12 Questions
What is the primary source of energy in an earthquake?
The sudden release of energy in the Earth's crust
What is the primary cause of tectonic earthquakes?
Sudden displacements along faults or fissures in the solid and rigid layer of the earth
What is the term used to describe earthquakes caused by the rising lava or magma beneath active volcanoes?
Volcanic Earthquakes
According to Richter (1958), what type of data is shown in Figure 1?
Major earth disturbances recorded by seismographs
What is a common characteristic of all types of earthquakes, as described in the text?
Ground shaking caused by the sudden release of energy
What type of earthquake is caused by human activities, such as mining or the collapse of underground cavities?
Mining-induced or large reservoir-induced earthquakes
What is the primary cause of volcanic earthquakes, and where do they typically occur?
Volcanic earthquakes are caused by fracturing of rocks, rising magma/lava, or the upward flow of magma, and they typically occur beneath the edifice of active volcanoes at very shallow depths (less than 1 kilometer to about 30 kilometers deep).
What is the difference between the focus and epicenter of an earthquake?
The focus is the point from which the seismic wave first emanates, while the epicenter is the point on the ground directly above the focus.
What is the classification of an earthquake with a focus depth of 250 kilometers?
The classification of an earthquake with a focus depth of 250 kilometers is intermediate focus.
What is the primary characteristic of shallow focus earthquakes that makes them the most destructive type?
Shallow focus earthquakes release 75% of their energy during the earthquake, making them the most destructive type.
What is the cause of collapse earthquakes, and where do they typically occur?
Collapse earthquakes are caused by the sudden collapse of the roof of a mine or cavern, and they typically occur in regions of underground caverns and mines.
What is the depth range of deep focus earthquakes?
Deep focus earthquakes have a focus depth greater than 300 kilometers.
Study Notes
Causes of Earthquakes
- Earthquakes are caused by the sudden release of energy in the Earth's crust, which can originate from various sources such as dislocations of the crust, volcanic eruptions, man-made explosions, or the collapse of underground cavities.
Types of Earthquakes
- Fault rupture-induced earthquakes
- Volcanic earthquakes
- Mining-induced earthquakes
- Large reservoir-induced earthquakes
Characteristics of Earthquakes
- Earthquakes can be defined as natural disturbances that cause ground shaking
- Ground shaking can range from feeble to violent trembling
Tectonic Earthquakes
- Tectonic earthquakes are caused by sudden displacements along faults or fissures in the solid and rigid layer of the earth
- They are of particular interest to structural engineers
Classification of Earthquakes according to Source Mechanism
Tectonic Earthquakes
- Caused by movement of the earth's surface plates or sudden displacement along fault fissures
- Can occur at shallow (0-70 km), intermediate (70-300 km), or deep (300-700 km) depths
Volcanic Earthquakes
- Caused by volcanic activities, such as fracturing of rocks, rising magma or lava, or the upward flow of magma
- Occur at very shallow depths (less than 1 km to about 30 km)
Other Types of Earthquakes
- Explosion Earthquakes: caused by underground detonation of chemical or nuclear devices
- Collapse Earthquakes: occur in regions of underground caverns and mines due to sudden collapse of the roof
- Earthquakes due to massive landsliding
Classification of Earthquakes according to Depth of Focus
Shallow Focus
- Focus depth less than 70 km
- Most destructive type, accounting for 75% of energy released during an earthquake
Intermediate Focus
- Focus depth from 70 to 300 km
Deep Focus
- Focus depth greater than 300 km
Key Terms
- Focus: the point from which the seismic wave first emanates
- Epicenter: the point on the ground directly above the focus
This quiz covers the different sources of earthquakes, including dislocations of the crust, volcanic eruptions, and human activities.
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