Evidence for seismic destruction and tsunamis associated with mid-8th-century CE earthquake(s) is documented in Caesarea and offshore of Caesarea. Goodman-Tchernov et al. (2009) identified offshore tsunami deposits in cores taken near the harbor of Caesarea, which Goodman-Tchernov and Austin (2015) dated to the 5th–8th centuries CE. Initially attributed solely to the 551 CE Beirut earthquake, later reinterpretation linked most of the deposit to one of the mid-8th century Sabbatical Year Quakes, suggesting possible reworking of older material within a younger tsunami layer. Dating was based on ceramics, radiocarbon, and OSL analyses, while a multiproxy approach was used to differentiate tsunami deposits from other types of deposits (e.g. storm surge deposits). Further evidence of the same event was identified ~1.5–4.5 km north just offshore from Jisr al-Zakra, where Tyuleneva et al. (2017) reported a tsunamite in core JZ-6 dated to 658–781 CE, consistent with the so-called “Holy Desert Quake” of the Sabbatical Year earthquake sequence.

Complementing the offshore evidence, Goodman-Tchernov and Austin (2015) described a potential tsunami deposit uncovered in excavations of the shallow intermediate harbor (TN area). They report that the deposit contained a “broadly mixed” 4th–8th century assemblage of refuse, including broken amphorae, domestic wares, intricate hair combs, coins, a statuette, and “a satchel of copper coins,” all exhibiting “varying erosion states” suggestive of rapid, non-deliberate burial. The range of materials — spanning domestic, commercial, and religious contexts — they argue, differs markedly from typical harbor deposits and thus supports interpretation of the layer as tsunami-related.

Ad et al. (2018) describe excavations in Area LL, located north of the inner harbor, where an Umayyad-period warehouse shows signs of collapsed ceilings and fire damage, followed by the accumulation of more than 2 m of sand and collapsed masonry interpreted as tsunami deposits. During a subsequent Abbasid occupation, the site was leveled and rebuilt above the debris, preserving the destruction evidence. Sediment cores and a baulk analyzed by Everhardt et al. (2023) identified a sequence of layers from top to bottom: an upper clean-sand unit interpreted as a tsunami deposit; a sand unit containing marine-encrusted sherds and heat-altered clusters, interpreted as a mix of earthquake debris, fire remains, and tsunami material; an organic-rich layer with abundant cultural artifacts referred to as the "Umayyad archaeological fill"; and a compact earthen floor. Everhardt et al. (2023) further report that radiocarbon dates of charcoal and organic material from the upper contact of the Umayyad archaeological deposit (Unit C) range from 605 to 779 CE. These results align with the stratigraphic phasing proposed by Ad et al. (2018) and are consistent with destruction layers attributed to the 749 CE event.

Dey, H. et al. (2014) interpret a marine layer between the Temple Platform and the Theater, south of where the Crusaders would build their fortifications, as a tsunami deposit. They report that late 7th–early 8th-century terraced gardens were buried beneath extensive marine strata containing Glycymeris, a non-edible deeper-water bivalve, and in some areas capped by a burial ground that provided an 870 CE terminus ante quem through an epitaph on one of the graves. A c. 500 CE terminus post quem for the marine layer was provided by a reflecting pool which was found below the marine layer. Dey, H. et al. (2014) argue that a tsunamogenic inundation best explains the transformation from gardens to burials, noting the presence of disarticulated human remains and at least one intact skeleton within the 8th-century CE marine deposit.

Dey et al. (2014) also argue that archaeological evidence of seismic destruction associated with one of the mid-8th-century earthquakes is present around the Temple Platform in Area TPS.. Drawing on Raban & Yankelevitz (2008) and Arnon (2008), they report that a thick debris layer on the southern side of the Temple Platform "marks the end of the Umayyad occupation of the Late Byzantine bath complex." This debris layer is attributed to structural collapse triggered by one of the mid-8th-century earthquakes. Furthermore, citing Holum et al. (2008), Dey et al. (2014) propose that the octagonal church located above the platform also likely collapsed during the same seismic event.

Seismic and Core cross sections showing interpreted tsunamigenic strata - To the left are individual cores from Caesarea and to the right are composite cores from Caesarea and Jisr el Zarka (~1.5-4.5 km. from Caesarea. Click on either image to open in a new tab.