Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 1 Tsunami Basics

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 2 "Know your enemy and know yourself and you can fight a hundred battles without disaster." Sun Tzu Chinese general and author, b.500 BC

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 3

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 4 Some “Known” Large Tsunami Events: Prehistoric (100 – 200 ka) - Hawaii Landslides 1600 BC Santorini Explosion 1491 Mahuika Crater impact, New Zealand (est Mw > 9.0) 1700 Cascadia (est Mw > 9.0) 1755 Lisbon, Portugal ( Mw = 8.5, 90,000 dead) 1883 Krakatau (est 36,000 dead) 1896 Sanriku, Japan (Ms = 7.0, est 22,000 dead) 1960 Chile (Mw = 9.5, dead) 1964 Alaska (Mw = 9.2, 122 dead) 2004 Indonesia (Mw = 9.0, > 225,000 dead) See For historic earthquake data

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 5 1.Terminology 2.Waves in the Open Ocean 3.Exercise – Wave travel times 4.Tsunami Generation Mechanisms Outline:

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 6 Terminology - : Amplitude Schematic of water wave

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 7 Terminology: Deep Water Wave? > 1/20? Deep water waves are usually driven by surface shear forces. The energy goes into the water from the surface (like with wind)

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 8 Terminology: Shallow Water Wave? < 1/20? Shallow water waves have energy distributed thoughout the water depth. They “feel” the bottom of the ocean.

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 9 Other things that we often talk about with waves. Long wave? Small Amplitude Wave? Answers to these and other questions about the waves we are studying lead us to decide on whether to use: Linear shallow water wave theory Non-linear shallow water wave theory Finite amplitude wave theory And other options…

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 10 How do tsunamis differ from “day at the beach” waves? Order of magnitude estimates: Wind WavesTsunamis Wavelength m100 km Period 10 – 100 sec10 min Ocean Amplitude m1 m Shore Amplitude 1-10 m1-10 m * Water motion More near surfaceEntire column *except very near field events (100 m)

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 11 A word about energy The energy carried by a wave must come from somewhere. For example in wind waves it is the wind that transfers energy to the water by pushing on the water surface. In terms of mechanical energy there are two main components: Potential Energy: Raising a body of water up above its original level And Kinetic Energy: The energy of the moving water If we keep in mind that all waves take energy to create, then the issue of tsunamis becomes somewhat more straightforward…

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 12 A little exercise to amaze your friends: Calculate the propagation time (travel time) of a tsunami using only a calculator and a map. Recall: Tsunamis behave like shallow water waves. Their speed is governed by water depth. In fact, a good first order estimate is: c

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 13 Krakatau Let’s estimate how long it took the wave to travel from Indonesia to Madagascar

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 14

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 15 Now you try…

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 16 Causes of Tsunamis: Any impulse that causes large scale displacement of the sea surface. Seismic Rupture Landslide Undersea Eruption or Explosion Meteor Impact

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 17 More on energy Some estimates put the seismic energy released during the Sumatra 2004 tsunami at 500 million tons of TNT – or about 33,000 times the energy released by the bomb at Hiroshima. Where did all that energy go? Deforming a large part of the earth’s crust Seismic waves (earthquake) Tsunami waves - raising up (potential energy) and accelerating (kinetic energy) the water

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 18 Magnitude 9.0 OFF THE WEST COAST OF NORTHERN SUMATRA Sunday, December 26, 2004 at 00:58:53 UTC

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 19 Surface Projection of Slip Distribution Courtesy of Chen Ji, Caltech

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 20 Projected Surface Displacements (by Chen Ji, Caltech)

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 21 Tsunami Generation: Efficiency of tsunami generation by crustal deformation: Controlled by the speed at which the rupture propagates down the fault Earthquakes with slow rupture velocities are the most efficient tsunami generators, “tsunami earthquakes”. This capacity for tsunami generation is commonly characterized by a Tsunami Magnitude, Mt.

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 22 Recall: Basic Concept of Seismology Seismic moment - measure of work done by earthquake. Mo = m A D where m = shear modulus of rock A = rupture area D = average displacement over rupture area Moment magnitude M w = log M o 1.5

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 23 Tsunami Magnitude: One formula for tsunami magnitude is: Mt = log H2 + log X Mt: Tsunami magnitude H2: Maximum crest-to-trough amplitude on tide gage record in meters X: Distance from epicenter to station along the shortest oceanic path in km (Ref. Abe, K., Phys. Earth Planet. Inter., 27, , 1981)

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 24 Tsunami Magnitude: Some tsunami events with Mt = 9.0 and greater: 1837 Valdivia, Chile Kamchatka Arica, Chile Iquique, Chile Aleutians Kamchatka Aleutians Chile Alaska Sumatra, Indonesia 9.0 Ref: (Abe, K., J. Geophys. Res., 84, , 1979):

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 25 Landslide generation of tsunamis So if we understand that a tsunami is generated by an impulse that causes large scale displacement of the sea surface then it is easy to see that landslides can also generate tsunamis. Skagway, Alaska 1994

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 26 Skagway, Alaska 1994 Possible lanslide generated tsunami

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 27 Example of landslide source computation

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 28 What about Volcanoes? So if we understand that a tsunami starts with a large scale displacement of the sea surface then it is easy to see that volcanoes can also generate tsunamis. The surface displacement can be caused by lava flows, sea floor motion or even the release of a large amount of gas.

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 29 And what about Meteors? So if we understand that a tsunami is generated by an impulse that causes large scale displacement of the sea surface then it is easy to see that meteor/asteroid impacts can also generate tsunamis.

Dr. Catherine Petroff, University of Washington - July 22, 2007 UW Educational Outreach – Tsunami Science & Preparedness Program (Su 07) Sponsored by NOAA and USAID under the U.S. Indian Ocean Tsunami Warning System Program Page 30 Phases of a Tsunami Event: Generation Propagation Shoaling Inundation