Warm Up: Epicenters

What is the number of seismic stations needed to find an epicenter and why?

• You need two, because two will intersect at two points and one will be offshore so it is not the epicenter

• You only need one because the epicenter will be somewhere along that circle

• You will need 3 because 3 is the minimum number of circles that will intersect at one point.

• It is not possible to locate the epicenter with seismic data.

How do you determine the distance to an earthquake epicenter?

• Calculate the difference between the P and S waves arrival times

• take the number of seconds for the P wave to arrive and multiply by 100 miles

• It is the difference in arrival times of the S and Surface Waves.

• Take the time for the Surface waves to arrive and multiply by 100 km

The 2011 Japan earthquake was estimated to have killed approximately 20,000 people. What can you infer about the location of its focus?

• It was shallow

• It was deep

• it was unknown

• it was intermediate

What method do seismologists use in locating an epicenter?

• Focus Group Discussion

• Interview

• Observation

• Triangulation

Where is the epicenter for this earthquake located based on triangulation?

• A
• B
• C
• D

Tags

NGSS.MS-ESS2-3

Where are the P-waves located on this seismogram?

• A
• B
• C
• D

Which seismogram represents a city that is far from the epicenter of an earthquake?  

• New York, NY
• Nome, Alaska
• Guadalajara, Mexico

Tags

NGSS.MS-ESS3-2

A seismic P-wave is recorded at 2:25 p.m. at a

seismic station located 7600 kilometers from the

epicenter of an earthquake. At what time did the

earthquake occur?

Answer explanation

Epicenter distance (x axis) at 7600 km, it takes P wave 11 minutes to arrive (y axis). So 2:14 PM

The fi rst S-wave reaches a seismic station

19 minutes after an earthquake occurred. How

long did it take the fi rst P-wave to reach the same

seismic station?

The first S-wave reaches a seismic station

10 minutes after an earthquake occurred. How

long did it take the first P-wave to reach the same

seismic station?

Tags

NGSS.HS-PS4-1