Lecture 10 Flashcards
What is an earthquake?
An earthquake is the vibration of Earth produced by the rapid release of energy.
What is the hypocentre?
Point of energy released during earthquake, radiating in all directions
What is the epicentre?
Location on Earth’s surface directly above hypocentre.
What is elastic rebound?
springing back of rocks after stress is overcome
What are foreshocks and aftershocks?
Foreshocks: Small earthquakes that often precede a major earthquake.
Aftershocks: Smaller earthquakes that follow a major earthquake.
What is seismology?
The study of earthquake waves, dating back 2000 years to the Chinese.
What are seismographs?
Instruments that record seismic waves by detecting Earth’s movement relative to a stationary mass.
What are seismograms?
Records that reveal the behavior of seismic waves.
What are the two main categories of seismic waves?
Body waves: Travel through Earth’s interior (P and S waves).
Surface waves: Travel along Earth’s outer part (L waves).
Describe P waves and S waves.
P waves: Push-pull motion; travel through solids, liquids, and gases.
S waves: Shear motion; travel only through solids.
What are surface (L) waves?
Complex motion waves that cause :
- greatest destruction
- largest amplitude
- slowest velocity
How is the epicentre of an earthquake located?
By analyzing the difference in arrival times of P and S waves at three seismic stations.
What are the two measurements of earthquake size?
- Intensity (Degree of shaking + damage)
- Magnitude (Energy released at source)
What is the Richter scale?
A scale introduced by Charles Richter in 1935, measuring the amplitude of the largest seismic wave.
What is the Moment Magnitude (MW) scale?
A scale that measures the amount of displacement, area of rupture, and shear strength of rocks.
What factors influence destruction from seismic vibrations?
Intensity and duration of vibrations.
Nature of the material beneath the structure.
Design of the structure.
What is liquefaction?
When saturated, unconsolidated materials behave like a liquid during an earthquake, causing instability.
What causes tsunamis?
Vertical displacement along a shallow oceanic fault or earthquake-triggered submarine landslides.
What are other hazards associated with earthquakes?
Landslides, ground subsidence, and fires.
Can earthquakes be predicted?
Short-range predictions: Not reliable; focus on precursors like uplift and strain in rocks.
Long-range forecasts: Probabilities over 30–100 years based on repetitive cycles and seismic gaps.
How do seismic waves reveal Earth’s interior?
Their travel times vary based on material properties, indicating Earth’s distinct layers.
Why can’t S waves travel through liquids?
S waves rely on shear motion, which liquids cannot support.
The ________ is the point of origin for an earthquake.
Hypocentre.
________ is the widely accepted explanation for the mechanism that generates earthquakes.
Reid’s elastic rebound theory.
