LOCATING THE EPICENTER

Seismic WavesSeismogramMeasuring Lag TimeFinding the Epicenter

Start here

Seismic WavesThere are three seismic waves

Pri

mary

• P-Waves• These waves

move in a compress and expand motion

• They are the first to arrive to the epicenter S

econd

ary

• S-Waves• These waves

vibrate in a side to side motion

Surface

• L-Waves• These waves

move in an up and down circular motion

• Most destructive wave

Continue to Seismogram

Video of P-wave and S-wave

P-Wave and S-Wave Movement

Back

How the P and S Waves Move

Back to Seismic Waves

How the L Wave Moves

Back to Seismic Waves

•The picture with the squiggly line is called a seismogram•It measures how big the seismic waves are•The seismogram is a piece of paper located on seismograph•A seismograph measures the intensity of the earthquake at a certain location• It does this by having a weight hold a pen as the earth

shakes, the pencil stays still as a squiggly line is created • The more shaking the bigger the lines• The picture to the right is a seismograph

Seismogram

Let’s see how we use this

Seismogram

This is when the P-wave arrives

This is when the S-wave arrives

The difference in time between when the P-wave arrives and when the S-waves arrives, also know as lag time. This is important because it will tell you how far away you are from the epicenter.

How would you find the distance from the epicenter?

A. Locate the how long the P-Wave shakes the seismogram.

B. Find when the S-wave arrives, then the P-wave, and find the lag time between the two.

C. Find when the P-wave arrives, then the S-wave, and find the lag time between the two.

D. HELP!!

I AM SORRY THAT IS INCORRECTTRY AGAIN

This is when the P-wave arrives

This is when the S-wave arrives

The difference in time between when the P-wave arrives and when the S-waves arrives, also know as lag time. This is important because it will tell you how far away you are from the epicenter.

This May HelpTRY AGAIN

This is when the P-wave arrives

This is when the S-wave arrives

The difference in time between when the P-wave arrives and when the S-waves arrives, also know as lag time. This is important because it will tell you how far away you are from the epicenter.

That’s CorrectLets Try Another Question

NE

XT

Which One of These Lag Tables Is Correct?

City P-wave Arrival Time

S-wave Arrival Time

Lag Time

Washington DC 2:10 2:11 1 hourNew York 2:14 2:17 3 minutesChicago 2:19 2:24 4 minutes

City P-wave Arrival Time

S-wave Arrival Time

Lag Time

Washington DC 2:10 2:11 1 minuteNew York 2:14 2:17 3 minutesChicago 2:19 2:24 5 minutes

A.

B.

That is Incorrect

City P-wave Arrival Time

S-wave Arrival Time

Lag Time

Washington DC 2:10 2:11 1 hourNew York 2:14 2:17 3 minutesChicago 2:19 2:24 4 minutes

City P-wave Arrival Time

S-wave Arrival Time

Lag Time

Washington DC 2:10 2:11 1 minuteNew York 2:14 2:17 3 minutesChicago 2:19 2:24 5 minutes

A.

B. This is one should be 1 Minute

This one should be 5 minutes

Correct!Now Let’s See How to Use Your Lag Time to

Locate the Epicenter.

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1st Step – Figure out the size of the lag time. Let’s use 1 minute as an example.

2nd Step – Find where the P-wave and S- Wave have the measurement of the lag time.

1. This is how big one minute is

3rd Step - find the distance below.3. Your distance is about 300 miles

2.This is where the lag time is one minute

I do not understand .

Let’s move on

Now Let’s See How to Use Your Lag Time to Locate the Epicenter.

1st Step – Figure out the size of the lag time. Let’s use 1 minute as an example.

2nd Step – Find where the P-wave and S- Wave have the measurement of the lag time.

1. This is how big one minute is

3rd Step - find the distance below.3. Your distance is about 300 miles

2.This is where the lag time is one minute

This graph is available at bryonspicci.sslpowered.com

I do not understand .

Let’s move on

Introduction to Finding the Epicenter

Now You Try

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Let say that at your location the P-wave arrives at 9:30 and the S-waves arrives 9:33, how far are you away from the epicenter?

A. 9000 B. 1200C. 1000D. 900

That is IncorrectUse This Hint and Try Again

This graph is available at bryonspicci.sslpowered.com

Let say that at your location the P-wave arrives at 9:30 and the S-waves arrives 9:33, how far are you away from the epicenter?

A. 9000 B. 1200C. 1000D. 900

That is IncorrectHere is Another Hint

Try Again

This graph is available at bryonspicci.sslpowered.com

Let say that at your location the P-wave arrives at 9:30 and the S-waves arrives 9:33, how far are you away from the epicenter?

A. 9000 B. 1200C. 1000D. 900

That is IncorrectThis is Your Final Hint

This graph is available at bryonspicci.sslpowered.com

Let say that at your location the P-wave arrives at 9:30 and the S-waves arrives 9:33, how far are you away from the epicenter?

A. 9000 B. 1200C. 1000D. 900

900

That’s CorrectLets Move on

NE

XT

Here Are Our Three Locations

Washington, DC

New YorkChicago

The Epicenter is Where the Circles Meet

Washington, DC

Washington, DC is 900 miles away click on it

New York is 1200 miles awayclick on it

Chicago is 1900 miles awayClick on it

New YorkChicago

This is epicenter!

Click here to take the quiz.

I think I need more help before taking the quiz

Epicenter Quiz

1. When locating the epicenter, the first thing someone must do is…A. Draw three circles B. Find the arrival time of the p-wave and s-waveC. Find the lag timeD. Locate the focus

2. When locating the epicenter, the second thing someone must do is…A. Draw three circles B. Find the arrival time of the p-wave and s-waveC. Find the lag timeD. Locate the focus

3. Lag time is the difference in time between the _________ and ___________.A. Seismic wave and tsunami B. P wave and T waveC. Shake and AftermathD. P wave and S wave

4. After you find the distance a location is from the epicenter, you need to…A. Draw a circle and find the possible locationsB. Draw a square and find the possible locationsC. Call it a dayD. Decide how big of a circle you need to draw around the epicenter

5. What is the minimum amount of locations you need to locate an epicenter?

Write the answer in the box to the right.

Click here when all questions have been answered

B

CDA3

Correct Answers