same source
Earthquakes can occur just below the surface or deep below the surface.
FACT:[/B] Earthquakes occur in the crust or upper mantle, from the earth's surface to about 500 miles below the surface. Seismologists use earthquakes to study the interior of the earth and to pinpoint faults and geologic structures such as the core-mantle boundary, subduction zones, and the subsurface extent of the San Andreas Fault. Using earthquakes and waves from earthquakes, scientist can see all of the earth's interior.