Earth Science: Earthquakes & Earthquake Waves

Circle

Energy travels in a _____

Focus

Point inside the earth where movement first occurs and energy is released (created an earthquake)

Stress, plate boundaries, faults

Most major earthquakes occur because of _____, _______ or ______

Friction

Stress

Causes of earthquakes

Epicenter

Point on the earth’s surface directly above focus

Where the earthquake appears to start on the earth’s surface — used to locate earthquake on a map

Body waves

Waves that travel from focus through the body of the earth

Surface waves

Travel along Earth’s surface

When P & S waves reach the surface, they produce surface waves

P-Waves (Push-Pull)

Known as primary or compressional waves

Travel through solids, liquids, & gases

First & fastest waves

Liquids, gases, solids

P-Waves can travel through…

s-waves

Known as secondary or shear waves

Can ONLY travel through SOLIDS

Second, slower

Solids

S-waves can only travel through…

Surface waves

Travel like ripples in a pond across earth’s surface

SLOWEST waves arrive LAST

Causes MASSIVE destruction to buildings, roadways, railroad tracks, etc.

Ground moves up and down, side to side

Slowest, last

____ surface waves arrive ____

SP time difference/lag time formula:

S-waves — P-waves

Small, close

When the S-P time difference is ____ the earthquake epicenter is ____

Large, farther away

When the S-P time difference is ____, the earthquake epicenter is _________

Distance, time difference, Scrap paper

To determine the _______ and __________ you must use ____

Origin time formula

P-wave arrival time — P-wave travel time

Distance to epicenter

Origin time

Magnitude

3 important things you can get from 1 seismic recording station

Compression

→ ←

Layers get thicker $ shorts

Convergent boundaries

Tension

← →

Pulls rock apart

Layers get thinner & longer

Occurs at divergent boundaries

Shear

→

←

Twists rock

Rocks are distorted & change shape

Occurs at transform boundaries

Syncline

Sinners = down

Down fold in rock layers

Anticline

Upfold in rock layers

Faulting

Stress applied rapidly, causes rock to break instead of fold

Normal fault

Hanging wall moves down

Tension is pulling crust apart

Reverse Fault

Hanging wall moves up

Compression pushes plates towards each other

Strike-Slip Fault

Rock on opposite sides of fault plane move horizontally past each other

Shearing plates slide past each other