After an Earthquake

You have recorded something, is it an earthquake?

A large, distant earthquake will be recorded across the network

After 10-15 minutes, the parameters for a large event will be available from the USGS

 

No, it isn’t an earthquake.

Do these signals disrupt display and are so common that they interfere with recording earthquakes? If so try to determine what the problem might be, and seek assistance.

If the signal is not disruptive to the display… this is a chance for you and your students determine the source of these signals. REAL science! Does the signal recur? Is there a pattern to the time of day when the signal occurs? These are just a few of the questions you might consider as you begin your investigation.

 

Yes, it is an earthquake! We have time to discuss it now (or tomorrow)!

Items like magnitude, location and news reporting may contribute to this decision.

  • Check out our classroom ready presentations:  Teachable Moments
  • Steps for students working with the data:
    • Step 1: Estimate the distance and the location.
    • Step 2: Determine the magnitude of the event.
    • Step 3: Record event into the station log.
    • Step 4: Share with others!

 

Yes, it is an earthquake! No time to discuss it.

  • Visit the USGS web site and record the magnitude, distance, and origin time on a station catalog.
  • Print a copy of the seismogram to post next to a world map.
  • Student team or seismology club analyze the event and report to the class later.
  • Extract event starting at the origin time and continuing through the surface waves and save as a .sac file. Upload the file to IRIS!

 

We heard about an earthquake, but it doesn't seem like we recorded it.

  • Examine your helicorder record for some indication of the event after the time of the event. The first arrival, if it’s visible, may be 20 minutes after the origin time of the earthquake. The surface waves may not peak for an hour or more.
  • For distant events, try filtering the helicorder record with a band pass filter from 12 to 25 seconds. The gain will need to be increased by about a factor of 10 at the same time.
  • If the event is not recorded on your system but comes booming in on all of the other educational seismograph records that are posted on the web, then you possibly have a technical problem. Send us an email sishelp@iris.edu!