Science Grade 8 | Focus & Epicenter | Intensity & Magnitude|Active & Inactive Fault| Week 2

Bregilyn Balao-Sabado

11 Jan 202107:12

Summary

TLDRThis video explains earthquakes, their causes, and types of faults: normal, reverse, and strike-slip. It discusses how earthquakes are measured using the Richter and Mercalli scales, with magnitude indicating total energy and intensity describing observed effects. The video also covers the Philippine-specific PEIS scale, highlighting the country's high seismic activity due to its location along the Pacific Ring of Fire. Additionally, it addresses the importance of identifying active faults, earthquake preparedness, and emergency management phases: mitigation, preparedness, response, and recovery.

Takeaways

🌏 Earthquakes are caused by the movement of tectonic plates and the release of energy along fault lines.
📐 Faults are categorized into three types based on plate movement: normal, reverse, and strike-slip faults.
📍 The focus is the point within the Earth where rock displacement occurs, and the epicenter is the point on the surface directly above it.
🏗️ Structures near the epicenter experience more shaking and damage during an earthquake.
📊 To locate the epicenter, seismologists use seismograms from at least three different stations and a travel time graph for P and S waves.
🔍 Earthquakes are measured using two scales: magnitude, which is a single number representing total energy released, and intensity, which describes the observed effects.
🌡️ The Richter scale measures magnitude, while the Mercalli scale measures intensity using Roman numerals.
📊 The Peis or Fivox earthquake intensity scale is a scale developed specifically for the Philippines, ranging from 1 (scarcely perceptible) to 10 (completely devastating).
🌋 The Philippines experiences an average of 2000 earthquakes annually due to its location along the Pacific Ring of Fire.
🔬 Active faults are likely to cause future earthquakes and are considered geological hazards, while inactive faults have not shown seismic activity for thousands of years.
🗺️ The Philippines has five major active fault lines, and awareness of these can help in planning for and mitigating earthquake risks.
🛡️ Emergency management involves four phases: mitigation, preparedness, response, and recovery, which are crucial for dealing with disasters like earthquakes.

Q & A

What is a fault in the context of earthquakes?
-A fault is a crack or break in the Earth's crust due to the movement of tectonic plates. When these plates move along fault lines, energy is released that causes an earthquake.
What are the three types of faults based on the relative motion of tectonic plates?
-The three types of faults are normal fault, reverse fault, and strike-slip fault.
What is the focus of an earthquake?
-The focus of an earthquake is the zone within the Earth where rock displacement happens, causing an earthquake.
What is the epicenter of an earthquake?
-The epicenter is the point directly above the focus on the Earth's surface. Structures near the epicenter experience more shaking and more damage.
How do scientists locate the position of an earthquake's epicenter?
-Scientists use a seismogram reading from at least three different seismograph stations and a travel time graph, which shows the speed of both P and S waves, to locate the epicenter.
What are the two major scales used to measure earthquakes?
-The two major scales are magnitude and intensity. Magnitude measures the total energy released by an earthquake, while intensity measures the effects of the earthquake as perceived by an observer.
What is the Richter scale?
-The Richter scale measures the magnitude of an earthquake, which is a single number representing the total energy released at the focus.
What is the Mercalli scale?
-The Mercalli scale measures the intensity of shaking and is expressed using Roman numerals.
What is the PEIS and why was it developed?
-The PEIS, or PHIVOLCS Earthquake Intensity Scale, is a seismic scale used and developed by PHIVOLCS to measure the intensity of an earthquake. It was developed in response to the 1990 Luzon earthquake.
Why does the Philippines experience frequent earthquakes?
-The Philippines experiences frequent earthquakes because it lies along the Pacific Ring of Fire, which causes the country to have frequent seismic and volcanic activities.
What is an active fault?
-An active fault is a fault that is likely to become the source of another earthquake in the future, with movement observed or evidence of seismic activity during the last 10,000 years.
What are the five major active fault lines in the Philippines?
-The five major active fault lines in the Philippines are the Western Philippine Fault, Eastern Philippine Fault, South of Mindanao Fault, Central Philippine Fault, and Marikina Valley Fault System.
Can seismologists predict earthquakes?
-Seismologists cannot predict the exact time and date of an earthquake, but they can predict the locations where earthquakes are likely to occur due to the presence of faults.
What are the four phases of emergency management?
-The four phases of emergency management are mitigation, preparedness, response, and recovery.

Outlines

00:00

🌍 Introduction to Earthquakes and Faults

In this video, we revisit the concepts of earthquakes and faults. A fault is a crack in the Earth's crust caused by the movement of tectonic plates. When these plates move along fault lines, energy is released, causing an earthquake. Faults are classified into three types: normal, reverse, and strike-slip, based on the relative motion of the plates. The earthquake originates at the focus, a zone within the Earth where rock displacement occurs, with the epicenter being the point directly above it on the surface. Structures near the epicenter experience more shaking and damage.

05:01

📉 Measuring Earthquakes: Magnitude and Intensity

To locate an earthquake's epicenter, readings from at least three seismograph stations and a travel time graph are needed. Earthquakes are measured by two major scales: magnitude and intensity. Magnitude, measured by the Richter scale, is the total energy released by an earthquake at its focus and does not vary by location. Intensity, measured by the Mercalli scale, refers to the damage observed and varies depending on the observer's location. The intensity is expressed in Roman numerals.

🔢 The PHIVOLCS Earthquake Intensity Scale

PHIVOLCS (Philippine Institute of Volcanology and Seismology) developed the PHIVOLCS Earthquake Intensity Scale (PEIS) to measure earthquake intensity in the Philippines. This scale ranges from 1 (scarcely perceptible) to 10 (completely devastating). The table shows the corresponding descriptions for each intensity level. The Philippines experiences about 2000 earthquakes annually due to its location along the Pacific Ring of Fire, resulting in frequent seismic activities.

🌐 Active Fault Lines in the Philippines

The Philippines, an archipelago, has numerous faults with five major active fault lines: Western Philippine Fault, Eastern Philippine Fault, South of Mindanao Fault, Central Philippine Fault, and Marikina Valley Fault System. The Central Philippine Fault Zone is the most seismically active. Seismologists cannot predict the exact time and date of an earthquake, but they can predict locations based on fault lines. Knowing the location of active faults is crucial for preparedness and emergency management.

🚨 Emergency Management and Preparedness

Preparedness for earthquakes involves understanding the location of active faults and ensuring no important structures are built near them. PHIVOLCS provides maps and mobile apps to help locate active faults in the Philippines. Emergency management involves four phases: mitigation, preparedness, response, and recovery. Planning ahead for potential earthquakes helps in anticipating and effectively managing emergencies.

Mindmap

Keywords

💡Fault

A fault is a crack or break in the Earth's crust caused by the movement of tectonic plates. This concept is central to understanding earthquakes, as the movement along these faults is what releases energy, leading to seismic activity. In the video, faults are discussed in relation to their types—normal, reverse, and strike-slip—and their role in earthquake generation.

💡Tectonic Plates

Tectonic plates are large slabs of Earth's lithosphere that move over the asthenosphere. Their movement can cause earthquakes, volcanic activity, and the creation of mountain ranges. In the video, tectonic plates are explained as the drivers of fault movement, which ultimately leads to earthquakes.

💡Epicenter

The epicenter is the point on Earth's surface directly above the earthquake's focus, where the seismic waves first reach the surface. The video explains that the epicenter is the location that scientists calculate when determining where an earthquake occurred, and areas near the epicenter experience the most shaking and damage.

💡Focus

The focus is the point within the Earth where an earthquake originates, where rock displacement occurs. The video contrasts the focus with the epicenter, emphasizing that while the epicenter is on the surface, the focus is located underground and is the actual source of the earthquake.

💡Magnitude

Magnitude refers to the amount of energy released by an earthquake, measured on a scale such as the Richter scale. It is a single number that represents the size of the earthquake. The video discusses magnitude in relation to its consistency regardless of location and its role in determining the earthquake's strength and potential destructiveness.

💡Intensity

Intensity measures the effects of an earthquake at different locations, often expressed in Roman numerals on scales like the Mercalli intensity scale. Unlike magnitude, intensity varies based on the observer's location relative to the earthquake's epicenter. The video highlights the intensity as a subjective measure of the earthquake's impact.

💡Seismogram

A seismogram is a recording of the seismic waves produced by an earthquake, captured by a seismograph. The video mentions the need for seismogram readings from at least three different stations to accurately determine the earthquake's epicenter.

💡Pacific Ring of Fire

The Pacific Ring of Fire is a region around the Pacific Ocean where many earthquakes and volcanic eruptions occur due to tectonic plate boundaries. The video explains that the Philippines is part of this zone, which is why the country experiences frequent seismic and volcanic activity.

💡Active Fault

An active fault is a fault that has shown evidence of seismic activity in the last 10,000 years and is likely to produce future earthquakes. The video describes active faults as geologic hazards and discusses their presence in the Philippines, explaining why the country experiences frequent earthquakes.

💡Emergency Management

Emergency management involves preparing for, responding to, and recovering from disasters, including earthquakes. The video outlines the four phases of emergency management: mitigation, preparedness, response, and recovery, emphasizing the importance of planning ahead to minimize the impact of earthquakes.

Highlights

Introduction to earthquakes and faults and their significance in understanding seismic activities.

Explanation of fault as a crack or break in the earth's crust due to tectonic plate movements.

Description of how energy release along fault lines causes earthquakes.

Identification of three types of faults based on plate motion: normal, reverse, and strike-slip.

Definition of the focus as the zone within the earth where rock displacement occurs, causing an earthquake.

Explanation of the epicenter as the point directly above the focus, where scientists calculate the earthquake's location.

Observation that structures near the epicenter experience more shaking and damage.

Introduction to seismogram readings and the need for data from at least three seismograph stations to locate an earthquake's epicenter.

Explanation of how the travel time graph shows the speed of P and S waves.

Illustration of the relationship between the epicenter, focus, and fault line.

Description of the two major scales for measuring earthquakes: magnitude and intensity.

Explanation of how the Richter scale measures the magnitude of an earthquake using Hindu-Arabic numerals.

Introduction to the Mercalli scale for measuring the intensity of shaking using Roman numerals.

Introduction to the PHIVOLCS Earthquake Intensity Scale (PEIS) developed in response to the 1990 Luzon earthquake.

Description of the PEIS scale ranging from intensity 1 (scarcely perceptible) to intensity 10 (completely devastating).

Observation that the Philippines experiences an average of 2000 earthquakes annually due to its location along the Pacific Ring of Fire.

Distinction between active and inactive faults, with active faults showing movement or seismic activity in the last 10,000 years.

Identification of five major active fault lines in the Philippines: Western Philippine Fault, Eastern Philippine Fault, South of Mindanao Fault, Central Philippine Fault, and Marikina Valley Fault System.

Emphasis on the inability of seismologists to predict the exact time and date of earthquakes, but their ability to predict locations based on fault presence.

Recommendation for people to study maps to identify active faults near their locations and to prepare for potential earthquakes.

Introduction to emergency management phases: mitigation, preparedness, response, and recovery.

Suggestion to use PHIVOLCS maps and apps for locating active faults in the Philippines.