1. Earthquakes (1) John Townend EQC Fellow in Seismic Studies john.townend@vuw.ac.nz Cotton 520, ph. 463-5411

2. Outline What have we seen in the last couple of years? What is an earthquake? How do we observe earthquakes scientifically? How do we describe earthquakes?

3. Our home

4. Colours represent peak ground acceleration expected at 10% probability in 50 years Figure courtesy of GNS Science

6. What is listening near Christchurch?

7. Seismographs

8. Satellite radar interferogram spanning the 22 February Christchurch earthquake. Image provided by the Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET+). What else is watching?

9. Greendale fault → Darfield EQ United States Geological Survey (USGS)

10. Big fleas have little fleas... A day-long record of seismic activity recorded at McQueen’s Valley (western Banks Peninsula) almost one month after the M6.3 Christchurch earthquake. Image provided by GeoNet.

11. And they keep biting A day-long record of seismic activity recorded at McQueen’s Valley (western Banks Peninsula) twelve months after the M6.3 Christchurch earthquake. Image provided by GeoNet.

12. The rate of aftershock activity generally decreases with time...

13. But there can be surprises...

14. For every large earthquake there are many little ones...

15. But size isn’t everything... Stacy Squires/The Press Carys Monteath/The Press

16. Ground accelerations Figures provided by GNS Science/GeoNet — see RSNZ/PMSAC briefing for further details

17. 東日本大震災, 11 March 2011 The earth rings like a bell

18. Regional deformation Preliminary GPS displacement data (version 0.1) provided by the ARIA team at JPL and Caltech. All Original GEONET RINEX data provided to Caltech by the Geospatial Information Authority (GSI) of Japan. Animated version

20. Expected tsunami wave heights across the Pacific basin computed by the National Oceanic and Atmospheric Administration (NOAA) Center for Tsunami Research.

21. Tsunami

22. Tsunami propagation A tsunami travels over the abyssal plain (d~5.5 km) at a velocity of ~235 m s –1 (~850 km hr –1 ).

24. Why such a big tsunami? Ide et al., 2011, Science Sato et al., 2011, Science

25. Kodaira et al., JAMSTEC Why such a big tsunami?

26. What are all these waves? The P and S waves travel through the Earth’s interior and lose energy (attenuate) faster than the Rayleigh surface waves

27. Where to with early warnings? A public warning was issued 8 s after seismic waves were first detected, 31 s after rupture started (27 bullet trains stopped) Magnitude underestimated, meaning ground motions and tsunami heights were also underestimated

28. Suggested reading material Geosystems (8 th ed.), Christopherson  Chapter 12, especially p. 338–343, 349–355  Chapter 16, p. 466–472 Earthshaking science: what we know (and don't know) about earthquakes, Hough Predicting the unpredictable, Hough Caught in the crunch, Ansell and Taber Magnitude eight plus, Grapes

29. Online resources GeoNet  http://www.geonet.org.nz http://www.geonet.org.nz United States Geological Survey  http://earthquake.usgs.gov/earthquakes/eqinthenews/2011/usc0001xgp/ http://earthquake.usgs.gov/earthquakes/eqinthenews/2011/usc0001xgp/ Earthquake Research Institute, University of Tokyo  http://outreach.eri.u-tokyo.ac.jp/eqvolc/201103_tohoku/eng http://outreach.eri.u-tokyo.ac.jp/eqvolc/201103_tohoku/eng GEO Geohazards Supersite  http://supersites.earthobservations.org/honshu.php http://supersites.earthobservations.org/honshu.php Geospatial Information Authority of Japan  http://www.gsi.go.jp/cais/topic110313-index-e.htmlhttp://www.gsi.go.jp/cais/topic110313-index-e.html Seismological Laboratory, Harvard University  http://seismology.harvard.edu/research_japan.html http://seismology.harvard.edu/research_japan.html UNAVCO  http://www.unavco.org/community_science/science_highlights/2011/M8.9-Japan.html http://www.unavco.org/community_science/science_highlights/2011/M8.9-Japan.html

30. Quake-safeing Chimneys Water cylinders Foundations Roof tiles Solid fuel stoves Bookcases And who has an earthquake kit prepared?