Lessons 3-5 Notes
Lesson 3 “Recording Earthquake Waves”
• Vibrations from an earthquake can be
recorded with a seismograph; a seismogram is
a recording made by a seismograph.
– In the seismograph lab, the harder we hit the
table, the larger the waves were on the
seismogram.
• The larger the earthquake  larger waves on
seismogram.
• The direction of the vibrations also affected the
seismogram. This is why seismologists need recordings
from several seismographs so that they can get an
accurate reading.
Focus vs. Epicenter
• The smaller wave on a seismogram is a Pwave.
• The focus of an earthquake is the place where
the rupture begins and energy is released.
The place on the earth’s surface directly above
the focus is the epicenter.
Seismograms
• Seismologists use seismograph stations from
multiple locations.
• The location with the smallest amount of lag
time between the P and S wave is the one that
is closest to the epicenter of the earthquake.
• The time between each earthquake wave
arrived at each city are different because they
are different distances away from the
epicenter.
Lesson 4 “Plotting Earthquakes”
• Earthquakes and volcanoes occur in many of the
same specific locations that are on plate
boundaries.
• The Ring of Fire, the Mid-Atlantic Ridge, and
Mediterranean-Himalayan Belt are areas of
intense earthquake activity.
– Ring of Fire: around edges of Pacific Ocean
– Mid-Atlantic Ridge: runs down the middle of the
Atlantic Ocean floor
– Mediterranean-Himalayan Belt: extends from west
Indonesia through the Himalayas in Asia and the
Mediterranean region.
Intensity vs. Magnitude
• Intensity is the measure of damage done by
an earthquake and magnitude is the measure
of the total amount of energy released at the
focus of an earthquake.
Lesson 5 “Using Earthquakes to Study the
Earth’s Interior”
Crust:
Lithosphere
Mantle:
asthenosphere
directly below
lithosphere
Outer Core:
Liquid
Inner Core:
Solid
Lithosphere vs. Asthenosphere
• Lithosphere – solid outer shell of earth that is
broken up into segments.
• Asthenosphere – directly below lithosphere
and flows like taffy.
How seismologists use earthquakes to
study the earth’s interior:
• Earthquake waves travel through some
substances, but not others, and travel at
different speeds depending on the substance.
• Patterns of earthquakes and their waves
provide information about plate boundaries
and the interior structure of the earth.