Earth Science - Earthquakes

What is an earthquake?

Vibrations of Earth produced by the rapid release of energy.

What causes earthquakes?

Movements along faults and release of stored energy through elastic rebound.

What is a fault?

A fracture between two blocks of rocks.

What is rock deformation?

The process where energy is stored in rocks.

What is elastic rebound?

The release of stored energy causing rocks to snap back.

What are foreshocks?

Small earthquakes that occur before a larger one.

What are aftershocks?

Smaller earthquakes that follow a main earthquake.

What is seismology?

The study of earthquake waves.

What is a seismograph?

An instrument that records earthquake waves.

What is a seismogram?

The recorded data of earthquake waves.

What are surface waves?

The slowest waves with complex motion that travel along Earth’s surface.

What are body waves?

Waves that travel through the interior of the Earth.

What are P waves?

Fastest waves with push-pull motion that travel through solids

What are S waves?

Slower waves with shaking motion that travel only through solids.

What is the focus of an earthquake?

The place within Earth where earthquake waves originate.

What is the epicenter?

The point on Earth’s surface directly above the focus.

How do scientists locate an earthquake?

By using the difference in arrival times of P and S waves from three stations.

Where do most earthquakes occur?

Along plate boundaries.

What is earthquake intensity?

A measure of the degree of shaking at a location based on damage.

What scale measures intensity?

The Mercalli intensity scale.

What is earthquake magnitude?

A measure of the energy released based on wave amplitude.

What scale measures magnitude?

The Richter scale.

What factors affect earthquake destruction?

Intensity

What is liquefaction?

When saturated ground turns fluid during shaking.

What hazards can earthquakes cause?

Ground shaking

Can earthquakes be predicted in the short term?

No reliable method has been devised.

What is long-range earthquake forecasting?

Predicting probability based on past patterns.

What are the four layers of Earth?

Crust

What is the crust?

The thin

What is the mantle?

The layer below the crust made mostly of igneous rock.

What is the outer core?

A liquid layer made mostly of iron and nickel.

What is the inner core?

A solid layer made mostly of iron and nickel.

How do we know about Earth’s interior?

By studying P and S wave travel times.

What happens to seismic waves in different materials?

Their speeds change depending on the material.

What is a shadow zone?

An area where P waves are absent between 105° and 140°.

What evidence supports Earth’s layered structure?

Changes in wave velocity