Earthquakes How they happen and what we can learn from them.
What causes most earthquakes on Earth? 1) Stress pressure is applied to sections of rock in different directions 2) Strain rocks deform from their original shape 3) Fracture rocks break 4) Faulting rocks move along the break as they ‘snap’ back to their original shape
Q1: The description of how earthquakes happen given on the previous slide is often referred to as… • Plate Tectonic Theory • General Relativity Theory • Special Relativity Theory • Elastic Rebound Theory • Mohorovicic Discontinuity Theory
Q2: Which option gives the correct name for each of the letters on the diagram? • A = Focus; B = Epicenter C = Fault • A = Epicenter; B = Focus C = Fault • A = Fault; B =Focus C =Epicenter • None of these A B C
When energy is released from a focus, it propagates out from that point through the interior of the Earth as two different types of waves.
When the P & S waves reach the epicenter, they produce surface waves, called…
Q5: Which type of earthquake wave is able to pass through liquid layers of earth’s interior—thus helping us figure out earth’s structure? • P waves • S waves • Raleigh waves • Love waves
How we know about earth’s interior: • Waves refract (thus changing the timing and positioning of their arrival) when encountering a different density layer. • S-waves cannot pass through the liquid outer core.
Q6: What is this? • Richter Scale • Seismograph • EKG Device • Quakemeter • None of these
A Siesmograph… • Uses inertia to measure the amount of shaking experienced. • 3 different ones needed to record shaking in all directions.
Q7: A Siesmogram sheet shows that… • The p-wave arrives before the s-wave • The s-wave arrives before the p-wave • Both p & s waves arrive at the same time
P-wave = primary wave—travels fastest S-wave = Secondary wave
Q8: Since we know how fast each type of wave travels, the amount of time between the arrival of the p-wave and the arrival of the s-wave will indicate… • The magnitude of the earthquake • How far away the epicenter is located • The exact location of the epicenter • How destructive the earthquake was • How long the earthquake lasted
Since you only can tell distance to the epicenter from once siesmograph, the only thing you can do is plot that value as a circle. At least three recording stations are needed to pinpoint the exact epicenter.
Q9: How does a magnitude 7 earthquake compare to a magnitude 6 earthquake? • It is 2 percent stronger • It is 10 percent stronger • It is 31 percent stronger • It is 2 times stronger • It is 10 times stronger • It is 31 times stronger
Richter Scale magnitudes are logarithmic values, thus increasing from a magnitude 6 to a 7 is actually 31 times greater in terms of energy. • The Richter Scale is a logarithmic scale of wave amplitude (meaning that going from a 6 to a 7 is a 10X increase in amplitude). M5 M6 M7
Liquefaction Niigata, Japan 1964
Landslide caused by an earthquake: Turnnagin Heights,Alaska,1964