BASIC TERMS Flashcards
(25 cards)
What is an earthquake?
An earthquake is a shaking or trembling of the earth’s surface caused by seismic waves due to a sudden release of energy in the Earth’s crust or upper mantle.
What is the focus (hypocenter) of an earthquake?
The point inside the Earth where the energy is released during an earthquake.
What is the epicenter of an earthquake?
The point on the Earth’s surface directly above the focus where the earthquake is first felt.
What is an isoseismic line?
A line connecting all points on the surface where the intensity of an earthquake is the same.
What are foreshocks?
Mild earthquakes that precede the main earthquake event.
What are aftershocks?
Smaller earthquakes that follow a major earthquake.
What are earthquake swarms?
A series of small earthquakes occurring in a region for months without a major earthquake.
What is a fault zone?
A region where fractures in the Earth’s crust cause earthquakes due to the release of stress.
What are the three main types of faults associated with earthquakes?
Normal faults (divergent boundaries), reverse faults (convergent boundaries), and strike-slip faults (transform boundaries).
What are megathrust earthquakes?
The most powerful earthquakes that occur at subduction zones where one tectonic plate is forced beneath another.
How can volcanic activity cause earthquakes?
By the movement of magma and the release of elastic strain energy near volcanoes.
What are human-induced earthquakes?
Earthquakes caused by human activities like mining, petroleum extraction, artificial lakes, and nuclear tests.
What is reservoir-induced seismicity?
Earthquakes caused by the pressure from large artificial lakes altering stresses along existing faults.
What are the three depth categories of earthquakes?
Shallow (0-70 km), Intermediate (70-300 km), and Deep (300-700 km).
What is the Wadati–Benioff zone?
A zone of subduction along which deep-focus earthquakes are common.
What is the Circum-Pacific Belt?
The world’s most earthquake-prone region, also known as the Pacific Ring of Fire.
What is the Alpine Belt?
A seismic belt extending from Mexico through the Mediterranean to the Himalayas.
What is the Richter magnitude scale?
A logarithmic scale used to measure the energy released by an earthquake.
How does the energy release scale on the Richter magnitude scale?
An increase of 1 magnitude corresponds to 32 times more energy release.
What magnitude range is considered a ‘Great’ earthquake?
8.0 or higher.
What is the deadliest recorded earthquake?
The 1556 Shaanxi earthquake in China, which killed over 800,000 people.
What are the effects of earthquakes?
Shaking, ground rupture, landslides, fires, soil liquefaction, tsunamis, and floods.
What is soil liquefaction?
When water-saturated soil temporarily loses its strength and behaves like a liquid during an earthquake.
How do tsunamis form due to earthquakes?
Sudden displacement of large water volumes by megathrust earthquakes.
