Seismology: Understanding Seismographs and Waves
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Questions and Answers

A hanging heavy mass with a pen at the end does not move regardless of vibrations during an ______.

earthquake

To determine the location of the ______, one must measure and compare arrival times of seismic waves at different locations.

epicenter

Seismic tomography is an imaging technique using seismic wave data to create computer-generated ______ of Earth’s interior.

images

The measure of shaking and damage caused by an earthquake is referred to as its ______.

<p>intensity</p> Signup and view all the answers

The largest recorded earthquakes have had a magnitude of approximately ______.

<p>9</p> Signup and view all the answers

SEISMIC WAVE data provides information about __________.

<p>EARTHQUAKES</p> Signup and view all the answers

The __________ is referred to as the FOCUS of an EARTHQUAKE.

<p>HYPOCENTER</p> Signup and view all the answers

A network of stations monitoring SEISMIC WAVES exists around the __________.

<p>globe</p> Signup and view all the answers

A SEISMOGRAPH is a tool that records data about __________.

<p>SEISMIC WAVES</p> Signup and view all the answers

The __________ is a sensor on a SEISMOGRAPH that detects movements.

<p>SEISMOMETER</p> Signup and view all the answers

SEISMOMETERS can sense any vibrations traveling through the __________.

<p>Earth</p> Signup and view all the answers

SEISMIC WAVE data also provides information about the structure of the __________.

<p>Earth</p> Signup and view all the answers

The data recorded by SEISMOGRAPHS is essential for identifying the location of the __________.

<p>EPICENTER</p> Signup and view all the answers

A SEISMOMETER senses/detects any vibrations travelling through the Earth's ______.

<p>rocks</p> Signup and view all the answers

The SEISMOMETER transmits vibrational signals to a ______ that detects movements.

<p>SEISMOGRAPH</p> Signup and view all the answers

The data generated by a SEISMOGRAPH is known as a ______.

<p>SEISMOGRAM</p> Signup and view all the answers

If no vibrations are present in the Earth, the SEISMOGRAM shows a straight ______.

<p>line</p> Signup and view all the answers

A SEISMOGRAPH monitors three types of motion: up/down, East/West, and ______.

<p>North/South</p> Signup and view all the answers

The ______ of a wave is defined as the maximum displacement or height relative to its equilibrium position.

<p>AMPLITUDE</p> Signup and view all the answers

In terms of waves, the distance between two CRESTS or two ______ is referred to as WAVELENGTH.

<p>TROUGHS</p> Signup and view all the answers

In simpler SEISMOGRAPHS, a HEAVY MASS connected to a pen records vibrations onto a roll of ______.

<p>paper</p> Signup and view all the answers

The ______ scale is an outdated method for measuring magnitude of earthquakes.

<p>Richter</p> Signup and view all the answers

The magnitude of an earthquake is commonly reported as a single ______ regardless of location.

<p>number</p> Signup and view all the answers

A magnitude of 8 or greater indicates an earthquake that can destroy communities near the ______.

<p>epicenter</p> Signup and view all the answers

The magnitude scale is ______, meaning each increase by one unit results in a tenfold increase in size.

<p>logarithmic</p> Signup and view all the answers

Earthquakes with a magnitude of 2.5 or less are usually not felt by ______.

<p>humans</p> Signup and view all the answers

The __________ scale measures the magnitude of earthquakes based on the amplitude of seismic waves.

<p>Richter</p> Signup and view all the answers

The __________ Magnitude Scale has largely replaced the Richter scale for measuring larger earthquakes.

<p>Moment</p> Signup and view all the answers

Volcanic earthquakes occur in parallel with __________ activity.

<p>volcanic</p> Signup and view all the answers

Collapse earthquakes are caused by the underground __________ of caves or mines.

<p>collapse</p> Signup and view all the answers

Explosion earthquakes are triggered by explosions of __________ or chemical devices.

<p>nuclear</p> Signup and view all the answers

To determine the magnitude of an earthquake, one must measure the largest __________ on a seismogram.

<p>amplitudes</p> Signup and view all the answers

The time difference between the arrival of p-waves and __________ is used to calculate the location of an earthquake.

<p>s-waves</p> Signup and view all the answers

Predicting earthquakes is challenging due to the many __________ involved in their occurrence.

<p>variables</p> Signup and view all the answers

Flashcards

Seismograph

A tool that records seismic waves, measuring movements of Earth caused by earthquakes.

Seismic wave

Waves produced by earthquakes, carrying energy through the Earth.

Epicenter

The point on the Earth's surface directly above the focus (hypocenter) of an earthquake.

Hypocenter

The point beneath the earth's surface where an earthquake originates; also called focus.

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Seismometer

A sensor on a seismograph that detects ground movements.

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Earthquake data

Information about earthquakes, including their location, size, and effects.

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Earth's structure

The physical composition of the layers of the earth.

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Global network

A worldwide network of seismograph stations measuring earthquakes globally

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Amplitude

The maximum displacement of a wave from its normal position.

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Wavelength

The distance between two similar points on a wave (e.g., two crests).

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P-waves and S-waves

Types of seismic waves.

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Simple Seismograph

A seismograph design with a stationary heavy mass and moving paper.

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3-axis Seismograph

Measures ground motion in three directions: up/down, East/West, and North/South.

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Earthquake Magnitude

A measure of the size or strength of an earthquake determined at its source.

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Richter Scale

A logarithmic scale used to measure the magnitude of earthquakes, developed by Charles Richter in 1932.

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Logarithmic Scale

A scale where each increment represents a tenfold increase in the quantity being measured.

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Magnitude 2 vs. Magnitude 1

An earthquake with a magnitude of 2 is 10 times stronger than an earthquake with a magnitude of 1.

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Magnitude

A measure of the energy released by an earthquake, calculated based on the amplitude of seismic waves recorded on a seismograph.

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Intensity

A measure of the shaking and damage caused by an earthquake at a specific location, determined by observing and measuring the effects.

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How do we find the epicenter?

By comparing the arrival times of seismic waves at different seismograph stations, we can triangulate the location of the earthquake's epicenter on the Earth's surface.

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Seismic Tomography

A technique that uses seismic wave data to create 3D images of Earth's interior, providing information about its structure and composition.

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How does a seismograph work?

A heavy mass suspended on a spring remains relatively still during an earthquake, while the surrounding framework, connected to a recording device, moves and records the ground motion.

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Moment Magnitude Scale

A scale for measuring earthquake magnitude that considers the energy released, replacing the Richter scale for larger earthquakes.

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Volcanic Earthquakes

Earthquakes caused by volcanic activity, often occurring alongside eruptions.

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Collapse Earthquakes

Small earthquakes caused by the collapse of underground structures like caves or mines.

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Explosion Earthquakes

Earthquakes caused by explosions, such as nuclear or chemical detonations.

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Notable Earthquakes

Significant earthquakes that have caused notable impacts, such as casualties, damage, or rescue efforts.

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Predicting Earthquakes

The process of forecasting when and where earthquakes will occur, which remains a significant challenge due to complex factors.

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Study Notes

Seismograph Stations

  • Seismograph stations are located around the world.
  • Red dots on the world map indicate seismograph stations.

Studying Seismic Waves

  • Seismic wave data provides information about earthquakes and the structure of the Earth.
  • Data identifies the location of epicenters and hypocenters (focus).
  • A network of stations globally monitors seismic waves.

Seismograph

  • A tool that records seismic waves generated by earthquakes.
  • Records Earth's movements using a sensor placed deep in the ground.
  • A seismometer is a sensor on a seismograph that detects movements.
  • The seismometer detects vibrations traveling through the Earth.
  • The seismometer sends vibrations to the seismograph.

Seismogram

  • Data generated by the seismograph based on vibrations detected by the seismometer.
  • A straight line indicates no vibrations.
  • "Jumps" represent increased amplitude, indicating vibrations (increased energy).
  • Three lines are used to monitor up/down, east/west, and north/south motions.
  • The seismogram is used to generate earthquake waves.
  • Seismograms show P-waves and S-waves.

Wave Review: Amplitude and Wavelength

  • Amplitude: Maximum displacement of a wave relative to its equilibrium position.
  • Wavelength: Distance over which a wave shape repeats (distance between crests or troughs).

Simple Seismograph

  • Lab scale seismographs are simpler and record data onto a roll of paper.
  • The paper constantly moves, with the pen recording vibrations.
  • A weighted pen sits still, while the paper moves as the Earth moves.
  • Wave movement is visible on the paper.
  • The seismic waves produce jumps recorded on the seismogram that reflect amplitude increase.

Seismic Wave Data

  • Seismic waves (P & S) travel from the hypocenter.
  • Determining epicenter location - measuring and comparing arrival times of seismic waves at different stations.
  • Determining hypocenter location is more complex, requiring analysis of seismic wave patterns and sometimes using seismic tomography.

Seismic Tomography

  • Imaging technique using seismic wave data to create 3D images of Earth's interior.

Recording Earthquakes

  • Earthquakes are energy releases causing ground vibrations.
  • Energy travels from the hypocenter as seismic waves.
  • Earthquakes vary; some are destructive, others are not.
  • Magnitude and intensity are measures of earthquake strength.
  • Intensity: measure of shaking/damage.
  • Intensity varies with location.
  • Magnitude is a single number to show earthquake size, measured at the source of the earthquake.
  • Magnitude is the amount of energy released, which will change exponentially with magnitude.

Richter Scale

  • Outdated method for measuring earthquake magnitude, developed by Charles Richter in 1932.
  • Uses a logarithmic scale (each increase in whole number = 10 times bigger).
  • No upper or lower limit.
  • Logarithmic scale from 1 to 10, measuring the amplitude changes.

Calculation of Richter Scale Magnitude

  • Measures the largest signals (greatest amplitudes) on the seismogram.
  • Measures the time difference between the arrival of P-waves and S-waves.
  • Accounts for the distance from the earthquake source.

Moment Magnitude Scale

  • Replaced Richter Scale for magnitudes greater than 6.5 due to Richter scale undervaluing magnitude.
  • Moment magnitude measures energy release.

Other Earthquake Sources

  • Earthquakes may occur from tectonic plate collisions, volcanoes, cave collapses, or explosions.

Notable Earthquakes

  • In-class discussion on a notable earthquake.
  • Gather information about the location, date, magnitude, casualties, damage caused, and rescue efforts.

Predicting Earthquakes & Tsunamis

  • Predicting earthquakes is challenging.
  • Volcanoes can trigger tsunamis.

Thank you for Listening

  • Earthquake in Charlevoix, Quebec happened in February 1663.

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Description

This quiz focuses on the essential concepts of seismography, including the function and importance of seismograph stations worldwide. You'll learn about seismic waves, how data is recorded, and how seismograms represent earthquake activity. Test your knowledge of the tools and methods used to monitor and analyze seismic events.

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