What Is a Sonic Boom? Here's What Causes It And Why It's Not an Earthquake

In the South California regions of Long Beach and Orange County, a sonic boom recently struck the residents. This caused shaking which, for many, seemed like a familiar earthquake.

However, there are key differences between the two events, so much so that the U.S. Geological Survey (USGS) can barely measure if a sonic boom has occurred.

Newsweek breaks down what can cause a sonic boom and the differences between this and an earthquake.

What Is a Sonic Boom?

According to NASA a sonic boom is a thunder-like noise which is heard when something travels faster than the speed of sound.

This can be an aircraft or aerospace vehicle, and is caused when air is displaced by such a vehicle, forming a shock wave, which is then sharply released when the resulting pressure is released.

An example of how this works is similar to when a boat creates a small wave in the water. When the boat moves through water, it pushes water aside, thus creating a wake.

Similarly, if a plane flies quickly through the air, it forces air aside, which can create a shockwave, due to built-up air molecules. As the pressure of these molecules releases, the boom is heard.

The change in air pressure is what makes the sound ring out. However, some have suggested there can be seismic qualities to such an event.

The Difference Between a Sonic Boom and an Earthquake

According to the USGS, they would not use seismic instruments to measure a sonic boom, as they occur in the atmosphere rather than on the ground.

However, there are some who, due to the power of a sonic boom, have reported shaking in their area, which means it has been brought to the attention of seismologists.

A sonic boom can have some seismic qualities which are felt by individuals on the ground. But, generally speaking, they do not affect what is happening at ground level very often or to any great extent.

The key differences include the length of the high-frequency signal. If a signal is picked up at all by seismologists, it would only be for a very short time due to the difference in the speed of sound in air to the speed of seismic waves in rock, which causes earthquakes.

The second defining factor is the area affected. Usually, when a sonic boom is heard, there is a wider area of reports from those who have felt something, whereas earthquakes tend to be more localized.

Finally, often the military may inform the USGS of their intentions to fly planes in an area, which would usually indicate the shaking or boom heard by residents is more likely to be a sonic boom, rather than an earthquake.

When it comes to earthquakes, the confusion can often be found in the fact that, sometimes, earthquakes can bring about similar noises as they occur.

A plane almost breaking the sound barrier
A sonic boom is caused when a plane breaks the sound barrier Getty Images