identified scarps near Woodinville which trenching has confirmed to be tectonically derived and geologically recent. Subsequent mapping shows the SWIF wrapping around the eastern end of the Seattle Basin to merge with the Rattlesnake Mountain Fault Zone (RMFZ); the RMFZ, despite the approximately 15° bend and different context, is now believed to be the southern extension of the SWIF. Reckoned between Victoria and approximately Fall City the length of the SWIF is around 150 km (90 miles). It has been suggested that the SWIF might extend past its intersection with the RMFZ (with only peripheral strands turning to join the RMFZ) to cross the Cascades and eventually merge with or cross the Olympic–Wallowa Lineament; a study of regional features suggests such a pattern. But detailed mapping just past the intersection shows only a complex and confused pattern of faulting, with no indication that there is, or is not, through-going faulting. Mapping of areas further east that might clarify the pattern is not currently planned. Paleoseismological studies of the SWIF are scant. One study compared the relative elevation of two marshes on opposite sides of Whidbey Island, and determined that approximately 3,000 years ago an earthquake of M 6.5–7.0 caused 1 to 2 meters of uplift. Another study identified an unusually broad band of scarps passing between Bothell and Snohomish, with several scarps in the vicinity of King County's controversial Brightwater regional sewage treatment plant showing at least four and possibly nine events on the SWIF in the last 16,400 years. Such seismic hazards were a major issue in the siting of the plant, as it is tucked between two active strands, and the influent and effluent pipelines cross multiple zones of disturbed ground. USGS QFFDB Fault #572, Southern Whidbey Island Fault Rogers Belt North of Everett is an area of parallel ridges and stream drainages oriented approximately NW-SE, evident even on non-geological maps. These ridges (part of a broader regional pattern that reflects the roots of the former Calkins Range) are formed of sediments that collected in the Everett basin during the Eocene, and were subsequently folded by northeast-directed compression against the older Cretaceous and Jurassic rock to the east that bound the Puget Lowland. At the edge of this older rock is the Rogers Belt, a geologically interesting zone running from the area of Sultan (due east of Everett) to Mount Vernon (just north of the bend in the