Seismic Calendar


Activity Source: 

Barker, J. (2005) Student-centered experiments with earthquake occurrence data. The Earth Scientist 21(2), 21-23 (Spring 2005)


This activity allows you to investigate how often earthquakes of various magnitudes happen within a geographic region of your choice. You will use the online resources of the Incorporated Research Institutions for Seismology (IRIS) to do the investigation. These resources are available at


For a group of four:

  • Access to the Internet and Windows to download free software
  • Notebook to record data
  • Semi-log graph paper (optional)


  1. Download free Seismic /Eruption software (PC only) from
  2. Start Seismic/Eruption and observe earthquakes occurring on various maps of the world, sped up in time.
  3. Select an area with a significant number of earthquakes and "Make Your Own Map" of the area (under Map on the menu bar).
  4. Select a time period using Set Dates, under Control on the menu bar. Start in 1960 or later, and include between 10 and 40 years.
  5. "Play" the earthquake data set using the audio-style controls, and attempt to predict when the next earthquake of a certain magnitude will plot on the map based on observed rhythms.
  6. Increase the "EQ Cutoff" (controls at bottom of main screen) to 8.0 and set the speed of playback to 10 years per second
  7. Replay the earthquake data set using the Repeat button. Read the number of earthquakes with magnitude greater or equal to 8.0 from the counter in the upper right corner of the screen. Record this number.
  8. Decrease the magnitude threshold to 7.5, replay the data set, and record the total number of earthquakes of magnitude 7.5 or larger.
  9. Repeat the above procedure, decreasing the magnitude cutoff in 0.5 magnitude increments to 3.5.
  10. Divide the total number of earthquakes by the number of years in the chosen time period to find the number per year of earthquakes with magnitudes larger than or equal to each of the values from 3.5 to 8.0.
  11. Plot your data on semi-log graph paper to create a Gutenberg-Richter plot (optional).