Event 3 was identified in trench T-18, which was excavated on the Shehoret alluvial fan within the central part of the left-lateral Elat fault zone. At this location, localized transtensional deformation has produced a north-trending asymmetrical graben, and trench T-18 was excavated approximately perpendicular to its north-trending bounding normal faults across the southern end of the graben. The broader central Elat fault zone is characterized by sinistral strike-slip faulting accompanied by local compressional and extensional structures, including grabens, push-ups, and flower structures. Shallow seismic reflection data show that the Elat fault zone is several hundred meters wide and consists of several subparallel, north-northeast-trending fault splays, including flower structures. Amit et al. (2002) note that these subsurface structures are generally consistent with the mapped surface traces across the alluvial-fan surfaces and playa deposits.

Before graben formation, the Shehoret alluvial-fan surface had been abandoned at ca. 30 ka for at least 10 k.y., allowing a Reg soil (unit 3) to develop on its surface. Renewed fluvial activity then deposited younger alluvial units 4-6 over unit 3, and the surface was abandoned again at ca. 12 ka, resulting in the present exposed surface on which another Reg soil profile developed during the past 12 k.y. on unit 6.

Event 3 represents one of the early tectonic events associated with the initial development of the Shehoret graben in trench T-18. Amit et al. (2002) describe the earliest stage of graben development as the opening of three wide cracks (Faults A, B, and C in Figure 8 below) which became filled with collapsed sediment without clear colluviation. The evidence therefore appears to derive mainly from fissure opening and collapse fill rather than from a fault scarp leading to the development of a colluvial wedge. Structurally, Event 3 belongs to the development of the Shehoret graben. The deformation is consistent with local extension within the central Elat fault zone while the broader central zone formed part of a sinistral strike-slip system.

Amit et al. (2002) do not explicitly assign numbered events to the deformation stages described for Trench T-18, nor are numbered events identified on the trench log itself (Figure 8 below). Instead, the paper describes a sequence of graben-development stages involving fissure opening, collapse fill, and later events which produced clearer vertical displacements and led to colluvial deposition. Consequently, the correspondence between the numbered events listed in Amit et al. (2002:Table 1) and the specific tectonic developments described in the text is partly interpretive. It is therefore possible that Events 1-3 in Table 1 correspond to the early fissure-opening stage associated with Faults A-C, although this correlation is not stated explicitly by the authors. According to Table 1, Event 3 was dated to 7000-3000 BCE (7 ± 2 ka) based on IRSL and pedogenic interpretation and produced an estimated maximum vertical displacement of 0.2 m. Event 3 is perhaps less clearly expressed than the later graben-development stages and may represent continued fissure development or minor extensional reactivation within the early Shehoret graben system. If the Wells and Coppersmith (1994) maximum-displacement relation for normal faults is applied, 0.2 m of vertical displacement for Event 3 corresponds to an estimated moment magnitude of approximately M_W 6.1.

• Fig. 2 Geomorphic Map of the
  Figure 2
  
  Map of the southern Arava Valley showing the main morphologic and morphotectonic elements of the southern Arava Valley. Notice marginal and central fault zones, the distribution of the trenches across the selected fault lines, and the location of the seismic lines. Trenches T-6, T-17, and T-16 are located along the same fault line.
  
  JW: Trench T-20 apppears to be mislocated on this map and should be further north
  
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  Amit et al. (2002)
  southern Arava showing the location of Trench T-18 from Amit et al. (2002)
• Fig. 2 Geomorphic Map of the
  Figure 2
  
  Geomorphic map of the southern Arava valley in the Avrona basin.
  
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  Zilberman et al. (2005)
  southern Arava from Zilberman et al. (2005)
• Fig. 9a Aerial photograph showing
  Figure 9a
  
  An aerial photograph of the Shehoret alluvial fan. Most of the trenches discussed in the paper are marked on this photograph. Notice the Holocene alluvial fan (Qa3) crossed by an asymmetrical, north-trending graben structure, marked by arrows.
  
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  Amit et al. (2002)
  location of Trench T-18 from Amit et al. (2002)
• Fig. 1b Location Map for
  Figure 1b
  
  Geomorphological map of the Nahal Shehoret alluvial fan showing lineaments and faults, Pleistocene and Holocene surfaces and Trench T-18 across the graben (modified from Enzel et al., 1996).
  
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  Porat et al. (2009)
  Trenches T-1, T-6, and T-18 from Porat et al. (2009)
• Figure 1c Aerial Location Map
  Figure 1c
  
  An aerial photo of roughly the same area as in part (b). Note other trenches west of the road. The area on the top left is part of a large quarry and the original geomorphic features cannot be observed.
  
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  Porat et al. (2009)
  for Trench T-18 from Porat et al. (2009)

Figure 8

Log of the southern wall of trench T-18, showing a graben structure located in the central fault zone. Boxes show detail of areas adjacent to faults. The location of trench T-18 is shown in Figures 2 and 9A.

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Amit et al (2002)