Correlation between P & S Arrivals and Earthquake Depth

Charlena Sieve
Bloomington High School North

Problem: Is their any correlation between the depth of an earthquake and the P and S arrival times?

Objective:
• Recognize and mark the P and S arrivals on a seismogram.
• Compare and contrast the pulses represented by each of the waves associated with an event.
• Evaluate P and S arrivals and the depth of an earthquake.

Materials:
5 Seismograms
Rulers

Procedure:
1. Acquire seismograms with depth (received at the same location) from 5 different earthquakes occurring in the same region.
2. Mark the P and S waves on each of the Seismograms. Record times on data table.
3. Calculate the difference between the P and S arrival time.
4. Observe any similarities or major differences in the P or S waves either within the individual seismogram or among all 5. Record observations.
5. Record depth listed on each seismogram in data table. Note which category the depth occurs:
Shallow <70 Km
Intermediate 70 – 300 Km
Deep > 300 Km

Observations:

Earthquake                           Seismograph Similarities                                        Seismograph Differences

Data Table:

 Earthquake location Date/Time Latitude Longitude Magnitude Depth of Earthquake P-wave Arrival Time S-wave Arrival Time Difference Between P & S Arrival

Analysis Questions:

1. Is there a correlation between the arrival times of the P waves and the depth of the earthquake?
2. Is there a correlation between the difference between the P and S waves and the depth of the earthquakes?
3. Were there any observable similarities on the seismograms of the deep earthquakes?
4. Were there any observable differences between the seismograms based on their depth?
5. Did any of these earthquakes coincide with a plate boundary? If so, which ones?

Conclusion:

Teacher Notes

There are several variations to this Lab. Students can use seismograms which you have printed off for this activity. Students can use the Eqlocate program to assist them in this activity. Students can go into the IRIS Homepage and find events of interest which you can download, and be viewed in the Winquake program for this activity.