Earthquake Flashcards
The three basic types of stress that causes deformation in rocks
Compression
Tension
Shear
Rocks near the surface of the earth are ______
elastic
when a force (stress) that is acting on them is removed, the rocks will:
return to their original shape
All elastic materials have an _________________, which is the point in which they no longer behave elastically and deformation becomes
permanent.
Elastic Limit
Difference between fractures and faults
All faults involve some type of slippage or movement, whereas
fractures do not.
Seismic waves generated by earthquakes and human made explosions will ________ and _________ when encountering layers of different density.
reflect and refract
He is a Scottish geologist who authored the The Dynamics of Faulting and Dyke Formation with Application to Britain (Edinburgh, 1942, 1951) and systematized our knowledge of the geometry and stress fields of various faults. He contended that the direction of the maximum principal stress along normal faults is ________.
A. Ernest Masson Anderson; vertical
B. John Graham Ramsay; vertical
C. Charles Lyell; horizontal inward
D. James Hutton; diagonal
A. Ernest Masson Anderson; vertical
refers to vibrational waves that travel through solid earth
materials which may be magmatic, tectonic, or artificial in origin
Seismic Waves
Seismic waves are divided into two parts, which are:
Body Waves and Surface Waves
compressional waves; parallel to direction the wave is travelling, causing rocks to alternately compress and decompress as successive waves pass through
P waves
transverse/perpendicular to direction of wave propagation
S waves
P waves travel at the speed of _________ km/sec
4 to 7 km/sec
S waves travel at speeds of _________ km/sec
2 to 5 km/sec
What is the main difference between a P wave from an S wave?
P waves can pass through solid and liquid materials, While S waves cannot pass through liquids..
It is the instrument used to detect seismic waves. A heavy suspended mass is held as motionless as possible, suspended by springs or hanging it as a pendulum. When the ground moves, the frame of the instrument moves with it.
Seismometer
It is a seismometer with a recording device that produces a permanent record of earth motion, usually in the form of wiggly line drawn on a moving strip of paper.
Seismograph
It is the paper record of earth vibration. The different waves travel at different rates, so they arrive at seismograph stations in a definite order: first P waves, then S waves, and finally, the surface waves.
Seismogram
What factor is used to calculate the distance of the seismograph station from the earthquake source?
The interval of arrival between S and P waves
How many seismograph stations are needed to pinpoint the exact location of an earthquake?
At least three seismograph stations
How were the major layers of Earth inferred?
Using seismic waves. When seismic waves travel through the Earth, they encounter different materials, which cause them to change speed and direction, inferring that the wave has crossed a new layer beyond the crust.
How do Earthquakes occur?
Stresses between / within rocks, tectonic movement
Two types of earthquakes
Volcanic and tectonic
This theory holds that earthquakes originate when a force (stress) acts on a rock body, causing it to deform and accumulate strain. Eventually the rock reaches its elastic limit, at which point it ruptures or fails suddenly, releasing the strain it had accumulated.
Elastic rebound theory
why do earthquakes do not occur deeper than 435 miles (700 km) below the surface?
because the higher temperatures cause the rocks to become so ductile that they deform only by plastic flow, hence do not rupture
