1 / 30

Types of Faults and seismic waves

Types of Faults and seismic waves. What is a fault?. A fault is a break in the rocks that make up the Earth’s crust, along which rocks on either side have moved past each other. The direction of movement along the fault plane determines the fault type.

shannony
Download Presentation

Types of Faults and seismic waves

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. Types of Faults and seismic waves

  2. What is a fault? • A fault is a break in the rocks that make up the Earth’s crust, along which rocks on either side have moved past each other. • The direction of movement along the fault plane determines the fault type.

  3. GEOLOGICAL CONCEPTSTYPES OF FAULTFootwall/Hanging wall from Mining geology Miners put their lamps on the hanging wall and walk on the foot wall.

  4. Three major Faults Normal Reverse Strike-slip

  5. Normal Fault The hanging wall moves down relative to the foot wall. This fault type is caused by tensional stress.

  6. Normal Fault

  7. Normal Fault

  8. Normal Fault

  9. Reverse Fault The hanging wall moves up relative to the foot wall. This fault is caused by Compressional stress.

  10. Reverse Fault

  11. Reverse Fault

  12. Reverse Fault

  13. Strike-Slip Fault The fault exists between two pieces of crust and the Movement occurs horizontally where the sides slide past each other. This fault type is caused by shear stress.

  14. Strike-Slip Fault

  15. Strike Slip Fault

  16. Strike-Slip Fault

  17. Fault Movement = Earthquakes • An earthquake is caused by a sudden slip on a fault. The tectonic plates are always slowly moving, but they get stuck at their edges due to friction. When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the earth's crust and cause the shaking that we feel.

  18. Focus- where the slip happens below ground Epicenter-where the shaking is first felt above ground directly above the focus.

  19. Slippage along fault initiates seismic waves in all directions radiating from the focus. • Seismic waves are vibrations that travel through the Earth carrying the energy released during earthquakes

  20. There are two categories of seismic waves: • Body Waves: Can travel through Earth’s inner layers (core, mantle, crust)- • Primary and Secondary waves • Surface Waves: Can only travel through the surface layers (crust) • Love and Rayleigh

  21. Primary Waves P waves- are the first waves to arrive at a seismograph station. -fastest form of wave, sometimes called compression waves. • Can move through both liquids and solids. • These waves cause rock particles to move back and forth in the same direction as the wave is traveling (push-pull).

  22. Secondary Waves S-Waves- arrive after the primary waves at the seismograph station. -Can travel through solids only. -Cause particles to move back and forth at right angles to the line of wave movement

  23. SEISMOLGYEARTHQUAKE LOCATIONTravel time versus distance plots Can construct distance versus travel time for earthquakes knowing properties of earth’s interior Note that with increasing distance the arrival times for the various waves separates. The 3 min 45 sec difference between the arrival time of the P and S waves corresponds to a distance of 2000 km.

  24. SEISMOLOGYLOCATING EARTHQUAKESTriangulation -Need three different seismic stations to locate an earthquake. -Measure the P-S arrival times and convert these to distance. -Triangulate using radius given by P-S travel times. -Triangulation for position of an earthquake near New Madrid using stations in Columbus, St Louis and Memphis

  25. Surface Waves Rayleigh wave-surface wave causing the ground to shake in an elliptical motion Because of its motion, it moves the ground up and down, and side-to-side in the same direction that the wave is moving Most of EQ shaking is due to this type of wave

  26. Love wave- produceentirely horizontal motion Moves the ground side-to-side Named after A.E.H. Love a British mathematician

  27. http://web.ics.purdue.edu/~braile/edumod/waves/WaveDemo.htm#Particle_Motionhttp://web.ics.purdue.edu/~braile/edumod/waves/WaveDemo.htm#Particle_Motion

  28. Measuring Earthquakes • Magnitude- the amount of energy released during an EQ • Richter Scale- based on the largest seismic waves generated by the EQ on a factor of 10. • Moment Magnitude Scale- considers the size of the fault rupture, the amount of movement, and rock’s stiffness

  29. Modified Mercalli Scale Measures the intensity of the EQ using a rating system of the damage • Scientists compile information from various observers within different zip codes to get a better understanding of the devastation caused by an EQ to determine its intensity.

More Related