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Restoration Point!
Restoration Point!
Former sea cliff!
Raised wave-cut
terrace!
Present terrace!
Seattle Fault!
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Seattle fault uplift
South North !"#$$%"&
'#(%$&
!"#$$%"&
)#*+,&
N-S contraction drives
uplift and basin formation
South North !"#$$%"&
'#(%$&
!"#$$%"&)#*+,&
•! ~!"!#$!%&'%()*+,*!(+!-.!$(//(0+!1*23%!($4/(*%!2'0&5!.66!$7$(//(0+!1*23%!088%*5!0+!59*!:*255/*!;2&/5<!!
-! =8!*2,9!'(>!*2359?&2#*!$0@*)!59*!82&/5!.!$A!59*3*!$&%5!92@*!'**+!-66!*@*+5%!(+!59*!/2%5!$(//(0+!1*23%<!
-! B9(%!($4/(*%!0+*!*@*+5!*@*31!-6A666!1*23%<!1 km
Restoration
Point
1998 trenches
1999 trenches
Mossy Lane
Toe Jam Hill fault scarp
12-ft lidar DEM
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WEST POINT West Point Sewage Treatment Plant construction excavation
“Snags” in Lake Sammamish: 1100 years old
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Conclusions
•! An event that would have had catastrophic
consequences occurred about 900 AD.
•! Individual faults have long recurrence times
(1000’s of years).
•! Many active faults are known and more are
being identified.
•! Jury still out on how often we can expect a
devastating crustal quake.