CH 5 Geoscience

Which figure best illustrates a convergent plate boundary between oceanic and continental plates?

*d.* (red dots in the middle)

How much more grounds motion does a Richter scale magnitude 5 earthquake generate compared to a richter magnitude 3 earthquake

100 times

Three sites (L1, L2, L3) record earthquake magnitude and earthquake intensity for the same earthquake. L1 is located closest to the focus and L3 is farthest away. Where is the intensity greatest, and what happens to the earthquake magnitude calculated at the different sites?

A. Intensity is greatest at L1; calculated magnitude is the *same* at each site

What type of fault generated the Hebgen Lake earthquake, Montana?

A. Normal Fault

An earthquake occurred on the Erie fault 5 kilometers beneath *San Gabriel*. Damage from the earthquake was greatest in nearby Fremont. The farthest report of shaking was recorded in Stockton. Where was the earthquake's epicenter?

B. San Gabriel

How much would ground motion increase between a magnitude 4.5 and 5.5 earthquakes?

C. 10 times as much

What is the Mercalli Intensity scale based upon?

Damage and Human reports

This earth generated hazard can occur when seismic waves shake saturated soils.

Liquification

Which point on the graph shown below is most likely a mega-earthquake?

Point C (farthest from the midpoint)

The ___ in California is the boundary between the North American and Pacific plates.

San Andreas strike slip fault

On a typical seismogram,____ will show the highest amplitudes.

Surface waves

Suppose two earthquakes with the same magnitude, depth, and relative motion occur in two cities, A and B. City A is near a plate boundary, city B is far from a plate boundary. Which earthquake would cause the most shaking farthest from the epicenter?

The one in *city B* because there are *few nearby faults.*

A transform fault is___.

a *strike split fault* that forms the boundary between *tectonic plates.*

____________ have the *highest* velocities.

a. Primary waves

The elastic rebound theory for the origin of earthquakes was first proposed by ____________ following the ____________ earthquake.

a. Reid, 1906 San Francisco

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

a. XII

A transform fault is ____________.

a. a strike-slip fault .. transform, strike a pose!

Major earthquakes are often followed by somewhat smaller events known as __________.

a. aftershocks

A horst is ____________.

a. an *uplifted* block bounded by two *normal* faults

The mechanism by which rocks store and eventually *release energy* in the form of an earthquake is termed __________.

a. elastic rebound

The position on Earth's surface *directly above* the earthquake source is called the __________.

a. epicenter

The Sierra Nevada, CA, and Teton, WY ranges are examples of ____________.

a. fault blocks ..

The average composition of the *continental* crust most closely approximates that of __________.

a. granite

Folded limestones that occur high in the Himalayas were originally deposited as sediments in a ____________.

a. marine basin between *India* and *Eurasia*

P waves____.

are faster than S waves and surface waves

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

b. Liquefaction

The ____________ in California is the boundary between the North American and Pacific plates.

b. San Andreas strike-slip fault

The ____________ earthquake was accompanied by extensive fire damage.

b. San Francisco, 1906

A thrust fault is best described as ____________.

b. a low-angle, reverse fault

The lithosphere is defined as __________.

b. a rigid layer...

P waves ____________.

b. are *faster* than S waves and surface waves

The average composition of the *oceanic* crust is thought to approximate that of __________.

b. basalt

The asthenosphere is located __________.

b. in the upper mantle

In a ____________ fault, the hanging wall block move up with respect to the *footwall* block.

b. inverse

The term ____________ refers specifically to geologic mountain building.

b. orogenesis

The record of an earthquake obtained from a *seismic instrument* is a(n) __________.

b. seismogram

In thrust faulting, ____________.

b. the c*rust* is shortened ...

Which one of the following statements is correct?

c. *S waves* travel through *solids* and *P waves* travel through *liquids*.

The ____________ are a geologically old mountain range folded and deformed during the Paleozoic.

c. Appalachians in the eastern United States

The Mercalli Scale is a scale from ____________.

c. I to XII that...

A syncline is ____________.

c. a fold in which the strata dip *toward* the axis

A graben is characterized by ____________.

c. a hanging wall block that has moved *down* between two *normal* faults

A(n) ____________ is a thick accumulation of sediments and small, tectonic blocks formed of material scraped off a descending, lithospheric plate.

c. accretionary-wedge complex

The Richter magnitude of an earthquake is determined from the __________.

c. arrival time of P and S waves

Large circular downwarped structures are called __________.

c. basins

Brittle deformation would be favored over plastic deformation in which of the following conditions?

c. cooler temperatures

When an earthquake occurs, energy radiates in all directions from its source. The source is also referred to as the __________.

c. focus

The dense core of Earth is thought to consist predominantly of __________.

c. iron

*Tensional forces* normally cause which one of the following?

c. normal faults

Which one of the following statements about the *crust* is NOT true?

c. oceanic crust...

Most of our knowledge about Earth's interior comes from __________.

c. seismic waves

The instrument which records earthquake events is termed a __________.

c. seismograph

A ____________ fault has little or no vertical movements of the two blocks.

c. strike slip

Overall, this type of seismic wave is the most destructive.

c. surface wave

On a typical seismogram, ____________ will show the highest *amplitudes*.

c. surface waves

The mountains and valleys of the Basin and Range Province of western United States formed in response to ____________.

c. tensional stresses..

In a normal fault ____________.

c. the hanging wall block *above* an inclined fault plane ....

Which one of the following best characterizes tsunamis?

c. they have relatively *small amplitudes* ...

The Earth's magnetic field originates by ____________.

c. weak electrical currents..

The ____________ is (are) characterized by terrane accretion that has been active throughout most of Mesozoic and Cenozoic time.

c. western margin of North America

Which of the following combinations should favor folding rather than faulting?

d. *high* temperature and *high* confining pressure

Approximately how much more energy is released in a 6.5 Richter magnitude earthquake than in one with magnitude 5.5?

d. 30 times

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

d. Richter

The amount of destruction caused by earthquake vibrations is affected by __________.

d. all of these

The distance between a seismological recording station and the earthquake source is determined from the __________.

d. arrival times of P and S waves

The Black Hills of South Dakota are a good example of a(n) __________.

d. dome

A good example of a present-day, passive, continental margin is the ____________.

d. east coast of North America

Which one of the following is true regarding tsunamis?

d. they occur in the open ocean....

When an earthquake occurs, energy radiates in all directions from its source. the source is also refered to as the___.

focus.

Suppose you were near the epicenter and felt the Earth move as if you were in the ocean. What type of seismic wave would you have experienced?

surface wave