27 terms

# 8th Grade Earth Science CH 17A set 2

Earthquakes
###### PLAY
P Waves, S Waves, L Waves
Three types of Earthquake Waves
P Waves
First waves to reach sensors -- can go anywhere
S Waves
Second waves to reach sensors -- Do not go through core
Core is liquid
Why do second waves probably not go through core
L Waves
Slowest and most destructive waves -- travel on surface
Calculated by finding difference between arrival of P and S waves
How do you find the distance to an earthquake
Sensor is farther from epicenter
What is indicated by a bigger interval between the arrival of the waves at the sensor
Triangulation
How is location found by sensors since one cannot pinpoint location
Computers
Today location is quickly found by using...
Depth of focus
What can be found by studying arrival times of all three waves
Amplitude and Wavelength
What do all waves have in common
Fault
Feature of earth's surface -- first thought to cause earthquakes, then thought to be result, now known to be feature caused by movement of tectonic plates
San Andreas Fault
most well-known fault -- type is strike-slip between the Pacific and North American tectonic plates
70 km or deeper
How deep does a quake need to be before it will not be felt -- thought to be quakes along fault line where one plate is sub ducting under other plates
save lives not property
Why are prediction techniques being developed -- also why are building materials and methods being improved
Fault lines
What is identified in earthquake-prone areas
How long before scientists might be able to predict earthquakes
Where, When, Magnitude
What will be predicted
Pacific Rim or Ring of Fire
Circum-Pacific and Alpine Himalayan volcano belts are also known as
90%
How many earthquakes occur in Circum-Pacific or Alpine Himalayan
Volcanoes
What often trigger earthquakes
Volcanoes
what is sometimes preceded by an earthquake -- not known if the earthquake causes it though
Note places where lots occur and then see what gap between is and how often they occurred in the past
Today's prediction method
knowledge of deeper terrain (inner layers)
What is needed to understand why and when earthquakes will be happening
Being prepared
What is the next best line of defense if you aren't able to predict earthquakes
California
What state is often described as about to fall off into the ocean
No known reason
Multitude of sensors installed in California show that pressure sometimes builds up and then dissipates without an earthquake