It was thought we could predict earthquakes and their direction by using tools as simple as a vase. Overtime, scientists have developed complex warning system technologies we could rely on to anticipate earthquakes better. However, despite all the technological progress made, it still proves to be challenging to predict earthquakes.

Why Watch This Video?

  1. Have you ever wondered what warning systems we rely on to predict and prepare for earthquakes?
  2. Would you like to know the theories behind the occurrence of earthquakes?
  3. Have you ever been confused by how we still haven’t developed a fully reliable method for predicting earthquakes?

Key Terms

Faults/Fault Lines:

A fault is a surface consisting of broken rocks that have moved. Faults can include all sizes and are situated all around the world. During an earthquake these rocks will shift on the other side (horizontally, vertically, or any angle in between).

A fault line is the break on the ground caused by the shift of the tectonic plates.

  • Normal Fault: Forms when the block above the fault moves downwards compared to the block below.
  • Reverse(Thrust) Fault: Forms when the block moves up and over to the other side of the block below.
  • Strike-Slip (Transcurrent) Fault: Forms when two blocks move past each other in a horizontal direction and paralleling the fault line.

Seismic Waves: Seismic waves are waves of energy (that can be a result of earthquakes) travelling through Earth’s layers. Earthquakes will create distinct waves with distinct velocities. They could travel near or along earth’s surface or through earth’s interior.

Seismometer: An instrument that detects and responds to ground vibrations/motions. This device will detect as well as measure seismic waves. By gathering this data, a seismometer will locate earthquakes.

Loose Ends

There are multiple types of earthquakes.

Along with tectonic earthquakes, there are volcanic, explosion, and collapse earthquakes. Volcanic earthquakes are generally smaller than tectonic earthquakes. They occur as a result of the combination of a tectonic quake and volcanic activity. Explosion quakes are the result of a detonation of a nuclear or chemical device. And finally, collapse quakes are small earthquakes in underground caverns and mines. Seismic waves caused by the explosion of a rock on the Earth’s surface result in a collapse earthquake.

What’s the relationship between tectonic plates and earthquakes?

When tectonic plates shift, rocks can end up locked with each other resulting in them being unable to move. These activities can cause chemical and physical changes. The plates will continue shifting, despite the locked rocks, leading to the increase of pressure. This movement is what causes tectonic earthquakes. The shaking we feel is produced by the released energy moving through the Earth’s crust.

How do radon-thoron detectors predict earthquakes?

When uranium (present in rocks and soil) experiences radioactive decay, radioactive radon is produced and trapped in rocks that contain the uranium. The earthquake theory, regarding radon, suggests there are subterranean movements that lead to the release of the gas in high concentrations prior to a quake. However, radon alone can not predict earthquakes as it can be disrupted by ‘‘meteorological phenomena and tidal forces’’. Thoron on the other hand, a radioactive isotope of radon, could overcome these limitations (a study still in progress). The radon-thoron approach can result in recording earthquake signals without interference from other environmental effects.

5. Self-Test Questions

Scroll down for the answers.

1. Which of the following gases experience a concentration spike prior to earthquakes?

  1. Methane
  2. Ethane
  3. Radon
  4. Hydrogen

2. How much can tectonic plates move per year?

  1. 3cm-15cm
  2. 1cm-20cm
  3. 5cm-30cm
  4. 5cm-10cm

3. How many days in advance can radon-thoron detectors predict earthquakes?

  1. 1 week in advance
  2. 2 weeks in advance
  3. 1 month in advance
  4. 2 days in advance

4. Where do our most reliable clues for predicting earthquakes come from?

  1. long-term forecasting
  2. seismometers
  3. the global positioning system
  4. the strainmeter

5. Mineral fluids, released due to friction, can cause what?

  1. pressure build-up
  2. a reduction in friction between rocks
  3. no changes whatsoever
  4. plates to slip more


1. c: There are reports of spikes in the concentration of the gas radon prior to earthquakes. Due to the decay of uranium (present in rocks and soil), radon is released.

2. b: Tectonic plates, moving on a partially molten layer of Earth’s mantle, can shift anywhere from 1 to 20 centimeters per year.

3. a: After the observation of the high radon-thoron levels released before the quake that struck the east coast of Japan, scientists believed it could be a promising warning system. They believed it could warn them one week in advance.

4. a: Long-term forecasting is based on the knowledge of when and where earthquakes have occurred previously. This method is based on specified probabilities. Rather than waiting for a machine to sense an earthquake when it’s close, after analyzing previous gathered data, we can know when an earthquake is due.

5. According to some researchers, if mineral gel is present in faults during a quake, the gel may reduce friction to nearly zero in some situations.

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Item Credit: Jean-Baptiste P. Koehl, Ted-Ed

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