The document discusses the causes and characteristics of tsunamis, emphasizing their origin from seismic activities and the long travel distances they cover. It highlights the potential for multiple waves, the impact of depth on wave speed, and the destructive nature of tsunami waves as they reach shorelines. Additionally, it covers tsunami warning systems and the risks associated with tsunami 'run-up' zones.

1.  Made by :- Master ?Made by :- Master ?
 Class :- 10Class :- 10
 Roll no. :- ?Roll no. :- ?
 Subject :- English(ppt)Subject :- English(ppt)

2. The devastating impact of
seismic sea waves

3. Tsunami (harbor wave)
Seismic sea waves (NOT tidal waves)
Caused by processes that abruptly move large volumes
of ocean water:
earthquake submarine volcanic eruption
coastal/submarine landslide or rockfall
extraterrestrial impact

4. http://geology.com/articles/tsunami-geology.shtml

5.  Unless there is an underwater landslide,
strike-slip EQ WILL NOT cause tsunami
 Most tsunami generated by subduction zones
 Chile,Chile,
 Alaska,Alaska,
 Japan,Japan,
 Cascadia,Cascadia,
 Philippines,Philippines,
 New ZealandNew Zealand

6.  Long wavelengths (over 100 km)
 Periods longer than 1 hour
316,800 ft = 60 miles

7.  Travel at high speeds :
400 to 500 mph (~200 yards/sec)
 Alaska to CA 4 to 7 hrsAlaska to CA 4 to 7 hrs
 Alaska to Hawaii 4 to 6 hrsAlaska to Hawaii 4 to 6 hrs
 Chile to Hawaii 14 to 15 hrsChile to Hawaii 14 to 15 hrs
 Chile to Japan 22 to 33 hrsChile to Japan 22 to 33 hrs

8. v = speedv = speed ~~
 g = acceleration of gravity (9.8 m/sec2
)
 d = depth of ocean (m)
 deeper water means higher speed
 For d = 4,600 m, v = 763 km/hr
(speed of jet plane)
gd

9.  Tsunami slows down (shallower water)
 Example: d = 100 m, v = 113 km/hr
 Wave gets taller
 λ gets shorter, T gets shorter

10.  As wave gets into shallow water bottom of wave
drags along ocean floor
 Top of wave still moving fast: can cause cresting
of wave, and breaking onto shore

11.  Run-up = measurement of height of water onshore
observed above a reference sea level
 Generally don’t get big gigantic wave
 Water comes as a fast moving rise in tide that rapidly
moves inland
 NOT JUST ONE WAVE…multiple waves coming in
about ½ hour or so apart
 See tsunami wave simulator
http://www.seed.slb.com/en/scictr/watch/living_planet/tsunami_wave/index.
htm

12.  Loss of energy in a wave is inversely
proportional to λ
 Since λ very long, little energy lost
 Waves can travel great distances and still be
very distructive

13.  Waves often full of debris (trees, cars, pieces of
wood etc.)
 As the wave recedes, the debris drags more
stuff with it
 Can recede as much as a km out to see, leaving
shoreline empty with flopping fish, boats, etc.
on the bottom

14.  Pressure recorder on bottom of ocean
 Buoy to communicate readings via
satellite
 Tsunami Warning Centers issue
warning

15.  Hawaii and Alaska
 When EQ considered capable of generating
tsunami, send warning with estimated arrival
time
 Once tsunami hitsOnce tsunami hits
somewhere, tsunamisomewhere, tsunami
watch established towatch established to
monitor tide gaugesmonitor tide gauges
and ocean buoysand ocean buoys

16.  When warning is issued – low lying areas are
evacuated
 U.S. Coast guard issues warnings over marine
frequencies
 Some places have sirens

17. Tsunami
How could you evaluate the level of risk
due to tsunami?

18. Possible tsunami
“run-up” zones

19.  Standing wave in an enclosed or partially
enclosed body of water (similar to sloshing in
a bath tub)
http://earthquake.usgs.gov/learning/glossary.php?term=seiche
 Generated by windGenerated by wind
or seismic activityor seismic activity
 Often swimmingOften swimming
pools experience apools experience a
seiche during EQseiche during EQ
standing wave

20.  Scientists at UNR have determinsed the seiches
have occurred on Lake Tahoe in the past
 Low probability – on average once every 2000
to 3000 years