EarthquakeLocations and Vulnerabilities

Key Questions• Where do EQs occur?• What happens to the ground during an EQ?• Why do some places

suffer more than others?

• How can we mange the risks and vulnerabilities

to earthquakes?

Definition:A vibration in the earth’s crust caused by the sudden release of stored energy in the rocks.

See timelapse: https://www.youtube.com/watch?v=M3jHUGHOlhA

Why so many?• Majority of the plate

boundaries here are CONVERGENT boundaries.

• COMPRESSIONAL and DESTRUCTIVE nature of the plate movements here

• = plates more prone to fractures

• = more earthquakes found

How is energy built up in the crust?CLICK FOR LINK

Red is 0-33 km, Yellow is 33-100 km, Green is 100-400 km, Blue is >400 km depth

COMPARE:

Red is 0-33 km, Yellow is 33-100 km, Green is 100-400 km, Blue is >400 km depth

Red is 0-33 km, yellow is 33-100 km, green is 100-400 km, and blue is >400 km depth

COMPARE:

Anatomy of an Earthquake

Asperities (i.e. irregularities) in the crust cause the plates to become stuck. Pressure builds up

Anatomy of an Earthquake

Anatomy of an Earthquake

A?

B?

C?

What are the factors that can affect the impact

of an EQ?

Factors Magnitude of earthquake

Depth of focus Distance from the

epicentre Population density

Types of soil Level of preparedness

Magnitude• Magnitude of earthquake is measured on the Richter Scale which rates the magnitude of earthquake on a scale of 1 – 10

• Each increase in a whole number represents a tenfold increase in magnitude.

• Generally, the larger the magnitude, the greater the impact.

Danger

What is the relationship between high Mg EQs and Frequency?

Shallow vs Deep-focus

1. Crust is brittle and has more asperities

2. More solid, waves travel faster

1. Deeper into the mantle, the crust melts and asperities are less pronounced

2. Becomes more molten, waves travel slower

Other factors:• How does population density and dist. from epicentre affect the impact of an Earthquake?

• Level of preparation:• Is it possible to prepare for an

earthquake?• How?