Geohazard. Chona Mae Flashcards
This earthquake generated a tsunami that swept across the Indian Ocean, killing an estimated 225,000 people.
Magnitude 9.1 Indonesian earthquake in December 26, 2004
Is a very long-wavelength wave of water that is generated by sudden displacement of the seafloor or disruption of any body of standing water. Sometimes called as “seismic sea waves”
Tsunami
True or False. Tsunami is a series of multiple waves
True
The distance between three wave crests is 240 meters. Determine the wave base.
Answer: 60 meters
Wavelength: 120 meters
______ is the distance between 2 consecutive wave crests or 2 consecutive wave troughs. ______ meters is its value in normal ocean waves.
Wavelength. 100.
True or False. High energy wave is defined by shorter wavelength AND lower amplitude.
False. High energy wave = short wavelength (or high frequency) + high amplitude
refers to the distance between the trough of the wave and the crest of the wave
Wave height
height of the wave above the still water line, usually this is equal to 1/2 the wave height.
Wave amplitude
amount of time it takes for one full wavelength to pass a stationary point
Wave Frequency or Period
Can tsunamis be created in a man-made earthquake?
Yes
What movement/displacement mechanism in earthquakes is important to generate tsunami?
Vertical displacement
What is the velocity of the wave if it has 500 km wavelength and it takes 2 hours for one full wavelength to pass a stationary point
Velocity = wavelength / period
Velocity = 250 km/hr
Velocities of normal ocean waves are about _________
90 km/hr
If the trough of the tsunami wave
reaches the coast first, this causes a
phenomenon called ___________,
where it appears that sea level has
dropped considerably
Drawdown
If the crest of the tsunami wave
reaches the coast first, this causes a
phenomenon called ___________,
where it appears that sea level has
risen considerably
Run-up
is a standing wave in an enclosed or partially enclosed body of water. Also termed as “Lake Tsunamis”
Seiche
What depth and magnitude of earthquakes is important to generate tsunami?
Shallow (<70km) and at least M6.5 on Richter Scale
Which phenomenon do not generate tsunami.
1. Volcanic eruption
2. Landslide
3. Surface Waves
4. Nuclear Tests
5. Meteorite Impacts
6. Underwater Explosions
7. Subduction Zone Earthquakes
- Surface Waves. Although surface waves generate ocean waves, it is not enough force to generate tsunamis.
- Mw 7.3 earthquake occurred near Unimak Island in the Aleutian Islands west of Alaske, near the Alaska Trench
- Sediment accumulating in the trench slumped into the trench and generated a tsunami
April 1, 1946 Alaskan Tsunami
True or False. Tsunamis are waves that are generated to travel towards the nearest coast.
False. Tsunamis are waves that are generated to travel in ALL DIRECTIONS. Like ripples in a pond.
- Mw 9.5 earthquake occurred along the subduction zone off South America
- Also known as the “Great Chilean Earthquake”
The first tsunami wave had a run-up of 4.5 m whichhit the coast of Chile. But, about 1 hr. later, the second wave traveling at a velocity of 166 km/hr crashed in with a run-up of 8 m. - a third wave traveling at only 83 km/hr that crashed in later with a run-up of 11 m
- causalities listed: 909 dead with 834 missing
May 22, 1960 Valdivia Earthquake and Tsunami
- Mw 9.2 earthquake occurred along the subduction zone off of Alaska
- caused deformation of the crust where huge blocks where dropped down as much as 2.3 m
- Sediment accumulating in the trench slumped into the trench and generated a tsunami
March 27, 1964 Good Friday Earthquake in Alaska
- Mw 8.1 earthquake generated along the Cotabato Trench
- Up to 4.5-meter high waves
- devastated more than 700 kms of coastline bordering Moro Gulf in the North Celebes Sea
August 17, 1976 Moro Gulf Earthquake
True or False. The first wave in a series of wave in a tsunami event is not always the strongest.
True. May 22, 1960 Valdivia Earthquake and Tsunami produced its strongest wave on the third wave
The eruption of __________in the Straights of Sunda, between Java and Sumatra, in 1883 generated at least three tsunami that killed 36,417 people.
Krakatau
True or False. Formation of a Caldera (a collapse of a volcanic island) can trigger tsunamis.
True
Aside from volcanic earthquakes, what other volcanic phenomena generates tsunami?
Explosive eruptions can rapidly emplace pyroclastic flows into the water, LANDSLIDES AND DEBRIS AVALANCES produced by eruptions can rapidly move into water, displacing water and creating tsunamis.
Nuclear testing by the United States in the Bikini Atoll in Marshall Islands in the 1940s and 1950s generated up to ______-m high tsunamis
30
the apparent impact of a meteorite at the end of the Cretaceous Period, about 65 million years ago near the tip of what is now the ________________, produced tsunami that left deposits all along the gulf coast.
Yucatan Peninsula of Mexico
What administration has set up a warning system for areas in the Pacific Ocean, called the ___________________?
National Oceanic and Atmospheric Administration (NOAA); Pacific Tsunami Warning Center
Are passive margins safe from tsunamis?
No
Two mitigation measures for Tsunami
- Prediction And Early Warning
- Tsunami Safety Rules
