Characteristics, Measurement and Distribution of Earthquakes

What is an Earthquake?

A sudden and brief period of intense shaking of the ground, which is built from pressure of tectonic plate friction

What is the Epicentre?

The location on the surface of the Earth, directly above the focus

What is the Focus?

The centre of the earthquake underground

Which is more damaging : a shall focus or a deep focus?

A shallow focus because it is nearer the surface

What is an Afterschock?

Secondary earthquake that happens after an initial stronger earthquake

Why can the Aftershock sometimes be more damaging than the Earthquake itself?

They strike already weaker buildings, and may be the tipping point to destroying a building and taking lives

What are P Waves?

Longitudinal waves produced by seismic events like Eq's, and can go through both solids and liquids.

What are S Waves

Transverse waves produced by seismic events like Eq's, and can go through solids.

What is a Tsunami?

a series of large ocean waves caused by a sudden, powerful disturbance on the ocean floor, such as an earthquake, volcanic eruption, or underwater landslide

How is a Tsunami formed?

An earthquake causes plates to shift abruptly, causing a sudden displacement of water. A wave is then created that spread outwards, and can travel at up to 500mph across the deep ocean. The speed decreases near the shoreline, so the energy causes the wave to grow taller. It soon crashes onto the shoreline.

How can countries reduce vulnerability to Tsunami's?

Moving more populated areas in land, so that even if the tsunami hits the coastline, most people's lives would have been saved due to the direct wave not being in direct contact. They can also set up barriers that take the blow from a tsunami.

What is a Landslide?

The rapid downhill movement of and rock (mass movement).

How is a Landslide formed?

When gravities pull overpowers the strength and gradient of the slope, causing all the rocks and debris to move downwards.

How can countries reduce vulnerability to Landslides?

Placing people higher up, so that they are not at the bottom of elevated ground, as they therefore would not come in as much contact. Diverting the rocks away from populated areas with barriers and channels will also work

What is Liquefaction?

The process by which an earthquake's violent movement suddenly turns loose soil into liquid mud

How can countries reduce vulnerability to Liquefaction?

Strong buildings that are resistant to tilting or sliding when liquefaction occurs. Also moving people away from the area is the most reliable away. Well trained and well resourced excavators are highly necessary. Helicopters are also useful as they can't be affected by the ground.

What is the Richter Scale?

A scale that rates an earthquake's magnitude based on the size of its seismic waves.

What is the Mercalli Scale?

A scale that rates the intensity of an earthquake based on what people experience and the amount of damage done.