What is an Earthquake? The shaking of

earth’s crust caused by the release of energy

Deadliest Earthquakes Video What causes Earthquakes? How are earthquakes detected? Measured? Describe the different types of faults, and their

effects. Can earthquakes be detected early to prevent

damage? What are silent quakes? Interesting facts on Haiti, San Andreas Fault, Chile

Earthquake

Waves Earthquakes shake the earth by releasing

waves of energy

There are 3 different wave types

1. P waves

2. S waves

3. L waves

P Waves ComPressional or Primary waves

Cause the ground to expand and contract

S Waves Secondary or Shear

waves

Cause the land to move at right angles to the direction of the wave

L Waves Occur when the S and

P waves reach the surface

Make the ground move like ripples in a pond

Seismographs Instrument that records earthquake waves and

measures their strength

Seismogram: Collects earthquake data P waves are first, then S waves follow

What are the P and S wave arrival times? What is the difference between them in seconds

5sec 10 15 20 25 30 35 40

Earthquake Terms Focus: the point at which the first plate

movement occurs and the energy is released

Epicenter: the point on the surface directly above the focus

Locating Earthquakes

Time Travel Graph

Used to calculate the distance from the seismograph to the epicenter

Use interval times of p

& s arrival times

Cont’d Each seismograph

station has a different epicenter distance

Use 3 stations, the point at which all those distances intersect is the epicenter

The Richter Scale Measures the amount of energy released by an

earthquake (seismographs) Logarithmic Scale Increases ten fold Scale 1 - 10

The Mercalli Scale

Describes the intensity/severity of an earthquakes effect

Uses Roman Numerals 1 (I) through 12 (XII)

Earthquake Damage

1. Ground shaking release of energy & movement of waves, buildings cannot withstand damage

2. Foundation failure results from shaking, disrupts soil, causes buildings to collapse

The Earth’s LayersDivided in 2 ways Compositional Layers & Mechanical Layers

Compositional Layers

Crust: Felsic and mafic rock, 0-65 km

Mantle: Liquid and solid rock, 65-2890 km

Core: Inner and Outer levels, made of iron and nickel, 2890-6369 km

Earthquake Waves Inside the Earth

Earthquake wave velocity depends on the type of material and density

When waves move from one type of material to another, they change speed and refract

Earthquake Shadow Zone The areas that never receives earthquake

waves

Mechanical Layers Divided by how fast P

and S waves travel through them

Lithosphere: Crust and uppermost part of mantle, P and S waves move through them

Mechanical Layers

Aesthenosphere: P and S waves can move through them, but slow down and refract due to material change

Mesosphere: Mantle becomes more solid, P and S waves speed up

Outer Core: Liquid nickel and iron, P waves slow down, S waves stop

Inner Core: Solid iron and nickel, P waves speed up and refract due to state change

Elastic Rebound Theory Friction & stress builds between plates

as they try to move past each other

Faults A fault is a break in Earth’s crust along which

movement occurs, movement along the faults is what causes earthquakes

1. Strike Slip Fault

2. Oblique Normal Fault

3. Normal Fault

4. Reverse Fault

Example: India As the Indian plate pushed India

into the Eurasian plate, faults formed on all sides of the landmasses

This created many strike-slip faults, which has led to earthquakes

This also made the Himilayas

The Himilayas

Strike-Slip/Transform Fault In this fault, rocks on

either side of the fault move past each other

The San Andreas fault is an example

A B

A B

Normal Faults Occur when rocks on

one side drop relative to rocks on the other

These occur where tension is pulling the crust apart, and the side are diverging

A B

AB

Reverse Faults This fault occurs when

one side of the fault plane is driven up the other side

These faults play an important part in mountain building

The Moho In 1909, Andrija Mohorovic noticed an abrupt

change in speed of 2 P waves One had sped up faster than the other at a

depth of about 32 km This area was named the Moho after him,

and it is an area of dense rock that serves as the boundary between the crust and mantle