Summary:

An overview on why earthquakes are so hard to predict. We need to understand the steps that lead up to earthquakes, so we can precisely predict when an earthquake may happen. San Francisco has had to take many precautionary measures to ensure their infrastructure survives a ‘big earthquake.’

Why Watch this Video?

1. Have you ever wondered why there are minimal warnings prior to the occurrence of earthquakes?
2. Would you like to know how tectonic plates cause earthquakes?
3. Have you ever been confused by why some earthquakes are predicted, while others are not?

Key Terms:

Faults: a crack in the Earth’s crust

Tectonic plates: Plates (outer shell of the Earth) broken up into segments that sit upon the mantle. When they collide, earthquakes occur.

Seismic Sensors: devices that pick up waves underground. These sensors allows us to determine whether or not an earthquake will occur.

Loose Ends:

• How often does San Francisco experience earthquakes? Since 1836 there have been five earthquakes with  magnitude of 6.75 or higher. However, earthquakes with a magnitude of 3.0 or less occur multiple times a day, everyday.
• This video focuses on San Francisco specifically, however, the question is raised if there are ‘big earthquakes’ with magnitudes of 6.75 or greater around the world? Yes, there are ‘big earthquakes’ around the world.

Self-Test Questions:

1.How often is San Francisco hit by an earthquake of 6.75 or higher?

A. At least once a year

B. At least once every 100 years

C. Every 50 years

D. The exact timing is undetermined

2. What device is used to detect ground waves that cause earthquakes?

A. Speedometers in the ground that detect the speed of waves

B. Epicenter surface device

C.Satellite that detects underground movement

D. Seismic Sensors

3.  What is one issue surrounding earthquake warnings?

A. There are no faults to earthquake warnings

B. The only issue is, it does not give individuals enough notice to evacuate the area

C. The only bad thing about the warnings is it alerts people

D. All of the Above

4. How thick are tectonic plates?

A. 15 miles

B. 15 meters

C. 150 miles

D. 150 kilometers

5. What do scientists use to compare their lab structure to real life situations?

A. Ocean Faults

B. Wait for a ‘big earthquake’ to compare it to

C. Scientists do not have lab structures of faults

D. Answers A and B

Answers to self-test questions

1. B. It is almost impossible to predict when a big earthquake will hit. However, statistically there has been a big earthquake every 100 years in San Francisco.
2. D. Seismic sensors detect underground wave movement. This allows individuals time to turn off gas lines.
3. B. The warnings are great for ensuring people are notified about the earthquake, this gives people to find cover, turn off gas pipes, etc.
4.  A. plates are about 15 miles thick
5. A. Ocean faults are more frequent and productive. This gives scientists a way to calibrate their models with real faults.

Categories:

1. module 3, plate tectonics and super-continents

Sources to supplement loose ends:

https://earthquake.usgs.gov/learn/topics/megaqk_facts_fantasy.php