1 / 36

370 likes | 733 Vues

Earthquakes. Earthquake Basics. Earthquake – shaking of Earth’s crust caused by the sudden release of energy Energy build over time until stresses break the rocks Happen ~ every 30 seconds ~3,000 annually strong enough to move sections of Earth’s crust ~20 annually cause severe damage

Télécharger la présentation
## Earthquakes

**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

**Earthquake Basics**• Earthquake – shaking of Earth’s crust caused by the sudden release of energy • Energy build over time until stresses break the rocks • Happen ~ every 30 seconds • ~3,000 annually strong enough to move sections of Earth’s crust • ~20 annually cause severe damage • Can only occur in the rigid crust!**Causes**• Elastic Rebound Theory – • Pressure and stress begin to build along plate or fault boundaries • Pressure causes deformation and shape changes in rock • Stress becomes great enough to overcome friction • Plate or fault suddenly move • Plate or fault snap back to previous shape**Earthquake Definitions**• The point on the fault plane at which the first movement of the earthquake occurs • The point on the earth’s surface directly above the focus of the earthquake • A break or crack in the earth’s crust from which movement occurs. • Focus or Hypocenter • Epicenter • Fault**Seismic Waves**• Travel & act much like sound waves • 2 basic types • Body Waves (2 types) • Compressional, Primary or P wave • Shear, Secondary or S wave • Surface waves (2 types) • Product of P & S waves reaching the surface • Love or L Waves • Rayleigh waves**P Waves**• Fastest traveler • 1st to be recorded • Travel through all materials (rock, fluids, air) • Move straight along ground in an accordion fashion like a spring or slinky**S Wave**• 2nd fastest wave • Travels ~1/2 speed of P wave • Particles move at right angles to the direction of travel • Only move in solids • Cannot move in fluids or air**Love Waves**• Slower than both P & S waves • Travel like ripples in a pond • Very destructive!!!**Time Travel Graph**• A time travel graph is used to find the distance to the epicenter.**Time Travel Graph questions.**• 1a. If an earthquake occurred near where you live, would P waves or S waves arrive at your location first? • b. Explain your answer. • 2a. How long would it take for a P wave to travel from an earthquake epicenter to a location 8000 km away? • b. How long would it take for an S wave to travel the same distance. • 3. Approximately how far must an observer be from an earthquake epicenter if he or she received a P wave 8 minutes after it was produced by the earthquake. • 4. Explain how you could tell which of two observers was farthest from an earthquake epicenter by comparing the arrival times of P and S waves for the two locations.**Do Earth quake lab #1**• Finding the distance to the epicenter.**Locating an Earthquake**The Basics of Seismic Exploration**seismograph- instrument used to measure Earth’s movements.**• The pattern of seismic waves produced by a seismograph = seismogram • Richter Scale- measures earthquake’s magnitude (size of earthquake/amount of seismic waves)**Missoula**Denver San Francisco**Seismograph Print-outs**Guide to reading a seismogram**Use the data from the recording stations:**• Station A:San Francisco, California P-Wave arrival 3:02:20S-Wave arrival 3:06:30 What is the time difference between P and S wave arrivals? 4:10**Use the data from the recording stations:**• Station B:Denver, Colorado P-Wave arrival 3:01:40S-Wave arrival 3:05:00 What is the time difference between P and S wave arrivals? 3:20**Use the data from the recording stations:**• Station C: Missoula, Montana P-Wave arrival 3:01:00S-Wave arrival 3:03:00 What is the time difference between P and S wave arrivals? 2:00**Difference in arrival times:**San Francisco: 4:10 Denver, Colorado: 3:20 Missoula, Montana: 2:00**MOVE THE PAPER UNTIL THE TWO TICK MARKS LINE UP WITH THE P**AND S CURVES WHEN TICK MARKS LINE UP, GO STRAIGHT DOWN AND READ THE EPICENTER DISTANCE EPICENTER DISTANCE OF 2800 KM**Recording BoardDifference in arrival times:**San Francisco: 4:10 =2,800km Open your compass to the EXACT distance on the scale. 3,000 4,000 5,000 2,000 1,000**EPICENTER DISTANCES**San Francisco: 4:10 2,800km Denver, Colorado: 3:20 2,000km Missoula, Montana 2:00 1,100km**Use your carefully set compass to**draw a circle around each city. . 1,100km . . 2,800km 2,000km You've found the epicenter! Triangulation**How are the Size and Strength of an Earthquake Measured?**• Magnitude • Richter scale measures total amount of energy released by an earthquake; independent of intensity • Amplitude of the largest wave produced by an event is corrected for distance and assigned a value on an open-ended logarithmic scale**Site #1**Dist = 300km Amp = 50mm Site #2 Dist = 600km Amp = 5mm Site #3 Dist =100km Amp = 500mm

More Related