1 / 9

Tsunamis

Tsunamis. Preethi Ganapathy Physical Oceanography November 20, 2007. Tsunamis. Tsunami: “Tsu”=Harbor, “Nami”=Wave. Physics of Tsunamis Causes of Tsunamis. Physics of Tsunamis. Tsunamis have very long wavelengths and periods Equations of motion: x= x 0 sin(kx± ω t)

honey
Download Presentation

Tsunamis

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Tsunamis Preethi Ganapathy Physical Oceanography November 20, 2007

  2. Tsunamis Tsunami: “Tsu”=Harbor, “Nami”=Wave • Physics of Tsunamis • Causes of Tsunamis

  3. Physics of Tsunamis • Tsunamis have very long wavelengths and periods • Equations of motion: • x= x0sin(kx±ωt) • y= - y0cos(kx±ωt) • Vertical amplitude: y0= x0kH • Velocities: • Vx= x0(±ωt)cos(kx±ωt) • Vy= x0kH(±ωt)cos(kx±ωt) • Energies: • U=2ρLg x02kH2 • T= 2ρLω2x02 ω2 H/k • Dispersion Relation: ω2=gHk2

  4. Physics of Tsunamis • Dispersion Equation shows: • Phase velocity: vp=ω/k =√(gh) • Group velocity: vg=dω/dk =√(gh) • √H Speed and wavelength adjust to keep period constant • Increase in height due to conservation of energy

  5. Causes of Tsunamis Tsunamis from • Earthquakes • Landslides • Volcanism • Cosmic Impact

  6. Causes of Tsunamis Tsunami from Earthquakes • Most common cause of Tsunamis • Subduction of plate causes transfer of energy to water during rupture • Water rushes landward and seaward Cited from [4]

  7. Causes of Tsunamis • Tsunamis due to landslides may be caused by earthquakes • Volcanic eruptions can cause sudden displacement of water • Tsunamis caused by cosmic impact could cause massive destruction

  8. Tsunami History • The 1755 Lisbon earthquake, along with the resulting tsunami and fires, led to near total destruction of the Portuguese capital. • One of the worst tsunami disasters engulfed whole villages along Sanriku, Japan, in 1896. A wave more than seven stories tall (about 20 m) drowned some 26,000 people. • 1946: An earthquake in the Aleutian Islands sent a tsunami to Hawaii, killing 159 people (only five died in Alaska). • 1958: A very localized tsunami in Lituya Bay, Alaska was the highest ever recorded: more than 500 m (1500 ft) above sea level. It did not extend much beyond the outlet of the fjord in which it occurred, but did kill two people in a fishing vessel. • 1976: August 16 (midnight) a tsunami killed more than 5000 people in the Moro Gulf region (Cotabato city) of the Philippines. • 1983: 104 people in western Japan were killed by a tsunami spawned from a nearby earthquake. • July 17, 1998: A Papua New Guinea tsunami killed roughly 3,000 people. A 7.1 magnitude earthquake 15 miles offshore was followed within 10 minutes by a tsunami about 12 m tall. While the magnitude of the quake was not large enough to create a tsunami directly, it is believed the earthquake generated an undersea landslide, which in turn caused the tsunami. The villages of Arop and Warapu were destroyed. Cited from [7]

  9. References • Margaritondo, G Eur. J. Phys. 26, 401 • F Behroozi and N Podolefsky, Eur. J. Phys. 22, 225 • Thorne K S Applications of Classical Physics chapter 15 (available in pdf form in the site www.pma.caltech.edu/Courses/ph136/yr2002/index.html of Caltech). • http://geology.com/articles/tsunami-geology.shtml • www.geophys.washington.edu/tsunami/general/physics/physics.html of the University of Washington • http://www.ringsurf.com/online/2411-what_causes_a_tsunami_.html • Religion and Spiritual Beliefs Resource, http://www.important.ca/tsunami_history.html

More Related