Plate Tectonics Lecture by Engr. Ryan M. Layug

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Questions and Answers

What does the elastic rebound theory explain about earthquakes?

Earthquakes occur randomly without any buildup of stress.

One earthquake can prevent all future earthquakes along a fault.

Earthquakes are solely caused by volcanic eruptions.

Earthquakes relieve accumulated stress along a fault segment. (correct)

Which of the following is a consequence of the elastic rebound theory?

Accumulated stresses can take time to build back up before the next quake. (correct)

All earthquakes are of equal magnitude and frequency.

Fault segments can rupture multiple times within a short period.

The energy released is irrelevant to future earthquakes.

What does the plate tectonic theory propose about the Earth's crust?

It consists of several large rigid blocks called crustal plates. (correct)

It is primarily made of molten lava and magma.

It remains unchanged regardless of geological processes.

It is a single solid structure that does not move.

What type of plate boundary is characterized by plates moving towards each other?

Convergent boundary Signup and view all the answers

Which statement best describes a transform boundary?

Plates slide past each other without creating or destroying crust. Signup and view all the answers

How does the theory of continental drifts relate to plate tectonics?

Continental drifts contribute to the understanding of plate movements. Signup and view all the answers

What determines the boundaries of the tectonic plates?

They are based on the relative motion of crustal plates. Signup and view all the answers

What is the primary driving force behind the movement of tectonic plates?

Heat from the Earth's core causing convection currents. Signup and view all the answers

What does the PEIS specifically measure regarding earthquakes?

The effect of the earthquake on people and structures Signup and view all the answers

Why was the PEIS developed in the Philippines?

Due to the unique geological considerations of the region Signup and view all the answers

What is the PEIS intended to represent graphically during an earthquake?

The distribution of intensity using isoseismals Signup and view all the answers

How is earthquake magnitude represented?

By Arabic numbers like 4.8 or 9.0 Signup and view all the answers

What method is used to determine the total energy release of an earthquake?

Calculating ground displacement and vibration Signup and view all the answers

Which scale did the PEIS replace in the Philippines?

Rossi-Forel scale Signup and view all the answers

What happens to ground vibration as the distance from the earthquake's epicenter increases?

It gradually decreases Signup and view all the answers

What aspect makes magnitude a more precise measure than intensity?

Magnitude is calculated using instruments rather than subjective observations Signup and view all the answers

What occurs at a convergent boundary?

Plates collide and form mountain systems. Signup and view all the answers

Which term describes a fault that has moved within the last 10,000 years?

Active fault Signup and view all the answers

What characterizes divergent boundaries?

Tectonic plates move away from each other. Signup and view all the answers

What happens at transform boundaries?

Plates move sideways past each other. Signup and view all the answers

Which of the following is a well-known transform boundary?

San Andreas Fault Signup and view all the answers

What defines an earthquake?

Sudden shaking of the ground from rock movement. Signup and view all the answers

What is typically true of faults?

They can extend hundreds of kilometers across the surface. Signup and view all the answers

Which of the following statements about faults is incorrect?

All earthquakes occur far from tectonic plate boundaries. Signup and view all the answers

What primarily composes tectonic plates?

Oceanic or continental crust Signup and view all the answers

What occurs when an oceanic plate collides with a continental plate?

Formation of deep oceanic trenches Signup and view all the answers

What is the Pacific Ring of Fire known for?

Significant volcanic eruptions and earthquakes Signup and view all the answers

Which theory explains the origin of earthquakes related to plate movements?

Plate Tectonic Theory Signup and view all the answers

Which of the following describes earthquakes?

Vibrations caused by a disturbance of earth's equilibrium Signup and view all the answers

What factor contributes to the movement and formation of tectonic plates?

Mantle convection Signup and view all the answers

What is ultimately a result of the interactions between tectonic plates?

Elastic impulses or waves Signup and view all the answers

What geological feature often results from the subduction of an oceanic plate?

Volcanic island arcs Signup and view all the answers

What does intensity measure in relation to earthquakes?

The qualitative effects on structures and human reactions Signup and view all the answers

Which intensity scale is currently used in the United States for measuring earthquake effects?

Modified Mercalli Intensity Scale Signup and view all the answers

How is the Modified Mercalli Intensity Scale designated?

Using Roman Capital Numerals Signup and view all the answers

Which of the following best describes the nature of the Modified Mercalli Intensity Scale?

It is an arbitrary ranking based on observed effects Signup and view all the answers

At what intensity level do structural engineers typically provide information?

VIII or above Signup and view all the answers

What was the purpose behind developing the PHIVOLCS Earthquake Intensity Scale (PEIS)?

To evaluate the intensity of earthquakes specifically in the Philippines Signup and view all the answers

Which of the following key responses is NOT included in the intensity scale of the Modified Mercalli Intensity?

Magnitude estimation Signup and view all the answers

What kind of measure is the intensity of an earthquake considered?

A qualitative measure based on observations Signup and view all the answers

Study Notes

Plate Tectonics

Tectonic plates consist of oceanic and continental crust, influencing continental drift.
Oceanic plates slide beneath continental plates, forming deep oceanic trenches upon collision.

Pacific Ring of Fire

A geologically active region surrounding the Pacific Ocean, notable for frequent volcanic eruptions and earthquakes.

Earthquake Causes

Earthquakes are caused by disturbances in the elastic or gravitational equilibrium of rocks beneath the Earth's surface.
Major theories explaining earthquake origins include the Elastic Bound Theory and Plate Tectonic Theory.

Elastic Bound Theory

This theory describes earthquakes as a process that relieves accumulated stress on faults, leading to seismic moments measured as quake size.
After an earthquake, a segment of the fault does not rupture again until sufficient stress builds up, defining intervals between quakes.

Plate Tectonic Theory

Earth’s crust consists of large, rigid plates that can move in various directions, resulting in three types of boundaries:
- Divergent (constructive margin)
- Convergent (destructive margin)
- Transform (conservative margin)

Types of Plate Boundaries

Convergent boundaries: Where two plates collide, forming major mountain systems like the Himalayas.
Divergent boundaries: Plates move apart, exemplified by the Mid-Atlantic Ridge.
Transform boundaries: Plates slide past one another without creating or destroying lithosphere, e.g., San Andreas Fault, 1,200 km long.

Faults and Earthquakes

Faults are fractures where ground movement occurs; active faults have moved in the last 10,000 years.
Earthquakes predominantly originate along tectonic plate boundaries and faults.

Earthquake Intensity

Intensity measures the qualitative effect of an earthquake on structures and human perception, represented by Roman numerals.
The intensity scale considers factors like human reactions and structural damage.

Modified Mercalli Intensity Scale (MMI)

Developed in 1931, this scale quantifies earthquake effects from imperceptible shaking to catastrophic destruction based on observable effects, without mathematical basis.

PHIVOLCS Earthquake Intensity Scale (PEIS)

Created by the Philippine Institute of Volcanology and Seismology after the 1990 Luzon earthquake, it evaluates earthquake impacts based on local geography and structures.
PEIS replaced the Rossi-Forel scale in the Philippines in 1996.

Isoseismals

Graphical representation of seismic intensity distribution, with lines connecting areas of equal intensity during an earthquake.

Magnitude of Earthquakes

Magnitude quantifies the energy released, represented by Arabic numbers (e.g., 4.8, 9.0).
It is derived from the size of seismic waves measured with instruments, distinct from intensity which relies on observational effects.
Magnitude calculations account for the distance of measuring instruments from the earthquake epicenter, reflecting energy dissipation over distance.

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Description

This quiz covers the fundamental concepts of plate tectonics as presented in the lecture by Engr. Ryan M. Layug at Tarlac State University. Explore the dynamics of Earth’s lithosphere and the implications of tectonic movements. Test your understanding of geological processes and their impact on our planet.