At the Tanninim Creek dam site, Marco et al. (2014:1449–1450) documented abundant liquefaction features at a stratigraphic interface between an overlying dark-colored pedogenic clay-rich layer and an underlying lighter-colored lacustrine clay and silt-rich unit. Within this setting, load structures were observed sinking downward while flame-shaped injections penetrate upward across the interface. These complementary structures reflect instability generated when elevated pore-fluid pressures develop in the more permeable silty layer but cannot dissipate through the overlying low-permeability clay layer, resulting in vertical deformation and sediment mobilization. Flame-shaped injections are most abundant and largest within several meters of a breach in the seaward face of an older Byzantine dam, possibly formed by a large wave (e.g. a tsunami). The lower portions of these injections exhibit zigzag geometries and a pronounced asymmetry, with southeastward vergence directed away from the breach. This asymmetry contrasts with typical earthquake-induced sand blows, which are generally vertical and symmetrical, and suggests directional shear associated with lateral motion. The zigzag geometries are interpreted as the product of oscillatory flow within the impounded lake above, consistent with sloshing triggered by sudden water displacement. In addition, the size and frequency of these injections decrease with distance, disappearing entirely at ~100 m from the structure. These observations suggest that tsunami processes may have contributed to their formation.

These features formed within the lacustrine deposits that accumulated behind the dam, where water-saturated silts and clays were confined below relatively stiff clay layers. In this setting, rapid increases in pore-fluid pressure in the silty layer could lead to liquefaction, allowing silt to be injected upward into overlying strata. Marco et al. argue that such overpressure could have been generated either directly by seismic shaking or by a rapid increase in overburden pressure caused by a sudden rise in water level.

A tsunami-related mechanism is favored based on the features observed and their spatial distribution. A wave breaching or impinging upon the dam could have introduced several meters of additional water into the reservoir, increasing vertical stress by ~0.3 bars—sufficient to exceed the confining strength of the sediment package and trigger liquefaction. The resulting shear between flowing water and unconsolidated sediment would promote instability, including Kelvin–Helmholtz instability, which provides a plausible explanation for the observed zigzag geometries in the injections.

Marco et al. (2014) cited comparative analogues to support this interpretation such as asymmetric sand injections and similar deformation structures documented in Thailand as a result of the 2004 Indian Ocean earthquake and tsunami and lacustrine sequences associated with seiche or tsunami-induced resuspension in the Lisan Formation. These analogs demonstrate that strong, directional water motion can impose shear sufficient to deform and inject water-saturated sediment in a consistent orientation.

Despite this, a purely seismic origin cannot be excluded. Marco et al. (2014) noted that a M > 6.5 earthquake on the Dead Sea Fault, located ~60 km east of the site, would be capable of triggering liquefaction at Tanninim. The Carmel Fault (~25 km northeast) is considered less likely due to the absence of evidence for significant recent seismic activity. It can thus be concluded that while earthquake shaking could have initiated liquefaction, the morphology of the structures and the damage to the dam favor the involvement of a tsunami or tsunami-like hydraulic forcing.

Stratigraphically, these deformation features occur within a well-defined lacustrine sequence consistently observed across multiple trenches (T1–T5) and an excavation exposure (T6), indicating laterally extensive conditions of sedimentation. However, the timing of the event remains uncertain. The primary difficulty is that the soft-sediment deformation features formed at some depth below the soil–water or soil–air interface at the time of their development. This prevents direct dating of the top of the lacustrine layer and the base of the overlying clay-rich layer, thereby limiting the ability to establish a tightly constrained chronological bracket for the event.

Marco et al. (2014) used historical and archaeological data to propose that one of the 1759 CE Safed and Baalbek Quakes is a plausible candidate for the triggering event. Assuming that the dam’s reservoir was filled at the time the soft-sediment deformation features formed, Marco et al. (2014) examined evidence for the duration of reservoir impoundment. They cited nearby flour mills as indicating that the reservoir remained active into the Ottoman period, possibly extending into the eighteenth century. However, this interpretation is contradicted by their own stratigraphic model (Fig. 3), which places the end of deposition of the upper lacustrine unit shortly after ~1400 CE. The overlying clay-rich soil, interpreted as a pedogenic horizon formed following desiccation of the lake, nevertheless contains fossils indicating intermittent inundation.

Marco et al. (2014:1457) also cite historical accounts, referencing Ambraseys and Barazangi (1989), who described coastal effects during the 25 November 1759 CE earthquake, including reports of "boats that were swept ashore from the Akko harbor" and a seismic sea wave observed as far south as the Nile Delta. However, the primary sources underlying these assertions in Ambraseys and Barazangi (1989) could not be independently verified, as they are not explicitly cited in their work, and their provenance remains unclear.

Because the timing of these faetues are not precisely constrained, the assignment of the 1759 CE earthquake as the triggering event, while plausible, remains interpretative rather than definitive.

Fig. 3 - Columnar section of the sediments in a trench east of the dam. The photograph mosaic on the left shows the location of samples. Arrow shows the horizon where flame structures are observed (Fig. 2). A single ¹⁴C age of detrital charcoal from TN8 is 245 ± 30 BP. The earthquakes that were associated with tsunamis according to historical accounts are listed. The temporal constraints imposed on the observed sedimentary section and the correlation with the archeological stratigraphy indicate that the liquefaction and the damage to the dam occurred after the deposition of the laminated lake sediments and accumulation of some 30 cm of clayey soil, and before the construction of the flour mills toward the end of the Ottoman period. The earthquake of November 25, 1759 is the most plausible cause for these features - click on image to open in a new tab - Marco et al (2014)

Left - Fig. 2c - Right - Fig. 2d - Load structures were formed by liquefaction of the lower light-colored lacustrine silt that penetrated the overlaying dark clayey soil. We interpret the structure asymmetry and zigzag shapes as result of shear forces exerted on the lake bed sediments by waves sloshing back and forth - click on either image to open in a new tab - both images from Marco et al (2014)