Talk by: Peter J. Haeussler [email protected] 907-786-7447
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Transcript of Talk by: Peter J. Haeussler [email protected] 907-786-7447
The 1964 Great Alaska earthquake and tsunami: lessons learned in the 50 years since the dawn of plate tectonics
Talk by:
Peter J. [email protected] 907-786-7447 U.S. Department of the InteriorU.S. Geological Survey, Anchorage, Alaska
1964 earthquake damage in Anchorage, Alaska
Earthquakes define the plate margins ‘magmatic arcs’ are related to subduction zones
Active faults and significant earthquakes of Alaska
Alaska subduction zone cross sectionNW SE
Plates of the world
99% in Alaska
EQ energy release in the US 1960-2010
Mike West, Alaska Earthquake Center
The 1964 Great Alaska Earthquake March 27th, 1964,
5:36 PM. Good Friday
Magnitude 9.2 2nd largest ever
recorded shaking lasted 4.5
minutes Huge rupture area
(~250x800 km)
Anchorage
Uplift and Subsidenceup
lift
subs
iden
ce
Uplifted tidal flat Uplifted dock at high tide
Village of Portage had to be abandoned ‘ghost forest’
Uplift and subsidence pattern is only consistent with a “megathrust”
Uplift
Subsidence
Max subsidence over large area of 2 m
Max uplift over large area of 4 m
USGS Geologist Dr. George Plafker
Tsunami Generation
This mechanism of tsunami generation first recognized from USGS studies of the 1964 earthquake
Tsunami Generation - landslide
Locally generated tsunamis
Alaskan deaths 106 of 122 from
tsunamis (87%) 85 of the 106 from
submarine landslide generated tsunamis (80%)
Alaskan fjords are an ideal environment for producing submarine landslides
The scientific legacy of the 1964 event: the fingerprint of the worlds’ largest earthquakes
Occurred at a pivotal time earth science Helped lead to acceptance of plate tectonics Showed the worlds largest earthquakes are
caused at convergent margins Provided a mechanism for launching trans-
oceanic tsunamis All giant megathrust earthquakes are understood
in the shadow of what was learned from 1964 (e.g. 2011 Japan, 2004 Indonesia, 1960 Great Chile, etc.)
1964 earthquake gave birth to modern earthquake detectives
Repeated pattern of uplift and subsidence with each megathrust earthquake allows us to determine the history of ancient earthquakes
Cascadia megathrust earthquake hazard
1964 Alaska perspective allowed identification of coastal OR and WA earthquake hazard
Copalis River ghost forest at extreme high tide, December 1997 (Atwater and others, 2005).
Geodesy: pre1964, today, and the future
conventionalsurveying
continuousGPS
‘campaign’GPS surveys
Pre-1964today
today andthe future
New tools reveal earth deformation between and during earthquakes
2011 M9.0 Tohoku, Japan, earthquake
From Grapenthin and Freymueller (2012)
Motion during earthquake
verticalhorizontal
2011 M9.0 Tohoku, Japan, earthquake
Japan invested in seafloor geodesy Data revealed huge offshore slip (~50+ m),
which made a particularly big tsunami We don’t know how unusual this was Japan success: relative little shaking related
building damage
TAPS Denali fault crossing
Success: Trans Alaska Pipeline withstood 5.4m (18ft) of fault offset during M7.9 quake
Before After
In the 50 years since 1964…
We’ve made big gains in understanding earthquakes
We have success in reducing losses We need to be vigilant
The most recent disaster fades from memoryJust before the next one strikes
- Ancient Japanese proverb