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Deformed arches are often key elements of archaeoseismic studies; arches have been in use for more than three millennia and damage, particularly moved keystones, are clear indications of a seismogenic cause. We introduce a damage evaluation scheme that allows a straightforward determination of the degree of damage to an arch based on laser scan models and digital images. The scheme is applied to 90 arches of the Nimrod Castle, which is neighboring the Dead Sea fault and which was heavily damaged during the 1759 Lebanon earthquake. The analysis shows that the a priori assumption of a correlation between arch orientation and damage degree does not hold for the entire building. An exception is a large tower including a secret passage in which voussoirs have dropped along a more than 20 m long section.

In certain regions and under favorable geologic conditions, precariously balanced rocks may form. These types of unusual formations have been

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Archaeological structures built across active faults and ruptured by earthquakes have been used as markers to measure the amount of displacement caused by ground motion and thus to estimate the magnitude of ancient earthquakes. The example used in this study is the Crusader fortress at Tel Ateret (Vadum Iacob) in the Jordan Gorge, north of the Sea of Galilee, a site which has been ruptured repeatedly since the Iron Age. We use detailed laser scans and discrete element models of the fortification walls to deduce the slip velocity during the earthquake. Further, we test whether the in-situ observed deformation pattern of the walls allows quantification of the amount both sides of the fault moved and whether post-seismic creep contributed to total displacement. The dynamic simulation of the reaction of the fortification wall to a variety of earthquake scenarios supports the hypothesis that the wall was ruptured by two earthquakes in 1202 and 1759 CE. For the first time, we can estimate the slip velocity during the earthquakes to 3 and 1 m/s for the two events, attribute the main motion to the Arabian plate with a mostly locked Sinai plate, and exclude significant creep contribution to the observed displacements of 1.25 and 0.5 m, respectively. Considering a minimum long-term slip rate at the site of 2.6 mm/year, there is a deficit of at least 1.6 m slip corresponding to a potential future magnitude 7.5 earthquake; if we assume ~5 mm/year geodetic rate, the deficit is even larger.