Earthquakes, volcanic eruptions, tsunamis (why do we live here?) Tectonic plates. Tectonic plates: Juan de Fuca. Volcanism the past 37 million years

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1 Earthquakes, volcanic eruptions, tsunamis (why do we live here?) Tectonic plates Tectonic plates: Juan de Fuca Volcanism the past 37 million years

2 Tectonic plates: Juan de Fuca Volcanism the past 37 million years High magnitude (9.0), damaging eq that cause tsunamis

3 High magnitude (9.0), damaging eq that cause tsunamis Lower magnitude (5-7), less damaging eqs that do not cause tsunamis High magnitude (9.0), damaging eq that cause tsunamis Lower magnitude (5-7), less damaging eqs that do not cause tsunamis Low magnitude (1-4), hazards associated with volcanic activity, landslides Low magnitude eq with no affect on the coast Subduction zone earthquakes High magnitude (9.0), damaging eq that cause tsunamis Lower magnitude (5-7), less damaging eqs that do not cause tsunamis Low magnitude (1-4), hazards associated with volcanic activity, landslides Shallow Deep Subduction zone earthquakes Deep EQ < 20 miles depth < M7.5 Shaking few seconds-1 minute Small aftershocks Tsunamis unlikely Previous EQ s Vancouver Island, BC, M Scotts Mills, OR, M Eureka, CA, M6.5 Subduction zone earthquakes Shallow EQ < 5 miles depth ~ M9.0 Shaking several minutes Many aftershocks up to magnitude 7.0 Tsunami will quickly hit Cascadia coast followed by Alaska, Hawaii & Asia Injuries & fatalities expected in the thousands Previous EQ s (occur roughly every 500 yrs) -January 26, 1700 (large tsunami) -Years 900, 750, 400

4 Subduction zone earthquakes 2008/09/24 02:33:10 (UTC) Tsunami warning: Subduction zone earthquakes Evidence of M9.0, 1700 event Dead trees caused by 1.5 m coastal sinking Landslides on continental shelf Japanese records of a tsunami PNW: Recent earthquakes 1949 Olympia, M6.8-8 dead, $200 million in damage 1962 Corvalis, M Seattle, M6.5-7 dead, $100 million in damage 1976 Pender Island, M Satsop, M5.9 -$10 million in damage 2001 Nisqually, M injuries, $4 billion in damage Volcanic eruptions Volcanic eruptions Low magnitude (1-4), damage associated with volcanic activity Recent quakes:

5 Volcanic eruptions Stratovolcano: Mt. Ranier 9/26/08 All M<2.0 Recent quakes: Recent quakes: Stratovolcano: Mt. Ranier hazards hazards Mudflow Muddy River, southeast of Mount St. Helens

6 Mudflow Mudflow Mount St. Helens, 1982 Along Cowlitz River Pyroclastic flow Pyroclastic flow Mt. St. Helens, pyroclastic flows, moving over 60 mph and 800 F Tephra flow Tephra flow and ash fall Mt. St. Helens, 1980 Total volume of ash enough to cover a football field to a depth of 150 miles!

7 Tephra flow and ash fall Mt. St. Helens, 1980 Total volume of ash enough to cover a football field to a depth of 150 miles! Low magnitude eq with no affect on the coast Recent offshore: Axial seamount 700 m tall volcanically active Juan de fuca ridge Axial seamount 700 m tall volcanically active Juan de fuca ridge Source: NOAA ASHES hydrothermal vent field Discovered in sulfide chimneys, 5m high 1550 m deep Source: NOAA

8 Seattle Fault Seattle Fault Seattle Fault Thrust fault Seattle Fault Thrust fault 9 m of uplift over 16,000 yrs Seattle Fault Thrust fault Seattle Fault: Events 900 AD M 7.0 eq -7m uplift -Puget Sound tsunami -Landslides lake WA -Rock avalanches in Olympic Mtns Recurrence - 10,000s of years