Falcon Focus

Essential Question

Standard 8-3.8

EARTHQUAKESEARTHQUAKES

Assessing Prior Knowledge and Relativity

• What have you heard about earthquakes lately?

• Why should we study earthquakes?

INTRODUCTION

• http://video.nationalgeographic.com/video/player/environment/environment-natural-disasters/earthquakes/earthquake-101.html

The definition of an earthquake is… vibrations that cause the breaking of rocks.

These vibrations move in all directions through the earth. They begin at a point along a fault.

Earthquakes• If the __pressure___ or stress becomes too

great, the rock breaks at a weak point along the fault and ___energy_____ is released

FocusEpicenter

aaALONG THE FAULT

Parts of the Earthquake

• The energy spreads outward in all directions as vibrations called ____seismic waves_____.

• The _focus____ of the earthquake is the point in the crust, or mantle, where energy is released.

• The _epicenter___ is the point on Earth’s surface directly above the focus; energy that reaches the surface is greatest at this point.

Focus – point inside the Earth where an earthquake begins

Epicenter – point on Earth’s surface above focus

Focus, Epicenter, and Fault

RECAP

• (Take a minute to fill in the blank)

ANSWERS• Epicenter: is located right above the focus

and has the greatest amount of energy

• Focus: releases the energy (seismic waves)

• Fault: a break in the Earth’s Crust (is where an earthquake takes place)

• Seismic waves: is the energy that is being sent out from the focus

Use the words above to Label the Following parts of the earthquake.

ANSWERS

• A: FOCUS

• B: EPICENTER

• C: FAULT

• D: SEISMIC WAVES

Cause of Earthquakes

What Causes an Earthquake?

• An aftershock is a small earthquake that follows the main earthquake.

• A foreshock is a small earthquake that often precedes a major earthquake.

Aftershocks and Foreshocks

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are needed to see this picture.

…And that was just a 7.2 on the Richter scale!

SEISMIC WAVES

• 8-3.2 Explain how scientists use seismic waves – primary, secondary, and surface waves – and Earth’s magnetic fields to determine the internal structure of Earth.

3 TYPES OF SEISMIC WAVES3 TYPES OF SEISMIC WAVES

• PRIMARY (P) WAVESPRIMARY (P) WAVES

• SECONDARY (S) WAVESSECONDARY (S) WAVES

• SURFACE WAVESSURFACE WAVES

CONSIDERED AS BODY WAVESCONSIDERED AS BODY WAVES

SEISMIC WAVESSEISMIC WAVES

• _SEISMIC WAVES___ are waves generated by an earthquake that travel through the Earth. These waves can cause the ground to move forward, backward, up, down, and even to ripple. Seismic Waves are generated at the __SAME___ time but move in different ways, and at different speeds.

Seismic Waves in the Earth

http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

SEISMIC WAVES

• Scientists use the principle that the speed and direction of a seismic wave depends on the material it travels through.

How does scientist know or study the Earth’s Core?

• Because of the behavior of these different waves, scientists have indirect evidence for the solid inner core and liquid outer core of Earth because S waves don’t travel through the outer core because it’s a liquid. Also because earthquake waves travel faster through the mantle than through the crust, scientists know that the mantle is denser than the crust.

Seismic Waves

PRIMARY (P) WAVE

• First Wave to Move out from the earthquake focus, the point where the energy is released

• Travel the fastest of the three waves

• Push and pull rock creating a back-and-forth motion in the direction the wave is moving

• (known as longitudinal or compressional waves)

P WAVES

• Move through solid and liquid layers of Earth (therefore it can move through all layers)

Primary Waves (P Waves)Primary Waves (P Waves)

• A type of seismic wave that A type of seismic wave that compresses and expands the groundcompresses and expands the ground

• The first wave to arrive at an The first wave to arrive at an earthquakeearthquake

http://daphne.meccahosting.com/~a0000e89/insideearth2.htm

Secondary Waves (S Waves)

• 2nd wave to Move out from the earthquake focus

• Move slower than primary waves

• Move at right angles to primary waves causing rocks to move up and down and side to side (known as transverse wave: perpendicular to the wave motion)

S WAVES

• Can only move through SOLID rock therefore it CAN NOT TRAVEL THROUGH THE OUTER CORE because it is a LIQUID. IT STOPS AT THE OUTER CORE.

Secondary Waves (S Secondary Waves (S Waves)Waves)

• A type of seismic wave that moves the ground up and down or side to side

http://daphne.meccahosting.com/~a0000e89/insideearth2.htm

Comparing Seismic Waves

SURFACE WAVESSURFACE WAVES

• Form when PP and SS waves reach the surfacee• SLOWEST BUT MOST DESTRUCTIVE• Can cause the ground to shake making rock sway

from side to side and roll like an ocean wave

SURFACE WAVES

• Move through solid and liquid layers of Earth (therefore it can move through all layers)

Seismic Waves Paths Through the Earth

Earth’s Interior Showing P and S Wave Paths

Earthquake Waves & Earth’s Interior

• 8-3.3 Infer an earthquake’s epicenter from seismographic data.

Measuring EarthquakesMeasuring Earthquakes• The energy spreads outward in all

directions as vibrations called ___Seismic Waves____. Seismic waves can be measured and recorded by a ____seismograph_______.

SEISMOGRAPH

Measuring EarthquakesMeasuring Earthquakes

• The vibration record, called a seismogram, looks like jagged lines on paper. Measuring the time between the arrival of the P and SP and S waves determines the distance between the recording seismograph and the earthquake epicenter.

SEISMOGRAM

Seismograph

Types of Types of SeismographsSeismographs

Seismogram Seismogram PrintoutPrintout

•How to find the S-P INTERVALS

• To find the S-P intervals, you have to subtract the P Wave from the S Wave.

• Measuring the time between the arrival of the P and S waves determines the distance between the recording seismograph and the earthquake epicenter.

•Find the S-P interval: Show your steps.

PRACTICE

WHAT IS THE S-P INTERVAL?

WHAT IS THE S-P INTERVAL?

Locating an Earthquake

Locating an Earthquake Epicenter

• TriangulateTriangulate means to use three positions to determine an exact location.

• TRIANGULATION identifies the epicenter of an earthquake. The location of an earthquake’s epicenter is found by plotting 3 circles on a map from the records of three seismograph stations and finding the point where the three circles intersect. Note where the 3 circles meet is where the epicenter is located.

Locating Earthquakes

http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

Locating Earthquakes

http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

Locating Earthquakes

http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

TriangulatiTriangulation of 3 on of 3 stations to stations to locate locate earthquake earthquake epicenterepicenter

Earthquakes are measured using the Richter Scale. The strongest earthquake ever measured was a 9.5 on the Richter Scale. This is a measurement of the amount of energy released from the earthquake.

How are Earthquakes Measured? Richter Scale

HOMEWORK