EC project "Review of Historical Seismicity in Europe" (RHISE) 1989-1993

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Mohamed Reda Sbeinati*, Ryad Darawcheh *
and Mikhail Mouty *
* Department of Geology and Nuclear Ores, Atomic Energy Commission of Syria,
P.O. Box 6091, Damascus, Syria.

Field archaeological evidences
of seismic effects in Syria

It is of fundamental importance to collect all available information to reconstruct the maximum ground motion which occurred at archaeological sites in the proximity of which critical facilities are planned to be erected (Gürpinar and Margottini, 1994).
As Syria is rich in archaeological sites, field research was carried out to define the historical earthquake effects at archaeological sites located in north-western Syria along the northernmost part of the Syrian Lebanese Fault (SLF). This fault, which represents the northern extension of the Dead Sea transform fault system in Syria, is one of the most seismogenic fault zones in the region.
This study deals with five examples of archaeological sites. Fig. 1 shows location map of these monuments. This study involves:
- desk work oriented to define the archaeological sites damaged by earthquakes, their names during their life-times, time of their foundation and date of latest reconstruction;
- field investigation to define the type of earthquake damage and to distinguish seismic effects from non-seismic ones.

The history of archaeological sites investigated is briefly reviewed as follows:
- Qalaat Samaan (citadel of St. Simeon): situated on a limestone hill, it has splendid Byzantine monuments of the 5th century AD.
The cathedral surrounding the pillar, on top of which St. Simeon lived, is considered among the largest churches in the ancient world. The church was converted into a stronghold citadel during Sayf Ad Dawla Al-Hamadani's rule. There are ruins of a city on the slope of the hill (Zakariyya, 1984; Sha'ath, 1983).
- Qasr Al-Mshabak: located between Aleppo and Qalaat Samaan (3 Km. far from Daret Ezzeh), it has the shape of a rectangular church and probably it dates back to the Byzantine era. Unfortunately, historical information on this site is lacking.
- The archaeological sites in Barisha mountain (3 sites): located north-west of Idlib near the Turkish-Syrian border, they contain more than 200 of the so called "Dead Towns". These sites flourished during the Byzantine time and, for instance, they were described by Yakut al-Hamoui (1906), a geographer and historian who lived between 1178 and 1229, and occasionally visited them (Zakariyya, 1984). Among them, Sarfud, Kherbet Maez and Dahess are to be mentioned. The several churches, monasteries and temples in Barisha reflect the prosperous life enjoyed by the population. There are only few references available on these sites, poor in details (Tchalenko, 1953; Al-Satea, 1975).
Tab. 1 summarises the main characteristics of the five sites.

Fig. 1 - Location of the investigated archaeological sites.

Archaeological site
Time of construction
Building material
Dates of damaging earthquakes
(Ambraseys and Barazangi, 1989)
Present condition
Type of evidence
Grade of Damage according to
Qalaat Samaan (Citadel) =
St. Simeon
Byzantine Large size blocks of limestones 526,
1137, 1170,
1719, 1822\
Cathedral partially restored. Ruins of a city on the slope of the hill - Fractures
- Horizontal shifting
- Twisting
- Waving

Qasr Al-Mshabak (Palace) n.d. (Byzantine?) Medium size blocks of limestones   Church ceiling completely destroyed - Horizontal shifting
- Waved walls
- Extension

Dahess (Ruins) n.d. Large size blocks of limestones Most of earthquakes which hit Antioch In ruinous state with remaining individual wall - Rocking
- Horizontal shifting
- Waving

Sarfud = Al-Braeje (Convent) Byzantine Large size blocks of limestones Most of earthquakes which hit Antioch Partly destroyed - Fractures
- Horizontal shifting
- Tilting

Kherbet Maez (Ruins) Byzantine Large size blocks of limestones Most of earthquakes which hit Antioch Ruined considerably - Deformation
- Horizontal shifting
- Waving

Tab. 1 - Main characteristics of the investigated monuments.

Seismological and seismotectonic setting
The area where Samaan and Barisha mountains are located is very close to the Syrian Lebanese fault, and also close to another very active seismic zone, the Eastern Anatolian fault (EAF), outcropped to the north of the area (Fig. 1). The SLF, northern part of Dead Sea fault (DSF) is a N-S trending interplate transform fault between the Arabian plate (east) and the Sinai plate (west). It displays a left lateral displacement with minor components of extension and compression. Morphological and geological evidences for neotectonics along the SLF were evaluated by Radwan and Al-Najjar (1991). Moderate to large earthquakes occurred along the entire extension of this fault (Ministry of Electricity, 1988; Ambraseys and Barazangi, 1989; Sbeinati, 1994).
The area of Samaan and Barisha, like other areas along the DSF, seems to be stricken by large earthquakes (M >= 6.5) with long return period (200-350 years) (Ambraseys and Barazangi, 1989).

Evidences of possible seismic damage
Very frequent fracturing in the walls of these monuments can be observed. The origin of this fracturing is uncertain, i.e. they can be interpreted as effects of earthquake(s) or of deterioration of their structure (Fig. 2 and 9). The extension observed in Fig. 5 can be considered as a characteristic feature of the effects of seismic ground motion. An interesting example is displayed in Fig. 7, where the rocking of the western wall (Dahess) can be considered as a clear effect of seismic ground motion. Other evidence is shown in Figs. 3, 4, 6, 8 and 10. In Tab. 1, column 7 "Type of evidence", many types of possible seismic damage, observed at the investigated monuments, are listed.

Concluding remarks
The examples shown suggest that the study of archaeological sites can be a useful tool in understanding seismic history.
Archaeological evidence can be used to establish, in a very preliminary way, an upper limit of the seismic effects recorded at the site, if one assumes that:
- today evidence corresponds to the original earthquake record;
- the earthquake struck the site when it stood in good conditions and its vulnerability was the lowest possible.
If these two circumstances are not met, the archaeological evidence should be assumed as the result of lower shakings.
Following this point, Tab. 1 presents a very preliminary determination of the maximum macroseismic intensity which in principle might be correlated with the evidence rise.
In short, investigation on archaeological sites may give preliminary information on seismic effects, though they bear great uncertainties which necessitate concerted efforts to improve the reliability of the results.

This study is part of a research project entitled "Seismic Data for the Siting and Site Re-Validation of Nuclear Facilities" (No. 6247/RB), funded by International Atomic Energy Agency at Vienna. The authors express their sincere gratitude to the Director General of Syrian Atomic Energy Commission for his constant encouragement and support. We would also like to thank M. Stucchi and P. Albini for their valuable suggestions and remarks.

Al-Hamoui,Y., 1906. Moujam al-bouldan. Cairo [n. pub.].
Al-Satea, A. and Al-Satea, F., 1975. Al-Dalil al-Akhdar lil siyyaha wa al-athar. Dar al-Fukr, Damascus.
Ambraseys, N. and Barazangi, M., 1989. The 1759 earthquake in the Bekaa Valley: Implications for earthquake hazard assessment in the Mediterranean region. Journal of Geophysical Research, 94, B4: 4007-4013.
Gürpinar, A. and Margottini, C., 1994. Possible evidences of past seismic ground motion(s) in the historical town of Hatra (Central Mesopotamia). Proc. of the Regional Workshop on Archaeoseismicity in the Mediterranean region, Damascus (in press).
Ministry of Electricity, 1988. Report of macroseismic research in areas of NPP sites location (in English), Aleppo.
Radwan, Y., Al-Najjar, H. and Darawcheh, R., 1991. Investigations of active tectonics along the major faults in Syria using geomorphic techniques. In: S. Riad, A. Morelli and M. Miele (Editors), Proc. of the First Regional Seminar on Earthquake Research Activity and Risk Assessment in the Mediterranean region, Cairo.
Sbeinati, M. R., 1994. Evidences of seismic effects on selected archaeological sites in Syria. Report on scientific field study, Atomic Energy Commission of Syria, Damascus, pp. 4-28 [not public].
Sha'ath, Sh., 1983. Qalaat Samaan. The Directorate General of Antiquities and Museums, Damascus.
Tchalenko, G., 1953. Villages antiques de la Syrie du Nord. Librairie Orientaliste, Paris.
Zakariyya, W., 1984. Jawala athariyya fi baed al-bilad al-chamiyya. Dar al-Fukr, Damascus.

Fig. 2 - Fracturing and horizontal shifting in the western wall of a building at Samaan city.

Fig. 3 - Rotated pillars and waved wall at Samaan city.

Fig. 4 - Characteristic deformation of major earthquake at Al-Mshabak site.

Fig. 5 - Lateral extension and down sliding of the central key stones
of one internal arches: a characteristic
feature of earthquake effects
at Al-Mshabak site.

Fig. 6 - Rocking of the western wall
at Dahess site.

Fig. 7 - Horizontal shifting and waving in the southern wall at Dahess site.

Fig. 8 - Cracks in the bedrock (basement of the building),
Sarfud (Al-Breige) site.

Fig. 9 - Breakage and tilting of the pillar that supports a water reservoir, Sarfud (Al-Breige) site.

Fig. 10 - Flower-petals-like splitting of the western church at Kherbet Maez: stones rotation and fall are usually resulted by long seismic duration effect.