Download Section 9-2

yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

Earthquake wikipedia, lookup

Reflection seismology wikipedia, lookup

Seismic retrofit wikipedia, lookup

1992 Cape Mendocino earthquakes wikipedia, lookup

Earthscope wikipedia, lookup

Seismometer wikipedia, lookup

Surface wave inversion wikipedia, lookup

Earthquake casualty estimation wikipedia, lookup

Section 9-2
• Define seismic waves and focus.
• Explain the 3 types of seismic waves.
• Define epicenter and briefly explain how to
locate it.
• Describe the structure of the Earth.
• Define Moho discontinuity and shadow zone.
• Seismic waves – the energy waves in an
earthquake that move outward from the focus
and make the ground quake
• Focus – the point in Earth’s interior where
earthquake energy is released
Types of Seismic Waves
1. Primary waves – waves
of energy that travel
through Earth by
causing particles in
rocks to compress and
stretch apart in the
direction of the wave
2. Secondary waves –
waves of energy that
travel through Earth by
causing particles in
rocks to move at right
angles to the direction
of the wave
3. Surface waves – waves of energy that reach
Earth’s surface and travel outward from the
epicenter in all directions
• These waves travel by giving rock particles an
elliptical (curved) and side-to-side motion.
• Surface waves cause most of the destruction
during an earthquake.
• Epicenter – the point on Earth’s surface
directly above an earthquake’s focus
Locating an Epicenter
• Primary, secondary and surface waves do not
travel through Earth at the same speed.
• Primary waves are the fastest, surface waves
are the slowest.
• Scientists use the different speeds of seismic
waves to determine the distance to the
earthquake epicenter.
Seismograph Stations
• Because seismic waves arrive at seismic
stations at different times, scientists can
use the information to determine the
distance to an earthquake.
• The farther apart the waves (in time) the
farther away the epicenter is.
Epicenter Location
• If seismic wave information is obtained at 3
seismograph stations, the location of the
epicenter can be determined.
• The point where all three circles intersect is
the location of the earthquake epicenter.
Epicenter Location
Structure of Earth
• Inner core – the solid and dense center of
• Outer core – the liquid layer surrounding the
inner core
• Mantle – the largest layer located above the
outer core
• Crust – the outermost layer
Structure of Earth
Moho discontinuity – the boundary between
Earth’s crust and mantle; seismic waves travel
faster below the Moho and slower above it
• Shadow zone - the area on the other side of
the Earth where waves are not detected
• S waves are stopped completely
• P waves are slowed and deflected by the
liquid inner core