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Evaluation of supposed archaeoseismic damage in Israel
Journal
of Archaeological
Science 1978,5, 237-253
Evaluation of Supposed Archaeoseismic Damage in Israel Iaakov Karcz” and Uri KafrP Studiesof ancientseismicityin the Levant are basedon the interpretation of biblical, ecclesiasticand historic chronicles,all of which are plagued by exaggerationand misinterpretation.To verify the occurrenceof suchancient earth-tremors,archaeological archivesin Israel were searchedfor reports and evidenceof ancient catastrophic damage,attributable to earthquakes.Literature and responseto questionnairesrevealedabout 20 sitesat which featuresof ancient destructionwereassigned a seismicorigin. The actual field evidenceincluded horizons of total destruction, and mainly featuresof fracturing (joints, fissures,cracks and faults), tilting and subsidence, directedcollapseand parallelalignmentsof fallen columnsand masonry. About 75% of thesesiteslie within or near to the Dead Sea-JordanRift, confirming the seismogenic nature of this zone. In spiteof their significanceand usefulness, the archaeoseismic data cannot be employed asan entirely independenttechniquefor the verification of ancient chroniclesand the study of past seismicity.In addition to problemsof operator’s bias, and bias due to historic information, the critical examinationof field evidencecited in supportof ancientseismicityhasshownthat the individual featuresare difficult to distinguishfrom featuresof damagedue to poor construction and adverse geotechnicaleffects. It is essentialtherefore, in the descriptionof ancientdamageand of considerationof its origin, to maintaina proper balancebetweengeological,geomorphologicalandgeotechnicalfactorson onehand, and historic, anthropogeographicand archaeologicalfactors on the other. Keywords:
ISRAEL, ARCHAEOSEISMICITY,
SEISMIC AND
ASEISMIC
DAMAGE.
Introduction Probability of destructive earthquakes and their recurrence intervals are estimated from the available regional tectonic and seismic data. In many areas, instrumental seismic records cover too short a time to allow a probabilistic assessment of long-term earthquake hazards and must be augmented by information from ancient and historic chronicles and documents. Such accounts of past earth tremors are plagued by superstition, exaggeration and misinterpretation of natural phenomena and require careful verification (e.g. Ambraseys, 1971, 1975). Numerous attempts were made to estimate the long-term distribution and recurrence of earthquakes in the Levant by delving critically into historic and biblical sources and earthquake-catalogues (e.g. Willis, 1928; Sieberg, 1932; Shalem, 1949, 1952; Amiran, 1951; Ben Menahem et al., 1976). The results indicate two to three stronger shocks per ‘Departmentof Geology,StateUniversityof New York, Binghamton,N.Y. 13901,U.S.A. bGeological Surveyof Israel,Jerusalem, Israel. 237 0305’-403/78/030237
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century on the average, but estimates of incidence, intensity and distribution of individual events differ considerably and a search for an independent technique of verification and assessment is called for (Table 1). Recently, Ambraseys (1973, 1975) and Fleming (1969) emphasized the potential significance of archaeological data in evaluation of crustal activity. Israel is rich in wellexplored archaeological sites, together spanning several thousand years of continuous history, at which destructive earthquakes of the past should have left evidence of ancient damage and destruction. The archaeological records were searched therefore for references to earthquake-damaged sites which could be used in cross-verification of historic and literary data. It appeared immediately that a seismic origin was assigned in the past to the various features of damage to ancient structures and buildings at numerous sites, and that desertion and decay of erstwhile prosperous communities were attributed to the effects of major earthquakes (Anon., 1970). The reported “earthquake-indicators” are of two main types. The first includes a general and often ambiguous aspect of a “total disaster”, i.e. evidence pointing to a sudden destruction of the entire site or its greater Table 1. Earthquakes in Israel according to historic, literary and biblical sources Number of events Century BC
AD
21 20 16 13 12 11 10 9 8 5 2 1 1 2 3 4 i 7 8 9 10 11
Willis
Sieberg
Amiran’
---__Shalemb
1 1
Ben Menahemc
Number of sites with archaeoseismic damaged
1
1 1 I 1 2 1
5
2
2 1 3
1
1 1
1
2
2 5 1
3
6 2 5 162(3) 5
10
1: (6)
9
1
This table summarizes the published data without attempting to evaluate, compare or relate the interpretations of the individual authors. “Amiran’s catalogue commences with data for 1st century BC. %halem’s data were presented in a discursive (but scientifically admirable) fashion and not as a rigorous list of events. Some events refer to the whole of Levant rather than to Israel. Figures in brackets refer to strong events in Israel, indicated in the original paper. ‘Based on previous catalogues of historic earthquakes and refering mainly to the Judea and Dead Sea regions. dArchaeological information suggests also a 4th millennium BC earthquake at Telleilat Ghassul and a 27th century BC earthquake at Ai.
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part, unrelated to war or strife. The other type of evidence includes features of architectural and structural damage, such as fissured and displaced walls, buildings and reservoirs, tilted columns, walls and aqueducts and subsided and collapsed buildings and structures (Table 2). It is well known however, that such (and similar) features are caused also by poor construction and adverse geotechnical effects unrelated to seismicity. Thus the individual sites reputed to have been hit by ancient earthquakes were examined and the presumed earthquake-evidence was reassessed in light of local geological and geotechnical conditions and information from areas recently affected by major shocks.
r
,2 1
,:; Figure 1. Reference map including all locations mentioned in the text.
Features of Ancient Damage The description of the main types of features of earthquake-damage at the archeological sites visited differs somewhat from the pattern generally followed in modern earthquakeengineering reports. Usually such reports focus on damage to major buildings and structures, attempting to determine the most critical structural components that failed (e.g. Anon., 1962; Berg, 1963; Wiegel, 1970; Benfer, 1941; Lew et al., 1971; Steinbrugge, 1972). Less attention appears to be paid to the orientation, direction and distribution of collapse, tilting, failure and fractures, information difficult not only to analyse but also difficult to recover from mass-disaster urban areas. Furthermore, standards of building and types of construction for which modern data are available, differ from those of the ancient Levant. Thus for example, Ambraseys (1973) warned that earthquakes which would have caused practically no damage to ancient Athens could have a devastating effect on the modern cities. Conversely, little detailed engineering information is available
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about earthquake response of unreinforced masonry and mud-cemented stone walls such as found at numerous archeological sites. The following sections discuss the three main types of features of damage, presenting in each case a summary of observations and an appraisal of their significance in the recognition of ancient seismic events. Fissures and Fractures Fractured and sheared walls, buildings, structures and pavements represent a common form of damage reported from earthquake-disaster areas (op. cit.). Most sites in Table 2 display such features, which range from fissures and hairline joints on which separation and displacements are hardly perceptible, to cracks in which separation is clear and faults show a clear displacement and local breakage (Figure 2). However, no shear cracks were observed nor any consistent patterns of jointing and displacement. Interpretation and dating of fissures and fractures is equivocal, the more so, in that damage of this kind is cumulative and may represent the combined effect of numerous events, not necessarily of a great magnitude. After all, joints and fissures occur also at sites for which no ancient earthquakes were postulated in the literature. It is equally well known that excavation works, however careful, cause local changes in stresses that affect the buried ruins and structure, and may result in relaxation joints. Relaxation may have occurred also during earlier times, when supports were demolished and earth reshuffled, or when the entire site was planed off between successive periods of occupancy. Table 2. Damage attributed to earthquakes at archaeological sites in Israel Site Ai Avdat Beit Shean Caesarea Ein Hanaziv Hazor Jericho (Tel el Sultan) Jericho (Tel Abu Aleik) Jericho (Khirbet Mafjar) Khirbet Qumran Khirbet Maqari Khirbet Shama Kypros Massada Massada Shivta Susita Tel Apheq (Antipatris) Tel Masos Telleilat Ghassul Tiberias
Evidence Widespread destruction, collapse of buildings, tiled walls, breakage Damaged, subsequently repaired city walls, cracks, damaged buildings Disturbances and collapse in the northern cemetery Displaced offshore moles and port installations, tiled walls Directed collapse, oriented fallen masonry Tilted columns and walls, collapse of buildings Slides and features of collapse Tilted and distorted walls, subsidence, collapse and breakage in buildings and water installations Widespread destruction and collapse Breakage and displacement in a water reservoir, cracks and damage to buildings Violent destruction Tilted and distorted walls, collapsed buildings Features of collapse and sliding, imbricated fallen masonry Damaged and cracked floors Tilted walls, oriented fallen masonry, collapse of parts of buildings over the rock cliffs Collapse and damage, and subsequent repairs in the northern area Oriented fallen columns, tilted walls and buildings Tilted and distorted walls, collapse, subsided arches Collapse and oriented fallen masonry Breakage and displacement, cracks, tilts Desertion of the southern part of the city
Time 27th century BC 5-6th century AD
? 2nd century AD 7th century AD 8th century BC 1 1st century BC 8th century AD 1st century BC 7-8th century BC 4th century AD ? 1st century BC 1st century BC and later shocks 5-6th century AD 5th cent&
AD
40th century BC 1lth century AD
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Difficulties in distinction of earthquake-induced fractures from those due to geotechnical effects are well illustrated by the case of Khirbet Qumran, a 1st century BC Essene community near the Dead Sea. Here a prominent fault of 25 cm vertical displacement cuts across the staircase of a water reservoir. This fracture (Figure 2), cited by Zeuner (1955) and Bender (1958) as a proof of recent tectonic activity along the Dead Sea-Jordan Rift, is regarded as evidence of damage and subsequent desertion of the site due to the earthquake of 31 BC reported in historic chronicles. Though this interpretation enjoys official status (as witnessed by the text on tourist post-cards), the actual field evidence per se is inconclusive. The settlement is located in Lisan Marl, a late Pleistocene formation which consists of alternating calcareous and clayey layers. This substratum is unstable and is prone to differential swelling, desiccation and compaction which result in cracks, rills and landslides. Furthermore, a small sediment-settling basin is located just behind the damaged staircase, so that its collapse may have been caused by seepage,
Figure 2. Displacement across the staircase of a water reservoir, at Khirbet Qumran, attributed to the 31 BC earthquake. The structure is located in the geotechnically unstable Lisan Marl. in which differential swelling, compaction and desiccation occur.
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percolation or piping (Figure 3). The non-tectonic explanation of the Qumran displacement was originally offered by Zavistock, who supervised the excavations, but was subsequently rejected (de Vaux, 1961). Joints and fissures, subject to similar reservations occur also in several other buildings and structures at Khirbet Qumran. The 31 BC earthquake is believed to have affected a number of other sites such as Massada and Jericho but not the nearby Fashkha, where a break in occupation appears to be unrelated to any seismic shock (de Vaux, 1961). Indeed the cracks and fissures in the walls of the Fashkha citadel encountered in our survey, are not ancient and represent the result of too deep an excavation of the fundaments by a bulldozer (Mincker, personal communication).
Figure 3. A small settling basin at the aqueduct entrance to the damaged reservoir at Khirbet Qumran (Figure 2). Seepage and percolation may have undermined the reservoir staircase.
Not only the origin, but also the age of individual fractures is questionable. Thus for example, though all advocates of the seismic origin of the Qumran displacement attributed it to the 3 1BCearthquake, Picard (193 1) in a regional geological study of the Judean desert, antedating the archeological excavations, mentions a N-S “cleft” produced in the strong earthquake of 1927. Yet another enigma is presented by the dense jointing across the cliffs rising above the northern Herodean palace on Massada. Figure 4 shows that the joints and cracks do not affect the remnant walls and columns, suggesting that jointing occurred before the construction. However, one is left wondering why the ancient builders ignored the dangers of rockfalls from such strongly jointed cliffs, especially when the various archaeological sources suggest that a strong earthquake (probably that of 31 BC) occurred in the course of construction (Yadin, 1966). Yet another controversy exists in the interpretation of ancient damage and destruction at Telleilat Ghassul, a Chalcolithic settlement on the east side of the Jordan Valley. The earlier investigators attributed the observed tilting, fracturing and collapse to a series of ancient earthquakes, whereas North (1960) argued that the mudbrick buildings are unstable and collapse after only a short period of time. The recent work of Hennessey (1969) presents, however, photographs which demonstrate quite clearly the occurrence of tilts, clefts, gauge, wide cracks and a conspicuous displacement of about 60 cm, unlikely to result solely from poor construction. Oriented Collapse and Tilting
Tilt and collapse in a given direction of buildings, walls and structures, encountered in
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the various earthquake disaster areas (op. cit.) are generally attributed either to shocktriggered mass movements of the ground, such as liquefaction and slope failure (e.g. the Niigata 1964 earthquake, the Alaska 1964 earthquake), or to earthquake-induced shears which alter the original stress distribution within a given structure (e.g. such as expressed in a differential displacement of the various parts of a building). Table 2 indicates that the occurrence of such features at several archeological sites was interpreted as an imprint of ancient seismicity. Tilted columns (Figure 5) are found at Hazor, where also numerous walls deviate from the vertical, The tilt is not uniform, but in most cases the structures dip eastwards and northeastwards. This tilt of the 9th century BC buildings and columns is tentatively attributed to an 8th century BC violent earthquake (cf. Table 1). Tilted walls appear to be quite common. At Tel Abu Alek (Jericho) the eastern wall of the Hasmonean palace dips to the east, a tilt tentatively attributed to the 31 BC earthquake (Nezer, personal communication). At the same time, it also appears that the wall
Figure 4. Dense joints and cracks in the dolomite rockcliffs above the northern Herodean villa on Massada. The plaster along the walls and columns appears to be unaffected.
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Figure 5. Tilted columns of 9th century BC building at Hazor, attributed to an 8th century BC shock. Similar tilts occur where construction is poor and the ground is unstable.
Figure 6. One of the subsided arches at Tel Afek (Antipatris) attributed to the 419 AD$:earthquake. Sagging of columns and arches occurs also in aseismically subsiding ground. In the present case, arch subsidence is accompanied by strongly tilted and distorted walls and joints.
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of the adjoining Herodean palace is distorted and tilted eastwards, thus allowing the possibility that the tilting occurred at a date later than 3 1 BC, Similar tilted and distorted walls and subsiding arches were encountered in the excavations of the Byzantine town of Antipatris (Aphek) and led Kochavi (1976, and personal communication) to attribute the destruction and decay of this prosperous community to the violent earthquake of 419 AD, reported in the historic records (Figure 6). Recently, Ecker & Olshina (personal communication) found that the walls of the Roman buildings at Caesarea are tilted to the northwest, and a submerged tilted structure was discovered by Raban (1976) in an underwater archaeological study of this ancient port. The later, Byzantine structures are not tilted, and it would appear from the analysis of historic records, that if the distortion of the Roman walls is indeed related to a strong earthquake, it may have occurred in the 130 AD destructive shock. At a number of sites believed to have been affected by ancient earthquakes, tilted walls are accompanied by features of a preferred collapse of walls and parallel alignment of the fallen masonry. Such evidence was reported by Yadin (1966) from the store-room complex of Massada, where walls are tilted westwards and the fallen stones are aligned in parallel rows. Somewhat similar collapse of the walls of an ancient synagogue at Ein Hanaziv in a preferred direction led Vito (personal communication) to the assumption that the building was destroyed by the 7th century AD earthquakes. A more extreme example of imbricate disposition of fallen masonry was encountered at Kypros, a hilltop fort near Jericho (Figure 7; Meshel, personal communication). Probably the most impressive, though somewhat enigmatic, case of preferred collapse and alignment was encountered at Susita, where the fallen columns of a Byzantine church are almost perfectly parallel to each other, and where other buildings show strongly tilted walls (Figures 8,9 and 10). The site is reputed to have been affected by a destructive earthquake, but so far no specific date has been proposed. In spite of the undoubted significance of such features, tilting and directional collapse should not be treated as unequivocal evidence of ancient seismic disasters. The standards of original workmanship may have been less than perfect and walls need not have been perfectly vertical and straight when built (e.g. Meyers, 1972). Furthermore, the distortion and collapse of walls need not necessarily be of a seismic origin. Soil creep and slides occur on both natural and artificial slopes, especially in seasonally waterlogged formations and in poorly compacted ground. A recent example of such creep was observed in the village of Maghar in Central Galilee, where the unstable clayey slopes abound in ground cracks and terracettes, where columns and piles of buildings are deflected from the vertical, and where steps and pavements are displaced downslope (Hayati, personal communication). Displacements and differential bending were observed also in various studies of stability of intensely jointed rock-cliffs (e.g. Hoffman, 1973). Yet another possible mechanism leading to tilting of floors, aqueducts and walls is represented by small-scale vertical crustal movements. Such vertical shifts were reported from various parts of Israel (Kafri, 1969; Karcz & Kafri, 1973, 1975) and if persistent in sense and magnitude, could have led to distortion and tilting of existing structures. Subsidence, Sagging and Collapse Features of subsidence and collapse of architectural and engineering structures were reported from all earthquake-disaster areas, and were observed at virtually all the sites indicated in Table 2. However, in this case, distinction between seismic and aseismic mechanisms of collapse and sagging presents considerable difficulties. Several examples will suffice to illustrate the problem.
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Figure I1 shows the local collapse and subsequent repair of the outer walls of the Byzantine acropolis at Avdat, attributed conversely to the effects of a 5th century AD earthquake, to poor construction, and to wilful damage (Negev, personal communication). Figure 12 shows characteristic examples of collapse and subsidence to a Herodean aqueduct system and the adjoining floors and walls at Tel Abu Alek, Jericho, a site believed to have been affected by at least one ancient violent earthquake (Nezer, personal communication, op. cit.). However, such damage may have been caused by the repeated swelling and desiccation of the marly and clayey alluvium through which the primitive aqueducts run, without any relation to seismic activity. The disastrous rockfall of a large block of Lisan Marl, which caused loss of life and damage at Neot Ha’Kikar not far from the Dead Sea in 1969 provides a good example of such geotechnical effects.
Figure 11. Damaged and subsequently repaired retaining walls of the acropolis, Avdat, tentatively attributed to a 5-6th century AD earthquake.
Figures 13 and 14 show a pronounced subsidence, tilting and damage to the floors, walls and buildings of the Ommayad period (7th century AD) in Jerusalem. Though such features of damage may have been triggered by one or more of the rather weak earthquakes mentioned by Shalem (1949) in his analysis of historical sources, other explanations are equally possible. The foundations rest here on artificial dirt fills and screes, derived mostly from the destruction of older buildings and levelling prior to new construction (Figures 14 and 15). Such fills which are also very common at the various “tells” (mounds) with a long record of occupation, and at hilltops where they were used to extend the building space at the summit, display a prominent stratification marked by differences in size and composition of the constituent particles. Usually, the beds are moderately to steeply inclined and display characteristics of slope-scree deposits. When no effective means of pre-construction compaction are available, this type of ground is unstable and creep, sliding and differential compaction may occur, no matter whether or not it is induced by seismic shocks.
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Figure 12. Subsidence and collapse at and near water conveyance structures, Jericho, Tel Abu Aieik, in an unstable Lisan Marl alluvium.
(below) Figure 13. Strong tilting of walls and columns in structures of the Ommayad period, Jerusalem.
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Figure 14. Subsidence of floors of Ommayad buildings, Jerusalem. Note the cross stratification in the underlying fill material.
Figure 15. Typical cross stratification of dirt fills, St Anne’s, Jerusalem.
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Discussion and Summary A critical survey of theavailable archaeological earthquakeevidenceinIsrae1 suggests that though this information may provide a further dimension in the study of ancient seismicity, great care is needed in its evaluation. Limitations on the use of such data as an entirely independent instrument of cross-verification of historic records appear to stem from the following sources. First, the decision of an individual archaeologist to assign features of destruction to seismic causes may well be affected by his awareness (or lack thereof) of historic references to establish a chronological reference horizon for the site in question. Second, in some cases, an earthquake may provide a deus ex machina explanation of otherwise inexplicable desertion or decay of a prosperous township in peacetime, adding a touch of drama to the site history. Finally, in restricted excavations and isolated ruins, features of seismic damage are difficult to distinguish from those due to poor construction or adverse geotechnical effects. It is well known that the location of ancient settlements in the Middle East was dictated largely by site defensibility and by the availability and retention capacity of water, considerations which may have brought the ancient planners into a conflict with standards of soil and rock stability and construction safety. Indeed, many settlements and forts lie above steep rock cliffs or above steep natural or artificial slopes, where aseismic rockfalls, landslides and creep may occur. Many buildings are founded on alluvium, marls and clayey ground (or where such water-retaining formations appear in the shallow subsurface), which may be unstable even to a minor shock, which under more favourable soil conditions would have left no imprint on any buildings or structures. Tuble 3. Proposed damage
I. 2. 3. 4. 5. 6. 7. 8. 9.
10. 1I. 12. 13. 14. 15.
general
scheme
of’ description
of suspected
archaeoseismic
Location and size of site Main periods of occupancy Age of damaged structures Nature of excavation works (rescue and salvage operation, preliminary, single-season, continuing, etc.) Mode and mechanism of excavation (equipment employed, amount of overburden removed, programme of operations etc.) Extent of excavated area and number and size of the exposed buildings and structures Type and quality of construction of the damaged buildings and structures (e.g. masonry, stone, adobe etc.; type of cement, reinforcements and fundaments) Type of damage (e.g. collapse, oriented collapse, tilting, breakage, subsidence, fractures and displacement) Extent and distribution of damage across the site (number of damaged elements, changes in amount and intensity of damage, direction of features of damage and of any possible alignment of the fallen components, etc.) Occurrence of similar damage at other contemporary sites Differences between the observed features of damage and those characteristic of man-induced damage Physiographic setting of the site (relief, distance from cliffs and slopes, slope characteristics, distance from watercourses and shores etc.) Type and composition of the ground (e.g. rock, alluvium, clay; depth to bedrock, etc.) Features of recent ground instability (e.g. slides, creep, rockfalls, desiccation cracks, erosion gullies and rills, occurrence of karst features) Structural settings of the site (e.g. distance from faults and their orientation, occurrence of joints and their orientation, inclination and structural position of the strata
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Some of the uncertainties in evaluations of archaeoseismic data could be removed by the introduction of a standard, systematic method of description of ancient damage, which would ensure a proper balance between the geological, geomorphological and geotechnical factors, and the historic and anthropogeographic considerations. Table 3 lists some of the factors to which attention should be paid in the course of any interpretation of potential field evidence of ancient seismic activity. Notwithstanding the doubts and uncertainties outlined above, the analysis of archaeological data should be included in all systematic evaluations of regional seismicity and in assessments of regional seismic hazards. Thus for example, in Israel it may be pertinent to note that the great majority of archaeological sites at which seismic activity was inferred are located along the Dead Sea-Jordan Rift, the main seismogenic zone in this part of the Levant. This concentration (about 75 %) is significantly greater than that which may be inferred from the study of historical sources (only 15-307; of the references indicate activity along the Rift and its margins) which would suggest a more even distribution of past earthquake damage (Karcz et al., 1977). Acknowledgements The help and advice of numerous members of the archaeological community in Israel, as well as field guidance and discussionswith M. Ben Dov, D. Bahat, M. Kochavi, Z. Meshel, Y. Mincker, E. Nezer, M. Negev and F. Vitto, helped to identify and clarify the nature of the evidence and arguments cited in support of ancient earthquakes. Needlessto say, none of our colleagues share the blame for our errors. Grants in aid from National Academy of Sciences(Day Fund), and SUNY Research Foundation (I.K.) are gratefully acknowledged. References Ambraseys,N. N. (1971).Value of historic recordsof earthquakes.Nature 232, 375-379. Ambraseys,N. N. (1973).Earth sciencesin archaeologyand history. Antiquity 47, 229-230. Ambraseys, N. N. (1975). Studies in historical seismicity and tectonics. In (W. Brice, Ed.) Historical Geography of the Middle East. London: Academic Press. Amiran, D. K. (1951).A revisedearthquakecatalogueof Palestine.Israel Exploration Journal 1,223-246. Anon. (1962). The Agadir Morocco Earthquake, February 29, 1960.New York: American Iron and SteelInstitute, 112pp. Anon. (1970).Encyclopedia of Archeological Excavations in Eretz, Israel. Hebrew Edition, ~01s 1, 2 (1975; EnglishEdition, vols 1 and 2, out of 4). Massada.Jerusalem. Arie, E. (1967).Seismicityof Israel and adjacentcountries.Geological Survey of Israel, Bulletin No. 43, 1-14. Bender, F. (1958).Geofogie von Jordanien. Berlin: Gebruder Borntraeger, 230 pp. Benfer, N. A. (1974). Sun Fernando, California, Earthquake of February 9, 1971. Vol. 1, parts A, B. US Department of Commerce,841 pp. Ben Menahem,A., Nur, A. & Vered, M. (1976).Tectonics,seismicityand structure of the AfroEurasianjunction, the breakingof an incoherentplate. Physics of Earth and Planetary Interiors 12, l-50. Berg, G. V. (1963).The Skopje, Yugoslavia Earthquake of Jury 26, 1963.New York: American Iron and SteelInstitute, 78 pp. Fleming, N. C. (1969).Archeological evidencefor eustaticchangeof sealevel and earth movementsin the westernMediterranean during the last 2,000 y. Geological Society of America, Special Paper No. 109, 125pp. Hennessey,I. B. (1959).Preliminary report on a first seasonof excavationsat Telleilat Ghassul. Levant 1, l-25.
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Hoffman, H. (1973). Steep slopes in regularly jointed material. Geologia Applicata 8, 91-103. Kafri, U. (1969).Recent crustal movementsin northern Israel. Journal of Geophysical Research 74,42464261. Karcz, I. & Kafri, U. (1973). Recent vertical crustal movementsbetweenMediterranean and the Dead SeaRift. Nature 257, 296-297. Karcz, I., Kafri, U. & Meshel,Z. (1977).Archeological evidencefor subrecentseismicactivity along the Dead Sea-JordanRift. Nature %9,234-235. Kochavi, M. (1976).Tel Aphek-1975.Israel Exploration Journal 25, 51-52. Lew, H. S.,Leyendecker,E. V. & Dikkers, R. D. (1971).Engineering Aspects ofthe San Fernando Earthquake. National Bureau of Standards,US. Bldg. Sci. Ser., Vol. 40, 419 pp. Meyers, E, M. (1972).Khirbet Shemaand Meiron. Israel Exploration Journal 22, 174-175. North, R. (1960).Ghassul1960Excavation. Analecta Biblica 14, l-88. Raban, A. (1976). Marine Archueo1og.y Study of Caesareu. Haifa University, Marine Studies Center, 64 pp (in Hebrew). Shalem,N. (1949).Earthquakesin Jerusalemhistory. Jerusalem 2, 1-3, 22-54 (in Hebrew). Shalem,N. (1952).La seismiciteau Levant. Bulletin of the Research Council of Israel 2, 1-16. Sieberg,A. (1932).Untersuchungeniiber Erdbebenund Bruchscholenbauim OstlichenMittelmeergebiet.Denkschriften Medizin und Naturwissenschaft Gesellschaft Jena,18, 161-273. Steinbrugge,K. V. (1972). Comparative building damage.In (A. F. Espinosa& S. T. Algermissen,Eds) A Study of Soil Amplification Factors in Earthquake Damage Areas, Caracas, Venezuela. NOAA Techn. Rept., ERC 280-ESL 31. de Vaux, R. (1961).L’ArchPologie et les Manuscripts de /a Mer Morte. London: Oxford University Press,107 pp. Wiegel, R. L. (1970).Earthquake Engineering. Englewoods,N.J.: Prentice-Hall, 518 pp. Willis, B. (1928).Earthquakesin the Holy Land. Bulletin of the Seismological Society of America 18,73-103. Wu, F. T., Karcz, I., Arie, E., Kafri, U. & Peled,U. (1973).Microearthquakesalong the Dead SeaRift. Geology1, 159-161. Yadin, Y. (1966).Massada. New York: Random House,272 pp. Zeuner, F. (1955).Recentmovementon the westernfault of the DeadSea.Geologische Rundschau 43, 2-3.
of Archaeological
Science 1978,5, 237-253
Evaluation of Supposed Archaeoseismic Damage in Israel Iaakov Karcz” and Uri KafrP Studiesof ancientseismicityin the Levant are basedon the interpretation of biblical, ecclesiasticand historic chronicles,all of which are plagued by exaggerationand misinterpretation.To verify the occurrenceof suchancient earth-tremors,archaeological archivesin Israel were searchedfor reports and evidenceof ancient catastrophic damage,attributable to earthquakes.Literature and responseto questionnairesrevealedabout 20 sitesat which featuresof ancient destructionwereassigned a seismicorigin. The actual field evidenceincluded horizons of total destruction, and mainly featuresof fracturing (joints, fissures,cracks and faults), tilting and subsidence, directedcollapseand parallelalignmentsof fallen columnsand masonry. About 75% of thesesiteslie within or near to the Dead Sea-JordanRift, confirming the seismogenic nature of this zone. In spiteof their significanceand usefulness, the archaeoseismic data cannot be employed asan entirely independenttechniquefor the verification of ancient chroniclesand the study of past seismicity.In addition to problemsof operator’s bias, and bias due to historic information, the critical examinationof field evidencecited in supportof ancientseismicityhasshownthat the individual featuresare difficult to distinguishfrom featuresof damagedue to poor construction and adverse geotechnicaleffects. It is essentialtherefore, in the descriptionof ancientdamageand of considerationof its origin, to maintaina proper balancebetweengeological,geomorphologicalandgeotechnicalfactorson onehand, and historic, anthropogeographicand archaeologicalfactors on the other. Keywords:
ISRAEL, ARCHAEOSEISMICITY,
SEISMIC AND
ASEISMIC
DAMAGE.
Introduction Probability of destructive earthquakes and their recurrence intervals are estimated from the available regional tectonic and seismic data. In many areas, instrumental seismic records cover too short a time to allow a probabilistic assessment of long-term earthquake hazards and must be augmented by information from ancient and historic chronicles and documents. Such accounts of past earth tremors are plagued by superstition, exaggeration and misinterpretation of natural phenomena and require careful verification (e.g. Ambraseys, 1971, 1975). Numerous attempts were made to estimate the long-term distribution and recurrence of earthquakes in the Levant by delving critically into historic and biblical sources and earthquake-catalogues (e.g. Willis, 1928; Sieberg, 1932; Shalem, 1949, 1952; Amiran, 1951; Ben Menahem et al., 1976). The results indicate two to three stronger shocks per ‘Departmentof Geology,StateUniversityof New York, Binghamton,N.Y. 13901,U.S.A. bGeological Surveyof Israel,Jerusalem, Israel. 237 0305’-403/78/030237
+ 17
$02.00/O
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AcademicPressInc. (London)Ltd.
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century on the average, but estimates of incidence, intensity and distribution of individual events differ considerably and a search for an independent technique of verification and assessment is called for (Table 1). Recently, Ambraseys (1973, 1975) and Fleming (1969) emphasized the potential significance of archaeological data in evaluation of crustal activity. Israel is rich in wellexplored archaeological sites, together spanning several thousand years of continuous history, at which destructive earthquakes of the past should have left evidence of ancient damage and destruction. The archaeological records were searched therefore for references to earthquake-damaged sites which could be used in cross-verification of historic and literary data. It appeared immediately that a seismic origin was assigned in the past to the various features of damage to ancient structures and buildings at numerous sites, and that desertion and decay of erstwhile prosperous communities were attributed to the effects of major earthquakes (Anon., 1970). The reported “earthquake-indicators” are of two main types. The first includes a general and often ambiguous aspect of a “total disaster”, i.e. evidence pointing to a sudden destruction of the entire site or its greater Table 1. Earthquakes in Israel according to historic, literary and biblical sources Number of events Century BC
AD
21 20 16 13 12 11 10 9 8 5 2 1 1 2 3 4 i 7 8 9 10 11
Willis
Sieberg
Amiran’
---__Shalemb
1 1
Ben Menahemc
Number of sites with archaeoseismic damaged
1
1 1 I 1 2 1
5
2
2 1 3
1
1 1
1
2
2 5 1
3
6 2 5 162(3) 5
10
1: (6)
9
1
This table summarizes the published data without attempting to evaluate, compare or relate the interpretations of the individual authors. “Amiran’s catalogue commences with data for 1st century BC. %halem’s data were presented in a discursive (but scientifically admirable) fashion and not as a rigorous list of events. Some events refer to the whole of Levant rather than to Israel. Figures in brackets refer to strong events in Israel, indicated in the original paper. ‘Based on previous catalogues of historic earthquakes and refering mainly to the Judea and Dead Sea regions. dArchaeological information suggests also a 4th millennium BC earthquake at Telleilat Ghassul and a 27th century BC earthquake at Ai.
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part, unrelated to war or strife. The other type of evidence includes features of architectural and structural damage, such as fissured and displaced walls, buildings and reservoirs, tilted columns, walls and aqueducts and subsided and collapsed buildings and structures (Table 2). It is well known however, that such (and similar) features are caused also by poor construction and adverse geotechnical effects unrelated to seismicity. Thus the individual sites reputed to have been hit by ancient earthquakes were examined and the presumed earthquake-evidence was reassessed in light of local geological and geotechnical conditions and information from areas recently affected by major shocks.
r
,2 1
,:; Figure 1. Reference map including all locations mentioned in the text.
Features of Ancient Damage The description of the main types of features of earthquake-damage at the archeological sites visited differs somewhat from the pattern generally followed in modern earthquakeengineering reports. Usually such reports focus on damage to major buildings and structures, attempting to determine the most critical structural components that failed (e.g. Anon., 1962; Berg, 1963; Wiegel, 1970; Benfer, 1941; Lew et al., 1971; Steinbrugge, 1972). Less attention appears to be paid to the orientation, direction and distribution of collapse, tilting, failure and fractures, information difficult not only to analyse but also difficult to recover from mass-disaster urban areas. Furthermore, standards of building and types of construction for which modern data are available, differ from those of the ancient Levant. Thus for example, Ambraseys (1973) warned that earthquakes which would have caused practically no damage to ancient Athens could have a devastating effect on the modern cities. Conversely, little detailed engineering information is available
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about earthquake response of unreinforced masonry and mud-cemented stone walls such as found at numerous archeological sites. The following sections discuss the three main types of features of damage, presenting in each case a summary of observations and an appraisal of their significance in the recognition of ancient seismic events. Fissures and Fractures Fractured and sheared walls, buildings, structures and pavements represent a common form of damage reported from earthquake-disaster areas (op. cit.). Most sites in Table 2 display such features, which range from fissures and hairline joints on which separation and displacements are hardly perceptible, to cracks in which separation is clear and faults show a clear displacement and local breakage (Figure 2). However, no shear cracks were observed nor any consistent patterns of jointing and displacement. Interpretation and dating of fissures and fractures is equivocal, the more so, in that damage of this kind is cumulative and may represent the combined effect of numerous events, not necessarily of a great magnitude. After all, joints and fissures occur also at sites for which no ancient earthquakes were postulated in the literature. It is equally well known that excavation works, however careful, cause local changes in stresses that affect the buried ruins and structure, and may result in relaxation joints. Relaxation may have occurred also during earlier times, when supports were demolished and earth reshuffled, or when the entire site was planed off between successive periods of occupancy. Table 2. Damage attributed to earthquakes at archaeological sites in Israel Site Ai Avdat Beit Shean Caesarea Ein Hanaziv Hazor Jericho (Tel el Sultan) Jericho (Tel Abu Aleik) Jericho (Khirbet Mafjar) Khirbet Qumran Khirbet Maqari Khirbet Shama Kypros Massada Massada Shivta Susita Tel Apheq (Antipatris) Tel Masos Telleilat Ghassul Tiberias
Evidence Widespread destruction, collapse of buildings, tiled walls, breakage Damaged, subsequently repaired city walls, cracks, damaged buildings Disturbances and collapse in the northern cemetery Displaced offshore moles and port installations, tiled walls Directed collapse, oriented fallen masonry Tilted columns and walls, collapse of buildings Slides and features of collapse Tilted and distorted walls, subsidence, collapse and breakage in buildings and water installations Widespread destruction and collapse Breakage and displacement in a water reservoir, cracks and damage to buildings Violent destruction Tilted and distorted walls, collapsed buildings Features of collapse and sliding, imbricated fallen masonry Damaged and cracked floors Tilted walls, oriented fallen masonry, collapse of parts of buildings over the rock cliffs Collapse and damage, and subsequent repairs in the northern area Oriented fallen columns, tilted walls and buildings Tilted and distorted walls, collapse, subsided arches Collapse and oriented fallen masonry Breakage and displacement, cracks, tilts Desertion of the southern part of the city
Time 27th century BC 5-6th century AD
? 2nd century AD 7th century AD 8th century BC 1 1st century BC 8th century AD 1st century BC 7-8th century BC 4th century AD ? 1st century BC 1st century BC and later shocks 5-6th century AD 5th cent&
AD
40th century BC 1lth century AD
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Difficulties in distinction of earthquake-induced fractures from those due to geotechnical effects are well illustrated by the case of Khirbet Qumran, a 1st century BC Essene community near the Dead Sea. Here a prominent fault of 25 cm vertical displacement cuts across the staircase of a water reservoir. This fracture (Figure 2), cited by Zeuner (1955) and Bender (1958) as a proof of recent tectonic activity along the Dead Sea-Jordan Rift, is regarded as evidence of damage and subsequent desertion of the site due to the earthquake of 31 BC reported in historic chronicles. Though this interpretation enjoys official status (as witnessed by the text on tourist post-cards), the actual field evidence per se is inconclusive. The settlement is located in Lisan Marl, a late Pleistocene formation which consists of alternating calcareous and clayey layers. This substratum is unstable and is prone to differential swelling, desiccation and compaction which result in cracks, rills and landslides. Furthermore, a small sediment-settling basin is located just behind the damaged staircase, so that its collapse may have been caused by seepage,
Figure 2. Displacement across the staircase of a water reservoir, at Khirbet Qumran, attributed to the 31 BC earthquake. The structure is located in the geotechnically unstable Lisan Marl. in which differential swelling, compaction and desiccation occur.
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percolation or piping (Figure 3). The non-tectonic explanation of the Qumran displacement was originally offered by Zavistock, who supervised the excavations, but was subsequently rejected (de Vaux, 1961). Joints and fissures, subject to similar reservations occur also in several other buildings and structures at Khirbet Qumran. The 31 BC earthquake is believed to have affected a number of other sites such as Massada and Jericho but not the nearby Fashkha, where a break in occupation appears to be unrelated to any seismic shock (de Vaux, 1961). Indeed the cracks and fissures in the walls of the Fashkha citadel encountered in our survey, are not ancient and represent the result of too deep an excavation of the fundaments by a bulldozer (Mincker, personal communication).
Figure 3. A small settling basin at the aqueduct entrance to the damaged reservoir at Khirbet Qumran (Figure 2). Seepage and percolation may have undermined the reservoir staircase.
Not only the origin, but also the age of individual fractures is questionable. Thus for example, though all advocates of the seismic origin of the Qumran displacement attributed it to the 3 1BCearthquake, Picard (193 1) in a regional geological study of the Judean desert, antedating the archeological excavations, mentions a N-S “cleft” produced in the strong earthquake of 1927. Yet another enigma is presented by the dense jointing across the cliffs rising above the northern Herodean palace on Massada. Figure 4 shows that the joints and cracks do not affect the remnant walls and columns, suggesting that jointing occurred before the construction. However, one is left wondering why the ancient builders ignored the dangers of rockfalls from such strongly jointed cliffs, especially when the various archaeological sources suggest that a strong earthquake (probably that of 31 BC) occurred in the course of construction (Yadin, 1966). Yet another controversy exists in the interpretation of ancient damage and destruction at Telleilat Ghassul, a Chalcolithic settlement on the east side of the Jordan Valley. The earlier investigators attributed the observed tilting, fracturing and collapse to a series of ancient earthquakes, whereas North (1960) argued that the mudbrick buildings are unstable and collapse after only a short period of time. The recent work of Hennessey (1969) presents, however, photographs which demonstrate quite clearly the occurrence of tilts, clefts, gauge, wide cracks and a conspicuous displacement of about 60 cm, unlikely to result solely from poor construction. Oriented Collapse and Tilting
Tilt and collapse in a given direction of buildings, walls and structures, encountered in
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the various earthquake disaster areas (op. cit.) are generally attributed either to shocktriggered mass movements of the ground, such as liquefaction and slope failure (e.g. the Niigata 1964 earthquake, the Alaska 1964 earthquake), or to earthquake-induced shears which alter the original stress distribution within a given structure (e.g. such as expressed in a differential displacement of the various parts of a building). Table 2 indicates that the occurrence of such features at several archeological sites was interpreted as an imprint of ancient seismicity. Tilted columns (Figure 5) are found at Hazor, where also numerous walls deviate from the vertical, The tilt is not uniform, but in most cases the structures dip eastwards and northeastwards. This tilt of the 9th century BC buildings and columns is tentatively attributed to an 8th century BC violent earthquake (cf. Table 1). Tilted walls appear to be quite common. At Tel Abu Alek (Jericho) the eastern wall of the Hasmonean palace dips to the east, a tilt tentatively attributed to the 31 BC earthquake (Nezer, personal communication). At the same time, it also appears that the wall
Figure 4. Dense joints and cracks in the dolomite rockcliffs above the northern Herodean villa on Massada. The plaster along the walls and columns appears to be unaffected.
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Figure 5. Tilted columns of 9th century BC building at Hazor, attributed to an 8th century BC shock. Similar tilts occur where construction is poor and the ground is unstable.
Figure 6. One of the subsided arches at Tel Afek (Antipatris) attributed to the 419 AD$:earthquake. Sagging of columns and arches occurs also in aseismically subsiding ground. In the present case, arch subsidence is accompanied by strongly tilted and distorted walls and joints.
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of the adjoining Herodean palace is distorted and tilted eastwards, thus allowing the possibility that the tilting occurred at a date later than 3 1 BC, Similar tilted and distorted walls and subsiding arches were encountered in the excavations of the Byzantine town of Antipatris (Aphek) and led Kochavi (1976, and personal communication) to attribute the destruction and decay of this prosperous community to the violent earthquake of 419 AD, reported in the historic records (Figure 6). Recently, Ecker & Olshina (personal communication) found that the walls of the Roman buildings at Caesarea are tilted to the northwest, and a submerged tilted structure was discovered by Raban (1976) in an underwater archaeological study of this ancient port. The later, Byzantine structures are not tilted, and it would appear from the analysis of historic records, that if the distortion of the Roman walls is indeed related to a strong earthquake, it may have occurred in the 130 AD destructive shock. At a number of sites believed to have been affected by ancient earthquakes, tilted walls are accompanied by features of a preferred collapse of walls and parallel alignment of the fallen masonry. Such evidence was reported by Yadin (1966) from the store-room complex of Massada, where walls are tilted westwards and the fallen stones are aligned in parallel rows. Somewhat similar collapse of the walls of an ancient synagogue at Ein Hanaziv in a preferred direction led Vito (personal communication) to the assumption that the building was destroyed by the 7th century AD earthquakes. A more extreme example of imbricate disposition of fallen masonry was encountered at Kypros, a hilltop fort near Jericho (Figure 7; Meshel, personal communication). Probably the most impressive, though somewhat enigmatic, case of preferred collapse and alignment was encountered at Susita, where the fallen columns of a Byzantine church are almost perfectly parallel to each other, and where other buildings show strongly tilted walls (Figures 8,9 and 10). The site is reputed to have been affected by a destructive earthquake, but so far no specific date has been proposed. In spite of the undoubted significance of such features, tilting and directional collapse should not be treated as unequivocal evidence of ancient seismic disasters. The standards of original workmanship may have been less than perfect and walls need not have been perfectly vertical and straight when built (e.g. Meyers, 1972). Furthermore, the distortion and collapse of walls need not necessarily be of a seismic origin. Soil creep and slides occur on both natural and artificial slopes, especially in seasonally waterlogged formations and in poorly compacted ground. A recent example of such creep was observed in the village of Maghar in Central Galilee, where the unstable clayey slopes abound in ground cracks and terracettes, where columns and piles of buildings are deflected from the vertical, and where steps and pavements are displaced downslope (Hayati, personal communication). Displacements and differential bending were observed also in various studies of stability of intensely jointed rock-cliffs (e.g. Hoffman, 1973). Yet another possible mechanism leading to tilting of floors, aqueducts and walls is represented by small-scale vertical crustal movements. Such vertical shifts were reported from various parts of Israel (Kafri, 1969; Karcz & Kafri, 1973, 1975) and if persistent in sense and magnitude, could have led to distortion and tilting of existing structures. Subsidence, Sagging and Collapse Features of subsidence and collapse of architectural and engineering structures were reported from all earthquake-disaster areas, and were observed at virtually all the sites indicated in Table 2. However, in this case, distinction between seismic and aseismic mechanisms of collapse and sagging presents considerable difficulties. Several examples will suffice to illustrate the problem.
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Figure I1 shows the local collapse and subsequent repair of the outer walls of the Byzantine acropolis at Avdat, attributed conversely to the effects of a 5th century AD earthquake, to poor construction, and to wilful damage (Negev, personal communication). Figure 12 shows characteristic examples of collapse and subsidence to a Herodean aqueduct system and the adjoining floors and walls at Tel Abu Alek, Jericho, a site believed to have been affected by at least one ancient violent earthquake (Nezer, personal communication, op. cit.). However, such damage may have been caused by the repeated swelling and desiccation of the marly and clayey alluvium through which the primitive aqueducts run, without any relation to seismic activity. The disastrous rockfall of a large block of Lisan Marl, which caused loss of life and damage at Neot Ha’Kikar not far from the Dead Sea in 1969 provides a good example of such geotechnical effects.
Figure 11. Damaged and subsequently repaired retaining walls of the acropolis, Avdat, tentatively attributed to a 5-6th century AD earthquake.
Figures 13 and 14 show a pronounced subsidence, tilting and damage to the floors, walls and buildings of the Ommayad period (7th century AD) in Jerusalem. Though such features of damage may have been triggered by one or more of the rather weak earthquakes mentioned by Shalem (1949) in his analysis of historical sources, other explanations are equally possible. The foundations rest here on artificial dirt fills and screes, derived mostly from the destruction of older buildings and levelling prior to new construction (Figures 14 and 15). Such fills which are also very common at the various “tells” (mounds) with a long record of occupation, and at hilltops where they were used to extend the building space at the summit, display a prominent stratification marked by differences in size and composition of the constituent particles. Usually, the beds are moderately to steeply inclined and display characteristics of slope-scree deposits. When no effective means of pre-construction compaction are available, this type of ground is unstable and creep, sliding and differential compaction may occur, no matter whether or not it is induced by seismic shocks.
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Figure 12. Subsidence and collapse at and near water conveyance structures, Jericho, Tel Abu Aieik, in an unstable Lisan Marl alluvium.
(below) Figure 13. Strong tilting of walls and columns in structures of the Ommayad period, Jerusalem.
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Figure 14. Subsidence of floors of Ommayad buildings, Jerusalem. Note the cross stratification in the underlying fill material.
Figure 15. Typical cross stratification of dirt fills, St Anne’s, Jerusalem.
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Discussion and Summary A critical survey of theavailable archaeological earthquakeevidenceinIsrae1 suggests that though this information may provide a further dimension in the study of ancient seismicity, great care is needed in its evaluation. Limitations on the use of such data as an entirely independent instrument of cross-verification of historic records appear to stem from the following sources. First, the decision of an individual archaeologist to assign features of destruction to seismic causes may well be affected by his awareness (or lack thereof) of historic references to establish a chronological reference horizon for the site in question. Second, in some cases, an earthquake may provide a deus ex machina explanation of otherwise inexplicable desertion or decay of a prosperous township in peacetime, adding a touch of drama to the site history. Finally, in restricted excavations and isolated ruins, features of seismic damage are difficult to distinguish from those due to poor construction or adverse geotechnical effects. It is well known that the location of ancient settlements in the Middle East was dictated largely by site defensibility and by the availability and retention capacity of water, considerations which may have brought the ancient planners into a conflict with standards of soil and rock stability and construction safety. Indeed, many settlements and forts lie above steep rock cliffs or above steep natural or artificial slopes, where aseismic rockfalls, landslides and creep may occur. Many buildings are founded on alluvium, marls and clayey ground (or where such water-retaining formations appear in the shallow subsurface), which may be unstable even to a minor shock, which under more favourable soil conditions would have left no imprint on any buildings or structures. Tuble 3. Proposed damage
I. 2. 3. 4. 5. 6. 7. 8. 9.
10. 1I. 12. 13. 14. 15.
general
scheme
of’ description
of suspected
archaeoseismic
Location and size of site Main periods of occupancy Age of damaged structures Nature of excavation works (rescue and salvage operation, preliminary, single-season, continuing, etc.) Mode and mechanism of excavation (equipment employed, amount of overburden removed, programme of operations etc.) Extent of excavated area and number and size of the exposed buildings and structures Type and quality of construction of the damaged buildings and structures (e.g. masonry, stone, adobe etc.; type of cement, reinforcements and fundaments) Type of damage (e.g. collapse, oriented collapse, tilting, breakage, subsidence, fractures and displacement) Extent and distribution of damage across the site (number of damaged elements, changes in amount and intensity of damage, direction of features of damage and of any possible alignment of the fallen components, etc.) Occurrence of similar damage at other contemporary sites Differences between the observed features of damage and those characteristic of man-induced damage Physiographic setting of the site (relief, distance from cliffs and slopes, slope characteristics, distance from watercourses and shores etc.) Type and composition of the ground (e.g. rock, alluvium, clay; depth to bedrock, etc.) Features of recent ground instability (e.g. slides, creep, rockfalls, desiccation cracks, erosion gullies and rills, occurrence of karst features) Structural settings of the site (e.g. distance from faults and their orientation, occurrence of joints and their orientation, inclination and structural position of the strata
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Some of the uncertainties in evaluations of archaeoseismic data could be removed by the introduction of a standard, systematic method of description of ancient damage, which would ensure a proper balance between the geological, geomorphological and geotechnical factors, and the historic and anthropogeographic considerations. Table 3 lists some of the factors to which attention should be paid in the course of any interpretation of potential field evidence of ancient seismic activity. Notwithstanding the doubts and uncertainties outlined above, the analysis of archaeological data should be included in all systematic evaluations of regional seismicity and in assessments of regional seismic hazards. Thus for example, in Israel it may be pertinent to note that the great majority of archaeological sites at which seismic activity was inferred are located along the Dead Sea-Jordan Rift, the main seismogenic zone in this part of the Levant. This concentration (about 75 %) is significantly greater than that which may be inferred from the study of historical sources (only 15-307; of the references indicate activity along the Rift and its margins) which would suggest a more even distribution of past earthquake damage (Karcz et al., 1977). Acknowledgements The help and advice of numerous members of the archaeological community in Israel, as well as field guidance and discussionswith M. Ben Dov, D. Bahat, M. Kochavi, Z. Meshel, Y. Mincker, E. Nezer, M. Negev and F. Vitto, helped to identify and clarify the nature of the evidence and arguments cited in support of ancient earthquakes. Needlessto say, none of our colleagues share the blame for our errors. Grants in aid from National Academy of Sciences(Day Fund), and SUNY Research Foundation (I.K.) are gratefully acknowledged. References Ambraseys,N. N. (1971).Value of historic recordsof earthquakes.Nature 232, 375-379. Ambraseys,N. N. (1973).Earth sciencesin archaeologyand history. Antiquity 47, 229-230. Ambraseys, N. N. (1975). Studies in historical seismicity and tectonics. In (W. Brice, Ed.) Historical Geography of the Middle East. London: Academic Press. Amiran, D. K. (1951).A revisedearthquakecatalogueof Palestine.Israel Exploration Journal 1,223-246. Anon. (1962). The Agadir Morocco Earthquake, February 29, 1960.New York: American Iron and SteelInstitute, 112pp. Anon. (1970).Encyclopedia of Archeological Excavations in Eretz, Israel. Hebrew Edition, ~01s 1, 2 (1975; EnglishEdition, vols 1 and 2, out of 4). Massada.Jerusalem. Arie, E. (1967).Seismicityof Israel and adjacentcountries.Geological Survey of Israel, Bulletin No. 43, 1-14. Bender, F. (1958).Geofogie von Jordanien. Berlin: Gebruder Borntraeger, 230 pp. Benfer, N. A. (1974). Sun Fernando, California, Earthquake of February 9, 1971. Vol. 1, parts A, B. US Department of Commerce,841 pp. Ben Menahem,A., Nur, A. & Vered, M. (1976).Tectonics,seismicityand structure of the AfroEurasianjunction, the breakingof an incoherentplate. Physics of Earth and Planetary Interiors 12, l-50. Berg, G. V. (1963).The Skopje, Yugoslavia Earthquake of Jury 26, 1963.New York: American Iron and SteelInstitute, 78 pp. Fleming, N. C. (1969).Archeological evidencefor eustaticchangeof sealevel and earth movementsin the westernMediterranean during the last 2,000 y. Geological Society of America, Special Paper No. 109, 125pp. Hennessey,I. B. (1959).Preliminary report on a first seasonof excavationsat Telleilat Ghassul. Levant 1, l-25.
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Hoffman, H. (1973). Steep slopes in regularly jointed material. Geologia Applicata 8, 91-103. Kafri, U. (1969).Recent crustal movementsin northern Israel. Journal of Geophysical Research 74,42464261. Karcz, I. & Kafri, U. (1973). Recent vertical crustal movementsbetweenMediterranean and the Dead SeaRift. Nature 257, 296-297. Karcz, I., Kafri, U. & Meshel,Z. (1977).Archeological evidencefor subrecentseismicactivity along the Dead Sea-JordanRift. Nature %9,234-235. Kochavi, M. (1976).Tel Aphek-1975.Israel Exploration Journal 25, 51-52. Lew, H. S.,Leyendecker,E. V. & Dikkers, R. D. (1971).Engineering Aspects ofthe San Fernando Earthquake. National Bureau of Standards,US. Bldg. Sci. Ser., Vol. 40, 419 pp. Meyers, E, M. (1972).Khirbet Shemaand Meiron. Israel Exploration Journal 22, 174-175. North, R. (1960).Ghassul1960Excavation. Analecta Biblica 14, l-88. Raban, A. (1976). Marine Archueo1og.y Study of Caesareu. Haifa University, Marine Studies Center, 64 pp (in Hebrew). Shalem,N. (1949).Earthquakesin Jerusalemhistory. Jerusalem 2, 1-3, 22-54 (in Hebrew). Shalem,N. (1952).La seismiciteau Levant. Bulletin of the Research Council of Israel 2, 1-16. Sieberg,A. (1932).Untersuchungeniiber Erdbebenund Bruchscholenbauim OstlichenMittelmeergebiet.Denkschriften Medizin und Naturwissenschaft Gesellschaft Jena,18, 161-273. Steinbrugge,K. V. (1972). Comparative building damage.In (A. F. Espinosa& S. T. Algermissen,Eds) A Study of Soil Amplification Factors in Earthquake Damage Areas, Caracas, Venezuela. NOAA Techn. Rept., ERC 280-ESL 31. de Vaux, R. (1961).L’ArchPologie et les Manuscripts de /a Mer Morte. London: Oxford University Press,107 pp. Wiegel, R. L. (1970).Earthquake Engineering. Englewoods,N.J.: Prentice-Hall, 518 pp. Willis, B. (1928).Earthquakesin the Holy Land. Bulletin of the Seismological Society of America 18,73-103. Wu, F. T., Karcz, I., Arie, E., Kafri, U. & Peled,U. (1973).Microearthquakesalong the Dead SeaRift. Geology1, 159-161. Yadin, Y. (1966).Massada. New York: Random House,272 pp. Zeuner, F. (1955).Recentmovementon the westernfault of the DeadSea.Geologische Rundschau 43, 2-3.