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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>I agree with Rus’ proposed addition
and parameters for the Stonewall anticline.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>On <st1:PlaceType w:st="on">Mt.</st1:PlaceType>
Angel, we were funded to trench it this fall, but when we went out to perform
detailed GPR and magnetic surveys over the fault traces discussed by Rus as
equivocal. We were unable to image any shallow deformation at the <st1:Street
w:st="on"><st1:address w:st="on">Dominic Road</st1:address></st1:Street> sites
and abandoned our plans to trench there. At the <st1:Street w:st="on"><st1:address
w:st="on">Miller Rd</st1:address></st1:Street> site (where we had seismic lines
of various resolutions that imaged the fault) we found no GPR evidence for shallow
deformation, but did find a small ragged scarp? Less than a meter high that was
spatially associated with magnetic anomalies modeled by Rick Blakely (see
attached) as likely due to faulting. We will be flying LIDAR of the entire Mt.
Angel fault this winter and so have decided to defer the trenching till next
fall.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
pnw-earthquake-hazards-bounces@geohazards.cr.usgs.gov
[mailto:pnw-earthquake-hazards-bounces@geohazards.cr.usgs.gov] <b><span
style='font-weight:bold'>On Behalf Of </span></b>Joan S Gomberg<br>
<b><span style='font-weight:bold'>Sent:</span></b> Monday, October 30, 2006
8:39 AM<br>
<b><span style='font-weight:bold'>To:</span></b>
pnw-earthquake-hazards@geohazards.cr.usgs.gov<br>
<b><span style='font-weight:bold'>Subject:</span></b> [PNW-Earthquake-Hazards]
PNW Fault Working Group</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
</span></font><font face=Times><span style='font-family:Times'>Thank you all
for agreeing to participate in the PNW Fault Working Group. I have
'volunteered' to facilitate the business of the group with the primary goal of
helping it to come to informed decisions that can be passed on to the national
seismic hazard mapping project. Secondarily, I hope this will be
educational for all involved. For those of you I have not met or only
recently have met, my principal qualification to do this is that I begin from a
state of nearly complete ignorance (and geologic expertise) and thus, can
guarantee that I have absolutely no biases! If it’s okay with all of you,
I’d like to try having our electronic exchanges using a listserv, which
is basically just a moderated email discussion group with the benefit of
keeping an online archive. As this listserv has already been set up, but was as
yet unused, I thought this might be a great way to both begin our discussions
and try out this tool (possibly for use more broadly). I’ve taken
the liberty of subscribing all of you to the listserv and have sent this email
through it; for more information about it please see the webpage at</span></font>
<br>
<u><font color=blue face=Times><span style='font-family:Times;color:blue'>http://geohazards.cr.usgs.gov/mailman/listinfo/pnw-earthquake-hazards</span></font></u><font
face=Times><span style='font-family:Times'>. Please note that although
described as for more general purposes, currently only the Working Group is
subscribed to it, so no one else will receive our emails or be able to look at
the archive (although I see no reason why ultimately we shouldn’t use it
as a means of helping to document the basis of any recommendations). If
you think this is not a good idea, please don’t hesitate to let me know.
If not, please send all email, attachments, etc. to pnw-earthquake-hazards@geohazards.cr.usgs.gov,
and after I screen them (as the listserv moderator) the entire group will
receive them. </span></font> <br>
<br>
<font face=Times><span style='font-family:Times'>As you’ve all received
Art’s emails, there’s no need to repeat the PNW Fault Working
Group’s current charge. 4 additions and 4 modifications to existing
fault parameters are being considered . These are listed below with a few
comments about background information with which to evaluate each. We hope that
the person suggesting the change and/or who is an obvious source of information
about the particular fault will provide the group with additional information.
I have attached the comments of Bob Yeats and responses from Rus Wheeler
that you have already been sent again for convenience. An overview of what
fault parameters are currently used, why, etc. is in the presentation under
"Introduction: Overview of scientific issues: why are we here?" by
Frankel made at the National Map workshop held this Spring. Most of the
presentations from the workshop and referenced below can be found at http://earthquake.usgs.gov/research/hazmaps/whats_new/workshops/pacNW_workshop.php.
</span></font><br>
<br>
<font face=Times><span style='font-family:Times'>Please also note that Art
emphasizes that when thinking about deciding whether changes should be made,
one should consider the policy of the National Maps that only faults where a
slip rate or recurrence time has been estimated or determined from measurements
on that fault can be used (e.g. slip rates based entirely on analogs are not
sufficient). Please provide your contributions, using the listserv,
before the end of November (the earlier the better). When enough
information has been exchanged I will try to schedule a conference call, or if
it appears necessary, a face-to-face meeting. Please keep in mind the
goal of providing final recommendations my mid-January.</span></font> <br>
<br>
<font face=Times><span style='font-family:Times'>Thanks very much!</span></font>
<br>
<font face=Times><span style='font-family:Times'>Joan Gomberg</span></font> <br>
<br>
<br>
<b><font face=Times><span style='font-family:Times;font-weight:bold'>***
Changes to be Considered ***</span></font></b> <br>
<br>
<b><font face=Times><span style='font-family:Times;font-weight:bold'>New
additions:</span></font></b> <br>
<br>
<font face=Times><span style='font-family:Times'>The Stonewall anticline (<st1:place
w:st="on"><st1:City w:st="on">Newport</st1:City>, <st1:State w:st="on">OR</st1:State></st1:place>)</span></font>
<br>
<font face=Times><span style='font-family:Times'>This has been suggested by Bob
Yeats and is discussed by he and Rus Wheeler in the attachments.</span></font> <br>
<br>
<font face=Times><span style='font-family:Times'>More faults in <st1:City
w:st="on"><st1:place w:st="on">Yakima</st1:place></st1:City> fold belt</span></font>
<br>
<font face=Times><span style='font-family:Times'>This has been suggested by Bob
Yeats and is discussed by he and Rus Wheeler in the attachments.</span></font> <br>
<br>
<font face=Times><span style='font-family:Times'>Boulder Creek fault (has
multiple events with age constraints)</span></font> <br>
<font face=Times><span style='font-family:Times'>Brian Sherrod has new
information to share.</span></font> <br>
<br>
<font face=Times><span style='font-family:Times'>Little River fault (has
multiple events with age constraints)</span></font> <br>
<font face=Times><span style='font-family:Times'>See presentation under
"Faults in the Puget Sound region and elsewherein western <st1:State
w:st="on"><st1:place w:st="on">Washington</st1:place></st1:State>" by Alan
Nelson.</span></font> <br>
<br>
<br>
<b><font face=Times><span style='font-family:Times;font-weight:bold'>Slip rate
changes:</span></font></b> <br>
<br>
<font face=Times><span style='font-family:Times'>Portland Hills fault</span></font>
<br>
<font face=Times><span style='font-family:Times'>Change slip rate from 0.1
mm/yr (in 2002 maps) to 0.07 mm/yr; proposed by Ian Madin</span></font> <br>
<br>
<font face=Times><span style='font-family:Times'>Bolton fault</span></font> <br>
<font face=Times><span style='font-family:Times'>Change slip rate from 0.013
mm/yr (in 2002 maps) to 0.015 mm/yr; proposed by Ian Madin</span></font> <br>
<br>
<font face=Times><span style='font-family:Times'>Mt Angel fault</span></font> <br>
<font face=Times><span style='font-family:Times'>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.</span></font> <br>
<br>
<font face=Times><span style='font-family:Times'>SWIF</span></font> <br>
<font face=Times><span style='font-family:Times'>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.</span></font> <br>
<font face=Times><span style='font-family:Times'>Also see presentations under
"South Whidbey Island Fault experience" by Rick Blakely</span></font>
<br>
<br>
<br>
<br>
<br>
<font size=2 face=sans-serif><span style='font-size:10.0pt;font-family:sans-serif'>Joan
Gomberg<br>
US Geological Survey<br>
<st1:place w:st="on"><st1:PlaceType w:st="on">University</st1:PlaceType> of <st1:PlaceName
w:st="on">Washington</st1:PlaceName></st1:place><br>
Dept of Earth and Space Sciences<br>
<st1:address w:st="on"><st1:Street w:st="on">Box</st1:Street> 351310</st1:address><br>
<st1:place w:st="on"><st1:City w:st="on">Seattle</st1:City>, <st1:State w:st="on">Washington</st1:State>
<st1:PostalCode w:st="on">98195-1310</st1:PostalCode></st1:place><br>
206-616-5581<br>
gomberg@usgs.gov</span></font><o:p></o:p></p>
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