Earthquakes and Faults
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Earthquakes and Faults. 1. Faults. A fault is a break or fracture between two blocks of rocks in response to stress. Three types of stresses produce faults Tension Compression Shear One block has moved relative to the other block.
Earthquakes and Faults
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Presentation Transcript
1. Faults • A fault is a break or fracture between two blocks of rocks in response to stress. • Three types of stresses produce faults • Tension • Compression • Shear • One block has moved relative to the other block. • The surface along which the blocks move is called a fault plane.
2. Components of Faults • STRIKE – a horizontal line along the direction of a fault plane. • DIP – the angle between the fault plane and the horizontal.
2. Components of a Fault • Fault plane – line of intersection between the fault line and the earth’s surface • Fault scarp – cliff of exposed fault plane above the surface of the earth.
2. Components of Faults • Foot wall – bottom layer of the fault. This is where your feet would be located. • Hanging wall – upper layer of the fault, where the lantern would be located. • Terminology comes from mining.
3. Types of Faults • Dip slip faults – movement of the faults is vertical. • Normal fault – footwall moves up, hanging wall moves down. Caused by tension. • Reverse fault – footwall moves downwards. Hanging wall moves upwards. Caused by compression.
3. Types of Faults • Strike Slip Faults – movement is horizontal • Left Lateral - opposing block moves to the left. • Right lateral – opposing block moves to the right.
3. Types of Faults c. Oblique Fault – block moves vertically and horizontally.
4. Earthquakes • An earthquake is a sudden release of energy in the earth’s crust that causes seismic waves. (In other words, the earth shakes.) • The main parts of an earthquake are: • focus – point where the crust moved or slipped • Epicenter – point on the earth’s surface above the focus.
5. Seismic Waves -Shock waves given off by earthquakes • Primary waves – originate from the focus and travel through the earth. They are used to locate the epicenter. • P waves – compression waves, travel faster through solids than liquids, arrive first. • S waves – shear waves; can’t travel through liquids, only half as fast as P waves.
5. Seismic Waves-Shock waves given off by earthquakes • L waves – start when body waves reach the surface at the epicenter. Cause the most damage. • Love waves – horizontal shear • Rayleigh waves – vertical shear • The combined effect of horizontal and vertical shear causes damage.
