Questions and Answers
What is the exact point inside the crust where a tremendous amount of energy starts to be released?
What does hypocenter refer to in relation to an earthquake?
Earthquake focus
Which term is used to describe the waves that originate from the earthquake focus?
A shallow-focus earthquake occurs at depths of 0-70 km below the ground surface.
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What is the depth range for intermediate focus earthquakes?
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What term is synonymous with a shallow-focus earthquake?
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Deep-focus earthquakes are more common than shallow-focus earthquakes.
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The point on the earth's surface vertically above the focus is known as the ______.
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What instrument is used to measure earthquakes?
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Who invented the first seismograph?
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Which scale is used to determine the magnitude of an earthquake?
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Magnitude is expressed in a ______ value.
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Study Notes
Earthquake Focus and Hypocenter
- The earthquake focus, or hypocenter, is the precise location beneath the Earth's surface where seismic energy is first released.
- Vibrating waves originate from the focus, traveling outward in all directions.
Types of Earthquakes
- Shallow-focus earthquakes occur at a depth of 0-70 km, also referred to as crustal earthquakes, often causing more damage due to their proximity to the surface.
- Intermediate focus earthquakes occur at depths between 70-300 km.
- Deep-focus earthquakes, also known as intraplate earthquakes, occur at depths of 300-700 km; they are less common than shallow-focus earthquakes.
Characteristics of Shallow-Focus Earthquakes
- Shallow-focus earthquakes typically have smaller magnitudes but release energy more explosively due to their location.
- They are more frequent than deep-focus earthquakes and typically result in more severe damage because of their shallower depth.
- The first ground movements are felt at the epicenter, which is directly above the focus.
Epicenter and Seismic Waves
- The epicenter is the point on the Earth's surface directly above the focus, experiencing the strongest effects of an earthquake.
- Seismic waves, generated during an earthquake, radiate outwards from the focus in all directions.
Seismography
- Seismographs are instruments designed to measure and record the intensity and duration of seismic waves.
- Seismologists use seismographs to monitor earthquakes and understand their characteristics.
- A seismograph includes a seismometer and a voice recorder, and is sensitive enough to detect even the weakest seismic movements.
Seismograms and Measurements
- Seismograms display the vibrations detected during an earthquake as zigzag lines, indicating ground motion intensity.
- Magnitude and intensity of earthquakes are quantified using the Richter Magnitude Scale and are expressed as numeric values.
Historical Context
- The first seismograph was created by Cheng Heng, a Chinese mathematician and astronomer, known as the Earthquake Weathercock.
- John Milne invented the first modern seismograph, advancing the study of seismic activity.
Additional Concepts
- Electrical charges are produced during an earthquake, and electromagnets are used to convert these charges into digital signals for recording and processing.
- Understanding earthquake weather and conditions can provide insights into seismic activity, although predicting earthquakes remains complex.
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Description
Test your knowledge of key terms related to earthquakes with these flashcards. Learn about the earthquake focus, hypocenter, and their significance in seismology. Perfect for students studying geology or earth sciences!
