An earthquake is a sudden shaking of the Earth caused by the shifting of tectonic plates beneath the surface of the planet. Earthquakes strike without warning, often occurring when nobody expects them. The unpredictability of earthquakes makes them dangerous, especially in large cities prone to have them. Earthquakes can devastate entire communities if they do not take the proper precautions ahead of time. There are fault lines in 45 states and territories, placing the United State at moderate to high risk of earthquakes. Learn more about earthquakes and how to better prepare for them.
What Are Earthquakes?
An earthquake occurs when two crust plates of the Earth slip past one another suddenly. The place where these plates meet and slip is called a fault. An earthquake starts below and above the Earth’s surface. The point where it starts below the Earth’s surface is called the hypocenter. The epicenter is where the earthquake starts above the surface. An earthquake consists of three major phases that often surprise people. The first part of an earthquake is called the foreshock. Foreshocks are smaller earthquakes that occur right before the big earthquake, also known as the mainshock. Scientists often find it difficult to differentiate the foreshock from the mainshock. The aftershock follows the mainshock, and aftershocks can continue for weeks, months, or even years after the big earthquake.
- Earthquakes for Kids: Learn all about earthquakes by asking a geologist at the United States Geological Survey (USGS).
- Why Do Earthquakes Happen?: Find out why earthquakes happen when you try this experiment.
- How Earthquakes Work: HowStuffWorks explains everything there is to know about earthquakes.
- Earthquakes 101: Watch this video to learn about earthquakes, including when and why they happen.
- Earthquake Fast Facts: The USGS provides a list of facts about earthquakes.
- Earthquake Information: Learn about the science behind earthquakes on this page.
What Are Faults and Plate Tectonics?
The Earth has four major layers, including the inner core, the outer core, the mantle, and the crust. The crust and the upper part of the mantle make up a thin layer over the surface of the planet. This layer has many pieces that resemble a jigsaw puzzle. These puzzle pieces, also known as tectonic plates, do not stay still. In fact, they move around and slip past one another across the edges of the plates. The edges of the plates are called plate boundaries. Plate boundaries have many faults, sticking points where most earthquakes occur on the planet. When two plates slip past one another, the edges of the plates stick. This creates stored energy that is released when the edges of the plates get unstuck. This results in a ripple of seismic waves that shake the Earth and everything on it.
- Plate Tectonics: The Pacific Northwest Seismic Network describes how the shifting of tectonic plates creates earthquakes.
- An Introduction to Plate Tectonics: An educational website provides an introduction to faults and plate tectonics.
- All About Plate Tectonics: Look at the diagrams to see how plate tectonics work.
- Mountain Maker, Earth Shaker: PBS Kids shares an experiment that kids can do at home to see how plate tectonics work.
- Tectonics: Find out how continents move to create mountains on this page.
- Plate Tectonics: Watch these animations to see how plate tectonics work.
How Are Earthquakes Measured?
Scientists measure earthquakes using the recordings made on seismographs at the surface of the planet. The size of the fault and the amount of slip between two tectonic plates determine the size of an earthquake. A seismograph charts seismic activity in the form of wiggly lines. A short wiggly line usually indicates a small earthquake, and a long wiggly line means a large earthquake. The size of the earthquake is called the magnitude. The intensity of the shaking largely depends on the location of a person when the earthquake happens. Most scientists measure the magnitude of an earthquake using the Richter scale.
- Earthquakes: The USC explains why an earthquake happens on Earth.
- Facts About Earthquakes: The Idaho Public Television Network teaches kids facts about earthquakes.
- Measuring Earthquakes: Find out how seismologists measure earthquakes using the Richter scale.
- Measuring the Size of an Earthquake: Seismologists measure the size of an earthquake by the signal produced on a seismograph.
- Fault Lines: How Earthquake and Their Effects are Measured Learn how the Richter scale and other seismographs help seismologists determine how big an earthquake was and the fault lines in California.
- The Richter Scale: Observe how the Richter scale works when measuring the intensity of an earthquake.
What Happens After an Earthquake?
The aftermath of an earthquake can leave many people in need. A big earthquake causes a lot of damages to buildings and homes. It can even take people’s lives, depending on the magnitude of the earthquake. The aftershocks of an earthquake can cause further damage for many weeks, months, or even years. Tsunamis may occur, which can further devastate entire communities. Therefore, people need to be cautious after a major earthquake happens. First, check yourself and others for injuries and get help right away if you need it. Search the area for signs of damage, especially for leaking valves. Turn on the radio to hear updates. Stick with family and friends to remain safe and sound.
- Earthquakes: After an Earthquake: Find out what happens during the aftermath of an earthquake.
- Ready.gov: After an Earthquake: A lot of things can happen after an earthquake that people should watch out for, including aftershocks, tsunamis, fires, and falling debris.
- What to Do Immediately After an Earthquake: Follow these steps to protect yourself during the aftermath of an earthquake.
- Earthquake Safety: After an Earthquake: Follow these guidelines before, during, and after the aftermath of an earthquake to ensure the safety of yourself and others.
- During and After an Earthquake: Learn what happens during and after an earthquake that makes it dangerous.
- What Should I Do in the Immediate Aftermath of an Earthquake?: Find out what you should do during the aftermath of an earthquake.
How Can Communities Prepare for an Earthquake?
Communities and individuals can prepare for earthquakes before, during, and after their arrival. Start by fastening shelves securely to walls and placing heavy objects closer to the floor. Secure all loose items to ensure that they do not fall. Adults should fix electrical wiring and make other repairs to their home. Kids can help their parents by learning drills and memorizing emergency phone numbers. When an earthquake happens, children should learn to take cover beneath a sturdy surface. This will protect them from falling objects. If out in the open, move away from buildings, street lights, and utility wires. After the earthquake, children should stay out of damaged buildings and help others within the limits of their abilities. Call 911 in case of an emergency.
- Prepare for an Earthquake: The Environmental Protection Agency (EPA) shares tips for properly preparing for an earthquake.
- Earthquake Preparedness: The American Red Cross shares some important preparation tips to protect yourself during and after an earthquake.
- Being Prepared for an Earthquake: The Centers for Disease Control (CDC) shares tips for protecting families and entire communities during and after and earthquake.
- What Can I Do to Prepare for an Earthquake?: An educational website tells people what to do to prepare before, during, and after an earthquake occurs.
- Preparing for an Earthquake: What You Can Do to Stay Safe: ABC News shares ten steps that will help prepare anyone for an earthquake.
- What Can I Do to Prepare for an Earthquake?: Find out the necessary steps to take before, during, and after an earthquake.
By Ted Burgess