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Earthquakes are frightening events that can injure or kill people and cause incredible damage to structures. Scientists have developed technology to detect earthquakes so that people can be alerted as soon as an earthquake starts.
What Causes an Earthquake?
An earthquake is the shaking of Earth’s surface. There are many huge rocky plates under Earth’s surface, and these plates continually move very slowly past one another. As the plates move, they put pressure on themselves and on each other. If the pressure becomes strong enough, the plates crack. This crack is called a fault.
When a fault is created, the pressure on the plates turns into waves of energy that move through the ground, making it shake. The area around the fault experiences an earthquake.
The focus of an earthquake is the place where the underground plates first start to crack. The epicentre of an earthquake is the part of Earth’s surface that is directly above the focus.
More than one million earthquakes happen each year, but many cause only gentle shaking. Some earthquakes take place in areas where there are few people or human-built structures. These earthquakes do not cause much harm. When an earthquake happens in a place where many people live, the effects can be devastating.
How Do Scientists Detect and Measure Earthquakes?
Scientists use instruments called seismometers (size-MAWM-i-ters) to measure the motion of Earth’s surface. Seismo comes from a Greek word that means “shaking,” and meter is a Greek word that means “to measure.” Seismometers can detect the beginning of an earthquake, measure how strong it is, and measure how long it lasts.
A seismometer uses electronic sensors to detect the shaking of the ground during an earthquake. When a seismometer detects that an earthquake is happening, computers and alarms are used to warn people. The diagram below shows a very simple seismometer that does not use electronic sensors. The seismometers that scientists use are much more complicated.
The base of the seismometer and the arm the weight is attached to move back and forth as the ground shakes. The string allows the round weight to stay in the same position during the shaking, even though the rest of the seismometer is moving. A small pen-like device at the bottom of the weight draws a line that shows how much the seismometer and the ground are moving.
Why Are Emergency Alert Systems Important?
Seismometers can detect the very beginning of an earthquake, when the ground is moving so little that most people do not notice. At the first signs of an earthquake, alarms notify people to move to a safe place. There might be very little time before the shaking becomes much stronger, but even a few seconds’ warning can save lives. People might have time to duck under sturdy tables or safely stop their cars. In areas where earthquakes happen frequently, some hospitals, homes, offices, and classrooms have earthquake alarms installed.
What Do Seismologists Do?
Seismologists are scientists who study waves that travel through the ground. Some seismologists study earthquakes and try to predict when and where earthquakes will happen. These seismologists might also study the effects of earthquakes, such as tsunamis and landslides. Other seismologists study active volcanoes to watch for signs that one might be about to erupt.
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1.Some seismologists try to predict when an active volcano will erupt. Based on information in the article, how might seismologists do this?
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Type your response above.
2. How many earthquakes happen each year?CorrectIncorrect
3. Fill in the blank using information from the text.
The focus of an earthquake is the place where the first start to crack.
4. Fill in the blank using information from the text.
The epicentre of an earthquake is the part of Earth’s surface that is the focus.
5. Scientists use very simple seismometers.CorrectIncorrect