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