6. TYPES OF FAULT
A normal fault is a geological
fault where the hanging wall
has moved downward relative
to the footwall due to
extensional forces, typically
associated with divergent plate
boundaries.
Normal faults can be observed
in various geological settings,
such as rift zones and areas
undergoing tectonic stretching.
7. TYPES OF FAULT
A reverse/thrust fault is a
geological fault where the
hanging wall has moved
upward relative to the footwall
due to compressional forces,
often associated with
convergent plate boundaries.
This type of fault can result in
significant geological features
and can also generate
8. TYPES OF FAULT
A strike-slip fault is a
geological fault where the
movement of tectonic
plates occurs
predominantly horizontally,
parallel to the fault plane,
in opposite directions,
typically due to horizontal
shearing forces.
14. EARTHQUAKE
• Focus is the point
within Earth where the
earthquake starts.
• Epicenter is the
location on the surface
directly above the focus.
• Faults are fractures in
Earth where movement
has occurred.
16. • An aftershock is a
small earthquake
that follows the
main earthquake.
• A foreshock is a
small earthquake
that often precedes
a major earthquake.
17. What is a seismologist? A seismologist
studies earthquakes and their waves to
figure out the Earth's structure and
composition.
Philippine Institute of Volcanology and Seismology
PHIVOLCS monitors volcano, earthquake,
and tsunami activity, and issues warnings as
necessary. It is mandated to mitigate
disasters that may arise from such
volcanic eruptions,earthquakes,tsunamis,
and other relatedgeotectonicphenomena
18. • The Philippines has a total of 65 seismic stations, 29 of which are manned,
30 are unmanned, and 6 volcano stations.The central operating station is
located at PHIVOLCS Main Office, Diliman, Quezon City. All
information is received at the Data Receiving Center (DRC), which is
operated 24/7 by the Seismological Observation and Prediction Division
(SOEPD)
19. Visayas cluster center is
comprised of nine (9)
staff-controlled seismic
stations, 25 satellite-
telemetered seismic
stations, six (6) sea level
monitoring stations for
tsunami detection, and
seven (7) community
tsunami alerting stations.
20. • The Department of Science and
Technology - Philippine Institute
of Volcanology and Seismology
(DOST-PHIVOLCS), in
partnership with the Municipality
of Dueñas and Central Azucarera
de San Antonio, Inc. (CASA),
inaugurated the Dueñas Iloilo
Seismic Station (DUIP) last 28
April 2022. DUIP, which is the
first satellite-telemetered seismic
station in Iloilo Province, is
located at CASA Sugarcane
Plantation, Brgy. Ponong Pequeño
in Dueñas.
21. •The Department of
Science andTechnology -
Philippine Institute of
Volcanology and
Seismology (DOST-
PHIVOLCS)
inaugurated the Ibajay
Seismic Station February
27, 2018 at Ibajay
Seismic Station in Aklan
State University, Ibajay,
Aklan.
23. • Seismograms are traces
of amplified,
electronically recorded
ground motion made by
seismographs
24. SEISMIC WAVES
Earthquakes generate four
principal types of elastic
waves; two, known as:
body waves, travel within
the Earth,
surface waves, travel along
its surface.
25. BODY WAVES
Body waves are those waves
that travel through the earth.
They originate at the epicenter
of the earthquake and travel
through the earth at amazing
speeds.
26. SURFACE WAVES
Surface waves are similar in
nature to water waves and travel
just under the Earth’s surface.
They are typically generated
when the source of the
earthquake is close to the Earth’s
surface.
Although surface waves travel
more slowly than S-waves, they
can be much larger in amplitude
and can be the most destructive
type of seismic wave.
27. There are two ways by which we can measure the strength of an
earthquake: magnitude and intensity.
Magnitude is proportional to the energy released by an
earthquake at the focus. It is calculated from earthquakes
recorded by an instrument called seismograph. It is represented
by Arabic Numbers (e.g. 4.8, 9.0).
Intensity on the other hand, is the strength of an earthquake as
perceived and felt by people in a certain locality. It is a numerical
rating based on the relative effects to people, objects,
environment, and structures in the surrounding. The intensity is
generally higher near the epicenter. It is represented by Roman
Numerals (e.g. II, IV, IX). In the Philippines, the intensity of an
earthquake is determined using the PHIVOLCS Earthquake
Intensity Scale (PEIS).
28. •Magnitude
Magnitude is the quantified value of seismic energy
produced during an earthquake.
•Intensity
Intensity is the quantum of negative impact of
earthquake on surrounding areas. Unlike magnitude, the
intensity that is the devastation caused by earthquake
varies with the location and is not a single numerical
value. The farther an area is from epicenter; lower is the
intensity of earthquake.
EARTHQUAKE MEASUREMENT SCALE
29. Magnitude Measurement Scale
•Measuring magnitude involves the use of the Richter
scale, which Charles F. Richter invented 1934.
•The scale for noting the magnitude, does not takes into
account the type of wave, but simply records the largest
seismic wave. Richter scale is a logarithmic scale, with
10 as base. Thus, the magnitude of 5 is ten times more
severe than a magnitude of 4. The calculation results of
this scale are precise and the smallest earthquakes with
negative magnitude values can also be recoded.
30. Richter Scale
Magnitude Level Category Effects Earthquakes per year
less than 1.0 to 2.9 micro
generally not felt by people,
though recorded on local
instruments
more than 100,000
3.0–3.9 minor
felt by many people; no
damage
12,000–100,000
4.0–4.9 light
felt by all; minor breakage of
objects
2,000–12,000
5.0–5.9 moderate
some damage to weak
structures
200–2,000
6.0–6.9 strong
moderate damage in
populated areas
20–200
7.0–7.9 major
serious damage over large
areas; loss of life
3–20
8.0 and higher great
severe destruction and loss
of life over large areas
fewer than 3
31. Intensity Measurement Scale
• Mercalli scale as invented in the year 1902 by Giuseppe Mercalli is a
method to measure intensity of the earthquake.
• The intensity scale is not considered a purely scientific scale as it is
dependent upon observations and responses of the people staying in
vicinity.
• For instance, an old structure might sustain severe damage as compared
with a new one, thus confusing upon the results of intensity
measurements. Mercalli intensity of an earthquake of magnitude 1.0 to
2.0 is recorded if the earthquake was barely noticeable.
• Intensity count is XII for magnitude 8.0 or more is recorded in case
where waves were seen on ground and the damage was high, with objects
thrown up in the air.
32. ABBREVIATED MODIFIED MERCALLI INTENSITY SCALE
I. Not felt except by a very few under especially favorable
conditions.
II. Felt only by a few persons at rest, especially on upper floors
of buildings.
III. Felt quite noticeably by persons indoors, especially on
upper floors of buildings. Many people do not recognize it as
an earthquake. Standing motor cars may rock slightly.
Vibrations similar to the passing of a truck. Duration
estimated.
IV. Felt indoors by many, outdoors by few during the day. At
night, some awakened. Dishes, windows, doors disturbed;
walls make cracking sound. Sensation like heavy truck striking
building. Standing motor cars rocked noticeably.
33. V. Felt by nearly everyone; many awakened. Some dishes,
windows broken. Unstable objects overturned. Pendulum
clocks may stop.
VI. Felt by all, many frightened. Some heavy furniture moved;
a few instances of fallen plaster. Damage slight.
VII. Damage negligible in buildings of good design and
construction; slight to moderate in well-built ordinary
structures; considerable damage in poorly built or badly
designed structures; some chimneys broken.
VIII. Damage slight in specially designed structures;
considerable damage in ordinary substantial buildings with
partial collapse. Damage great in poorly built structures. Fall
of chimneys, factory stacks, columns, monuments, walls.
Heavy furniture overturned.
34. IX. Damage considerable in specially designed structures;
well-designed frame structures thrown out of plumb.
Damage great in substantial buildings, with partial
collapse. Buildings shifted off foundations.
X. Some well-built wooden structures destroyed; most
masonry and frame structures destroyed with
foundations. Rails bent.
XI. Few, if any (masonry) structures remain standing.
Bridges destroyed. Rails bent greatly.
XII. Damage total. Lines of sight and level are distorted.
Objects thrown into the air.
35. Magnitude Typical Maximum Modified Mercalli
Intensity
1.0 – 3.0 I
3.0 – 3.9 II – III
4.0 – 4.9 IV – V
5.0 – 5.9 VI – VII
6.0 – 6.9 VII – IX
7.0and higher VIIIor higher
The following table gives intensities that are typically observed
at locations near the epicenter of earthquakes of different
magnitudes.
Editor's Notes
#6:Normal faults are two blocks of crust layer pulling apart, extending the crust into a valley thus, creating a space. A normal fault has the upper side or hanging wall appears to have moved downward with respect to the footwall. The Basin and Range Province in North America and the East African Rift Zone are two notable districts where normal fault is spreading apart Earth's crust.
#19:PVCMCET features near real-time display and monitoring of earthquake and tsunami using data from the Philippine Seismic Network (PSN). Currently, DOST-PHIVOLCS has 125 seismic stations with upgraded computer systems for data acquisition and processing, newly installed tools for decision support, mapping, and information dissemination that are capable of near real-time streaming of seismic waveforms and real-time instrumental intensity reporting. The
#24:vibration generated by an earthquake, explosion, or similar energetic source and propagated within the Earth or along its surface.
#26:vibration generated by an earthquake, explosion, or similar energetic source and propagated within the Earth or along its surface.
Augustus Edward Hough Love
Lord Raylegh ( John William Strutt)
#28:It is a specific value with no correlation to distance from epicenter. In other words, magnitude is the earthquake’s size, at the source. For calculations, the maximum displacement is taken into account. The numerical value of the magnitude that is the earthquake’s size remains constant and is not dependent upon the affect of earthquake on populace. Intensity
Intensity is the quantum of negative impact of earthquake on surrounding areas. Unlike magnitude, the intensity that is the devastation caused by earthquake varies with the location and is not a single numerical value. The farther an area is from epicenter; lower is the intensity of earthquake. For calculating intensity, the responses of people in surrounding areas, worsened condition of structures and changes in natural surroundings are noted. Areas near to the epicenter severely feel the shaking intensity and thus are affected critically as compared to those staying farther away.
