How Earthquakes are Measured
Name: _____________________________________
Date: __________________
Directions: Read the passage and answer the questions.
An earthquake is a sudden release of energy caused by moving
rock. Most earthquakes happen at the boundary of two tectonic plates.
When the plates move, energy builds up until the rocks break. A crack
where rock breaks is called a fault.
The ground shakes in an earthquake. After a big earthquake, the
ground may shake for days or weeks! These extra shakes are called
aftershocks. When the rock along the fault completely stops moving, the
aftershocks stop.
Scientists use a special tool called a seismograph to record the
shaking caused by earthquakes. Seismographs measure the strength of
an earthquake and how long the earthquake lasts. The strength of an
earthquake is called its magnitude.
The strength, or magnitude, of an earthquake is identified by a
number between 1 and 10. This is called the Richter scale. The higher
the number, the stronger the earthquake. Each number is ten times
stronger than the number before it, so a magnitude 5 earthquake is ten
times stronger than a magnitude 4 earthquake. That also means that a
magnitude 6 earthquake is one hundred times stronger than a magnitude 4
earthquake!
Seismograph machines create a diagram of the earthquake called a
seismogram. A seismogram shows each type of wave made by the
earthquake. It also shows when the waves were made. This helps
scientists measure the strength and duration of an earthquake.
How Earthquakes are Measured
Name: _____________________________________
Date: __________________
Directions: Answer the questions with the information in the reading.
1. What is an earthquake?
An ______________________________ is a sudden release of ___________________
caused by moving __________________.
2. What is a fault?
A ________________________ is a _______________________ where rocks break.
3. When will aftershocks stop?
______________________________ stop when rock along the ___________________
completely _______________________ moving.
4. What tool is used to record the shaking of an earthquake?
A ________________________________ is a tool used to ______________________
the ________________________ caused by an earthquake.
5. What is “magnitude”?
The ____________________________ is the ___________________ of an earthquake.
6. What is the name of the scale that measures the magnitude of an earthquake?
The _______________________ ________________
7. How many times stronger is a magnitude 5 earthquake than a magnitude 4 earthquake?
_________ times stronger
8. What is a “seismogram”?
A _________________________ is a diagram that shows each type of _____________
made by the earthquake and _________________ the waves were made.