Welcome to Virtual Earthquake

Virtual Earthquake is an interactive Web-based program designed to introduce you to the
concepts of how an earthquake EPICENTER is located and how the RICHTER MAGNITUDE
of an earthquake is determined. The Virtual Earthquake computer program is running on a Web
Server at California State University at Los Angeles. You can interact with Virtual Earthquake
using your Web browser.
Virtual Earthquake will show you the recordings of an earthquake's seismic waves detected by
instruments far away from the earthquake. The instrument recording the seismic waves is called
a seismograph and the recording is a seismogram. The point of origin of an earthquake is called
its focus and the point on the earth's surface directly above the focus is the epicenter. You are to
locate the epicenter of an earthquake by making simple measurements on three seismograms that
will be sent to you by the Virtual Earthquake program. Additionally, you will be required to
determine the Richter Magnitude of that quake from the same recordings. Richter Magnitude is
an estimate of the amount of energy released during and earthquake.
1. Go to the website listed above, and follow all the directions provided.
2. Each person in the group is required to complete the virtual lab, and print out a certificate
of completion. (Each group member must complete a different epicenter location.)
3. After the certificate is printed, calculate the % of error for each of your findings. These
should be recorded on a separate sheet of paper.
4. The certificate, along with your % errors and this sheet, will be collected and will count as a
5. One additional certificate per person will be accepted for extra credit.
1. What is the point of origin of an
earthquake called?
2. Label the S-wave arrival time, Pwave arrival time, and the
amplitude, on the diagram to the
3. How many seismograph
locations are needed to locate an
earthquake’s epicenter?
4. Aside from measurement errors, what other factor could result in the three circles not
meeting at an exact point?
5. Aside from the S-P interval or epicenter distance, what other information is needed to
determine the Richter magnitude of an earthquake?
6. From which wave, P or S, is the above information obtained?
Recording Station
Your Data
Actual Data
Epicentral Distance
Epicentral Distance
Sample Calculation for percent error:
Answer w/ units
Percent errors