Introduction to Seismology

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Questions and Answers

What do strong ground motions typically originate from?

Only simulated computer models

Observations from accelerometers or seismometers (correct)

Human activities such as construction

Natural disasters only

What is the foundation of the theory of plate tectonics?

Theory of continental drift and floor spreading (correct)

Expanding universe theory

Surface weather patterns

Volcanic activity

What does the term 'Elastic Rebound' refer to in seismic studies?

A method of predicting earthquakes

A phase of rock formation after an earthquake

The ability of rocks to bounce back after deformation (correct)

The initial release of energy before an earthquake

What type of materials make up the crust part and the rigid uppermost part of the mantle?

Solid and rigid rocks Signup and view all the answers

What behavior is associated with materials in the upper mantle with low viscosity and shear strength?

They can flow like liquid over geological timescales. Signup and view all the answers

According to Reid's studies, what event led to the formulation of the Elastic Rebound theory?

The 1906 San Francisco Earthquake Signup and view all the answers

What can strongly influence the occurrence of earthquakes?

The movement of tectonic plates Signup and view all the answers

What is a key characteristic of how ground motion is recorded or simulated?

Observations can come from both natural and simulated sources. Signup and view all the answers

What is the primary focus of engineering seismology?

Assessing seismic hazards for engineering Signup and view all the answers

Which of the following is NOT included in the study of seismology?

Meteorological phenomena Signup and view all the answers

What aspect of earthquakes does paleoseismology help to infer?

Past earthquakes Signup and view all the answers

Which of the following methods is utilized in assessing expected ground motions from an earthquake?

Studying strong ground motions Signup and view all the answers

Which element is associated with the field of seismology?

Creation of synthetic seismograms Signup and view all the answers

What is the purpose of studying earthquake history and tectonics in engineering seismology?

To assess future earthquake occurrences and characteristics Signup and view all the answers

How fast do tectonic plates typically move?

5 cm per year Signup and view all the answers

What percentage of the earth's volcanoes are found near the tectonic plate boundaries of the Pacific Ocean?

80% Signup and view all the answers

Which of the following best describes a fault?

A zone where two sides of the earth's crust have moved. Signup and view all the answers

Which of the following best describes the relationship between seismology and earthquake engineering?

Seismology provides data critical for assessing earthquake hazards in engineering. Signup and view all the answers

What is the primary speed range of the lateral movement of tectonic plates per year?

50-100 mm Signup and view all the answers

What kind of seismic sources does seismology study?

Artificial and natural sources Signup and view all the answers

What happens to a tectonic plate during subduction?

It plunges into the mantle. Signup and view all the answers

What is a characteristic of small earthquakes related to tectonic plate movement?

They happen relatively frequently. Signup and view all the answers

Which geological events are commonly associated with plate boundaries?

Earthquakes and volcanoes Signup and view all the answers

What is indicated about the depth of faults?

They can vary from one to over one hundred miles deep. Signup and view all the answers

Which of the following regions is known for subduction activity?

The west coast of South America Signup and view all the answers

In which area does the Pacific plate subduct beneath the North American plate?

Pacific Northwest Signup and view all the answers

What signifies a subduction zone?

One plate sliding beneath another Signup and view all the answers

What is the relationship between plate boundaries and tectonic activity?

Natural disasters are frequent at plate boundaries. Signup and view all the answers

Which of these processes typically occurs due to subduction?

Magmatic activity leading to volcanism Signup and view all the answers

Which natural feature is formed along subduction zones?

Mountainous ranges Signup and view all the answers

What is a common consequence of the tectonic plates in the Pacific basin subducting beneath continental plates?

Subduction-zone volcanism Signup and view all the answers

Where are earthquakes generally concentrated?

In the vicinity of faults Signup and view all the answers

What characteristic tends to increase the likelihood of a fault producing a large earthquake?

The rapidity of its movement Signup and view all the answers

Which type of fault is defined by movements that occur obliquely across the fault surface?

Oblique-slip fault Signup and view all the answers

What is true about earthquakes occurring on 'unknown' or 'inactive' faults?

They continue to occur despite being labeled as inactive Signup and view all the answers

What typically characterizes the seismicity of larger faults?

They are more likely to produce larger earthquakes Signup and view all the answers

Study Notes

Seismology Overview

Scientific study of earthquakes and the propagation of elastic waves through Earth.
Encompasses environmental effects like tsunamis and various seismic sources including volcanic and tectonic processes.
Includes paleoseismology, which infers information about past earthquakes through geological studies.

Engineering Seismology

Focuses on assessing seismic hazards for engineering purposes.
Analyzes earthquake history and tectonics to understand potential earthquakes and their characteristics.
Examines strong ground motions from earthquakes, either from accelerometers, seismometers, or computer simulations.

Theory of Plate Tectonics

Derived from continental drift and sea-floor spreading theories.
Plates consist of the Earth's crust and upper mantle, with fluid-like behavior on geological timescales.

Elastic Rebound Theory

Concept introduced by Reid based on the 1906 San Francisco Earthquake.
Describes the release of energy caused by the sudden slip of tectonic plates, resulting in earthquakes.

Plate Boundaries and Earthquake Activity

Lateral movement of tectonic plates occurs at speeds of 50-100 mm annually.
Earthquake activity, volcanic eruptions, and the formation of mountains and oceanic trenches typically occur along plate boundaries.

Subduction Zones

Key regions where one tectonic plate plunges beneath another.
Characterized by volcanic activity as the subducted plate melts and re-emerges as lava.
Major subduction zones include:
- Nazca and South American Plate boundaries (West Coast South America)
- Cocos and Caribbean plates (Central America)
- Philippine and Eurasian plates (Taiwan and Japan)
- Juan de Fuca and North American Plates (Pacific Northwest)

Pacific Ocean and Volcanoes

Approximately 80% of Earth's volcanoes are located near the Pacific tectonic plate boundaries.
The Pacific Basin features extensive subduction of plates beneath continental plates.

Faulting

A fault is a fracture zone where sections of Earth's crust have moved.
Faults can be extensive and deep but may not always be visible on the surface.
Earthquakes are more frequent near active faults, with larger faults likely to produce significant seismic events.

Fault Types and Movement

Oblique-slip faults exhibit both strike-slip and dip-slip movements.
Seismic activity can occur on "unknown" or "inactive" faults, as seen in multiple earthquakes during the 1980s without surface faulting.

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Description

This quiz explores the fundamentals of seismology, focusing on the scientific study of earthquakes and the propagation of elastic waves through the Earth. It also delves into the environmental effects caused by earthquakes, providing a comprehensive understanding of the subject.