Geology Chapter: Lithosphere and Asthenosphere

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Questions and Answers

What is the lithosphere primarily composed of?

Solid rock (correct)

Weak and soft minerals

Liquid magma

Metamorphic layers

Which layer beneath the lithosphere is characterized as a soft, weak zone?

Asthenosphere (correct)

Core

Crust

Mantle

Where do most earthquakes occur on Earth?

In the polar regions

Along ocean trenches and continental edges (correct)

At the tops of mountains

In the center of continents

What primarily constitutes the surface along which most slip occurs during an earthquake?

The actual fault surface Signup and view all the answers

What geological feature is associated with a high frequency of earthquakes?

Mid-ocean ridges Signup and view all the answers

What is a common consequence of large earthquakes near ocean trenches?

Generation of tsunamis Signup and view all the answers

In which fault type did the 1983 Borah Peak earthquake occur?

Normal fault Signup and view all the answers

What was the magnitude of the Hebgen Lake earthquake in 1959?

7.3 (Mw) Signup and view all the answers

Which term refers to processes that deform the crust and mantle?

Tectonic activity Signup and view all the answers

Which of the following formations is made by the movement along a fault?

Fault scarp Signup and view all the answers

What was one consequence of the Tohoku earthquake in 2011?

Destruction of 125,000 buildings Signup and view all the answers

Which of the following statements about fault scarps is true?

They are created by normal faults and can obscure with erosion. Signup and view all the answers

Which areas are noted for having abundant earthquakes?

Middle East, China, and Tibet Signup and view all the answers

What is the main role of geophysical instruments in earthquake studies?

To record and process data on seismic waves Signup and view all the answers

What does the term 'asthenosphere' mean?

Soft, weak zone Signup and view all the answers

Where was the epicenter of the 2011 Tohoku earthquake located?

On the seafloor east of Japan Signup and view all the answers

How deep was the main hypocenter of the Tohoku earthquake?

32 km Signup and view all the answers

What characterizes the East California Shear Zone?

It is associated with a zone of strike-slip faults. Signup and view all the answers

How do earthquake waves travel through rocks?

As seismic vibrations Signup and view all the answers

What natural disaster was triggered by the Tohoku earthquake?

Tsunami Signup and view all the answers

Which city was notably affected by the 2010 Haiti earthquake?

Port-au-Prince Signup and view all the answers

What does the term 'seismic' derive from?

A Greek word for earthquake Signup and view all the answers

What type of fault was involved in the Hebgen Lake earthquake?

Normal fault Signup and view all the answers

Which of the following describes the economic impact of the Tohoku earthquake?

Most expensive natural disaster in history Signup and view all the answers

What event is described as the most severe and destructive earthquake experienced in the Philippines during the last 20 years as of 1968?

Casiguran Earthquake Signup and view all the answers

What was the intensity of the Casiguran Earthquake according to the Rossi-Forel Intensity Scale?

VIII Signup and view all the answers

What geological process is happening at the plate boundary involving the Indian-Australian plate?

Subduction Signup and view all the answers

What happens to a seismic wave when it passes from a slower material to a faster one?

It is refracted to a shallower angle Signup and view all the answers

What does the Engineering Geology and GeoHazard Assessment process require from land development project proponents?

A site geological scoping survey request Signup and view all the answers

Which building collapsed instantly during the Casiguran Earthquake?

Ruby Tower Signup and view all the answers

What type of earthquake-related damage was sustained by several major buildings near Binondo and Escolta in Manila?

Minor structural damages Signup and view all the answers

What is the purpose of the DENR AO2000-28 issued by the Philippine government?

To protect lives and property from geologic hazards Signup and view all the answers

What effect can liquefaction have on structures built over it?

Sinking or tilting of structures Signup and view all the answers

Which of these is NOT a common effect of landslides triggered by earthquakes?

Formation of quicksand Signup and view all the answers

What type of earthquake hazard is characterized by a series of waves caused by seismic activity under the sea?

Tsunami Signup and view all the answers

How does soft ground affect earthquake vibrations?

It amplifies the effects of vibrations Signup and view all the answers

Which construction technique is most likely to protect buildings from earthquake damage?

Ensuring proper mortar is used to hold bricks Signup and view all the answers

What is the primary characteristic of resonance frequency in buildings?

It depends on the building's height Signup and view all the answers

What is a common cause of damage in tall buildings during an earthquake?

Concentration of motion in the upper storeys Signup and view all the answers

Which factor contributes to better survival rates in buildings during earthquakes?

Incorporation of lightweight materials Signup and view all the answers

Study Notes

Earth's Layers and Tectonics

The lithosphere, meaning "stone" in Greek, is a rigid layer formed by the upper mantle and crust.
The asthenosphere is a soft, weak zone beneath the lithosphere, with a thickness of approximately 80 to 150 km, reaching depths of about 250 km.

Earthquake Distribution

Earthquakes are concentrated in specific belts, particularly along the western coasts of North and South America and mid-ocean ridges.
Regions like the Middle East, China, and Tibet experience abundant earthquakes, while many continental interiors are relatively quiet.
Areas with narrow continental shelves see more earthquakes, while wider shelves, like the eastern coasts of the Americas, experience fewer.
Ocean trenches and island arcs are characterized by a high frequency of earthquakes, often linked to the largest and most destructive events.

Notable Earthquake Events

The 2011 Tohoku earthquake in Japan had a magnitude of 9.0, one of the largest ever recorded, resulting in over 24,000 casualties and extensive damage exceeding $300 billion.
The 2010 Haiti earthquake, magnitude 7.0, occurred near Port-au-Prince, causing significant devastation due to its proximity to an active fault line.
The 1959 Hebgen Lake earthquake (magnitude 7.3) resulted in the formation of Earthquake Lake in Montana due to massive ground movement.

Seismic Waves

Seismic waves, generated by earthquakes, travel through rocks and are studied by seismologists using geophysical instruments for data on their patterns and origins.
The rupture area can significantly affect the characteristics of seismic waves during an earthquake, which may differ based on materials they pass through.

Earthquake Hazards

Liquefaction occurs when saturated sediments behave like liquids, leading to potential sinking or tilting of structures.
Landslides can result from strong shaking, causing erosion and blockage of infrastructure.
Tsunamis are series of waves triggered by underwater earthquakes, leading to flooding and coastal damage.

Civil Engineering Considerations

Soft ground amplifies earthquake vibrations, increasing structural vulnerability, while harder rocks mitigate shaking effects.
Effective building design and materials are crucial; lightweight materials and proper construction techniques enhance survival rates during seismic events.
Resonance frequency, influenced by building height, can lead to increased damage; tall buildings may sustain more damage at lower frequencies.

Ground Conditions and Building Design

Structures built on flood plains or reclaimed land are more susceptible to damage due to amplified vibrations.
Poor construction practices, like inadequate tying of slab walls and floors, increase the risk of structural failure during earthquakes.
Buildings constructed with high-quality materials and proper bracing generally fare better in seismic events.

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Description

This quiz explores the characteristics and functions of the lithosphere and asthenosphere. Discover how these layers of the Earth's structure interact and their significance in geological processes. Test your understanding of these fundamental concepts in geology.