Science Grade 8 | Focus & Epicenter | Intensity & Magnitude|Active & Inactive Fault| Week 2
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
- đ Earthquakes are caused by the movement of tectonic plates and the release of energy along fault lines.
- đ Faults are categorized into three types based on plate movement: normal, reverse, and strike-slip faults.
- đ The focus is the point within the Earth where rock displacement occurs, and the epicenter is the point on the surface directly above it.
- đïž Structures near the epicenter experience more shaking and damage during an earthquake.
- đ To locate the epicenter, seismologists use seismograms from at least three different stations and a travel time graph for P and S waves.
- đ Earthquakes are measured using two scales: magnitude, which is a single number representing total energy released, and intensity, which describes the observed effects.
- đĄïž The Richter scale measures magnitude, while the Mercalli scale measures intensity using Roman numerals.
- đ The Peis or Fivox earthquake intensity scale is a scale developed specifically for the Philippines, ranging from 1 (scarcely perceptible) to 10 (completely devastating).
- đ The Philippines experiences an average of 2000 earthquakes annually due to its location along the Pacific Ring of Fire.
- đŹ 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.
- đșïž The Philippines has five major active fault lines, and awareness of these can help in planning for and mitigating earthquake risks.
- đĄïž 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
đ 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.
đ 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.
đą 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.
đ 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.
đš 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
đĄFault
đĄTectonic Plates
đĄEpicenter
đĄFocus
đĄMagnitude
đĄIntensity
đĄSeismogram
đĄPacific Ring of Fire
đĄActive Fault
đĄEmergency Management
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.
Transcripts
in our previous video
you learned about earthquakes and faults
if you haven't watched it yet
you can post this video and watch it for
better understanding of our lesson
do you still remember what fault is a
fault is a crock or break on earth's
crust due to the movement of tectonic
plates
and when tectonic plates move along
fault lines
energy is released that cause an
earthquake
fault has three types based on relative
motion of the plates
they are normal fault reverse fault and
strike slip fault
the earthquake occurs at the focus this
is a zone within the earth
where rock displacement happens and
causes an earthquake
the point directly above the focus is
called epicenter
this is the location that scientist
calculates while focus is directly below
however scientists cannot determine its
depth
structures near the epicenter experience
more shaking and more damage
[Music]
in addition to locate the position of
the earthquake's epicenter
we need a seismogram reading from at
least three different seismograph
stations and travel time graph which
shows the speed of both
p and s waves
this illustration shows the epicenter
focus and fault line
[Music]
there are two major scales in which
earthquakes are measured we have
magnitude and intensity the magnitude of
a particular earthquake is a single
number which does not vary from place to
place
magnitude is the total energy released
by an earthquake
at its focus earthquake of large
magnitude are stronger and generally
more destructive than those of
small magnitude the richter scale
measures earthquake becomes weaker
outward from the epicenter
magnitude uses hindu arabic numerals
while intensity is all about damages or
effect of the earthquake as perceived by
an observer
[Music]
the mercury scale measures the intensity
of shaking
intensity is expressed using roman
numerals
let us see the measure of intensity and
magnitude corresponds to each other as
shown by the table
[Music]
what is peis peis
or fivox earthquake intensity scale
is a seismic scale used and developed by
the fevox to measure the intensity of an
earthquake
it was developed as upon a specific
response to 1990 luzon earthquake
the vox uses the following scale to
describe the intensity of earthquake in
the philippines
this table shows us the vivox earthquake
intensity scale
we have intensity scale 1 to 10 and its
description
one is scarcely persistable 2
is slightly felt 3 week
four moderately strong five
strong six very strong
seven destructive eight very destructive
nine devastating and then
completely devastating
according to data recorded by fivox our
country has an average of 2000
earthquakes every year this is because
the philippines lies
along the pacific ring of fire which
causes the country to have frequent
seismic and volcanic activities
[Music]
many earthquakes of smaller magnitude
occur very regularly due to the
convergence of major tectonic plates in
the region
earthquakes occur mostly along fault
lines
a fault may either be active or inactive
according to its activity
in addition there are several acting
faults in our country
which explains why we experience
earthquake very often
when we say active fault it is a fault
that is likely to become the source of
another earthquake sometime in the
future
geologists commonly consider faults to
be active
if there has been movement observed or
evidence of seismic activity
during the last 10 000 years
active faulting is considered to be a
geologic
hazard inactive fault is a fault which
has not displayed any seismic activity
for more than thousands of years
our country which is an archipelago
consists of numerous numbers of faults
there are five major active fault lines
in the country
namely western philippine fault eastern
philippine fault
south of mindanao fault central
philippine fault
and marikina valley fault system
[Music]
the central philippine fault zone
consisting of ginayangan
mesbate and central lady fault are the
most seismically active regions
transacting the islands of bundok to
leyte
can we predict earthquakes seismologists
cannot predict the time and date in
which an earthquake may occur
but they can predict the places that an
earthquake will occur
due to the presence of faults
[Music]
study the map and find out where you
live is there an active fault
passing by your town province or region
if so are you and your family prepared
for the occurrence of an earthquake
it is important to know the location of
active vaults
as much as possible no important
structure should be built near on them
vvox has a map that shows the active
faults in the philippines
they also have apps that can be
installed in our cellular phones
the best thing to do is to plan ahead it
is the same as anticipating the words to
come up with the best solution
to an unexpected and desirable event
such as
that of calamity or disaster
we term these as emergency management
there are four phases in an emergency
management
we have mitigation preparedness
response and recovery
[Applause]
you
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