Earthquakes - Science

What is a seismic gap?

A section of an active fault that hasn't experienced a significant earthquake for a long time

T or F- S-waves do not enter the core because they cannot travel through solids

S-waves do not enter the core because they cannot travel through liquids They can travel through solids, but not liquids

Famous California Strike-Slip fault

San Andreas

Causes rock to move at right angles to the direction in which the wave travels

Secondary Waves

A paper or computer record of earthquake vibrations is called a _______

Seismogram

A _____ is a intrument that records earthquake vibrations

Seismometer

What is tension?

Stress that pulls a material apart

Causes rock to move both up and down and from side to side

Surface waves

Travels only along earths surface

Surface waves

Seismic activity in seismic belts is a result of movements among Earth's _____ _____

Techtonic Plates

Which occurs at a lower stress value, ductile deformation or elastic deformation?

elastic deformation

Maximum earthquake intensity is usually found at the earthquake's

epicenter

The amount of damage done to structures by an earthquake is the earthquake's...

intensity

As the distance from a quake's epicenter increases

intensity decreases

How is the height of a building related to damage caused during an earthquake?

Builings that sway with the same period of vibration as the earthquake waves sway violently and are destroyed.

Nearly 80 percent of earthquakes occur in the seismic belt known as the _____________ ______

Circum-Pacific Belt

Upon what two factors is the probability of earthquake occurance based?

Earthquake history in a area and strain accumulation, or the rate at which strain builds up in the rocks.

T or F- On seismograms, seismic waves recorded from more distant facilities are closer together than those recorded from facilities close to the epicenter

False, On seismograms, seismic waves recorded from more distant facilities are FARTHER APART than those recorded from facilities close to the epicenter

T or F- Surface waves are the first to arrive at a seismic facility

False, PRIMARY WAVES are the first to arrive at a seismic facility

The moment magnitude scale takes into account the size of an earthquake's

Fault rupture

The modified-Mercalli scale ranges from...

I to XII

About 15 percent of all earthquakes occur in the __________ ______, which stretches across Europe and Asia

Mediterranean-Asian Belt

Can the location of an epicenter be determined from the distance between one seismic station and the epicenter? If not, what information is needed?

No, you need 3 stations or more are needed to find the location of the epicenter.

Most other earthquakes occur on the crests of _____ ______

Ocean Ridges

Can pass through earths interior

P and S waves

To determine an epicentral distance, scientists consider the arrival times of what waves types?

P-Waves and S-Waves

Squeezes and pulls rock in the same direction as the wave travels

Primary waves

What is strain?

The deformation of a material in response to stress

What is stress?

The force per unit area acting on a material

On the stress-strain curve, what part of the curve represents the elastic deformation of a material? What part represents ductile deformation?

The lower straight segment of the curve represents the elastic defomation

What can happen during earthquakes in areas where the ground contains fluid-saturated sand?

The sand and subsurface materials may liquify and behave like quicksand, generating landslides and causing houses to fall and pipes to rise to the surface.

What is compression?

The stress that decreases the volume of a material

What takes place during the process called "pancaking"?

The supporting wall of the ground floor of a building fail and cause initially intact upper floors to fall and collapse. The debris resembles a stack of pancakes.

Studies of how waves reflect deep inside Earth show that Earth's inner core is solid

True

T or F- Seismologists have resoned that Earth's outer core must be liquid based on the disappearance of S-Waves

True

The P-Wave shadow zone does not recieve direct P-waves

True

Epicentral distance

When a quake occurs, a seismic monitoring station can determine how far away it was from the shock wave pattern -- that is called the "epicentral distance" -- but not the exact direction. But with three or more monitoring stations' epicentral distances, one can draw intersecting circles to pinpoint the exact location. the distance between the seismic station and the side

Most earthquakes occur near the _______ of techtonic plates.

boundaries

T or F - S-waves do not travel through Earth's mantle

false, S-waves travel through the upper mantle

Fracture along which movement occurs

fault

Fault surface along which movement takes place

fault plane

One factor that determines the strength of an earthquake is the depth of its

focus

All seismometers include a ______ that is anchored to the ground and vibrates during an earthquake

frame

The Richter scale is a numerical scale use to describe an earthquake's...

magnitude

The amount of energy released by an earthquake is measured by its...

magnitude

All seismometers include a ______ suspended from a wire

mass

Fracture caused by horizontal tension

normal fault

Fracture that forms as a result of horizontal compression

reverse fault

Are rocks near earth's surface genrally brittle or ductile? Rocks at great depths?

rocks near earth's surface are brittle and rocks at great depths are ductile

Most earthquakes occur in narrow _______ ________ that lie between large regions with little or no seismic activity.

seismic belts

Each whole-number increase on the Richter scale corresponds to a 32-fold increase in...

seismic energy

Moment-magnitude values can be estimated from the...

seismic wave size

The focus of a catastrophic earthquake with high intensity values is almost always

shallow

Fracture caused by horizontal shear

strike-slip fault

Earthquake intensity depends primarily on the height of...

surface waves

What happens when stress exceeds the strength of a material?

the material fails

Seismic Station

the place at which earthquake waves are recorded. what records P and S waves three stations are needed to locate the focus and epicenter the center of the circle on the diagram

Epicenter

the point on the earth's surface vertically above the focus of an earthquake.

T or F - P-waves travel through Earth's mantle

true

T or F - Seismic waves change speed and direction when they encounter different materials

true

T or F- P-waves are bent when they strike the core

true