Excavations across Beirut reveal destruction layers dating to the mid-6th century CE, associated with the 551 CE Beirut Earthquake. In Sector BEY 004, Saghieh-Beydoun (1997) documented soft-sediment liquefaction features, including diagnostic flame structures at the base of a thick destruction and debris-flow deposit. These features, produced by pore-fluid overpressure during seismic shaking, occur beneath deposits likely associated with tsunami inundation. Their stratigraphic position suggests that seismic shaking followed a tsunami, a sequence consistent with historical accounts by John of Ephesus and Pseudo-Dionysius of Tell-Mahre, who report that the tsunami preceded the main shock.

Archaeological excavations throughout the city show a late antique destruction horizon up to 1 m thick, often capped by fire debris. According to Mordechai (2020), the evidence reveals “an archaeological inferno over the whole excavated area,” though the destruction layer varies in thickness across sites. Artifacts found within the debris — including wrapped coin rolls, a hanging bronze polykandelon , human and animal remains near collapsed walls, and clusters of coins — support a mid-6th-century date (see Mikati & Perring; Steiner). However, some teams noted that building collapses were not always catastrophic, citing the absence of smashed household goods and pottery assemblages (see Badre 2016; Butcher & Thorpe 1997).

Post-seismic rebuilding evidence complements this destruction record. Hall (2004) reports that mismatched column colors in a church or basilica identified by Lauffray likely represent repair work after the earthquake, contrasting with earlier descriptions by Zacharias Rhetor (c. 465 - after 536 CE) that emphasized perfectly matched white columns. Lauffray further proposed that the civic basilica, public baths, and porticoed street underwent repairs, though the identification of many buildings remains uncertain (Lauffray 1944–46).

Although Marriner et al. (2008) reports that researchers found no discrete tsunami deposits (tsunamites) in 20 sediment cores from Beirut’s buried harbor, other geoarchaeological and archaeological observations point strongly to tsunami impact. Excavations revealed large quantities of unabraded Roman pottery, rubble, and tree branches in 6th–7th century layers, suggesting rapid high-energy deposition. Unconformable harbor muds and silts overlying sea-scoured bedrock indicate powerful erosive currents, likely from tsunami backwash. These findings align with reports of major port damage, reconfiguration of harbor structures, and a long-term decline in Beirut’s maritime infrastructure following the event (Curvers & Stuart 2004).

Further support comes from evidence of widespread urban disruption: many neighborhoods were left in partial ruin or abandoned, reconstruction was limited, and trade patterns shifted significantly in the aftermath (Mikati & Perring 2006). Raised shoreline dating north of Beirut shows coseismic uplift of 50–80 cm (Morhange et al. 2006).

Synthesizing this evidence, Salamon et al. (2024) highlight a transition from fine-grained to coarser-grained sediments in harbor deposits, a signal commonly linked to harbor abandonment or decline following catastrophic events. They emphasize the presence of sea-scoured bedrock, the absence of infrastructure, partial abandonment, and limited rebuilding as diagnostic indicators of tsunami impact. Reconstruction of the mid-6th-century harbor coastline further corroborates these findings, with shoreline positions aligning closely with modern configurations, implying large-scale geomorphological reshaping during the event.

The combined archaeological, paleoseismic, and tsunamigenic evidence converges on a picture of widespread destruction and profound urban transformation in Beirut following the 551 CE earthquake. Archaeological strata preserve signs of catastrophic collapse, fire, and repair, while sedimentary structures document intense shaking and possible foreshock-mainshock sequencing. Geoarchaeological and paleoseismic data reveal tsunami erosion, harbor abandonment, and uplift, reflecting both the earthquake’s seismic force and the hydrodynamic power of its associated tsunami. Together, these multidisciplinary datasets provide a coherent narrative of one of the most devastating seismic events in eastern Mediterranean history.