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TSUNAMI. BASIC INFO 1.) Tsunami are NOT tidal waves, they have nothing to do with tides 2.) They are caused by “BIG SPLASHES” from… *earthquake motion (Fig. 10-14) *landslides *extra terrestrial impacts. http://esminfo.prenhall.com/science/geoanimations/animations/86_Tsunami.html.
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TSUNAMI BASIC INFO 1.) Tsunami are NOT tidal waves, they have nothing to do with tides 2.) They are caused by “BIG SPLASHES” from… *earthquake motion (Fig. 10-14) *landslides *extra terrestrial impacts. http://esminfo.prenhall.com/science/geoanimations/animations/86_Tsunami.html
TSUNAMI SPEEDS 1.) velocity=(square root of gravity) x (ocean depth) g=9.8m/sec2 depth for Pacific=5500meters on average so, velocity= 232meters/sec=518miles per hour SMOKIN’ 2.) Because of friction with bottom they slow down considerably but still hit the shore at freeway speeds.
TSUNAMI WAVE PROPERTIES Let’s compare to wind-blown waves PeriodWavelength Wind blown 10 sec. 156 meters(130 ft.) Tsunami 3,600(60min.) 837,000 meters(520 miles)
TSUNAMIS AT THE SHORELINE 1.) Misconception: it is the height of the wave that does the damage 2.) Is it like “Deep Impact” NO-VIDEO of Deep Impact 3.) The shore first recedes in response to movement. Credit: V.Gusiakov, 2005, Novosibirsk Tsunami Laboratory
TSUNAMIS AT THE SHORELINE (continued) 4.) The crest then propagates toward shore. 5.) Low amplitude (meters-tens of meter) long wavelength 6.) Hits the shore like a rapidly rising tide. 4.) Recall the period about 60 minutes. 5.) This means as the water rushes inland for about 30 minutes before withdrawing AND CREATING ANOTHER SURGE VIDEO-http://www.cbsnews.com/elements/2004/12/27/world/videoarchive663162.shtml
TSUNAMI CASE HISTORIES ALASKA April 1, 1964 1.) Tectonic Setting-Subduction-convergent 2.) 2 different events occurred 3.) 20 min. after the 2nd a 30m tsunami approached Scotch Gap Lighthouse. 4.) Scotch Gap Lighthouse sat 14 meters above mean low-water level.
TSUNAMI CASE HISTORIES ALASKA April 1, 1964 Scotch Gap Lighthouse sat 14 meters above mean low-water level. Photo Courtesy of NOAA
TSUNAMI CASE HISTORIES ALASKA April 1, 1964 Hilo, Hawaii results 1.) Raced across the Pacific at speeds up to485m/h 2.) Hit Hilo at about 35 m/h 3.) Fastest sprinter doesn’t run 25m/h 4.) killed 159 people.
TSUNAMI CASE HISTORIES Papua New Guinea July 17, 1998 1.) 7.1magnitude 2.) Sounds like distant thunder where heard 3.) pulled back and 4-5 min. later…. 4.) 4m (13ft.) Surge approached 5.) second wave approached=14m(45ft) 6.) 2,200 fatalities. 7.) VERY low topography=? Photograph by H. Davies Courtesy NOAA Photograph by Fr Z Mlak. Courtesy of NOAA
TSUNAMI CASE HISTORIES Indian Ocean Dec. 26, 2004 Courtesy: USGS
TSUNAMI CASE HISTORIES Indian Ocean Dec. 26, 2004 1.) Moment magnitude=9.0 Pretty BIG 2.) 283,000 killed, 1.2 million displaced 3.) $8.4 billion, with Indonesia suffering the bulk of that at $5.4 billion. Refuge Camp Credit : Livescience.com Incoming wave crest Credit : Livescience.com
LANDSLIDE GENERATED TSUNAMI SEICHE July 9, 1958 largest historic rock fall * Lituya Bay Alaska (lots o’ action in Alaska) *On the opposite side of bay 520 ft up forest was stripped Lake Tahoe *Tectonic Setting active,subparallel faults tensional system *3-4% change of mag. 7 in next 50 years *is this a real concern? Evidence? *(ND pg. 93/fig. 3.43)
TSUNAMI WARNING SYSTEM Deep-ocean Assessment and Reporting of Tsunamis (D.A.R.T.)
TSUNAMI WARNING SYSTEM Systems placed in areas with history of tsunami generation
