Chapter 2 Flashcards
Stress
Force exerted when an object presses on, pulls on, or pushes against another object
Fault
Fracture or break in Earth’s lithosphere where blocks of rock move past eachother
Earthquake
Shaking of the ground caused by a sudden movement of large blocks along a fault
What is the direction of a strike slip fault?
Scrape past eachother in opposite directions
Strike slip fault
Moves horizontally
Like transform
Shallow earthquake
Normal fault
Moves apart
Like divergent
Moves vertically
Shallow and intermediate earthquakes
Reverse fault
Pushes together
Like convergent
Moves vertically
All types of earthquakes
Where are most earthquakes common?
Near places with big populations, along tectonic plate boundaries
Why do most earthquakes occur at tectonic plate boundaries?
That’s where faults are located
Seismic waves
Vibrations caused by an earthquake, how energy travels
Focus
Point underground where rocks first begin to move
Epicenter
Point on Earth’s surface directly above the focus
Seismograph
Instrument that records ground movement
Seismogram
The record made by a seismograph in response to ground motions
P wave
Primary wave
Goes in a straight line
Arrives first
Push and pull movement
S wave
Secondary wave
Up and down movement
Arrives second
Goes in a zig zag motion
Surface waves
Arrive last
On the surface
Waves move up and down like S wave
How are shallow focuses different from deep focuses?
A shallow focus causes more damage because it’s closer to the land.
Which waves are the most powerful?
Surface
What do the wiggles on a seismogram indicate?
How powerful the earthquake was
What can scientists learn from studying seismograms?
The location and strength
How many different seismic stations are needed to locate the epicenter?
3 each station must determine the distance of the earthquake
Seismic gap
A segment of an active fault known to produce significant earthquakes
Aftershock
A smaller earthquake that follows a more powerful one in the same area
Liquefaction
Where shaking of the ground causes soil to act like a liquid
Tsunami
Giant water wave triggered by an earthquake, volcanic eruption, or landslide
Name four damages done by earthquakes
Fires Landslides Tsunamis Aftershocks Liquefaction Avalanche
What are the two types of magnitude scales?
Richter scales calculate how fast the ground moves at a seismic station
Moment magnitude scales were used before Richter scales were invented. They can measure the strength
When are earthquakes most dangerous?
When they occur where a lot of people live
As a tsunami reaches shallower water around an island or continent what happens?
The tsunami slows when water gets shallower. The water level rises.
Why do the areas with the most risk are close together instead of spread out?
They’re by the same active fault
What are earthquake resistant methods?
Shear walls Shear core Base isolator Moat Cross braces
Base isolators do what?
Absorb the ground motion
Moats do what
Let the building shake more gently
Shear walls and core
Stop the walls from shaking and add strength to it
Cross braces
They help the structure keep its shape while being shaken
A subduction zone is which type of fault?
Reverse
Three characteristics of tsunamis
Tall
Dangerous
Powerful
Fast
What can scientists predict about earthquakes?
Risk in an area
Why can’t scientists predict earthquakes?
They don’t know exactly when it’s going to happen
