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We examine the long-term seismicity of the Marmara Sea region in Turkey over a period of twenty centuries to attempt to answer two questions: (1) how well recorded in history is the earthquake activity of this region? and (2) does seismicity over this long period of time differ from that over the present century? We study this densely-populated and fast-developing region because it is one of the most tectonically active regions on the continents that appears today to be relatively quiescent. 相似文献
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N. N. Ambraseys 《Journal of Seismology》1997,1(3):289-299
In this paper we assess the size and effects of the earthquakes of 12 May 1866, and 24 January 1916 in Anatolia (Turkey). We show that these events had a magnitude Ms 7.2 and that the former was associated with a 45-km long surface fault break along the north-east part of the East Anatolian Fault Zone. These two earthquakes are chosen among others in order to demonstrate how easy it is to miss out large earthquakes of the historical, even of the early instrumental period, and to draw the incompleteness of many existing catalogues to the attention of those who use them for the estimation of slip rates and the assessment of seismic hazard. Of the two earthquakes studied here, the former was only vaguely known and the latter is not included in Gutenberg and Richter's catalogue. 相似文献
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Magnitude calibration of north Indian earthquakes 总被引：13，自引：0，他引：13
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Attenuation laws predicting induced displacements generated by earthquakes of different magnitude at different distances as a function of the critical acceleration ratio of the foundation materials have been derived from a substantial data set of strong-motion records obtained worldwide. 相似文献
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N. N. Ambraseys 《地震工程与结构动力学》1985,13(3):307-320
A homogeneous and internally consistent body of regional magnitudes is needed not only for the statistical study of seismicity but also for the modelling of seismic sources and for the hazard assessment of engineering sites. Also the assessment of the design ground motions for engineering projects requires homogeneous magnitude estimates. The nature of the available data for U.K. and Northwestern European earthquakes, and of the events themselves, is such that we are concerned with the assessment of magnitudes at the lower end of the scale, and thus great importance focuses on the uniform calculation of magnitudes within a relatively narrow range of M values. The purpose of this study is to present the uniform re-assessment of magnitudes for British and Northwestern European earthquakes for the period 1900 to 1984. It is shown that, for the larger events, surface-wave magnitudes can be estimated uniformly and that neither a period constraint at 20 seconds nor distance effects for the regional conditions considered appear to play an important role. For smaller events, crustal phases at short distances have been used to derive calibration curves for a magnitude which, at larger distances and longer periods would fit the magnitude scale of surface waves. 相似文献
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N. N. Ambraseys 《地震工程与结构动力学》1985,13(3):361-399
The purpose of this paper is to present the results of an evaluation of the seismicity of western Scandinavia. Intensities, with reference to the MSK scale, have been assessed for the larger earthquakes, in most cases from primary sources, and isoseismal maps have been constructed for the most important events, while for smaller shocks one or more isoseismal radii were estimated. In all, over 3,200 earthquakes have been retrieved for Northwest Europe including about 300 artificial events such as chemical explosions, rock-bursts and mine explosions. Of these, 500 events occurred in western Scandinavia. Surface-wave magnitudes were reassessed for 205 events, using surface-wave amplitude-period data, and all earthquakes recorded by more than 6 stations were relocated for the period prior to 1955. A calibration formula, obtained from the combination of macroseismic and instrumental data of the 20th century, has been used to assign magnitudes to all events for which there is macroseismic information available, thus deriving a homogeneous body of data covering a period of 180 years. It is shown that the largest earthquake in the region since 1800 occurred on land and that it had a magnitude in excess of 6.0. This is contrary to the current belief, based on short-term data, that the larger events in western Fennoscandia occur offshore in the continental shelf areas. 相似文献
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This paper examines one of the largest earthquakes in the Balkans in this century which remains hitherto imperfectly known and in need of evaluation. It shows that, given certain conditions, it is perfectly feasible to study in detail an earthquake that occurred three-quarters of a century ago. This earthquake destroyed more than 300 villages and towns, killing over 2,000 people just north of the Dardanelles. The earthquake, which had a magnitude of M = 7.4, was associated with an oblique, 50 km long fault-break, and with the liquefaction of river deposits at large epicentral distances. Landslides and fire added to the damage which can be expressed in terms of a damage ratio that in turn allows the establishment of a loss–intensity relationship. The results may be used to estimate losses to houses of similar type due to future earthquakes. 相似文献
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N.N. Ambraseys 《Journal of Seismology》2001,5(2):263-268
In this note we examine the decay of intensity with distance of earthquakesoriginating in the southern part of the Aegean, offshore Egypt and in theEastern Mediterranean regions, events chiefly with epicentres at sea, whichhave caused concern and occasionally some damage in Lower Egypt, particularlyin Cairo. Also we derive an empirical formula for the assessment of thesurface-wave magnitude of crustal and intermediate depth earthquakes in theregion. 相似文献