10   a diversion, earthquakes and tsunamis
Upcoming SlideShare
Loading in...5
×
 

10 a diversion, earthquakes and tsunamis

on

  • 675 views

 

Statistics

Views

Total Views
675
Views on SlideShare
675
Embed Views
0

Actions

Likes
0
Downloads
8
Comments
0

0 Embeds 0

No embeds

Accessibility

Categories

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

10   a diversion, earthquakes and tsunamis 10 a diversion, earthquakes and tsunamis Presentation Transcript

  • Earthquakes and Tsunamis
  • Earthquakes
    • Late Thursday night (our time), an earthquake occurred of the coast of Japan.
    Earthquakes
    • Late Thursday night (our time), an earthquake occurred of the coast of Japan.
  • Earthquakes
    • One of the largest earthquakes since we’ve been measuring them (6 th strongest).
  • What is an Earthquake?
    • Earthquakes are movements of the earth that release pressure.
    • Occur along faults.
    • - planar breaks in rock where there is movement.
    • - occur in all sizes.
  • Faults
  • Faults
  • What Causes an Earthquake?
    • Build up of strain (gradual or sudden) deforms the earth until the elastic limit is reached – then things snap.
    • Elastic Rebound.
    • Energy is released in the form of seismic waves.
  • What Causes an Earthquake?
  • How do we Measure an Earthquake?
    • Most common way is by the Richter Scale.
    • Based on the amplitude of the seismic waves.
    • Scale is logarithmic! Difference in two whole numbers means in increase in vibrations by a factor of 10!
    • - ground that moves 1 inch in a 4.0 earthquake moves 10 inches in a 5.0 quake, and 100 inches in a 6.0 quake.
  • Where Does the Strain Come From?
    • Plate tectonics.
    • Outermost portion of our planet is broken into different pieces called plates.
    • The plates move all the time.
  • Tectonic Plates
  • Plate Boundaries
    • Most of the action occurs at the boundary between two plates.
    • Plates can move away from one another, towards one another, or just slide past one another.
  • Plate Boundaries
  • Convergent Plate Boundaries
    • When plates run into one another, the more dense plate is forced underneath the less dense plate, a process called subduction.
  • Convergent Plate Boundaries
    • When ocean material runs into continental material one gets a trench in the ocean, and a chain of volcanic mountains on the continent.
  • Convergent Plate Boundaries
    • When ocean material runs into continental material one gets a trench in the ocean, and a chain of volcanic mountains on the continent.
  • Convergent Plate Boundaries
    • When ocean material runs into ocean material one gets a trench in the ocean, and a chain of volcanic islands called an island-arc.
  • Convergent Plate Boundaries
    • When ocean material runs into ocean material one gets a trench in the ocean, and a chain of volcanic islands called an island-arc.
  • Earthquake Damage
    • Ground movement
    • Fire
    • Landslides
    • Liquefaction
    • Tsunamis
  • Earthquakes and Tsunamis
    • Sudden movement of the sea floor will displace a large volume of water.
  • Tsunami Speed
    • The speed of the tsunami is controlled by the depth of the water.
    • C (celerity) = √ g x d
    • where g is gravitational acceleration, and d is the depth of the water in which the wave is travelling.
    • Since g is a constant, the speed is mostly a function of water depth (wavelength also plays a role, but we’re neglecting it for now).
  • Tsunami Speed
    • Average depth of the ocean is 4000 m.
    • C (celerity) = √ g x d
    • C = √ 9.8 m/s 2 x 4000 m
    • C = √ 39,200 m 2 /s 2
    • C = 198 m/s
    • 1609 meters in a mile, 3600 seconds in an hour.
    • C = 198 m/s / 1609 m/mile x 3600 s/hr
    • C = 443 miles/hour!
  • Tsunami Speed
    • As the wave approaches the shore its speed decreases.
    • C (celerity) = √ g x d
    • Aside from slowing, other things happen to the wave as it enters shallower water.
  • Tsunami Occurrences
  • Indonesia, December 2004
    • 9.1 magnitude earthquake occurred only 8 miles deep.
    • Rupture was 1200 km long with 15 m of vertical displacement.
  • Indonesia, December 2004
  • Indonesia, December 2004
    • Magnitude 8.9.
    • Strong enough quake to affect our axis of rotation (a day on earth is now a little shorter).
    Japan, March 2011