page_title: Puget Sound faults
section_title: Doty Fault
hierarchical_section_title: Puget Sound faults / Doty Fault
caption_attribution_description: English: An excerpt from Washington DGER Geological Map 34 (reduced and modified) showing the principal known faults in the Centralia—Chehalis (Washington) area, including the Doty, Salzer Creek, Scammon Creek, Kopiah, Newaukum, Coal Creek, and two unamed faults; see USGS Bulletin 1053 for details. The Doty—Salzer Creek fault runs between the towns of Centralia and Chehalis, indicated by the black squares.
context_page_description: The Puget Sound faults under the heavily populated Puget Sound region of Washington state form a regional complex of interrelated seismogenic geologic faults. These include the:
  Devils Mountain Fault
  Strawberry Point and Utsalady Point faults
  Southern Whidbey Island Fault
  Rogers Belt
  Cherry Creek Fault Zone
  Rattlesnake Mountain Fault Zone
  Seattle Fault
  Tacoma Fault
  Saddle Mountain Faults
  Olympia structure
  Doty Fault
  Saint Helens Zone and Western Rainier Zone
context_section_description: The Doty Fault – the southernmost of the uplift-and-basin dividing faults reviewed here, and located just north of the Chehalis Basin – is one of nearly a dozen faults mapped in the Centralia—Chehalis coal district in 1958. While the towns of Centralia and Chehalis in rural Lewis County may seem distant (about 25 miles) from Puget Sound, this is still part of the Puget Lowland, and these faults, the local geology, and the underlying tectonic basement seem to be connected with that immediately adjacent to Puget Sound. And though the faults in this area are not notably seismogenic, the southeast striking faults seem to be en echelon with the Olympia structure (fault?), and headed for the definitely active Saint Helens Zone; this appears to be a large-scale structure. The Doty fault particularly seems to have gained prominence with geologists since it was associated with an aeromagnetic anomaly, and a report in 2000 credited it capable of a magnitude 6.7 to 7.2 earthquake.  The prospect of a major earthquake on the Doty Fault poses a serious hazard to the entire Puget Sound region as it threatens vital economic lifelines: At Chehalis there is but a single freeway (Interstate 5) and a single rail line connecting the Puget Sound region with the rest of the west coast; the only alternate routes are very lengthy.
  The Doty fault has been mapped from the north side of the Chehalis airport due west to the old logging town of Doty (due north of Pe Ell), paralleled most of that distance by its twin, the Salzer Creek Fault, about half a mile to the north.  Both of these are dip-slip (vertical) faults; the block between them has been popped up by compressive forces.  The Doty Fault appears to terminate against, or possibly merge with, the Salzer Creek Fault at Chehalis; the Salzer Creek Fault is traced another seven miles east of Chehalis.  The length of the Doty Fault is problematical: the report in 2000 gave it as 65 km (40 miles), but without comment or citation. Such a length would be comparable to the length of the Seattle or Tacoma faults, and capable of an earthquake of M 6.7.  But it does not appear that there have been studies of the deeper structure of these faults, or whether there has been any recent activity.
  
  The Doty—Salzer Creek Fault does not fully fit the regional pattern of basins and uplifts bounded by faults described above. It does bound the north side of the Chehalis basin, but the south boundary of the Black Hills Uplift is more properly the southeast striking Scammon Creek Fault that converges with the Doty—Salzer Creek Fault just north of Chehalis. In the acute angle between these is located the minor Lincoln Creek uplift, the Doty Hills, and an impressive chunk of uplifted Crescent basalt (reddish area at west edge of the map). The SE striking Scammon Creek Fault seems to be terminated by the Salzer Creek Fault (the exact relationship is not clear), with the latter continuing east for another seven miles. Yet the former is only the first of at least six more parallel southeast striking faults, which do cross the Salzer Creek Fault. These faults are: the Kopiah Fault (note the curious curve), Newaukum Fault, Coal Creek Fault, and three other unnamed faults. Just past them is the parallel Olympia Structure, which as a geophysical lineament has been traced to a point due east of Chehalis; these would seem to be related somehow, but the nature of that relationship is not yet known.
  Though these faults have been traced for only a little ways, the southeast striking anticlines they are associated with continue as far as Riffe Lake, near Mossyrock. They are also on-strike with a swarm of faults on the Columbia River, bracketing The Dalles. As all of these are thrust and reverse faults, they probably result from northeast directed regional compression. These faults also cross the Saint Helens Zone (SHZ), a deep, north-northwest trending zone of seismicity that appears to be the contact between different crustal blocks. How they might be connected is unknown.
  What makes the Doty—Salzer Fault (and the short Chehalis F
caption: Excerpt from Geologic Map GM-34, showing faults in the Centralia—Chehalis Coal District, Lewis County, Washington. Doty—Salzer Creek Fault runs east–west between Centralia and Chehalis (black squares). Map available on-line. Click on image for enlargement.
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