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
is the perceptible shaking of the surface of the Earth,
resulting from the sudden release of energy in
the Earth's crust that creates seismic waves.

are caused mostly by rupture of geological faults, but also
by other events such as volcanic activity, landslides, mine
blasts, and nuclear tests.

The seismicity or seismic activity of an area refers to the
frequency, type and size of earthquakes experienced over
a period of time.

Continuing adjustment of position results in aftershocks.

Most of the world's earthquakes (90%, and
81% of the largest) take place in the
40,000 km long, horseshoe-shaped zone
called the circum-Pacific seismic belt, known
as the Pacific Ring of Fire, which for the most
part bounds the Pacific Plate.

PHIVOLCS  Philippine Institute of
Volcanology and Seismology is the
government agency that monitors the
seismic activities in our country.

Seismograph  an instrument that
measures and records details of earthquakes,
such as force and duration.

Fault Line  is a break or fracture in the
ground that occurs when the Earth's tectonic
plates move or shift and are areas where
earthquakes are likely to occur.

AERIAL PHOTO OF SAN ANDREAS FAULT
The point within
Earth where faulting
begins is the focus, or
hypocenter.
 The point directly
above the focus on the
surface is the epicenter.

Seismologist  A person who studies
earthquakes.

They study earthquakes by using
seismographs and by venturing into the field
to view the damage caused by an earthquake.

Chang Heng invented the first seismograph
in 132 A.D. and called the instrument an
earthquake weathercock.

This instrument featured eight dragons, each with a
bronze ball in its mouth. Whenever a tremor occurred,
a mechanism within the seismograph would cause
one of the dragon's mouths to open. The ball fell into
one of the toad's mouths, providing an alert for an
earthquake.

Magnitude  is the measurement of the
amount of energy released during an
earthquake.

The Richter Scale is a numerical scale based
on the size of the largest seismic waves
generated by a quake that is used to describe
its magnitude.
HORIZONTAL SEISMOGRAPH
VERTICAL SEISMOGRAPH

The modified Mercalli’s scale, which
measures the amount of damage done to the
structures involved, is used to determine the
intensity of an earthquake.

This scale uses the roman numerals I-XII to
designate the degree of intensity.
Intensity
Scale
Description
I
Scarcely Perceptible - Perceptible to people under favorable
circumstances. Delicately balanced objects are disturbed
slightly. Still Water in containers oscillates slowly.
II
Slightly Felt - Felt by few individuals at rest indoors. Hanging
objects swing slightly. Still Water in containers oscillates
noticeably.
III
Weak - Felt by many people indoors especially in upper floors of
buildings. Vibration is felt like one passing of a light truck.
Dizziness and nausea are experienced by some people.
Hanging objects swing moderately. Still water in containers
oscillates moderately.
IV
Moderately Strong - Felt generally by people indoors and by
some people outdoors. Light sleepers are awakened. Vibration is
felt like a passing of heavy truck. Hanging objectsswing
considerably. Dinner, plates, glasses, windows and doors rattle.
Floors and walls of wood framed buildings creak. Standing motor
cars may rock slightly. Liquids in containers are slightly
disturbed. Water in containers oscillate strongly. Rumbling
sound may sometimes be heard.
V
Strong - Generally felt by most people indoors and outdoors. Many
sleeping people are awakened. Some are frightened, some run
outdoors. Strong shaking and rocking felt throughout building.
Hanging objects swing violently. Dining utensils clatter and clink;
some are broken. Small, light and unstable objects may fall or
overturn. Liquids spill from filled open containers. Standing vehicles
rock noticeably. Shaking of leaves and twigs of trees are noticeable.
VI
Very Strong - Many people are frightened; many run outdoors.
Some people lose their balance. motorists feel like driving in flat
tires. Heavy objects or furniture move or may be shifted. Small
church bells may ring. Wall plaster may crack. Very old or poorly
built houses and man-made structures are slightly damaged though
well-built structures are not affected. Limited rockfalls and rolling
boulders occur in hilly to mountainous areas and escarpments.
Trees are noticeably shaken.
VII
Destructive - Most people are frightened and run outdoors. People
find it difficult to stand in upper floors. Heavy objects and furniture
overturn or topple. Big church bells may ring. Old or poorly-built
structures suffer considerably damage. Some well-built structures
are slightly damaged. Some cracks may appear on dikes, fish
ponds, road surface, or concrete hollow block walls. Limited
liquefaction, lateral spreading and landslides are observed. Trees
are shaken strongly. (Liquefaction is a process by which loose
saturated sand lose strength during an earthquake and behave like
liquid).
VIII
Very Destructive - People panicky. People find it difficult to
stand even outdoors. Many well-built buildings are
considerably damaged. Concrete dikes and foundation of
bridges are destroyed by ground settling or toppling. Railway
tracks are bent or broken. Tombstones may be displaced,
twisted or overturned. Utility posts, towers and monuments
mat tilt or topple. Water and sewer pipes may be bent, twisted
or broken. Liquefaction and lateral spreading cause manmade structure to sink, tilt or topple. Numerous landslides and
rockfalls occur in mountainous and hilly areas. Boulders are
thrown out from their positions particularly near the epicenter.
Fissures and faults rapture may be observed. Trees are
violently shaken. Water splash or stop over dikes or banks of
rivers.
IX
Devastating - People are forcibly thrown to ground. Many cry
and shake with fear. Most buildings are totally damaged.
bridges and elevated concrete structures are toppled or
destroyed. Numerous utility posts, towers and monument are
tilted, toppled or broken. Water sewer pipes are bent, twisted
or broken. Landslides and liquefaction with lateral spreadings
and sandboils are widespread. the ground is distorted into
undulations. Trees are shaken very violently with some
toppled or broken. Boulders are commonly thrown out. River
water splashes violently on slops over dikes and banks.
X
Completely Devastating - Practically all man-made
structures are destroyed. Massive landslides and liquefaction,
large scale subsidence and uplifting of land forms and many
ground fissures are observed. Changes in river courses and
destructive seiches in large lakes occur. Many trees are
toppled, broken and uprooted.

The majority of tectonic earthquakes originate at the
ring of fire in depths not exceeding tens of
kilometers.

Earthquakes occurring at a depth of less than 70 km
are classified as 'shallow-focus' earthquakes.

In subduction zones, where older and colder oceanic
crust descends beneath another tectonic plate, Deepfocus earthquakes may occur at much greater depths
(ranging from 300 up to 700 kilometers).

Branch of engineering
that designs and
analyzes structures
with Earthquakes in
mind.

Goal is to make such
structures more
resistant to
Earthquakes.

Foresee the potential consequences of strong
earthquakes on urban areas and civil
infrastructure.

Design, construct and maintain structures to
perform at earthquake exposure up to the
expectations and in compliance with building
codes.
- application of an earthquakegenerated agitation to a structure.
Seismic loading depends on:

Anticipated earthquake's
parameters at the site - known as
seismic hazard

Geotechnical parameters of the
site

Structure's parameters

Characteristics of the anticipated
gravity waves from tsunami

a structure's ability to
sustain its main
functions, such as its
safety and
serviceability, at and
after a particular
earthquake exposure.

these are expensive
tests that are typically
done by placing a
(scaled) model of the
structure on a shaketable that simulates
the earth shaking and
observing its behavior
National Science Foundation
(NSF)

is the main United States
government agency that
supports fundamental
research and education in
all fields of earthquake
engineering.
Earthquake Engineering
Research Institute (EERI)

a leader in dissemination
of earthquake
engineering research
related information both
in the U.S. and globally.

a set of technical means
aimed to mitigate seismic
impacts in building and
non-building structures.

may be classified as
passive, active or hybrid.

Passive Control Devices have no feedback
capability between them, structural elements
and the ground.

Active Control Devices incorporate real-time
recording instrumentation on the ground
integrated with earthquake input processing
equipment and actuators within the structure.

Hybrid Control Devices have combined
features of active and passive control systems.
Dry-stone Walls Control

mortar-free construction
is proven to be apparently
more earthquakeresistant than using
mortar.
Lead Rubber Bearing

a type of base isolation
employing a heavy damping.

invented by Bill Robinson, a
New Zealander.
Tuned Mass Damper
 huge concrete blocks
mounted in skyscrapers or
other structures and
moved in opposition to
the resonance frequency
oscillations of the
structures by means of
some sort of spring
mechanism.
Friction Pendulum Bearing

bearings that use the
characteristics of a
pendulum to lengthen the
natural period of the
isolated structure so as to
avoid the strongest
earthquake forces
Building Elevation Control

a configuration that can
prevent buildings' resonant
amplifications since a
properly configured building
disperses the shear wave
energy between a wide range
of frequencies.
Simple Roller Bearing

a base isolation device
which is intended for
protection of various
building and non-building
structures against
potentially damaging
lateral impacts of strong
earthquakes.

is based on authorized
engineering procedures,
principles and criteria meant
to design or retrofit
structures subject to
earthquake exposure.

the manner by which an
earthquake induced failure is
observed

learning from each real
earthquake failure remains a
routine recipe for
advancement in seismic
design methods
Soft Story Effect
 Occurs when a level in a
multi-story building is less
than 70% as stiff as the
floor immediately above
it, or less than 80% as stiff
as the average stiffness of
the three floors above it.
Soil Liquefaction
 where the soil consists of loose
granular deposited materials with
the tendency to develop excessive
hydrostatic pore water pressure of
sufficient magnitude and
compact, liquefaction of those
loose saturated deposits may
result in non-uniform settlements
and tilting of structures.
Landslide Rock Fall
•
the action of gravity is the
primary driving force for a
landslide to occur though in
this case there was another
contributing factor which
affected the original slope
stability: the landslide
required an earthquake
trigger before being
released
Pounding against adjacent
building

Pounding usually caused
local damage around the
impacting areas, and in
extreme cases, collapse of
the building structures

Hydraulic fracturing  is a technique in which high-pressure fluid is
injected into the low-permeable reservoir rocks in order to induce
fractures to increase hydrocarbon production. This process
usually generates events that are very small to be felt at the surface (with
magnitudes ranging from -3 to 0)

Mining  leaves voids that generally alter the
balance of forces in the rock, many times causing rock
bursts. These voids may collapse producing seismic
waves and in some cases reactivate
existing faults causing minor earthquakes.

Extraction of fossil fuels  Large-scale fossil fuel
extraction can generate earthquakes.

Groundwater extraction  The changes in crustal
stress patterns caused by the large scale extraction of
groundwater has been shown to trigger earthquakes

We cannot prevent natural earthquakes from
occurring but we can significantly mitigate
their effects by identifying hazards, building
safer structures, and providing education on
earthquake safety. By preparing for
natural earthquakes we can also reduce the
risk from human induced earthquakes.

Shaking and ground rupture

Landslides and avalanches

Fires

Soil liquefaction

Tsunami

Floods

Human impacts

Shaking and ground rupture are the main effects created
by earthquakes, principally resulting in more or less severe
damage to buildings and other rigid structures.

Ground rupture is a visible breaking and displacement of
the Earth's surface along the trace of the fault, which may
be of the order of several meters in the case of major
earthquakes.

Ground rupture is a major risk for large engineering
structures such as dams, bridges and nuclear power
stations and requires careful mapping of existing faults to
identify any which are likely to break the ground surface
within the life of the structure.

A 6 2-magnitude earthquake struck Saturday
near the southern Philippine island of
Mindanao, Feb 16, 2013.

Earthquakes, along with severe storms, volcanic
activity, coastal wave attack, and wildfires, can
produce slope instability leading to landslides, a
major geological hazard.

A landslide in Mimami-Aso,Japan.


Earthquakes can cause fires by damaging electrical
power or gas lines. In the event of water mains rupturing
and a loss of pressure, it may also become difficult to stop
the spread of a fire once it has started. For example, more
deaths in the 1906 San Francisco earthquake were caused
by fire than by the earthquake itself.

Soil liquefaction occurs when, because of the shaking,
water-saturated granular material (such as sand)
temporarily loses its strength and transforms from
a solid to a liquid.

Soil liquefaction may cause rigid structures, like buildings
and bridges, to tilt or sink into the liquefied deposits.


Tsunamis are long-wavelength, long-period sea
waves produced by the sudden or abrupt
movement of large volumes of water.

Ordinarily, subduction earthquakes under
magnitude 7.5 on the Richter scale do not cause
tsunamis, although some instances of this have
been recorded. Most destructive tsunamis are
caused by earthquakes of magnitude 7.5 or
more.

A flood is an overflow of any amount of water that
reaches land.

Floods occur usually when the volume of water within
a body of water, such as a river or lake, exceeds the
total capacity of the formation, and as a result some
of the water flows or sits outside of the normal
perimeter of the body.

floods may be secondary effects of earthquakes, if
dams are damaged. Earthquakes may cause landslips
to dam rivers, which collapse and cause floods.

An earthquake may cause injury and loss of
life, road and bridge damage,
general property damage, and collapse or
destabilization (potentially leading to future
collapse) of buildings. The aftermath may
bring disease, lack of basic necessities,
mental consequences such as panic attacks,
depression to survivors, and higher insurance
premiums.
Are seismic waves that are created when
energy builds up in rocks and they fracture.
It is estimated that around 500,000
earthquakes occur each year, detectable
with current instrumentation. About
100,000 of these can be felt.
Seismic waves
Body waves
▪Primary or p-wave
▪Compression wave
▪Secondary or s-wave
▪Transverse waves
Surface waves
▪Love wave
▪Rayleigh wave
Compression
Is a region in a longitudinal wave where the particles are closest together.
Rarefaction
Is a region in a longitudinal wave where the particles are furthest apart.
Transverse
A wave vibrating at right angles to the direction of its propagation.

Are the waves of energy caused by the sudden
breaking of rock within the earth or an explosion.
They are the energy that travels through the earth
and is recorded on seismographs.

There are several different kinds of seismic waves,
and they all move in different ways.

The two main types of waves:
body waves and surface waves
P Waves (compression wave)

The first kind of body wave is the P wave or primary wave.
This is the fastest kind of seismic wave. The P wave can
move through solid rock and fluids, like water or the liquid
layers of the earth. It pushes and pulls the rock it moves
through just like sound waves push and pull the air.
S wave (transverse wave)

The second type of body wave is the S wave or secondary
wave, which is the second wave you feel in an earthquake.
An S wave is slower than a P wave and can only move
through solid rock. This wave moves rock up and down, or
side-to-side

Love Waves

The first kind of surface wave is called a Love wave, named
after A.E.H. Love. Augustus Edward Hough Love

A British mathematician who worked out the mathematical
model for this kind of wave in 1911. It's the fastest surface
wave and moves the ground from side-to-side

Rayleigh Waves

The other kind of surface wave is the Rayleigh
wave, named for John William Strutt

Lord Rayleigh, who mathematically predicted the
existence of this kind of wave in 1885. A Rayleigh
wave rolls along the ground just like a wave rolls
across a lake or an ocean. Because it rolls, it moves
the ground up and down, and side-to-side in the
same direction that the wave is moving. Most of the
shaking felt from an earthquake is due to the
Rayleigh wave, which can be much larger than the
other waves.