geology chapter 11

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Which one of the following statements concerning foci and epicenters is correct?

The epicenter is at the surface directly above the focus where the earthquake initiates.

What is the definition of the focus?

The exact location on the fault where slippage occurs

Which seismic waves are released first during an earthquake?

p waves

The ________ earthquake was accompanied by extensive fire damage.

san Fransisco 1906

What is the term for stored-up energy released by earthquakes?

seismic

_______ are records of seismic waves.

seismograms

The ________ is used to record ground shaking and the earthquake-magnitude scale was invented by ________.

seismograph; Richter

The strongest earthquakes occur primarily at _____.

subduction zones

The epicenter of an earthquake is the ________.

surface location directly above the point where the fault slip initiates

Generally speaking, which seismic waves will have the greatest amplitude on a seismogram?

surface waves

________ have the highest velocities.

Primary waves (P-waves)

The ________ magnitude scale is a measure of the energy released. It does not directly measure the extent of building damage.

Richter

______ are instruments that sense earthquake waves and transmit them to a recording device

Seismographs

You are watching TV with a friend when there is a special bulletin about a city in California being devastated by an earthquake. The news anchor reports that the epicenter of the earthquake is 45 miles east of Los Angeles. How would you explain the definition of the epicenter to your geologically impaired friend?

The location on Earth's surface directly above the point of slippage

Which of the following would be the most unstable during an earthquake?

Unconsolidated sediments

Which one of the following regarding the San Andreas Fault in California is true

a sliver of continent west of the fault is moving northward with the Pacific plate

are smaller earthquakes of lesser magnitude that follow a major earthquake.

aftershock

hat are the smaller magnitude quakes that follow a major earthquake?

aftershock

P waves ________.

are faster than S waves and surface waves

What are the two categories of seismic waves?

body waves and surface waves

Which tectonic boundary is associated with megathrust faults?

convergent

which plate boundary along the Circum-Pacific Belt is responsible for the majority of that belt's earthquakes?

convergent

Deep-focus earthquakes happen at _____.

convergent plate boundaries

S waves can travel through solid and liquid media.

false

Unconsolidated, water-saturated soils or sediments provide good foundation materials for buildings and other structures.

false

P waves arrive at the seismograph _____ and are _____ waves.

first and compressional

The ________ is the point of origination for an earthquake.

focus

During an earthquake, energy waves radiate outward in all directions through the interior from the ________ whereas energy waves radiate outward in all directions along the surface from the ________.

focus; EPICENTER

The largest lateral, ground displacement is produced by ________.

horizontally vibrating surface waves

refers to the tendency for a foundation material to lose its internal cohesion and fail mechanically during earthquake shaking.

liquefaction

The point of origin of an earthquake at depth is called

the focus

To locate the epicenter of an earthquake, you need information from at least _____ seismic station(s).

three

Most faults are locked in place, except for brief, abrupt movements when sudden slippage produces earthquakes.

true

The epicenter of an earthquake is on the surface of the Earth directly above the focus.

true

arthquakes with a Richter magnitude less than 2.0 are generally not felt by humans.

true

________ is the maximum possible damage designation on the Mercalli scale.

xii


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