EEPS (Folds Faults, Earthquakes, and seismic hazards)

Deformation

A change in the shape or volume of a material (like a rock) in response to an applied force (stress).

Rock deformation types

• Brittle deformation 

• Ductile deformation 

Brittle Deformation 

Rocks break along discrete surfaces (fracture or faults)

• The brittle strength of rocks insensitiveve to temperature and increase with pressure

• Deformation domintes in the shallow parts of the crust

Ductile Deformation 

Rocks change shape in a distributed way, like a fluid 

• Rocks decrease with temperature and are insensitive to pressure. 

• Dominates deep in the crust and throughout the mantle

Rupture area 

the surface area along a fault where rock displacement occurs during an earthquake.

Hypocenter

the point within the Earth where an earthquake’s rupture begins and seismic waves are generated. 

Epicenter

the point on the Earth’s surface directly above the hypocenter (or focus), where the earthquake’s rupture begins.

3 types of faults 

• Strike-slip faults 

• Normal faults 

• Reverse faults 

Strike-slip fault

a fault on which two blocks slide past one another. (left and right lateral)

Normal fault

a dip-slip fault in which the block above the fault has moved downward relative to the block below.

Reverse (thrust) fault

a dip-slip fault in which the upper block, above the fault plane, moves up and over the lower block. 

The style of deformation depends on:

Composition

Pressure

Temperature

Seismic moment

Estimates the energy released by an earthquake on the basis of

• stiffness of the rock

• The size of the rupture area

• the amount of slip

5 factors that lead to building damage 

• Earthquake magnitude

• Proximity

• Amplitude of waves

• Ground acceleration

• Duration of earthquakes

Where do we build?

• Bedrock: solid rock that mechanically coupled to the Earth

• Unconsolidated sediments: loose materials (sand clay) sitting on top of bedrock.