faults

FAULTSImagery from National Oceanic and Atmospheric Administration (NOAA)

NORMAL FAULT: Near Hebgen Lake, Montana just after a large earthquake

This part of the footwall that is now exposed is called a “scarp.”

REVERSE FAULT: Keystone Thrust near Las

Vegas, NV.

REVERSE FAULT:

NORMAL FAULT: Borah Peak, IdahoJust after large earthquake

STRIKE-SLIP FAULT

In a farm field in El Progresso, Guatemala

Notice how the fault line is not visible on the surface, but you can see how the rows of vegetables have been shifted sideways.

STRIKE-SLIP FAULT:

Just after 1906 San Francisco earthquake, along San Andreas fault, near Woodville, CA.

Note: fence is displaced, but you cannot see fault trace along surface.

STRIKE-SLIP FAULT:

Offset drainage ditch in Guatemala.

STRIKE-SLIP FAULT:

Almaden Winery in California.Notice offset drainage structure.

STRIKE-SLIP FAULTS CAN CAUSE RIVERS TO CHANGE THEIR COURSE:

OBLIQUE-SLIP FAULT: COMBINATION OF A NORMAL FAULT AND A STRIKE-SLIP FAULT

Pleasant Valley, Nevada

Note how fence is shifted sideways AND you can see the scarp where the hanging wall has slid down along footwall.

WHAT TYPE OF FAULT IS THIS?

(besides a pretty one….)

WHAT TYPE OF FAULT IS THIS?

(besides a pretty one….)

If you said Reverse Fault, you are correct!

footwall

hanging wall

You can see how the rock strata on the hanging wall are shifted UP compared to the rock strata on the footwall.

movement of

hanging wall

WHAT KIND OF FAULT IS THIS?

WHAT KIND OF FAULT IS THIS?

If you said Normal Fault, you are correct! This time, you can tell by the rock strata that the hanging wall has moved downward compared to the footwall.

Hanging wall

footwall

WHAT TYPE OF FAULT IS THIS?

aerial view

WHAT TYPE OF FAULT IS THIS?

Yep! It’s a Strike-Slip fault! You can tell because the tire tracks are out of alignment.

REVIEW:What type of stress causes each type of fault?

Normal Fault

Reverse Fault

Strike-Slip Fault

REVIEW:What type of stress causes each type of fault?

Normal Fault -- Tension

Reverse Fault -- Compression

Strike-Slip Fault -- Shearing

THE END!