[PNW-Earthquake-Hazards] PNW Fault Working Group Conference Call

[Joan S Gomberg]

PNW Fault Working Group,

I'd like to propose a conference call meeting for 1/16 at 10:00 am PST to 
discuss the possible changes to the PNW National Maps suggested in 
previous emails (listed below FYI).  If you are still intending to supply 
information to facilitate this (Craig, Brian, Elizabeth), and this date is 
too soon, please let us know asap.  Similarly if this date or time does 
not work for you, please let me know. 

Thanks and happy holidays!
Joan

New additions: 

The Stonewall anticline (Newport, OR) 
This has been suggested by Bob Yeats and is discussed by he and Rus 
Wheeler in the attachments.

More faults in Yakima fold belt 
This has been suggested by Bob Yeats and is discussed by he and Rus 
Wheeler in the attachments.

Boulder Creek fault (has multiple events with age constraints)
Brian Sherrod has new information to share. 

Little River fault (has multiple events with age constraints) 
See presentation under "Faults in the Puget Sound region and elsewherein 
western Washington" by Alan Nelson. 


Slip rate changes: 

Portland Hills fault 
Change slip rate from 0.1 mm/yr (in 2002 maps) to 0.07 mm/yr; proposed by 
Ian Madin 

Bolton fault 
Change slip rate from 0.013 mm/yr (in 2002 maps) to 0.015 mm/yr; proposed 
by Ian Madin 

Mt Angel fault 
There is new information, noted by Bob Yeats and and discussed by he and 
Rus Wheeler in the attachments, but it is not clear that any change is 
being advocated in the treatment of this fault. 

SWIF 
Change fault geometry and dimensions; see Art?s Introductory presentation 
that notes a change dip from 60 to 45 degrees,seismogenic layer thickness 
from 17.3 to 20 km, length from 63 to 86 km.  Assuming the same uplift 
rate of 0.6 mm/yr this changes the characteristic magnitude from M7.2 to 
M7.3 with Tchar from 3100 to 1700 yr, and for a M6.5 the recurrence time 
changes from 930 to 400 yr.  For 0.5 mm/yr strike slip component (derived 
assuming pure north-south convergence): Tchar=2900 yr and the recurrence 
time for a M 6.5 becomes 680 yr.  Combining these equally (1/2 reverse and 

1/2 strike-slip motion) results in Tchar= 1300 yr and a M 6.5 recurrence 
interval of 310 yr, which are much shorter times than used for the Seattle 

fault.
Also see presentations under "South Whidbey Island Fault experience" by 
Rick Blakely 


Joan Gomberg
US Geological Survey
University of Washington
Dept of Earth and Space Sciences, Box 351310
Seattle, Washington 98195-1310
206-616-5581(office) 
206-553-8350 (fax)
206-941-7498 (cell)
gomberg at usgs.gov
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