Historical Seismograms - Evidence from the AD 2000 Izu Islands ...

THE ANATOLIAN EARTHQUAKE OF 17 AUGUST 1668N. N. Ambraseys and C. F. FinkelDept. of Civil Engineering, Imperial College of Science and TechnologyLondon S W7 lBU, England, UK1. IntroductionOne of the largest earthquakes associated with the North Anatolian fault zoneoccurred on 17 August 1668, causing heavy damage within a narrow band about100 km wide and 600 km long, running along the fault zone from Bolu in thewest to near Erzincan in the east (see Figure 1). Virtually one-third of the entireknown length of the individual fault zone broke during this one shock, an eventsomewhat analagous to the 1939 Erzincan earthquake of magnitude 7.7 associatedwith a 350 km fault rupture in the same zone between Amasya and Erzincan.The great length of the epicentral region and the associated fault-breaks providean illustration of the very large magnitude of the earthquake of 1668, which waspreceded by widely-felt damaging foreshocks at its western end, and was followedby aftershocks that continued for six months. This earthquake was the largest lastevent of a series which affected Anatolia for almost six centuries, and was mostprobably responsible for the relative quiescence of the fault zone that has ensuedfor almost two and a half centuries.Existing earthquake catalogues for Anatolia are very incomplete for the periodbefore about 1930, and of little value for the study of the long-term seismicityof the region. The indiscriminate use of such catalogues often leads to the falseimpression that prior to the sequence of large earthquakes that began in 1938,the North Anatolian fault zone was, for all practical purposes, quiescent (see, forinstance, Toksoz et al., 1979, Figure 2). The same applies to Central Anatolia, to theBorder Zone (East Anatolian fault zone) and to its extension into the Dead Sea faultwhere, although recent seismicity has been very low, large historical earthquakesare known to have occurred with disastrous consequences (Ambraseys and Melville,1986).2. Sources of InformationEarthquake catalogues either ignore the Anatolian earthquake of 17 August 1668,or refer vaguely to a series of earthquakes that occurred in different parts of AsiaMinor during the period 3 July to 13 September 1668 (Hoff, 1840; Perrey, 1850;Mallet, 1850). Their source of information, the Dressdnische Gelehrte Anzeigen(1756), is an extract from the contemporary Theatrum Europaeum (1668), whichappears to have had access to reliable local information, most probably derivingfrom correspondence with European merchants living in different parts of westernAnatolia. Such information is remarkable for its lack of exaggeration. However,these early catalogues fail to identify not only the position of most of the placesmentioned in their source as having been affected by the earthquake, but also theexact date of the main event.With the exception of Stepanian (1942), authors since Mallet add nothing butconfusion, which distorts the effects of this earthquake. Thus Sieberg (1932), withoutquoting his source of information and without any good justification, splits theHistorical Seismogramsand Earthquakes of the World173Copyright (c) 1988 by Academic Press, Inc.All rights of reproduction in any form reserved