DOCUMENTATION OF ACTIVE FAULTING AND PALEOLIQUEFACTION OF THE DEAD SEA TRANSFORM IN THE MUNICIPALITY OF AQABA, JORDAN

Located along the northern shore of the Gulf of Aqaba, the city of Aqaba, Jordan is built upon the Dead Sea Transform (DST) plate boundary fault system. The DST is a sinistral fault system composed of a series of strike-slip faults arranged en-echelon. The underlying stratigraphy of the city is composed of alluvial fan sediments washed down from Wadi ‘Arabah and Wadi Yutim and deposited from the granitic mountains to the east of the city. These two valleys act as a large drainage system which deposits loosely consolidated sediments into the northern Aqaba coastal zone. Groundwater levels near the shore are shallow, 1-3 m deep, but increase to the north and northeast. In the spring of 2009, a ground survey of the Aqaba coastal zone was conducted as part of the Wadi ‘Arabah Earthquake Project. A 30-m wide fault zone as well as evidence of paleoliquefaction were documented in a large 5.5 m deep, 160 m by 110 m building foundation trench located 1.3 km north of the Gulf of Aqaba at elevations of between 10-13 m. The exposed faults along the southwest trench wall trend either northwest or northeast. Four dikes were also identified in the southwest wall of the trench, the largest of which (Dike A) is exposed 3.2 m above the ground surface of the trench and is 4-7 cm wide, however the depth of each dike is unknown. Dike A, composed of weakly cemented fine- to medium-grained sand, is injected into interbedded layers of sand and silt toward the bottom of the section and cuts through a gravel channel toward the upper section. Intense ground shaking caused by earthquakes on the DST likely caused sand at depth to become fluidized under pressure and migrate to the ground surface, reactivating a previous fault rupture, to form Dike A. Dikes B, C and D are composed of indurated silt and clayey silt, and are typically 1-2 cm wide and terminate 75 cm to 2.2 m above the ground surface of the trench. Discovery of this subsurface paleoliquefaction evidence confirms liquefaction potential and susceptibility studies conducted in and around the city of Aqaba, and signifies the first documentation of paleoliquefaction in the coastal zones of Aqaba or in the near-by city of Eilat, Israel. Ongoing research of the site will include using radiocarbon dating to resolve the sequence of faulting events in the exposed section, and to correlate these events to the episodes of paleoliquefaction.