Earthquake-resistant buildings

Earthquake-resistant structures are structures designed to protect buildings from earthquakes.

After a massive earthquake one wonders if it’s possible to build an earthquake-proof building? The answer is yes and no. 

There are of course, engineering techniques that can be used to create a very sound structure that will endure a modest or even strong quake. However, during a very strong earthquake, even the best engineered building may suffer severe damage. 

Engineers design buildings to withstand as much sideways motion as possible in order to minimize damage to the structure and give the occupants time to get out safely.

The anatomy of an earthquake

Professor Iain Stewart tells us more about the anatomy of an earthquake.

Activity at plate boundaries

Type of plate boundary	Description of changes	Earthquake / volcanic activity	Examples
Constructive zone	Two crusts / plates move away from each other.	Moderate volcanic and earthquake activity.	Mid-Atlantic ridge. Iceland.
Destructive zone	Oceanic crust / plate moves towards continental crust / plate. The oceanic crust is heavier and sinks.	Violent volcanic and earthquake activity.	Nazca and South American plates.
Collision zone	Two continental crusts / plates collide and are forced up into fold mountains.	Earthquake activity, (no volcanic activity).	Indo-Australian and Eurasian plates.
Conservative zone	Two plates move sideways past each other.	Violent earthquake activity (no volcanic activity).	Pacific and North American plates. San Andreas, California.

Type of plate boundary	Drawing
Constructive zone
Destructive zone
Collision zone
Conservative zone

The Richter scale - The magnitude of earthquakes

http://www.youtube.com/watch?v=wVqYg4NPvC4

The Richter scale is the best known scale for measuring the magnitude of earthquakes. The magnitude of an earthquake is determined from the logarithm recorded by seismographs. The scale ranges from 0 to 10. Each one-point increase on the scale indicates ten times the amount of shaking and 33 times the amount of energy. For instance an earthquake at Richter scale 6 has a magnitude ten times that at scale 5. Study Fig 4 that shows the magnitude, effects and frequency of earthquakes.

Richter Magnitude	Earthquake Effects
Less than 2.0	Very small earthquakes which are not felt.
2.0 - 2.9	Detected only by seismometers.
3.0 - 3.9	About 49,000 per year
4.0 - 4.9	Everyone notice them e.g. shaking of indoor items, no significant damage.
5.0 - 5.9	Slight damage to well-designed buildings but can cause major damage to poorly constructed buildings.
6.0 - 6.9	Much damage to buildings.
7.0 - 7.9	Can cause serious damage, houses may collapse.
8.0 - 8.9	Cause serious damage, most buildings collapse.
9.0 - 9.9	1 per 20 years
10.0+	Never recorded

San Andreas Fault

VIDEO - San Andreas Fault

 

San Andreas Fault is a geological fault that spans a length of roughly 1,300 kilometres through California in the United States.
Large faults within the Earth's crust are the result of motion and active fault zones are the causal locations of most earthquakes.
Earthquakes are caused by energy release during rapid slippage along faults.
The San Andreas Fault, a right-lateral strike-slip fault, marks a transform boundary between the Pacific Plate and the North American Plate.

All land west of the fault on the Pacific Plate is moving slowly to the northwest while all land east of the fault is moving to the southwest under the influence of plate tectonics. The rate of slippage is approximately of 0.6 cm a year.

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How do tsunamis relate to Earthquakes

Tsunami is a set of ocean waves caused by any large, abrupt disturbance of the sea-surface. If the disturbance is close to the coastline, local tsunamis can demolish coastal communities within minutes.

A tsunami, also called a tsunami wave train, and at one time referred to as a tidal wave, is a series of water waves caused by the displacement of a large volume of a body of water, usually an ocean, though it can occur in large lakes. Owing to the immense volumes of water and the high energy involved, tsunamis can destroy coastal regions.
Earthquakes, volcanic eruptions and other underwater explosions, landslides, underwater landslides and meteorite ocean impacts or similar impact events have the potential to generate a tsunami.

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How earthquakes work

http://www.youtube.com/watch?v=-zNyVPsj8zc&feature=related

Earthquake facts and a number of details about how Earthquakes work and form.

An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. Earthquakes are measured using observations from seismometers. Most earthquakes are measured mostly on the local magnitude scale, also referred to as the Richter scale. Magnitude 3 or lower earthquakes are mostly almost imperceptible and magnitude 7 and over potentially cause serious damage over large areas, depending on their depth. The largest earthquakes in historic times have been of magnitude slightly over 9, although there is no limit to the possible magnitude. The most recent large earthquake of magnitude 9.0 or larger was a 9.0 magnitude earthquake in Japan in 2011 (11-03-2011), and it was the largest Japanese earthquake since records began.

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