Earthquakes and Earth’s Interior Key Points are Green.
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Transcript of Earthquakes and Earth’s Interior Key Points are Green.
![Page 1: Earthquakes and Earth’s Interior Key Points are Green.](https://reader030.fdocuments.in/reader030/viewer/2022012916/5697bfc41a28abf838ca6013/html5/thumbnails/1.jpg)
Earthquakes and Earth’s Interior
Key Points are Green
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What is an earthquake?
Earthquake a rapid release of kinetic energy given off in the form of waves.
Sensitive instruments around the world record these events
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Earthquake faults
Fault lines and plate boundaries are the place where these movements normally originate from.
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Stored EnergyEnergy is stored over time in the ground and it gets released once the pressure is greater than the mechanical strength of the rocks can bare. Aftershocks - smaller earthquakes that follow a major earthquakeForeshocks - small earthquakes often preceding a major earthquake by days or, in some cases, by as much as several years.
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Seismology: is the study of earth quakes.
The study of earthquake wavesDates back almost 2000 years to the Chinese who looked into pots of water to record these movements.
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Seismographs: – are instruments that record seismic waves.
They work by recording the movement of Earth in relation to a stationary mass on a rotating drum or magnetic tape.
Records obtained are called seismograms
There are 3 types of seismic waves
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Fastest wave which travels only in through solids, liquids, and gases. Push-pull (compression motion).
Primary (P) waves
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Secondary (S) waves
Up down motion at mater moves at right angles to the direction of wave travel.
Travels only through solids Slower velocity than P waves But greater intensity and amplitude than P waves
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Surface Waves / Rayleigh waves
Cause greatest destruction Waves exhibit greatest amplitude and slowest velocity
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Focus - the place within Earth where earthquake waves originate
Epicenter – location on the surface directly above the focus.
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Locating the distance to the epicenter
At least Three station recordings are needed to locate an epicenter
Each station determines the time interval between the arrival of the first P wave and the first S wave at their location.
A travel-time graph is used to determine each station’s distance to
the epicenter
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Finding Epicenter: A circle with a radius equal to the distance to the epicenter is drawn around each station. The point where at least three
circles intersect is the earthquake epicenter.
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Two measurements that describe the size of an earthquake are
• Intensity – a measure of the degree of earthquake shaking at a given locale based on the amount of damage
• Magnitude – estimates the amount of energy released at the source of the earthquake
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Magnitude measurements
Richter scaleNumerical system used to quantify Earthquake strength. Largest magnitude Earthquake was a 9.5 recorded in Chile in 1960. Magnitudes less than 2.0 are not felt by humans Each unit of Richter magnitude increase corresponds to a tenfold increase in wave amplitude and a 32-fold energy increase.
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Locating the source of earthquakes
Earthquake depthsDefinite patterns exist • Almost all deep-focus earthquakes occur
in at convergent boundaries. • Many shallow focus occur along the
oceanic ridge system or divergent boundaries
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Earthquakes of magnitude 5 or greater over a 10 year period