EQ I is the most recent 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 I is the most recent event (MRE) identified in the Sisters’ School trench log. It is expressed in the upper part of the southwest trench wall, where six faults terminate within stratigraphic unit SS-3, with one exception in meter 14 where a fault continues into the lower portion of unit SS-4. The principal paleoseismic evidence consists of upward fault terminations, vertically offset stratigraphic units, and direct association with the large sand dike SD-1 in meter 21. This dike follows an EQ I fault upward and terminates only a few centimeters below the fault tip, strongly suggesting that seismic shaking during EQ I triggered liquefaction and upward sand injection. The layered internal fabric of SD-1, with finer sediment along the margins and coarser sediment in the center, led Allison to suggest possible multiple injection phases or fault reactivation for this sand dike. EQ I is defined mainly by fault terminations, offset stratigraphy, and associated paleoliquefaction. The single deeper fault in meter 14 may represent incomplete rupture to the surface during the same event, or possibly a separate event, but Allison regarded the former interpretation as more likely.
A terminus post quem for EQ I is established by the underlying fluvial sequence, particularly unit SS-5, which must predate the event. OSL sample #3, collected from SS-5, yielded an OSL age of 6.0 ± 0.3 ka, equivalent to 4300-3700 BCE. A terminus ante quem is established by overlying unit SS-2, the oldest unfaulted unit above the MRE. OSL sample #8, collected from SS-2, yielded an age of 5.2 ± 1.1 ka, equivalent to 4300-2100 BCE. OSL sample #6 from the upper portion of SS-3 yielded a younger age of 3.3 ± 0.6 ka (1900-700 BCE). Allison regarded this sample as stratigraphically anomalous and potentially contaminated by light exposure, and therefore did not rely on it. Taken together, these constraints indicate that EQ I most likely occurred sometime between approximately 4300 and 700 BCE or between 4300 and 2100 BCE if we accept Alison's rejection of sample #6. Based on the chart from Obermeier (1996), the approximately 3.8 m tall SD-1 sand dike reflects high local PGA values of approximately 0.4–0.5 g, which corresponds to an estimated local intensity of approximately VIII (8). .
- 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)- Fig. 5.10 Clastic sand dike
SD-1 trench log from Allison (2013)
Clastic sand dike SD-1 and associated EQ I (MRE) fault located in the southwest wall of the Sisters’ School trench. The dike is 2.5-6 cm wide in cross-section and reaches approximately 3.8 m above the ground surface of the trench floor.
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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)
