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EARTHQUAKES AND EARTH

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EARTHQUAKES AND EARTH S INTERIOR Core Innermost layer, where the magnetic field is generated and much geothermal energy resides Separated into outer core (liquid ... – PowerPoint PPT presentation

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Title: EARTHQUAKES AND EARTH


1
EARTHQUAKES AND EARTHS INTERIOR
2
Objectives
  • Explain the connection between earthquakes and
    plate tectonics.
  • Identify several earthquake-related hazards.
  • Define body waves and surface waves.
  • Explain how the materials in Earths interior
    affect seismic waves.
  • Define and describe the composition of Earths
    crust, mantle and core.

3
Megathrust earthquakes
4
Earthquakes and earthquake hazards
  • Seismology
  • The scientific study of earthquakes and seismic
    waves
  • Seismic waves
  • An elastic shock wave that travels outward in all
    directions from an earthquakes source
  • Seismic creep

5
Earthquakes and plate motion
  • The elastic rebound theory
  • Continuing stress along a fault
  • Results in buildup of elastic energy in the rocks
  • Energy abruptly released when an earthquake occurs

6
Earthquakes and plate motion
7
Earthquake Hazards and Predictions
  • Primary hazards
  • Collapsing buildings, bridges and other
    structures
  • Aftershock
  • Secondary hazards
  • Landslides, fires, ground liquefaction, tsunamis

8
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9
Earthquake hazards
Landslide, Huascaran, Peru
Open fissure, Golcuk, Turkey
10
Earthquake hazards
Fire, San Francisco, California
Ground liquification, Niigata, Japan
11
The Sumatra-Andaman Tsunami (2004)
12
Earthquake prediction
  • Short-term prediction and early warning
  • Precursor phenomena
  • Foreshocks
  • Long-term forecasting
  • Paleoseismology
  • The study of prehistoric earthquakes
  • Seismic gaps

13
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14
Earthquake Readiness
  • Preparation and readiness to earthquakes key to
    reducing fatalities
  • Reinforced structures
  • Bolting wood-framed buildings to foundation
  • Protecting utility lines from movement
  • Education

15
The Science of Seismology
  • Seismograph
  • An instrument that detects and measures
    vibrations of Earths surface
  • Advanced seismographs detect vibrations 10-8 of a
    centimeter
  • Seismogram
  • The record made by a seismograph

16
The Science of Seismology
17
Seismic waves
  • Body wave
  • Travels through Earths interior
  • Surface wave
  • Travels along Earths surface
  • Focus
  • Where rupture commences and an earthquakes
    energy is first released

18
Locating earthquakes
  • Compressional wave
  • Wave consisting of alternating pulses of
    compression and expansion
  • Can pass through any medium (solids, liquids,
    gases)
  • P (or primary) wave
  • Shear wave
  • Rock is subjected to side to side or up and down
    forces, perpendicular to waves direction of
    travel
  • S (secondary) wave
  • Not transmitted through water
  • Travel slower than P waves

19
Locating earthquakes
20
Locating earthquakes
21
Locating earthquakes
  • Epicenter
  • The point on Earths surface directly above an
    earthquakes focus

22
Locating earthquakes
23
Measuring Earthquakes
  • The Richter Magnitude Scale
  • A scale of earthquake intensity based on the
    recorded heights, or amplitudes, of the seismic
    waves recorded on a seismograph
  • A logarithmic scalea 10 fold increase in
    amplitude for each unit
  • Moment Magnitude Scale
  • A measure of earthquake strength that is based on
    the rupture size, rock properties, and amount of
    displacement on the fault surface

24
Measuring Earthquakes
Richter magnitude 7
Richter magnitude 6
Richter magnitude 8
25
Studying Earths Interior
  • Seismic discontinuity
  • A boundary inside Earth where the velocities of
    seismic waves change abruptly

26
Studying Earths Interior
27
Studying Earths Interior
  • Three things can happen to seismic waves when
    they meet a boundary
  • Refraction bent as they pass from one material
    to another
  • Reflection some or all of the wave energy
    bounces back
  • Absorption some or all of the wave energy is
    blocked

28
How geologists look into Earths interior
  • Seismic tomography
  • Allows geologists to image inside of Earth
  • Direct observation
  • Drilling
  • Xenoliths
  • Indirect observation
  • Magnetism
  • Density

29
Diamonds!
30
A Multilayered Planet
  • Crust
  • The outermost compositional layer of the solid
    Earth, part of the Lithosphere
  • Thickness ranges between 8 kilometers (oceanic)
    and 45 km (continental)

31
A Multilayered Planet
32
A Multilayered Planet
  • Mantle
  • The middle compositional layer of Earth, between
    the core and the crust
  • Comprised primarily of olivine and pyroxene
  • Asthenosphere mantle where rock is near melting
  • Mantle-core boundary mesosphere

33
A Multilayered Planet
34
A Multilayered Planet
  • Core
  • Innermost layer, where the magnetic field is
    generated and much geothermal energy resides
  • Separated into outer core (liquid) and inner core
    (solid)

35
Critical Thinking
  • If you were on a ship in the ocean, would you be
    able to feel an earthquake that occurred below
    you, on the ocean floor?
  • Do you think there is no limit to the magnitude
    of earthquakes?
  • What kind of wave would you expect to travel
    faster a seismic wave or a tsunami wave?
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