Journal of Seismology (2005) 9: 329–340 C Springer 2005 Historical earthquakes in Jerusalem–Amethodological discussion N. Ambraseys Department of Environmental Engineering, Imperial College, London SW7 2BU, UK, E-mail: [email protected] Received 14 March 2005; accepted in revised form 26 May 2005 Key words: earthquakes, historical seismicity, Jerusalem Abstract This article is of an inter-disciplinary nature, relevant to the fields of both earth sciences and historiography, which come together in the investigation of long-term earthquake hazard. The paper emphasises the need for systematic and consistent analysis of historical earthquake data and sets out an example for such a task. The results from the historical study of earthquakes will be of value to earth scientists and engineers only when historical information is converted into “numbers” representing epicentral location and magnitude of the events, accompanied by an estimate of the reliability of their assessment. However, as we go further back in time before our era, the historical record gradually disappears and the archaeological record takes over. Unfortunately, the archaeological record is too coarse and ambiguous, without any precise internal archaeological indicators. Dating is based on, or influenced by the very few historical records, such as in the Bible and inscriptions, which provide an example of how their assumed accuracy may influence archaeologists’ interpretation and dating. Quite often this develops into a circular process in which archaeological assumptions or theories are transformed into facts and used by earth scientists to confirm the dates and size of their proposed events. In this article we discuss the problems that arise when Biblical and archaeological information is used at face value to assess earthquakes in the Holy Land. This combination may produce earthquakes of hypothetical location and of grossly exaggerated magnitude with consequences for the assessment of seismic hazard. Introduction events, accompanied by an estimate of the reliability of their assessment. Having completed the retrieval and analysis of data As an example we chose to reappraise the effect from earthquakes of the last 20 centuries in the East- of three earthquakes in Old Jerusalem, a city with a ern Mediterranean region, and as matter of curiosity, long and well-documented history, not only because not knowing what the outcome would be, we extended it is situated relatively close to the active Dead Sea our studies into a much longer and little known period Fault zone but also because it is singular how, sur- that goes back to the times before our era for which rounded by all the destructive earthquakes with which there is relatively little or no textual information about old Syria and Palestine have suffered for so many cen- earthquakes, the data coming chiefly from the Bible turies, Old Jerusalem, considering its ancient construc- and from the fields of archaeology and indirectly from tion and its foundation mostly on caltural debris, has tectonics. been comparatively spared. We realised that the results from a historical study In later historians of the Byzantine, Muslim and will be of value to earth scientists and engineers only Crusade periods and of more recent times, in which when this information is converted into “numbers” Jerusalem was the central point of interest, we find representing epicentral location and magnitude of the again that of all the destruction of cities recorded in the 330 region, Jerusalem remained comparatively immune, stopped up, for the valley shall touch the side of it (of in spite of the fact that an earthquake in the Holy the mountain) [4, 5]. Land would have been classed as one of those which The source of this difference lies perhaps in the con- excites widespread interest rather on account of the fused reading of the Hebrew words for “shall be stopped geographical location than because of its special vio- up” (ve-nistam), and “you shall flee” (ve-nastem). The lence or large magnitude. consonants in both words are identical, but when at a later period the diacritical points were added to the Hebrew Bible to facilitate reading the text was Zechariah’s earthquake apparently misunderstood and the meaning changed, in this case (viz. editor’s note in Wachs and Levite, Among Biblical earthquakes we chose to reappraise 1984). the mid-8th century B.C. earthquake, known as the By adopting the latter reading as more plausible “Amos’s”, “Zechariah’s” or “Uzziah’s” earthquake, in relation to the natural phenomenon described, it is because of its importance. Modern writers date the obvious that there is no other explanation than a large earthquake to 759 BC and assign to it a magnitude of landslide, which may or may not had been triggered by ML(sic.) 8.2, with an intensity in Jerusalem between this or by another earthquake. VIII and IX (Ben-Menahem, 1979.262; Austin et al., Also, Josephus in his Antiquities of the Jews (93 2000). In addition the event is associated with a AD), a book written about six centuries later, refers coseismic left-lateral offset of the Jericho fault which to an earthquake that happened in the last months of is a segment of the north-south trending strike-slip King Uzziah’s life, which made a rent in the Temple Dead Sea Fault (Nur and Ron, 1996). Obviously, such at Jerusalem. Josephus adds that at a place called En- an important earthquake deserves authentication and rogel, outside the city, half of the mountain in the west its effects reappraisal. broke off from the rest and slid 800 metres up to the The earliest reference to a mid-8th century B.C. mountain on the east, spoiling the king’s gardens [6]. earthquake in Judea can be found in the opening verse Assuming that the two authors refer to the same event, of the Book of Amos who, without giving any details, this passage in Josephus seems to suggest that in all mentions in passing an earthquake in his days, some- probability what Zechariah describes is a landslide, per- where in Judea, in the reign of Uzziah (791–752 BC) haps triggered by an earthquake rather than a graben [for quotations see Appendix 1, 1], perhaps the same formed by normal faulting. event alluded to by Isaiah (c. 700 BC) [2]. Regarding the location of Azal, the name may de- About three centuries later, early in the 6th cen- note some place near the western extremity of the tury, Zechariah (c. 520 BC) mentions an earthquake in valley near Jerusalem or a hamlet on the outskirts of Judea, again in the days of King Uzziah and probably Jerusalem, but this is not certain. As for the location of the same event mentioned by Isaiah, which he says af- Er-rogel it has been suggested to be the fountain of the fected Jerusalem and caused Mount of Olives, east of Virgin, the modern Ain Umm al-Daraj. Others identify Jerusalem, to split and form a valley [3]. it with Bir Eyub, to the south of the Pool of Siloam, The interpretation of this passage in Zechariah and below the junction of the valleys of Kidron and [14.4–5], which seems to be a 5th or 4th century B.C. Hinnom, which seems to be a more probable location, insertion, is not clear. Other versions of the same pas- butagain this is not certain. sage say that the Mount of Olives will split in two and There is one more reference to these events in create a valley that will reach Azel. This valley will Uzziah’s days by Nathan ha-Bavli, who was writing run from east to west with half of the Mount of Olives in the middle of the second century A.D. He does not moving to the north, away from the position it occu- mention the earthquake but he says that at the time of pied, while the other half will move to the south. The the desecration of the temple by Uzziah, the temple valley will stop where the mountains will touch each split open and the fissure extended for twelve ‘miles’ other [3.1, 3–7]. in each direction [6a]. A somewhat different reading we find in the There remains the question of whether there is Masoretic Version, where following the mention of the any evidence today for active faulting in the immedi- splitting of the Mount of Olives, says that the valley ate vicinity of Old Jerusalem which can be associated shall reach unto Azal, as compared to the Revised Stan- with the ground deformations mentioned by Zechariah, dard Version which says instead that the valley shall be Josephus and Nathan. 331 Old aerial photographs of the chalky geological for- remain silent about damage anywhere in Judea and mations of region show only landslides on steep slopes Israel [7]. butnothrough-going faults. A relatively large slide Amos’ earthquake may be dated vaguely from the can be recognised on the Mount of Olives which is lo- line of Jewish kings chronicled in the Old Testament, cated on the slope which faces west towards the Old which provides us with 756 or 759 BC as a ter- City, the scarp of which can be seen halfway up the minus ante quem (Soggin, 1970, p. 120) or perhaps Mount of Olives, but which, according to the Geolog- earlier. ical Survey of Israel, is probably much more ancient Courville dates this earthquake to 751–750 B.C., than the Biblical times (viz. Wachs and Levite, 1984; based on the Jewish legend reported by Josephus in Frydman, 1997). The multitude of short scarps shown which the prophet Zechariah is quoted as a source in- in relatively recent geological maps of Jerusalem all dicating the severity of the earthquake.