Chapter 12 How and Why Earthquakes Occur

The composition of Earth's interior affects

• how long an earthquake will last
• the speed and direction of seismic waves
• the location of an earthquake's focus
• the strength of an earthquake

What are the fastest body waves?

• P waves
• T waves
• S waves
• Q waves

Earthquakes generally occur at plate boundaries, where

• stress on rocks is greatest
• the most rock is found
• stress on rocks is low
• magnetic pull is greatest

At what location does the first motion of an earthquake occur

• the focus
• the seismic gap
• the mantle
• the epicenter

A foreshock is

• a major earthquake
• a small earthquake
• another name for seismic gap
• a precusor to a tsunami

Why do earthquakes usually occur at plate boundaries?

• The rock on the edges of tectonic plates is soft and gives in easily to various pressures
• Rock in environments near tectonic plate boundaries experience great stress
• The boundaries between tectonic plates have been seismically active for millions of years
• Rockin environments near tectonic p late boundaries experience little stress

What is the epicenter of an earthquake

• the location along a fault where the first motion of an earthquake occurs
• a seismic wave tht travels along the surface of Earth
• the point on Earth's surface directly above the earthquake's focus
• the last place that motion in an earthquake is detected

This area is responsible for 90% of all earthquakes in  the world and contains numerous faults:

• Indian Ocean
• English Canal
• The Ring of Fire
• Mid-Atlantic Ridge

This famous transform fault is located in the western United States creates significant earthquake activity for California

• New Madrid
• Denali Fault
• Ramapo Seismic Zone
• San Andreas

This fault is found in the Mid-West and directly affects Missouri, Illinois, Indiana, Kentucky, Arkansas, Tennessee and Mississippi:

• Denali Fault
• New Madrid Fault
• Hayward Fault
• San Andreas Fault