ESC1000 Chapter 5 Earthquakes and Earth's Interior

Asthenosphere

A subdivision of the mantle situated below the lithosphere. This zone of weak material exists below a depth of about 100 kilometers (60 miles) and in some regions extends as deep as 700 kilometers (430 miles). The rock within this zone is easily deformed

Primary (p) wave

A type of seismic wave that involves alternating compression and expansion of the material through which it passes.

Circum-pacific belt

An area approximately 40,000 kilometers (24,000 miles) in length surrounding the basin of the Pacific Ocean where oceanic lithosphere is continually subducted beneath the surrounding continental plates, causing most of Earth's largest earthquakes.

Seismometer

An instrument that records earthquake waves. Also called a seismograph

Seismograph

An instrument that records earthquake waves. Also called a seismomete

Fault creep

Displacement along a fault that is so slow and gradual that little seismic activity occurs

Hypocenter

For an earthquake, the location within Earth where slippage begins. Also called the focus.

The epicenter of an earthquake is located using the distances from a minimum of ____________ seismic stations.

three

The difference in ____________ of P and S waves provides a method for determining the epicenter of an earthquake.

velocities

The concept and understanding that the outer core is liquid molten iron is supported by ______________.

Lehmann discontinuity S-wave shadow zones Earth's magnetic field *All of the choices are correct.*

What is the cool, rigid layer of Earth that includes the entire crust as well as the uppermost mantle called?

Lithosphere

Which of the following is not a major compositional zone of Earth?

Lithosphere

Precursor

Relative to earthquakes, an event or a change that precedes an earthquake and may provide a warning

Secondary (s) waves

Seismic waves that involve oscillation perpendicular to the direction of propagation

Surface waves

Seismic waves that travel along the outer layer of Earth

Body waves

Seismic waves that travel through Earth's interior.

Foreshocks

Small earthquakes that often precede a major earthquake

Aftershocks

Smaller earthquakes that follow a main earthquake

Mantle

The 2900-kilometer- (1800-mile-) thick layer of Earth located below the crust

Tsunami

The Japanese word for a seismic sea wave

In areas where unconsolidated materials are saturated with water, earthquakes can turn stable soil into a fluid during a phenomenon called ____________.

liquefaction

Earthquake epicenters are most closely correlated with ____________.

plate boundaries

Earthquake

Vibration of Earth produced by the rapid release of energy

Magnitude

With respect to an earthquake, the total amount of energy released during the earthquake.

Intensity

With respect to earthquakes, a measure of the degree of shaking at a given locale, based on the amount of damage

An increase in heat generally results in the ______________ of mechanical strength of Earth materials.

decrease

Seismic discontinuities are the result of changes in ___________ within Earth.

density composition pressure mechanical properties *All of the choices are correct.*

An earthquake with a magnitude of 6.5 releases about ____________ times more energy than one with a magnitude of 5.5.

30

A tsunami is a ____________.

series of waves created by a large displacement in the ocean

Modified mercalli intensity scale

A 12-point scale developed to evaluate earthquake intensity based on the amount of damage to various structures.

Fault

A break in a rock mass along which movement has occurred.

Outer core

A layer beneath the mantle about 2200 kilometers (1364 miles) thick that has the properties of a liquid

Moment magnitude

A more precise measure of earthquake magnitude than the Richter scale that is derived from the amount of displacement that occurs along a fault zone

Liquefaction

A phenomenon, sometimes associated with earthquakes, in which soils and other unconsolidated materials containing abundant water are turned into a fluid-like mass that is not capable of supporting buildings.

Inertia

A property of matter that resists a change in its motion

Seismic waves

A rapidly moving ocean wave generated by earthquake activity capable of inflicting heavy damage in coastal regions

Richter scale

A scale of earthquake magnitude based on the motion of a seismograph

Seismic gap

A segment of an active fault zone that has not experienced a major earthquake over a span when most other segments have. Such segments are probable sites for future major earthquakes

Core

The innermost layer of Earth, located beneath the mantle. The core is divided into an outer core and an inner core

Epicenter

The location on Earth's surface that lies directly above the focus of an earthquake

Megathrust fault

The plate boundary separating a subducting slab of oceanic lithosphere and the overlying plate.

Seismogram

The record made by a seismograph

Lithosphere

The rigid outer layer of Earth, including the crust and upper mantle.

Inner core

The solid innermost layer of Earth, about 1300 kilometers (800 miles) in radius

Seismology

The study of earthquakes and seismic waves

Paleoseismology

The study of the timing, location, and size of prehistoric earthquakes.

Elastic rebound

The sudden release of stored strain in rocks that results in movement along a fault.

Crust

The very thin outermost layer of Earth.