Earth Science, Chapter 6 - Earthquakes
Richter Scale
used by geologists to report earthquake magnitude to the public
mountain ranges
where most major faults in the USA are found.
convergent boundary
where subduction would most likely be occurring
joint vs fault
A joint is simply a crack in a rock that relieved stresses and in which no significant motion of the two parts of rock occurred. Joints can appear in patterns depending on the stresses that caused them. Faults are cracks in rock where the two parts of the rock have visibly moved relative to each other.
label the diagram
A=fault's strike; B=fault's dip; C=fault line
process of locating an earthquake's epicenter
Earthquakes produce different types of seismic waves, and each type travels at a different speed. By measuring the time difference between the arrival of P and S waves t a seismic station, seismologists can determine the distance to the epicenter. Bu using data from at least three seismic stations, they can determine the location of the epicenter.
Earthquake scales
Modified Mercalli Intensity scale, moment magnitude scale, Richter scale
types of earthquake waves
P & S waves are body waves--they move through the interior of the earth. P waves are fasted, have the smallest intensities, and can move through the core of the earth. S waves are slower but stronger than P waves. S waves cannot pass through the core. Surface waves (Rayleigh and Love waves) move at about the same speed as S waves and travel only along the earth's surface. They are the most destructive because they directly affect human structures.
earthquake's epicenter
Seismologists need data from at least three seismic stations to pinpoint it
tsunami vs tidal wave
Tsunamis are caused by underwater earthquakes or other tectonic activity and are not related in any way to tides
greatest cause of death in earthquake
While "ground shaking alone seldom causes deaths," according to your text, many deaths are caused by building collapse, especially in developing countries with low standards for constructions. Fires ignited and fueled by broken electrical and gas lines also destroy property and kill many people. Disrupted water service may complicate firefighting. Earthquakes that occur underwater can trigger tsunamis that cause drowning. In mountain areas, an earthquake could trigger an avalanche or landslide, causing further loss of life.
S wave
a body wave that cannot travel through Earth's core
fault
a crack in a rock where movement has occurred
risk
a possibility of injury or death to people and damage to property (able to reduce or even eliminate)
hazard
a source of danger (cannot be changed)
strike-slip
a transform fault
reverse fault
a type of dip-slip fault
Love wave
a type of surface wave
surface waves
also called Rayleigh waves and Love waves
seismograph
an instrument that both detects and record earth waves
seismometer
an instrument that simply detects earth waves
tsunami
an ocean wave caused by an earthquake
Richter scale divisions
each point on the scale is separated by 32 units of energy (Example a 5.0 would have 32 times more energy than a 4.0 would have.
Earthquakes most commonly occur
near the edges of tectonic plates
convergent boundaries
plates come toward each other
divergent boundaries
plates move apart
transform boundaries
plates slide past each other in opposite directions
brittleness and elasticity
properties of a material that allow it to change shape without breaking under stress
Modified Mercalli Intensity scale (MMI)
rates earthquakes on damage or destructivess, not magnitude
aftershocks
secondary, smaller earthquakes that result from a major earthquake
cause of earthquakes
slipping of a fault, eruption of a volcano, or a landslide
to locate an earthquake
study the focus, seismic wave, and epicenter
focus
the center of earthquake activity
P wave
the fastest body wave
example of tension
the force that a rock climber exerts on the rope as he rappels down a cliff
strike
the horizontal direction of a fault
magnitude/Richter scale
the indicator of the energy released by an earthquake
strike-slip fault or transform fault
the main movement was parallel to the strike of the fault
reverse fault
the opposite motion has occurred (one block pushes upward)
epicenter
the point on Earth's surface above the center of earthquake activity
shear stress
the type of stress most significant in causing earthquakes
normal fault
the upper block has dropped relative to the lower block
seismic waves
travel only on the earth's surface, through the earth, but not the core, and through the earth, including the core
