Talk by: Peter J. Haeussler pheuslr@usgs.gov 907-786-7447

2. The 1964 Great Alaska earthquake and tsunami: lessons learned in the 50 years since the dawn of plate tectonics Talk by: Peter J. Haeussler pheuslr@usgs.gov 907-786-7447 U.S. Department of the Interior U.S. Geological Survey, Anchorage, Alaska 1964 earthquake damage in Anchorage, Alaska

3. Active faults and significant earthquakes of Alaska • Earthquakes define the plate margins • ‘magmatic arcs’ are related to subduction zones

4. Alaska subduction zone cross section NW SE

5. Plates of the world

6. EQ energy release in the US 1960-2010 99% in Alaska Mike West, Alaska Earthquake Center

7. 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

8. Uplift and Subsidence uplift Uplifted tidal flat Uplifted dock at high tide subsidence Village of Portage had to be abandoned ‘ghost forest’

9. Uplift and subsidence pattern is only consistent with a “megathrust” • Max subsidence over large area of 2 m • Max uplift over large area of 4 m Subsidence Uplift USGS Geologist Dr. George Plafker

10. Tsunami Generation This mechanism of tsunami generation first recognized from USGS studies of the 1964 earthquake

11. Tsunami Generation - landslide

12. 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

13. 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.)

14. 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

15. 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).

16. Geodesy: pre1964, today, and the future today Pre-1964 ‘campaign’ GPS surveys today and the future conventional surveying New tools reveal earth deformation between and during earthquakes continuous GPS

17. 2011 M9.0 Tohoku, Japan, earthquake horizontal vertical From Grapenthin and Freymueller (2012) Motion during earthquake

18. 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

19. TAPS Denali fault crossing Before After • Success: Trans Alaska Pipeline withstood 5.4m (18ft) of fault offset during M7.9 quake

20. 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