Earthquakes Flashcards
What is an P wave? What does the P stand for?
The P stands for primary. Primary waves are compressed waves that move through the earth like sound waves. They are the fastest seismic waves therefore they are the first waves to arrive at a seismometer. They move through in interior of the earth.
What is a S wave? What does the S stand for?
S waves- secondary waves. Move through the interior of the earth. They are the second waves. They travel in the form of transverse waves.
What are L waves? What does the L stand for?
L wave or longitudinal waves are surface waves. They travel slower than P and S waves. Surface waves are responsible for the power and intensity of an earthquake.
What is the epicentre?
The epicentre is the point on the surface directly above the focus.
What is the focus?
The focus is the location in the earth where the earthquake started.
List some of the effects of earthquakes.
Shaking, ground rupture, landslides, tsunamis, and liquefaction and fire.
Explain how earthquakes occur.
Earthquakes are usually caused when rock underground suddenly breaks along a fault. This sudden release of energy causes the seismic waves that make the ground shake. When two blocks of rock or two plates are rubbing against each other, they stick a little. … When the rocks break, the earthquake occurs.
Distinguish between an earthquake and a tremor.
Earthquakes are the vibrations caused by rocks breaking under stress against an underground surface called a fault plane while a tremor is an involuntary movement of earth surface caused by stress in the underground rocks.
Explain why a tsunami only a few meters high in the open ocean can reach heights of 30m by the time it reaches land.
Tsunamis are a series of waves that occurs when water is displaced in the ocean by either an earthquake or a landslide. The waves then have a ripple effect they move slowly at first and in the deep ocean they are only a few meters in height. As the first set of waves arrives at the coastline they will slow further and when the other set of waves follow the water builds up to create a huge wave that can be up to 30m tall.
Explain the difference between a tsunami and a tidal wave.
Tidal waves are waves created by the gravitational forces of the sun or moon and cause changes in the level of water bodies. Tidal waves are phenomena seen most at coastal areas that occur daily.
While Tsunamis can be generated by earthquakes, erupting submarine volcanoes or due to any gas bubble erupting in the sea or ocean. These causes have the potential of creating tsunamis provided it occurs just below the body of water, is of moderate amplitude or displaces a large volume of water. These don’t occur frequently and have major impacts.
Explain how seismologists are able to make predictions about the likelihood of an earthquake.
Seismologists monitor the movement of the tectonic plates along critical boundaries and fault lines.
State in which order do seismic waves arrive at a seismometer.
P-waves arrive first as they are the fastest then S-waves then L-waves.
