Chapter 9 Crustal Deformation and Earthquakes

What was the largest earthquake ever recorded?

1960 Valdivia

Where was the largest earthquake ever recorded?

1960 Valdivia Chile

Which earthquake killed over 200,000 people as a result of the subsequent tsunami?

2004 Indian Ocean

An increase of one on the Richter scale is equivalent to an increase in energy released of ________.

32

n increase of one on the Richter scale is equivalent to an increase in actual ENERGY released of ________?

32

Syncline

A U-shaped, upward-facing fold with younger rocks in its core.

Ductile Deformation

A bending, squishing, or stretching style of deformation where an object changes shape smoothly.

Basin

A down-warped feature in the crust.

What is the difference between a joint and a fault?

A fault is a fracture with movement; a joint is a fracture with no movement.

Monocline

A one-sided fold-like structure in which layers of rock warp upwards or downwards.

Geologists define a geological formation as ______________________?

A recognizable, mappable rock unit

Dome

A rock up-warping of symmetrical anticlines.

Brittle Deformation

A style of strain in which an object suddenly breaks, fractures, or otherwise fails in a different way than ductile deformation.

Elastic Deformation

A type of deformation that reverses when the stress is removed.

Graben

A valley formed by normal faulting.

Yield Point

An amount of strain where the substance has a maximum amount of elastic deformation and switches to ductile deformation.

Which type of fold would be the most likely to trap oil and gas at its axis? (Oil and gas rise and float on groundwater.)

Anticlines

How will a rock respond if it is subjected to high heat and pressure?

Bend

Increasing rock strength results in what type of strain?

Brittle

If you crush a soda can, what type of stress are you applying?

Compression

When you crush a can, what type of stress are you applying?

Compression

Normal faults are formed by ___.

Crustal Stretching

What does the strike and dip of a rock represent?

Dip is the angle of greatest inclination down from horizontal and strike is the angle from true north or true south of a horizontal line on the stratum.

Anticline

Downward-facing fold, that has older rock in its core.

If you snap a green stick into two pieces, it will first undergo Elastic deformation, then Brittle deformation.

Elastic, Brittle

If you snap a "green" stick (freshly removed from a tree) into two pieces, it will first undergo __________ deformation, then __________ deformation.

Elastic; Brittle

Where on earth are strike-slip faults most common?

Fracture zones adjacent to midocean ridges

The State of Michigan is largely occupied by the Michigan Basin, a structural basin between Lake Michigan and Lake Huron that contains Cambrian through Pennsylvanian strata. Where are the Pennsylvanian rocks located?

In the center of the state

Seismograph

Instrument used to measure seismic energy.

What is the resulting strain of tensional stress on a rock?

Lengthening and thinning of the rock.

What is the resulting strain produced by tensional stress on a rock?

Lengthening and thinning of the rock.

Which seismic wave type is most damaging?

Love Waves

Which of these scales is a qualitative measure of seismic shaking?

Mercalli Scale

Which of these is a quantitative measure of seismic energy?

Moment Magnitude and Richter Scale

Increase Rock Strength

More Brittle

Increase Strain Rate

More Brittle

Increase Temperature

More Ductile

Greater seismic intensity occurs with constructive interference. This is a result of _____________?

Multiple seismic waves combining in sync with each other

In which type of fault does the hanging wall move down relative to the footwall?

Normal

The opening image at the top of Ch. 9 of your textbook shows small movements along several small faults. Examine the offset in this image and determine the type of fault.

Normal

Which seismic wave type is the fastest?

P

What is the name of the seismic wave that reaches land first?

P Wave

Which seismic wave type travels the fastest?

P-Waves

What is the resulting strain in ductile deformation?

Permanent change in shape

Geologists define geologic formations as:

Recognizable, mappable rock units

Which fault type is the result of compression?

Reverse Thrust

Which fault type would be most prominent at a transform plate boundary?

Strike-Slip

What are geologic cross sections designed to show?

Subsurface structural interpretations from surface and subsurface measurements

Which seismic wave type is most damaging?

Surface

When viewing folds on a map, which fold type has the oldest rock beds on the flanks, near its axis, and youngest beds in the middle?

Synclines

Folds (anticlines and synclines) are produced by____.

Tectonic compression

What is the principal type of stress is applied to crustal rocks at the mid-ocean ridge?

Tension

Which seismic wave shakes from side-to-side making the ground shake?

The S Waves

Epicenter

The location at the surface directly above the focus of an earthquake, typically associated with strong damage.

What does the series of horsts and grabens from the Wasatch Mountains of Utah to the Sierra Nevada Mountains of Nevada tell us about the dominant stress being applied to the crust of the region?

The normal faults producing the horst/graben structures tell us it is tension

Which of these faults are caused by strong compressional forces?

Thrust Reverse

Which fault type would be most prominent at a convergent plate boundary? Choose two.

Thrust and Reverse

Shear stresses are most common along which type of plate boundary?

Transform

How do we determine the location of an earthquake?

Triangulation

How do we find the location of an earthquake?

Triangulation

Which building type is LEAST resistant to earthquake damage?

Unreinforced Masonry

Which building type is least resistant to earthquake damage?

Unreinforced Masonry

If a rock layer has a dip of 90 degrees, how is that rock layer oriented relative to a horizontal plane?

Vertical

What is the focus of an earthquake?

Where the actual rupture of rock occurs in the subsurface producing the earthquake

The ____________ point is when permanent deformation is measurable.

Yield

When a force is exerted on a rock but the rock is also at a high temperature and pressure, the resulting strain will more likely be ______.

a bend

Strain Rate Measures

how quickly a material is deformed

When an earthquake occurs in a horst-graben situation, where is seismic shaking greatest?

in the poorly consolidated sediments of the valleys (grabens)

Geologic folds

layers of rock that are curved or bent by ductile deformation

In an anticline, where are the oldest rocks?

near the axis

The type of deformation a rock undergoes depends on

pore pressure, strain rate, rock strength, temperature, stress intensity, time, and confining pressure.

Strike and dip considered together are called

rock attitude

Cross Sections

subsurface interpretations made from surface and subsurface measurements

Shear stress applied to crustal rocks results in what kind of strain?

tearing (strike-slip faulting)

Strike and dip map symbols look like

the capital letter T, with a short trunk and extra-wide top line.

If stress are the forces applied to a rock, then strain is ______.

the deformation of the rock

What is required for liquefaction?

unconsolidated sediment water shaking