earthquake

Earthquakes:

Earthquakes

What are Earthquakes?:

What are Earthquakes? The shaking or trembling caused by the sudden release of energy Usually associated with movement along a plate boundary or breaking of rocks Continuing adjustment of position results in aftershocks

What is the Elastic Rebound Theory?:

What is the Elastic Rebound Theory ? Explains how energy is stored in rocks Rocks bend until the strength of the rock is exceeded Breaking occurs and the rocks quickly rebound to an undeformed shape Energy is released in waves that radiate outward from the fault

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The Focus and Epicenter of an Earthquake The point inside Earth where quake begins is the focus , or hypocenter The point directly above the focus on the surface is the epicenter

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Seismographs record earthquake events

Earthquake (Seismic) Waves:

Earthquake (Seismic) Waves

What are Seismic Waves?:

What are Seismic Waves? Energy released by an earthquake Two types : Body waves P and S Surface waves R and L

Primary Waves:

Primary Waves These are called 'P' for Primary Wave . travel fastest and are usually "felt" first . known as a longitudinal wave . Can travel through any substance – solid, liquid, or gas.

Secondary Waves:

Secondary Waves ‘S’ waves much slower and much more destructive than P-Waves. They are transverse waves . Can only travel through solids

Surface Waves: Rayleigh Waves:

Surface Waves: Rayleigh Waves Rolling wave . It's the same as an ocean wave . Particularly damaging because it tells structures to move in two directions at once.

Surface Wave: Love Waves:

Surface Wave: Love Waves Damaging! It tells the surface to move forward and backward AND left and right at the same time.

Surface Waves: R and L waves:

Surface Waves: R and L waves Surface Waves Travel just below or along the ground’s surface Slower than body waves ; rolling and side-to-side movement Especially damaging to buildings

Earthquakes:

Earthquakes How do we measure the intensity of an earthquake?

Time-Distance Graph:

Time-Distance Graph

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Seismograph records energy waves of the earth

Seismograph measures:

Seismograph measures Magnitude or the strength of an earthquake

How are the Size and Strength of an Earthquake Measured?:

How are the Size and Strength of an Earthquake Measured? Magnitude Richter scale measures total amount of energy released by an earthquake Amplitude of the largest wave produced by an event is corrected for distance and assigned a value

Richter Scale:

Richter Scale Earthquake Magnitudes Effects Less than 3.5 Generally not felt 3.5-5.4 Rarely causes damage. Under 6.0 Slight damage to well-designed buildings. 6.1-6.9 Destructive to about 100 kilometers across 7.0-7.9 Major earthquake. Serious damage over larger areas. 8 or greater Great earthquake.

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Each number is 10X stronger than the previous number . How much stronger is the 3 than the 1? 100 Times How much stronger is the 8 than the 1? 10,000,000 Write the number in scientific notation. 10 6

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V. People feel movement. Doors open Pictures fall off wall. VII. Some buildings lose bricks. Difficulty driving. IX. Considerable damage to homes. Cracks in earth. XII. Almost everything is destroyed. The ground moves in waves or ripples. Mercalli Scale I.People do not feel anything .

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Why is the Richter Scale more accurate than the Mercalli Scale? The Richter Scale is objective and based on mathematical measurements . The Mercalli scale is subjective and based on people’s perception and experience . On Mercalli scale if the area is unihabited there is no way to measure the magnitude of the earthquake.

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Richter Magnitude Number of Earthquakes per year 1.0 to 3.9 900,000 + 4.0-4.9 6200 5.0-5.9 800 6.0-6.9 226 7.0-7.9 18 8.0-8.9 Less than 2

How is an Earthquake’s Epicenter Located?:

How is an Earthquake’s Epicenter Located? Seismic wave behavior P waves arrive first, then S waves, then L and R Average speeds for all these waves is known After an earthquake, the difference in arrival times at a seismograph station can be used to calculate the distance from the seismograph to the epicenter.

How is an Earthquake’s Epicenter Located?:

How is an Earthquake’s Epicenter Located? Three seismograph stations are needed to locate the epicenter of an earthquake A circle where the radius equals the distance to the epicenter is drawn The intersection of the circles locates the epicenter

What are the Destructive Effects of Earthquakes?:

What are the Destructive Effects of Earthquakes? Ground Shaking amplitude, duration, and damage increases in poorly consolidated rocks