why do we look for faults?? geologists of the end of the 19th century (at that time geologists were...

WHY DO WE LOOK FOR

FAULTS??

Geologists of the end of the 19th century (at that time geologists were more like adventurers rather than scientists!) realized that some faults were required to explain why rock types that were so different to each other had come in contact.

For geologists, faults are among the most common and obvious features on this and other planets (if any of you one day decide to learn more about geology, you will see a few!).

are strongly deformed and rearranged

volumes of rock are displaced from their original position

ROCKS IN NATURE

THE BOUNDARY BETWEEN THESE BIG BLOCKS OF DIFFERENT ROCK IS IDENTIFIED BY FAULTS.

Faults must be identified on the surface, must be mapped in detail and reconstructed at depth because:

FAULTS ALLOW GEOLOGISTS TO SOLVE THE GEOLOGICAL PUZZLE: HOW DID THESE ROCKS GET HERE??

FAULTS ARE SURFACES OF CONCENTRATED MOVEMENT BETWEEN TWO BLOCKS

Often when a fault slips it shakes the ground.

EARTHQUAKE!

There is a lot of energy released at each earthquake.

The BIGGER the earthquake, the BIGGER is the deformation that can be observed in the area surrounding the fault.

The displacement on this fault after this earthquake was about 3 meters.

A vertical cross-section (slice through the Earth) across the bump in the previous slide would display something like this:

The thrust fault propagate and…

…the strata are compressed and folded This is a small

structure. See the hammer for reference.

A single slip event of 3 meters is followed by thousands of other slip events: 3m X 1000 events= 3km

THE MOUNTAIN RANGE GROWS!

HOW CAN A MOUNTAIN RANGE GROW FROM SUCH A SMALL THING?

To imagine what the folds in the previous photo might look like in cross section, we should take a look at this:

Sometimes the vertical displacement above the thrust fault can be the order of a few KM!

See the road sign for reference

If the city cannot be removed, the seismic hazard must be assessed so that the houses can be built strong enough to resist a possible earthquake

FAULTS ARE DANGEROUS!

We don’t want to build new cities close to active faults

We must predict where the fault will slip

YOU CERTAINLY DON’T WANT TO BUILD A CONDOMINIUM ON A POSSIBLE ACTIVE FAULT!

For every slip on the fault surface the rock volume surrounding the fault will break in many fractures

Fractures increase the potential for larger volumes of oil to flow to the surface

Oil wells will be more productive when they intersect an intensely fractured rock mass

FAULTS ARE IMPORTANT TO OIL COMPANIES

Oil companies need to know precisely where faults are to locate their wells…

…for better engineering the oil field complex production systems, and finally…

… BACK TO EVERYDAY LIFE!