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/sec2depth for Pacific=5500meters on averageso, velocity= 232meters/sec=518miles per hour SMOKIN’

2.) Because of friction with bottom they slow down considerablybut still hit the shore at freeway speeds.

TSUNAMI WAVE PROPERTIES

Let’s compare to wind-blown waves

Period WavelengthWind 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 TsunamiLaboratory

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 withdrawingAND 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 tsunamiapproached 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 HISTORIESALASKA April 1, 1964

Hilo, Hawaii results1.) Raced across the Pacific at speeds up to485m/h2.) Hit Hilo at about 35 m/h3.) Fastest sprinter doesn’t run 25m/h4.) killed 159 people.

TSUNAMI CASE HISTORIESPapua New Guinea July 17, 19981.) 7.1magnitude2.) Sounds like distant thunder where heard3.) pulled back and 4-5 min. later….4.) 4m (13ft.) Surge approached5.) second wave approached=14m(45ft)6.) 2,200 fatalities.7.) VERY low topography=?

Photograph by Fr Z Mlak. Courtesy of NOAA

Photograph by H. Davies Courtesy NOAA

Indian Ocean Dec. 26, 2004

TSUNAMI CASE HISTORIES

Courtesy: USGS

TSUNAMI CASE HISTORIES

Indian Ocean Dec. 26, 2004

1.) Moment magnitude=9.0 Pretty BIG2.) 283,000 killed, 1.2 million displaced3.) $8.4 billion, with Indonesia suffering the bulk of that at $5.4 billion.

Incoming wave crestCredit : Livescience.com

Refuge CampCredit : Livescience.com

LANDSLIDE GENERATED TSUNAMISEICHE

July 9, 1958 largest historic rock fall

* Lituya Bay Alaska (lots o’ action in Alaska)

*On the opposite side of bay 520 ft upforest was stripped

Lake Tahoe*Tectonic Setting

active,subparallel faultstensional 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 withhistory of tsunami generation