Earthquakes create seismic waves that travel through the Earth. By analyzing these seismic waves, seismologists can explore the Earth's deep interior. This fact sheet uses data from the 1994 magnitude 6.9 earthquake near Northridge, California to illustrate both this process and Earth's interior structure. The cutaway of Earth on the left shows the paths seismic waves traveled following the quake. The ground motion caused by the seismic waves is shown at the right (seismograms recorded at various locations around the world).
NOTE: Out of Stock; self-printing only.
- Seismic waves propogate outwards from an earthquake in all directions.
- Seismologists use the recordings of the ground motion caused by these waves to explore the Earth's deep interior.
- We do not see shear (S) waves passing through the outer core. Because liquids can not be sheared, we infer that the outer core is molten.
- We do, however, see S waves as they go through the inner core. Because the inner core transmits shear energy, we assume it is solid.
Requesting Fact Sheets:
To request hardcopies of E&O materials, please send an email to: EandOproduct@iris.edu with the following information:
- Names of item(s) you are requesting along with respective quantities. Please list posters and one-pagers on separate lines.
- Full mailing address, including phone number, where the materials should be sent.
- Indicate what purpose the materials will be serving.
- Date materials are needed by (if applicable).
PLEASE NOTE: Time-sensitive requests must be sent at least three weeks before the date they are needed. When e-mailing a time-sensitive request, please write "Time-Sensitive Request" in the subject line.