Understanding Earthquakes and Seismic Waves
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Questions and Answers

What primarily causes most earthquakes?

  • Human activities like mining
  • Meteorological changes
  • Volcanic activity
  • Tectonic plate movements (correct)

Which type of seismic wave arrives first at a seismograph?

  • S-waves
  • P-waves (correct)
  • Surface waves
  • Rayleigh waves

What is the focus of an earthquake?

  • The center of a tectonic plate
  • An area of weak rock prone to high seismic activity
  • The point on the Earth's surface directly above the earthquake
  • The point within the Earth where the earthquake originates (correct)

Which type of seismic wave typically causes the most damage?

<p>Love waves (C)</p> Signup and view all the answers

What depth range can the focus of an earthquake occur at?

<p>From a few kilometers to hundreds of kilometers below the surface (C)</p> Signup and view all the answers

Which seismic wave can travel through both solids and liquids?

<p>P-waves (A)</p> Signup and view all the answers

How does the amplitude of surface waves change with depth?

<p>It decreases with depth (A)</p> Signup and view all the answers

Which of the following human activities can induce earthquakes?

<p>Fracking (D)</p> Signup and view all the answers

What is the primary function of a seismometer?

<p>To detect and record seismic waves (A)</p> Signup and view all the answers

Which scale is considered more accurate for measuring an earthquake's magnitude?

<p>Moment Magnitude Scale (C)</p> Signup and view all the answers

Which of the following describes the epicenter of an earthquake?

<p>The point on the Earth's surface above the focus (A)</p> Signup and view all the answers

On the Modified Mercalli Intensity Scale, what does a level VIII signify?

<p>Very Destructive (C)</p> Signup and view all the answers

What geological feature is commonly associated with liquefaction during earthquakes?

<p>Loose saturated sand (A)</p> Signup and view all the answers

How are the geographical coordinates of the epicenter typically described?

<p>Using geographical latitude and longitude (D)</p> Signup and view all the answers

Which intensity level on the Modified Mercalli Intensity Scale corresponds to the description 'strong' shaking felt by most people indoors?

<p>V (C)</p> Signup and view all the answers

What typically happens at an intensity level of IX on the Modified Mercalli Intensity Scale?

<p>Most buildings are totally damaged (C)</p> Signup and view all the answers

At which intensity level do heavy objects, like furniture, typically overturn or topple?

<p>VII (B)</p> Signup and view all the answers

What does an intensity level of X on the Modified Mercalli Intensity Scale indicate?

<p>Completely Devastating impact (B)</p> Signup and view all the answers

What is the common effect of a VI intensity level earthquake?

<p>Heavy objects may shift (C)</p> Signup and view all the answers

What type of earthquake intensity scale measures the intensity of shaking based on observable effects?

<p>Modified Mercalli Intensity Scale (D)</p> Signup and view all the answers

Which scale would likely yield a higher reading during a very strong earthquake, the Richter Scale or the Moment Magnitude Scale?

<p>Moment Magnitude Scale will yield a more accurate value (B)</p> Signup and view all the answers

Which of the following earthquakes would most likely result in the strongest shaking reported at the epicenter?

<p>An earthquake with a moment magnitude of 7.2 (C)</p> Signup and view all the answers

Flashcards

Earthquake

The shaking of the Earth's surface due to energy release in the lithosphere.

Tectonic Plate Movement

Main cause of most earthquakes; plates sliding along faults.

Seismic Waves

Waves of energy released during an earthquake.

P-waves

Fastest seismic waves, traveling through solids, liquids, and gases.

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S-waves

Slower seismic waves; travel only through solids.

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Surface Waves

Seismic waves traveling along the Earth's surface.

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Focus (Hypocenter)

Earth's point where an earthquake originates.

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Earthquake Depth

Distance from the Earth's surface to the earthquake's origin.

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Epicenter

The point on Earth's surface directly above the earthquake's origin (focus).

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Location of Epicenter

It's usually described using latitude and longitude.

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Significance of Epicenter

It's the point typically reported in news about earthquakes, often where the strongest shaking occurs.

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Seismometer

An instrument used to detect and record seismic waves from earthquakes.

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Richter Scale

Measures earthquake magnitude (power) based on the size of seismic waves.

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Moment Magnitude Scale

A newer, more accurate scale that measures the total energy released by an earthquake.

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Modified Mercalli Intensity Scale

Measures the intensity of earthquake shaking and damage, from I (not felt) to XII (total destruction).

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Intensity Scale I

Scarcely Perceptible: Felt by a few under good conditions, like delicately balanced objects slightly shaking. Slow oscillations in still water.

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Intensity Scale II

Slightly Felt: More noticeable than I, felt by a few indoors, hanging objects swing slightly, water oscillates.

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Intensity Scale III

Weak: Felt by many indoors, especially upstairs, vibration like a light truck passing, dizziness for some.

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Intensity Scale IV

Moderately Strong: Felt by most indoors, light sleepers awakened, vibration like a heavy truck, hanging objects swing.

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Intensity Scale V

Strong: Felt by almost everyone, many awakened, strong shaking, light objects fall or overturn.

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Intensity Scale VI

Very Strong: Many frightened, furniture moves, old buildings damaged, some rockfalls.

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Intensity Scale VII

Destructive: Most people run outdoors, strong damage to buildings, limited liquefaction and landslides.

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Intensity Scale VIII

Very Destructive: People have trouble standing, many buildings severely damaged, widespread liquefaction.

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Study Notes

Earthquakes

  • Definition: An earthquake is the shaking of the Earth's surface, caused by sudden energy release in the lithosphere, producing seismic waves.
  • Causes:
    • Tectonic plate movements: Most earthquakes arise from fault movements along tectonic plates.
    • Volcanic activity: Can trigger earthquakes.
    • Human activities: Activities like mining, reservoir-induced seismicity, and fracking can induce earthquakes.
  • Seismic Waves:
    • P-waves (Primary waves): Compressional waves, travel fastest, pass through solids, liquids, and gases, arrive first on seismographs.
    • S-waves (Secondary waves): Shear waves, slower than P-waves, travel only through solids.
    • Surface waves: Travel along the Earth's surface, causing considerable damage.
      • Love waves (L-waves): Horizontal motion, causing twisting, largest amplitude decreasing with depth, detected third, strong horizontal motion damages foundations.
      • Rayleigh waves (R-waves): Rolling motion, both up-down and side-side, slower than Love waves, can occur on any surface, amplitude greater when originating from epicenter, detected by both seismograph mechanisms.

Focus (Hypocenter)

  • Definition: The point within the Earth where an earthquake originates, the point at which stress is released in the rocks.
  • Depth: Earthquakes can occur from a few kilometers to hundreds of kilometers below the surface.
  • Significance: The depth of the focus affects how intense and what type of shaking is experienced at the surface; shallow foci often cause more serious surface shaking.

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Description

This quiz covers the fundamentals of earthquakes, including their definitions, causes, and the different types of seismic waves. Test your knowledge on tectonic plate movements, volcanic activity, and how human actions can influence seismic events. Dive into the world of seismic waves and learn about P-waves, S-waves, and surface waves!

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