EQ IV is the second oldest paleoseismic event identified in the Sisters’ School trench in Aqaba, Jordan. The trench was an approximately 140 m by 100 m building foundation trench located about 1 km northeast of the head of the Gulf of Aqaba and about 1.3 km north of Early Islamic Ayla. The site exposed numerous fault strands within the urban Aqaba coastal zone, where the exact inland trace of the Aqaba fault remains difficult to identify because of modern development.
Allison (2013) interpreted the faults exposed at the Sisters’ School site as most likely related not to the Aqaba fault itself, but to the West-Aqaba fault, located west of the Aqaba fault strand. The trench also exposed evidence for northwest-trending cross faulting. Strike and dip measurements indicate that many faults trend close to north or northeast, broadly consistent with the West-Aqaba fault, while another group of faults trends northwest and may represent a transverse cross fault, possibly Cross Fault 6. The faulting therefore appears to record both strike-slip deformation and a normal-faulting component associated with local cross-fault motion.
EQ IV is expressed in the lower to middle part of the southwest trench wall, where faults cut all stratigraphic units from the basal sequence up through unit SS-15 and are capped by overlying unit SS-10. The principal paleoseismic evidence consists of upward fault terminations below the capping unit, vertically offset stratigraphic units, and mismatched unit thicknesses across fault lines. As with EQ V, Allison attributed these mismatched thicknesses to strike-slip deformation, implying lateral juxtaposition of originally separate portions of variably thick deposits. EQ IV therefore appears to record primarily strike-slip motion rather than a clearly expressed normal-faulting event. No sand dikes were directly attributed to EQ IV, although the small liquefaction feature SD-4, which is not clearly associated with any mapped fault, lies stratigraphically near the EQ IV horizon and may potentially be related to this event.
A terminus post quem for EQ IV is established by the buried sand unit sampled as OSL sample #2. This sample yielded an OSL age of 6.9 ± 1.7 ka, equivalent to 6600-3200 BCE. A terminus ante quem is provided by overlying unit SS-10, which caps EQ IV. OSL sample #4, collected from SS-10, yielded an age of 6.6 ± 1.6 ka, equivalent to 6200-3000 BCE. Additional constraint comes from radiocarbon sample RC-SS #1, recovered from a fire pit in the same SS-10 stratigraphic horizon approximately 10 m east of the trench log, which produced a laboratory age of 6015 ± 25 yr BP and a calibrated age range of 4986-4840 BCE (2σ). Taken together, these constraints indicate that EQ IV is constrained to the same broad chronological window as EQ V, between approximately 6600 and 4840 BCE. However, because EQ IV stratigraphically postdates EQ V, it must represent a younger earthquake within that shared time interval.
- Fig. 1.2 Location map from
Allison (2013)
Location map of research sites in southern Wadi ‘Arabah, Jordan
(Google Earth, 2013a)
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Allison (2013)- Fig. 4.1 Location map with
Geomorphology from Allison (2013)
Geologic map of the southern Wadi ‘Arabah. The Taba Sabkha trench location is shown at the top of the map (modified after Garfunkel, 1970). DST faults in Gulf of Aqaba from Hartman, 2012.
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Allison (2013)- Fig. 5.1 Location map with
faults from Allison (2013)
Location of Dead Sea transform faults mapped both offshore in the Gulf of Aqaba (white lines) and on land (dashed black lines). The solid back lines indicate transverse cross-faults mapped throughout the city of Aqaba, Jordan. Map from Tibor et al., 2010.
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Allison (2013)- Fig. 5.15 Fault Map around
trench site from Allison (2013)
Map of the city of Aqaba showing locations of the active cross faults (CF 1-5) mapped from aerial photos and discovered during the archaeological excavations of J-East in Roman-Byzantine Aila. The proposed location of cross fault 6 (CF-6) was determined as a result of this paleoseismic study at the Sisters’ School site. Locations of other major archaeological sites in the city are also shown (after Thomas et al., 2007).
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Allison (2013)- Fig. 5.2 Location map from
Allison (2013) (in Google Earth)
Location of Dead Sea transform faults mapped both offshore in the Gulf of Aqaba (white lines) and on land (dashed black lines). The solid back lines indicate transverse cross-faults mapped throughout the city of Aqaba, Jordan. Map from Tibor et al., 2010.
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Allison (2013)- Fig. 5.3 Detailed Location
map from Allison (2013)
Location map of Sisters’ School trench within the city of Aqaba, Jordan. The building foundation trench is outlined in black and the arrow points toward the southwest wall which contains the majority of faults identified at the site. Topographic contour lines, trending generally NW-SE, are shown with a 1 m contour interval.
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Allison (2013)- Fig. 5.4 Site plan from Allison (2013)
Top plan map of the Sisters’ School trench within the city of Aqaba, Jordan. The building foundation trench is outlined in black, and a red arrow points toward the southwest wall that contains approximately half of all the faults identified at the site. Faults and dikes identified in the trench walls are marked with either a short black line or a red strike and dip symbol where available and where space would allow. Fault lines in black are drawn perpendicular to their respective trench wall for uniformity and do not indicate direction of strike.
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Allison (2013)- Table 4.1 OSL and Radiocarbon Dating
Dating Results from Allison (2013)
Geochronology Of Sisters’ School Trench, Aqaba, Jordan
Optically Stimulated Luminescence (Osl) Dating Results And Radiocarbon Dating Results
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Allison (2013)Figure 5.8
Cross-section of both the north and south Taba Sabkha trench walls showing faulting, stratigraphic offset, and radiocarbon dates of charcoal samples collected.
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Allison (2013)
Figure 5.9
Paleoseismic faulting and a generalized stratigraphic section of the Sisters’ School southwest trench wall in Aqaba, Jordan. Colored stratigraphic units correlate to the colored cross-section of the SW trench wall (see Figure 5.8).
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Allison (2013)
