After the earthquake, examination of surface faults around Northridge did not reveal that any offset had occurred. Therefore, the fault that moved must be a blind thrust fault, and seismologists would need to analyze a variety of earthquake data to pinpoint its location.

To find the blind thrust fault responsible for the earthquake, geologists examined the location of the earthquake epicenter and aftershocks, ground shaking intensity maps, ground motion maps, and the depth to the earthquake’s focus.

  !   Click the buttons below to examine maps of earthquake data. Record the information on the maps on your student answer sheet.

2. On the map on your student answer sheet, draw a line around the area that was affected by aftershocks.

3. In another color, draw a line around the area that experienced the strongest ground shaking.

4. In a third color or pattern, draw a line around the area that had the highest velocity of ground motion.