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# 6th Grade Science - Earthquakes

Holt Science and Technology - Eatch Science. c 2005. Chapter 8
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seismology
the study of earthquakes
deformation
the bending, titling and breaking of the Earth's crust; the change in the shape of rock in response to stress
elastic rebound
the sudden return of elastically deformed rock to its undeformed shape
Plate Motion: Transfrom
Fault Type: Strike-slip
Plate Motion: Convergent
Fault Type: Reverse
Plate Motion: Divergent
Fault Type: Normal
seismic wave
a wave of energy that travels throught the Earth, away from an earthquake in all directions
P wave
a seismic wave that causes particles of rock to move in a back-and-forth direction, the fastest seismic wave
S wave
a seismic wave that causes particles of rock to move in a side-to-side direction, the secondary seismic wave
seismologists
are scientists who study earthquakes and sesmic waves
fault
a break in the Earth's crust along which blocks of the crust slide relative to one another; due to tectonic forces
plastic deformation
deformation that is like clay, moveable, does not cause earthquakes
elastic deformation
when the rock can only be stretched to a certain point before breaking(does lead to e quakes)
San Andreas Fault
An earthquake zone in California where the Pacific Plate and the North American Plate slide past each other, frequently causing earthquakes
earthquake zone
area where earthquakes are common; where a large number of faults are located
body waves
seismic waves that travel through the Earth's interior
surface waves
seismic waves that travel along the Earth's surface
seismograph
an instrument that records vibrations in the ground and determines the location and strength of an earthquake
seismogram
a tracing of earthquake motion created by a siesmograph
epicenter
point on Earth's surface directly above an earthquakes starting point, or focus
focus
the point along a fault at which the first motion of an earthquake occurs
Ricther scale
measures the magnitude or strength of an earthquake
earthquake hazard
This measures how likley an area is to have damaging earthquakes in the future, it is determined by past and present seismic activity
gap hypothesis
a hypothesis that states that a major earthquake is more likely to occur along the part of an active faults that have had relativley few earthquakes in a certain period of time
seismic gap
area along a fault where few earthquake have happened recently but where strong earthquakes have happened before
retrofitting
the process of making older structures more earthquake resistant
mass damper
What is a weight placed in the roof that is computer sensored to move and counteract an earthquake
active tendon system
a weight in the building's base, similar to the mass damper
base isolators
act as shock absorbers during an earthquake, makde of layers of rubber or steel wrapped around a lead core; absorb seismic waves to avert their travel through the building
cross braces
steel braces in between the floors that support the building during earthquakes
flexible pipes
help prevent water and gas lines from breaking during an earthquake
West Coast
part of the contenental US that has the highest earthquake-hazard level
how is the strength of earthquakes related to how often they occur
the higher the magnitude of the earthquake, the less frequently they occur
aftershock
an earthquake that occurs after a larger earthquake in the same area
is what architects and engineers use to design and build structures to withstand earthquakes
common way to retrofit an older home for earthquakes
is to securely fasten it to its foundation
what can you do to make your home safer before an earthquake
put heavier things on lower shelves and prepare food, water and first aid kits
what are some plans you can make now for things to do during an earthquake
find safe places in each room, make a plan with others where to meet after the earthquake
what is the best thing to do if you are indoors during an earthquake
crouch or lie face down under a table or desk in the center of a room
what is the best thing to do if you are outdoors during an earthquake
lie face down away from buildings, power lines and trees and cover your head with your hands
S-P time method
the simplest method seismologists use to find an earthquake's epicenter
seismogram
first step in finding an earthquake's epicenter is to collect several of these from different seismographic stations
magnitude
the measure of the strength of an earthquake
100
is the number of times stronger a 5.0 earthquake is compared to a 4.0 earthquake (in magnitude)
intensity
is the degree to which people feel an earthquake and the amount of damage it causes
XII
is the highest intensity level on the Modified Mercalli Intensity Scale
lowest level of intensity on the Modified Mercalli Scale describes an earthquake
not felt by most people
Alabama's earthquake level is
low
earthquake kit should contain
flashlight, food that won't spoil, water, first aid kit, radio, fire extinguisher, medicine, batteries, clothes
theory that states that sections of active faults that have relatively few earthquakes are likley to be the sites of strong earthquakes in the future is called
gap hypothesis
areas along a fault where relatively few earthquakes have taken place are called
seismic gap
not all seismologists believe that the following is an accurate way to forecast earthquakes
gap hypothesis
18
number of major earthquakes with magnitude 7.0 to 7.9 happen on average in the world each year
when rock is elastically deformed, energy builds up in it - seismic wave occur as this energy is
released