Tsunami Flashcards
What is a tsunami?
Series of waves caused by displacement of large volume of water.
What four things can cause a tsunami?
Volcanoes.
Earthquakes.
Landslides.
Meteor impact.
Define each:
- wave length
- wave height
- wave period
Wave length: distance from crest to crest.
Wave height: distance from crest to trough.
Wave period: time between passage of two wave crests.
Speed _____ as the wave approaches shore.
Decreases.
When a tsunami approaches shore, what happens to volume and height?
Volume stays the same as the wavelength shortens.
Height increases.
Regarding tsunami, what is run up?
Height that wave reaches as it rushes onshore.
During an earthquake-generated tsunami, wave height is dependent on what?
Vertical movement on fault.
Moment magnitude 8 could generate a _____ m wave at sea.
15.
Describe the process of an earthquale-generated tsunami.
Overriding plate is stuck on subducting plate; plate squeezed, begins bulging up at the end and dragging down towards the subducting plate; gets unstuck, plate relaxes, causes subsidence and sudden uplift causes tsunami.
During an landslide-generated tsunami, wave height is dependent on what?
Primarily height of fall, but also mass of rock/sediment.
Megatsunami typically happen in what areas?
Harbour areas.
In Greenland in 2017, what caused a tsunami?
4.1 earthquake caused landslide.
Describe the tsunami in Valley-Vajont in 1963.
Megatsunami, 50 million cubic metres of water overtopped dam in 250m wave.
What was the lateral and vertical movement of the 2004 Sumatra-Andaman tsunami?
10 m lateral; 5 m vertical.
During the Andaman-Sumatra tsunami, there was a large volume of beach sand over soil. How many cm were there in total, and how much came from the first wave?
73 cm total.
45 cm from first wave.
How large was the 2011 Tohoku tsunami in terms of rupture of the earthquake and the tsunami itself? How far did it travel inland?
500 km rupture.
40 m tsunami.
10 km inland.
The 2011 Japan earthquake was 9-9.1 (Mw), which is the equivalent energy of what hydrogen bomb?
45-Mt.
One way to determine a historical record is to see how a tsunami lays down a sheet of sand. Describe what happens before an earthquake, minutes to hours after an earthquake, and centuries after an earthquake.
Before earthquake: land subsides during earthquake (lowers).
Minutes to hours after: sand-laden tsunami overruns subsided landscape.
Centuries after: sand sheet over subsided land.
One evidence of historical tsunamis in Oregon are the presence of former _____ beneath the soil.
Hearths (fire pits).
List six methods for tsunami hazard mitigation.
Detection and warning.
Structural control.
Tsunami inundation maps.
Land use.
Probability analysis.
Education.
Deep-ocean assessment and recording of tsunamis follow what process?
Recorder on seabed monitors changes in pressure. Detects earthquake, sends first warning, water level checked, sends second warning.
