsed, but only one truly cataclysmic earthquake, that of 26 Rajab 1269/5 May 1853, in which about 9,000 people died.

Source: encycopedia.thefreedictionary.com


Geography and History, Zanjan  

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Persian Eagles: part 2    

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