may even be reentrant under north Seattle, forming the northwestern side of the Seattle Basin, and possibly connecting with the recently reported "Bremerton trend" of faulting running from the southern end of Hood Canal, through Sinclair Inlet (Bremerton), and across Puget Sound. Or the Crescent margin may simply (and quietly) just run south-southeast under Seattle to the WRZ. Other seismic tomography has tantalizingly suggested three north-striking strands under Seattle, and a fourth just east of Lake Washington. Although there is no direct evidence for any major north-striking faults under Seattle, this prospect appears to be endorsed by the geological community. How the CRBF might run north of Seattle (specifically, north of the OWL, which Seattle straddles) is unknown, and even questioned, as there is no direct evidence of such a fault. There is an intriguing view from (see Fig. 64, on-line) that the edge of the Crescent Formation offsets west along the Seattle Fault, with the Seattle Basin resulting from a gap between the main part of Siletiza and a northern block that has broken away. Seattle Fault The Seattle Fault is a zone of complex thrust and reverse faults – between lines E and F on the map – up to 7 km wide and over 70 km long that delineates the north edge of the Seattle Uplift. It stands out in regard of its east–west orientation, depth to bedrock, and hazard to an urban population center. The Seattle Fault was first identified in 1965 but not documented as an active fault until 1992 with a set of five articles establishing that about 1100 years ago (AD 900–930) an earthquake of magnitude 7+ uplifted Restoration Point and Alki Point, dropped West Point (the three white triangles in the Seattle Basin on the map), caused rockslides in the Olympics, landslides into Lake Washington, and a tsunami on Puget Sound. It extends as far east as (and probably terminates at) the Rattlesnake Mountain Fault Zone (RMFZ; the southern extension of the SWIF) near Fall City. This seems geologically reasonable, as both the SWIF and RMFZ appear to be the contact between Tertiary Crescent Formation basement of Puget Sound on the west and the older Mesozoic (pre-Tertiary) mélange belt basement rocks under the Cascades on the east. Structure The Seattle Fault is the most studied of the regional faults, which has led to several models of its structure, which may also be