What is an Earthquake? The shaking of earth’s crust caused by the release of energy.
Post on 27-Dec-2015
223 Views
Preview:
Transcript
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
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
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
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
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
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
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
top related