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

Summary

This 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.