The 1964 Great Alaska earthquake and tsunami: lessons learned in the 50 years since the dawn of plate tectonics Talk by: Peter J. Haeussler U.S. Department of the Interior U.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 section NWSE

Plates of the world

99% in Alaska EQ energy release in the US Mike West, Alaska Earthquake Center

The 1964 Great Alaska Earthquake  March 27th, 1964, 5:36 PM. Good Friday  Magnitude 9.2  2 nd largest ever recorded  shaking lasted 4.5 minutes  Huge rupture area (~250x800 km) Anchorage

Uplift and Subsidence uplift subsidence Uplifted tidal flatUplifted 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 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 conventional surveying continuous GPS ‘campaign’ GPS surveys Pre-1964 today today and the 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 BeforeAfter

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 memory Just before the next one strikes - Ancient Japanese proverb