GENERAL GEOLOGY (EQUAKE) Flashcards
catastrophic magnitude 7.0 Mw earthquake struck
January 12 2010
Epicenter of such earthquake
25 km of Port-au-Prince
Depth
10km
Ground shaking caused by sudden rapid omvement of one block of rock slipping past another along factures in earth’s crust
Earthquake
Fractures on Earth’s crust which are locked due to the enormous confining pressure exerte by the overlaying crust except for brief abrupt movements when sudden slippage
Faults
The location where slippage of fault begins
hypocenter or focus
The point on earth’s surface directly above the focus
epicenter
A form of energy that travels through the lithosphere and earth’s interior that causes the material that transmit such energy to shake
Seismic Waves
How many strong equakes mag 7 or greater happen every year?
15
Who first studied the actual mechanism of earthquake generation
H.F. Reid from John Hopkins University
What earthquake served as the model of such study
1906 San Fancisco Earthquake
What fault moved in the said earthquake
San Andres Fault
What plates moved?
Pacific and N. American
Earthquake generation according to Reid
1) Differential stress due to tectonic plates movement slowly bends crustal rocks on both sides
2) Once strength of rocks is exceeded, slippage occur along the fault to produce equake
3) The rocks return to their original shape but in a new location
this prevents the fault from fracturing and slipping
Frictional Resistance
How is friction enhanced?
Irregularities that occur along fault surface
The springing back of rock to its original, stress-free shape after slippage
Elastic Rebound
Lesser magnitude quakes that follow a large equakes due to the crust along the fault surface adjusting to the displacement caused by the main shock
Aftershocks
.
Foreshocks
theory wc states that large slabs of Earth’s lithosphere are continually grinding past one another
Plate tectonics
Seismometer
Instrument that record vibration
Seismograph
Resulting graph
Body waves
Emanate from the focus and travel in all direction through the body of the Earth
P wave
?Compressing and expanding movemnt
?Depends on the incompressibility (Bulk’s Modulus) and Rigidity (Shear Modulus)
?HIghestVelocity and will always reach seismographs first
S Wave
?Perpendicular shearing movement to the direction of the wave
?Depends on the resistance to shearing of a material (rigidity)
?Will always arrive second to Pwave
Surface Waves
?Do not travel through the Earth
?Travel along paths that are parallel to the Surface of the Earth
?Slower than S waves
Love Waves
?Side to Side perpendicular to wave direction
Rayleigh Waves
?Counterclockwise eliptical up and down
P-wave ShadowZone
Zone on the opposite side of earth from an earth focus that receive NO WAVES because waves are REFRACTED INWARD due to sudden decrease in velocity of Pwave at the boundary
S-wave shadow Zone
Zone on the opposite side of Earth from the focus where there is no S-wave reaching the area due to non passing of S-wave through the core
