Geology of Los Angeles: Kids’ Guide to Earthquakes

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.

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.

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.

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.

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.

By Ted Burgess