Kázmér et al. (2024:33) proposed that Umm al-Jimal was affected by two separate earthquakes, the second occurring toward the end of the Umayyad Caliphate. They suggested that this later event may have been one of the 749 CE Sabbatical Year Earthquakes. Archaeoseismological indicators attributed to the two episodes included tilted and bulged walls, U-shaped collapse features, and evidence of rotational and extensional deformation. Al-Tawalbeh et al. (2019) described similar deformation in the Barracks, including tilted and bulging walls, U-shaped collapses, twisted walls, torsion-related damage, and displaced ashlars. Although they did not associate these effects with a specific historical earthquake, they suggested that the deformation most likely resulted from the second earthquake identified at the site.

The principal difficulty in associating this archaeoseismic evidence with the 749 CE earthquakes is chronological. Osinga in Lichtenberger and Raja (2025:184, 184 n. 8) notes that early Abbasid pottery displays strong continuity with late Umayyad pottery, with significant changes in the ceramic record not appearing until around the turn of the ninth century. She also notes a lack of coin-secured deposits and other chronologically diagnostic finds at Umm al-Jimal. Consequently, although some earlier scholars suggested that Umm al-Jimal may have been abandoned following the 749 CE Sabbatical Year Earthquakes, Osinga in Lichtenberger and Raja (2025:194) concluded that “we simply cannot characterize or date the departure of the sedentary populace from Umm al-Jimal, other than to state that it almost certainly occurred prior to the ninth century.” Whether this abandonment occurred gradually or rapidly, and what caused it, therefore remain open questions.

Despite these chronological limitations, several contexts provide more specific constraints. One is the Roman Temple, which Osinga in Lichtenberger and Raja (2025:186) notes “was later converted into a domestic structure known as House 49.” The building contained Byzantine and Early Islamic debris, and Osinga in Lichtenberger and Raja (2025:187) notes collapsed architecture on the porch (loci 036 and 040) that “may date to the Early Islamic period.” A second and potentially more diagnostic context occurs in the Numerianos Church complex, where substantial architectural collapse directly overlies floors last used during the Umayyad period. This establishes a mid-7th-century CE terminus post quem for the major collapse observed in the complex. Osinga in Lichtenberger and Raja (2025) also reports possible mid-eighth-century archaeoseismic evidence in House 119.

Nevertheless, Osinga in Lichtenberger and Raja (2025:194) cautions that “while the AD 749 earthquake may have caused destabilization of some structures and collapse of certain features,” including portions of the Numerianos Church, “the archaeological record reveals no significant destruction that can be conclusively and solely dated to the mid-eighth century.” The archaeoseismic evidence at Umm al-Jimal is therefore extensive, but its attribution to a specific earthquake remains uncertain. If the sedentary population had abandoned or largely abandoned the site by the ninth century CE, the absence of substantial later rebuilding may have helped preserve evidence of earlier seismic damage. Some of this evidence may plausibly record one of the 749 CE Sabbatical Year Earthquakes, although a definitive attribution cannot currently be made.

Estimates of shaking severity indicate substantial ground motion. Kázmér et al. (2024:33) estimated a local intensity of IX (9) for the later event. Al-Tawalbeh et al. (2019) estimated a SW–NE strong-motion direction and intensities of VII–VIII (7–8) using the Earthquake Archaeological Effects chart of Rodríguez-Pascua et al. (2013:221–224). An independent survey of potential seismic effects by JW for DSEQC using the same Earthquake Archaeological Effects chart yields a minimum Intensity of VIII (8).