Earthquakes & Earthquake Hazards

Flashcards based on key concepts from the lecture on earthquakes and earthquake hazards.

What is an earthquake?

An earthquake is ground shaking caused by the sudden and rapid movement of one block of rock sliding past another, usually associated with plate boundaries.

What are foreshocks?

Foreshocks are small earthquakes that sometimes precede a major earthquake by days or years.

What is the process called when deformed rocks 'snap back' to their original position?

Elastic rebound.

What are aftershocks?

Aftershocks are smaller earthquakes that occur after a strong earthquake, diminishing in frequency and intensity over time.

What are thrust/reverse faults associated with?

Convergent plate boundaries and they produce most of Earth’s powerful earthquakes.

What are P waves?

Primary waves; compression waves that can travel through all materials.

What are S waves?

Secondary waves; shear waves that can only travel through solid material.

What is the Modified Mercalli Intensity scale?

A scale developed to estimate the intensity of an earthquake based on observed property damage.

What does the Richter scale measure?

The amplitude of the largest seismic wave recorded on a seismogram.

What is liquefaction?

The phenomenon where loosely packed, waterlogged sediments behave as a fluid during intense shaking of an earthquake.

What are seismic gaps?

Tectonically quiet zones along a fault where strain is currently building up, suggesting future earthquakes.

What is the moment magnitude scale?

A newer scale that measures the total energy released during an earthquake, calculated by the average amount of slip on the fault and the area of the fault surface that slipped.

What factors affect earthquake destruction?

Intensity and duration of vibrations, construction practices, and the nature of the material on which structures rest.

What is the main cause of tsunami generation?

Displacement of the ocean floor during an earthquake.

How can long-range earthquake predictions be helpful?

They provide probabilities of earthquakes of certain magnitudes occurring over decades, aiding in planning and construction codes.