Kehrberg-Ostrasz and Manley (2019) excavated a number of trenches from 2000-2002 along Jerash's city walls in order to determine their date of construction.

• from Chat GPT 4o, 22 June 2025
• sources: Kehrberg-Ostrasz in Savage et al. (2003); Kehrberg-Ostrasz and Manley (2019)

The city walls of Jerash (ancient Gerasa) form an enclosing fortification system dated primarily to the 4th–6th centuries CE. Excavation and architectural analysis indicate that their construction—carried out with considerable care and planning— may have occurred as early as the 4th century, during the reign of Constantius II (337–361 CE), or perhaps later in the 6th century under Emperor Justinian. The walls were built in massive courses using large, well-cut limestone ashlars and incorporated reused architectural fragments from earlier structures, including capitals and pedestals from Roman monuments.

The circuit included towers, parapets, and multiple gates, integrating older roads and urban features. The East City Wall was particularly well preserved and featured double-wall construction in places. The North and South Gates marked the main entrances to the city, aligned with the decumanus and cardo streets.

Substantial remains of tumble and collapsed masonry, especially in Trench 400 of the East Wall, reveal episodes of damage, including a sudden collapse of the parapet—possibly triggered by a seismic event in the 6th century CE. Stratigraphic evidence shows that this collapse occurred after the wall's original construction but before the accumulation of Islamic-period debris, offering a terminus ante quem for the wall's failure.

In addition to its defensive role, the wall functioned as an urban boundary during late antiquity, with modifications over time including gate blockages, repairs, and potential earthquake-induced reconstructions. As such, the city wall is a key feature in understanding the urban topography, chronology, and seismic history of Jerash.

• from Jerash - Introduction - click link to open new tab

• Jordan specific chronological framework used by Kehrberg-Ostrasz and Manley (2019)

Period Label	Date
Late Hellenistic	unstated -63 BCE
BC/AD	63 BCE - 135 CE
Roman	135 CE - 193 CE
Late Roman	193 BCE - 324 CE
Byzantine	324 BCE - 636 CE
Late Byzantine	unstated - 636 CE
Islamic	636 CE - unstated

Plans and Photos

Discussion

Kehrberg-Ostrasz and Manley (2019:21) ) describe a tumble layer in Trench 400 of the East Wall of Jerash. After the dumping (405, 407, 411), "a sudden partial collapse from the face of the City Wall occurred, resulting in the distribution of six rows of facing masonry (406) in the main trench." These facing stones "had fallen into neat rows, a little way from the base of the Wall," and their untouched arrangement suggests they had "not been disturbed since the event". Most of the stones "had vertical faces, and most had at least one dimension that was close to 0.45m or 0.4m, similar to the dimensions on the uppermost extant courses of the City Wall." They conclude this tumble likely represents the collapse of the rear parapet of the city wall. Associated Byzantine pottery indicates the wall survived intact into the Byzantine period. The collapse, they note, "may have been caused by an earthquake."

Kehrberg-Ostrasz in Savage et al. (2003:458) supports this interpretation, noting that a collapse of the wall "face down onto the western rocky slope already littered with residual rubbish" lay beneath a tip of Late Islamic and contemporary debris. Pottery and glass sherds below the tumble show that the destruction occurred "during the Late Byzantine period" and was "probably the result of an earthquake that was responsible for the destruction of other city buildings in the sixth century."

References

Effect	Location	Image(s)	Description
Collapsed Walls	East Wall - Trench 400 Fig. 1 JCW [Jarash City Walls] Project - trench locations: Tr/Wall 2000 (IFAPO season 2000) Tr/Wall 100,200,300 (JCWP season 2001) Tr/Wall 400,500 (JCWP 2002) The AD 2000 plan of Gerasa (IFAPO, JP Braun et al (2001) ADAJ Kehrberg-Ostrasz and Manley (2019)	Pl. 1:10 Tr 400: lower city wall tumble layers; N and S sections of tumble Kehrberg-Ostrasz and Manley (2019)	At some time after the dumping of 405,407 and 411, a sudden partial collapse from the face of the City Wall occurred, resulting in the distribution of six rows of facing masonry (406) in the main trench. The facing stones had fallen into neat rows, a little way from the base of the Wall, and clearly had not been disturbed since the event. Most of the stones had vertical faces, and most had at least one dimension that was close to 0.45m or 0.4m, similar to the dimensions on the uppermost extant courses of the City Wall. It seems highly probable that the six rows represent the fallen rear parapet of the City Wall of Gerasa. ... The sudden collapse of the rear parapet into the fallen rows of 406 may have been caused by an earthquake. - Kehrberg-Ostrasz and Manley (2019:21) This rubbish tip rested on neat rows of courses of the wall, which had fallen face down onto the western rocky slope already littered with residual rubbish. The pottery and glass under this tumbled wall section showed that the collapse must have occurred during the Late Byzantine period, probably the result of an earthquake that was responsible for the destruction of other city buildings in the sixth century. - Kehrberg-Ostrasz in Savage et al (2003:458)

• Modified by JW from Fig. 1 of Kehrberg-Ostrasz and Manley (2019)

• Earthquake Archeological Effects chart
  Earthquake Archeological Effects (EAE)
  
  Rodríguez-Pascua et al (2013: 221-224)
  of Rodríguez-Pascua et al (2013: 221-224)

Effect	Location	Image(s)	Description	Intensity
Collapsed Walls	East Wall - Trench 400 Fig. 1 JCW [Jarash City Walls] Project - trench locations: Tr/Wall 2000 (IFAPO season 2000) Tr/Wall 100,200,300 (JCWP season 2001) Tr/Wall 400,500 (JCWP 2002) The AD 2000 plan of Gerasa (IFAPO, JP Braun et al (2001) ADAJ Kehrberg-Ostrasz and Manley (2019)	Pl. 1:10 Tr 400: lower city wall tumble layers; N and S sections of tumble Kehrberg-Ostrasz and Manley (2019)	At some time after the dumping of 405,407 and 411, a sudden partial collapse from the face of the City Wall occurred, resulting in the distribution of six rows of facing masonry (406) in the main trench. The facing stones had fallen into neat rows, a little way from the base of the Wall, and clearly had not been disturbed since the event. Most of the stones had vertical faces, and most had at least one dimension that was close to 0.45m or 0.4m, similar to the dimensions on the uppermost extant courses of the City Wall. It seems highly probable that the six rows represent the fallen rear parapet of the City Wall of Gerasa. ... The sudden collapse of the rear parapet into the fallen rows of 406 may have been caused by an earthquake. - Kehrberg-Ostrasz and Manley (2019:21) This rubbish tip rested on neat rows of courses of the wall, which had fallen face down onto the western rocky slope already littered with residual rubbish. The pottery and glass under this tumbled wall section showed that the collapse must have occurred during the Late Byzantine period, probably the result of an earthquake that was responsible for the destruction of other city buildings in the sixth century. - Kehrberg-Ostrasz in Savage et al (2003:458)	VIII +

The archeoseismic evidence requires a minimum Intensity of VIII (8) when using the Earthquake Archeological Effects chart of Rodríguez-Pascua et al (2013: 221-224).