Association of earthquake footprints with different masonries
Different masonries at Qal’at al-Subayba have been reported by scholars [5]. However, this is the first study to define four different masonry styles, provide a chronological order for these masonries based on stratification, and to characterize the earthquake footprints associated with each style. A primary finding of this work is that the severity of earthquake damage is strongly associated with and confined to only two of the four masonries, namely the Massive and the Crusader. The Mamluk and the Ayyubic masonries are devoid of earthquake marks. It is currently assumed that the damage resulted from a single quake, namely the earthquake of 1759 [3, 6]. It should be taken into account, however, that in 1759 there were two earthquakes. The one that devastated Tiberias and Safed was different from that which devastated Baalbek, and the EQ that had the potential to affect the fortress was that which ran along the Serghaya Fault [18]. Based on this record and others, the intensity of this EQ in the Golan Heights cannot explain the damage to the fortress. In addition, on that date, the fortress was already deserted (Wilson FC, Caesarea Philippi: Banias, the Lost City of Pan, pp 163–164). By that time, the whole region had gone into obscurity; hence, supporters of damage caused by an EQ in 1759 need to account for the tremendous labor and resources required for the extensive restoration seen at the fortress. The discovery that the Ayyubic and Mamluk masonries were not damaged rule out possible association of post-medieval era earthquakes with the damage. A single earthquake can cause minor to major damage or even complete destruction. The extent of damage is highly correlated to magnitude and distance from the source but is also attributed to other factors, such as local surface motion, geological micro and macro constraints, masonry style, architecture, building height and more [19]. Focusing on masonry styles and architecture, it is well established that light buildings, low-quality masonries, and specific architectural designs are more susceptible than others [17, 20, 21]. Hence, if the fortress was hit by a single earthquake, then one would expect that the Ayyubic and the Mamluk masonries would have sustained the most damage and the Massive masonry the least. However, the opposite is found. While the Mamluk and the Ayyubic masonries harbor no earthquake-associated damage, the Massive masonry was devastated. This is even more striking when taking into account that trapezoid ashlars composed of massive block are known for being highly resistant to earthquake damage [22]. The more plausible explanation for this paradox is that the Ayyubic and Mamluk construction took place after the earthquake(s).
At the northwestern tower, the Massive masonry took the hardest hit, while the Crusader masonry at the same location sustained milder damage. This evidence, in addition to the observation that the stone wreckages are composed of only Massive elements, leads to the conclusion that the Massive masonry destruction preceded the Crusader masonry construction. Taken together, the fortress was hit by at least two major earthquakes, rather than one. The first earthquake caused the destruction of the Massive masonry while the second damaged the Crusader masonry. The Ayyubic and Mamluk masonries were built after the second earthquake.
Historical earthquake record and its implication on the fortress chronology
The Middle East has a long and continuous history of devastating earthquakes. Although no direct measurements of earthquake magnitude could have been taken, indirect geological and archaeological evidence, together with historical documentation, provide relatively accurate information for the date, site, epicenter, radius, and severity of these earthquakes. Current studies by Ben Menachem and Sbeinati provide a detailed description of the earthquakes recorded over the last 3000 years [23, 24]. Although there are some discrepancies between these reports with regard to time and severity, the discrepancies are insignificant. The illustration of earthquake chronology and severity in Fig. 8 is based on Sbeinati et al. [24].
The observation that the Mamluk masonry was spared rules out the association of the fortress’ damage to the earthquakes of A.D 1546, 1759, and 1837. The 1759 earthquake epicenter was far from Banias [24], further evidence that this earthquake did not damage the fortress. The earthquake most likely accountable for the damage is that of A.D 1202. Since this earthquake hit prior to the reign of Al-Malik Al-Aziz ‘Uthman, it rules out the Ayyubic theory of foundation and also provides an explanation as to why the Ayyubic masonry was principally spared. The Ayyubic inscription on the northwestern gate (Fig. 6c) appears to be carved on a section of Crusader masonry. According to Reuven Amitai [14], the terminology used in this Ayyubic inscription is ‘imara,’ meaning reconstruction or renewal, rather than ‘insha’ or ‘bina,’ the terms for establishment or construction. Hence, the association of the damage to the A.D 1202 earthquake is not contradicted by the Ayyubic texts.
Historical records provide further support for the pre-Ayyubic origin of the fortress. The Muslim historian Ibn-Chadded (1145–1234) described the construction by the Franks of a fortress above the city of Banias [5]. In his work, The Damascus Chronicle of the Crusades, the Muslim historian Ibn Al-Qalanisi (1107–1160) described the handing over in A.D 1128 of the frontier fortress of Banias to the Ismaili sect (Assassins) by Toghtekin, the Seljuk ruler of Damascus. According to the text, the fortress was partially destroyed [25]. Based on the current observations, the Franks had a central role in the fortress’ later construction. This conclusion is in agreement with by Deschamps who claimed that the fortress carries Hospitaller characteristics [5]. Ellenblum did not reject this notion; he claimed that the masons were locals who utilized the same technologies when building for the Crusaders, as well for their predecessors [3]. Although this hypothesis is not based on the historical record, it might seem sound. Nevertheless, some of the Frankish architectural characteristics were not adopted by the Muslims in their building. For example, basilica-like building designs and rib vaults, both symbolize the cross. The central hall, at the keep, might have basilica-like characteristics. However, since it was levelled to the ground the association is not definite (not shown). By contrast, rib vault elements can be clearly seen in the Eastern Hall (Fig. 4), providing direct evidence that this section was constructed by the Franks. Based on these findings, it can be concluded that the Crusader masonry is Frankish and that the earthquake damage to this masonry was the result of the A.D 1202 quake. This earthquake has been linked to the damage of several crusader castles in the region, including Vadum Jacob (Ateret), studied by Ellenblum and Marco [26,27,28].
The Massive masonry of the Northwestern Tower requires special attention. It appears to be the earliest section built and its destruction predated other constructions at the site. Based on the extent of damage and the scattering radius of the stones, the earthquake that hit must have been of exceptional magnitude and ‘devastating’ intensity [29, 30]. Of the earthquakes described by Sbeinati et al. [24], the only earthquake of such scale is the A.D 749 quake, with an estimated intensity of XI on the European macroseismic scale. If this is the earthquake that struck the Massive masonry, then the fortress chronology is pushed back to, at least, 500 years. Previous publications have associated the Massive masonry to the Mamluks [3, 6]. This association was made based on a Mamluk inscription found at nearby wreckage [6] that could well be associated with the northern tower, which is known to be Mamluk. In addition, no other examples for such masonry in Mamluk construction have been documented for the entire region. Hence, this association of the massive masonry to the Mamluks seems to lack supporting evidence.
The ancient origin of the fortress
Massive stone masonry is a very complex and expensive. It requires sophisticated architectural knowledge, highly skilled stone dressers, professional masons, special instruments and a large workforce to move and maneuver the stones [22]. Although this masonry was never common, there are fine examples of it in antiquity [31]. Locally, however, with the exception of Jerusalem, this type of masonry is found only at Qal’at al-Subayba. In ancient time, massive masonry relied heavily upon slave labor. It was abandoned in the early medieval period and replaced by more efficient and less laborious methods. The Mamluks were highly skilled masons [32]. Nevertheless, they did not have the knowledge or the means to utilize this technology. If they did have such skill, as suggested by Hartal [6], there should be examples of massive masonry at other Mamluk sites [15].
The Massive masonry at Qal’at al-Subayba resembles Hellenistic fortifications rather than Herodian or Roman [33]. Greco-Hellenistic masonry, characterized by trapezoid ashlars, can be seen in Hellenistic fortifications in Asia Minor [34]. The large slits for arrow ballistas (polivolos katapeltes) in the secret passage (Fig. 3f) are also found in other Hellenistic fortresses. Edward Robinson (1856), the 19th century explorer, recognized these characteristics and suggested that Qal’at al-Subayba was established in ancient times, either by the Phoenicians or the Greeks [2].
One can argue that if Qal’at al-Subayba is, indeed, of ancient origin, then it would have been mentioned in historical records such as Maccabean and Josephus Flavius chronologies. While this assertion is reasonable, many of the sites mentioned in these records have not been positively identified. For some, the same geographic description is given for different names. Yet, for others, the same name is associated with different geographic descriptions [35]. Gamla, for example, is described in Flavius’s The Jewish War IV as an isolated, naturally protected settlement situated upon a rough ridge between two deep valleys, and located at the lower Gaulanitis [36]. However, according to Flavius’s Antiquities of the Jews 13 [37] and The Jewish War I, Gamla (Gamala) is a strong fortress on the northern Gaulanitis near a deep valley called Antiochus Trench (Άντιόχου φάραγγα). This fortress was taken by Alexander Janneus during his expedition to the north. Polybius, in The Histories, Book 16, recounts Zeno’s telling of the battle of Panium. According to Zeno, Antiochus III (the Great) was positioned at the top of Mount Panium on the eve of the battle and his great victory over the Polemic Army [38].
It is possible to identify Mount Panium with the site of Qal’at al-Subayba. The fortress is situated on a narrow ridge with a protrusion resembling a camel hump, and the Antiochus Trench can be identified with the gorge of Wadi Sa’ar. It might be, therefore, that the fortress taken by Alexander Janneus and recorded as Gamla in Flavius’s Antiquities of the Jews 13 and in The Jewish War I is actually the earliest record of Qal’at al-Subayba. If this is the case, the fortress might have been founded by Antiochus the Great himself. This hypothesis is highly hypothetical and must be supported by further excavation. The hypothesis would explain, however, the singular regional use of the highly complex, expensive, and laborious Massive masonry at Qal’at al-Subayba.