Potential earthquake hazards:
1. Ground shaking
2. Ground rupture
3. Liquefaction
4. Earthquake-induced ground subsidence
5. Tsunami
6. Earthquake-induced landslide
Types of earthquakes
Tectonic
earthquake - Are
those generated by
the sudden
displacement along
faults in solid and
rigid layer of the
earth.
Types of earthquakes
Collapse
earthquake – it
is also called “
mine burst”. They
generally smaller
and most
commonly occur
near under
ground mines.
Type of Earthquakes
Explosion
earthquake - An
explosion
earthquake is an
earthquake that is
the result of the
detonation of a
nuclear and/or
chemical device.
Type of earthquakes
Volcanic
earthquake –
earthquake
induced by rising
lava or magma
beneath the active
volcanoes.
Phivolcs
Phivolcs ( Philippine
Institute Of Volcanology
and seismology) who is
the one mandated to
mitigate disaster that
may arise from volcanic
eruptions, earthquakes,
tsunami and other
geotechnic phenomena.
Way of describing
earthquake
Intensity
Perceived strength of an
earthquake based on relative
effect to people and
structures; generally higher
near the epicenter
Magnitude
Based on instrumentally
derived information and
correlated strength with the
amount of total energy
released at the earthquake’s
point of origin
VARIOUS
VOLCANIC
HAZARDS
Lahar
Ash Fall
Pyroclastic Flow
Volcanic Gases
Lava Flow
Ballistic Projectiles
Lahar
• Lahar is an Indonesian term that
describes a hot or cold mixture of water and
rock fragments that flowing down the
slopes of a volcano.
•A destructive mudflow or debris flow that
originates on the slopes of a volcano. Small
debris flows are common in the Cascades,
where they form during periods of heavy
rainfall, rapid snow melt and by shallow
landsliding.
Ash Fall
• Ash fall is a rain of airbone ash resulting
from a volcanic eruption. Volcanic ash
consists of tiny jagged particles of rock and
natural glass blasted into the air by a
volcano. Ash can threaten the health of
people and livestock, pose a hazard to flying
jet aircraft, damage electronics and
machinery, and interrupt power generation
and telecommunications. Wind can carry
ash thousands of miles, affecting far greater
areas and many more people than other
volcano hazards. • Volcanic ash consists of
fragments of pulverized rock, minerals and
volcanic glass, created during volcanic
eruptions.
Pyroclastic Flow
•A dence, destructive mass of very hot ash,
lava fragments, and gases ejected
explosively from a volcano and typically
flowing downslope at a great speed.
Pyroclastic flows are the most deadly of all
volcanic hazards and produced as a result of
certain explosive eruption; they normally
touch the ground hurtle downhill, or spread
laterally under gravity.
Volcanic Gases
•Volcanic gases are gases given off by active (or,
at times, by dormant) volcanoes. These include
gases trapped in cavities (vesicles) in volcanic
rocks, dissolved or
dissociated gases in magma and lava, or gases
emanating from lava, from volcanic craters or
vents.
Volcanic gases can also be emitted
through groundwater heated by volcanic action.
• Volcanic gases are mainly composed of water
vapor, carbon dioxide and sulfur dioxide
Lava Flow
• Lava flows are stream of molten rock that
pour or ooze from a erupting vent. Lava is
erupted during either nonexplosive activity or
explosive lava fountains.
The speed at which lava moves across the
ground depends on several factors, including
(1) type of lava erupted and its viscosity;
(2) steepness of the ground over which it
travels;
(3) whether the lava flows as a broad sheet,
through a confined channel, or down a lava
tube; and
(4) rate of lava production at the vent.
Ballistic Projectiles
• Ballistic projectiles are fragments of
solid (blocks) or fluid (bombs) material
ejected during the range of magmatic or
phreatic (steam) explosive eruptions.
They are centimeters to tens of meters in
diameter and follow near-parabolic
trajectories separate from the
main eruption column.
Different Volcanic
Hazards
Subduction Volcanoes
• Where two tectonic plates converge, if one
or both of the plates is oceanic lithosphere, a
subduction zone will form. An oceanic plate
will sink back into the mantle.
Oceanic plates are formed from mantle
material at midocean ridges. Young oceanic
lithosphere is hot and buoyant (low density)
when it forms at a midocean ridge.
But as it spreads away from the ridge and
cools and contracts (becomse denser) it is
able to sink into the hotter underlying
mantle. There is a deep ocean trench where
the oceanic plate bends downward.
Rift Volcanoes
• Rift
volcanoes form when magma rises
into the gap between diverging plates.
They thus occur at or near actual plate
boundaries.
Hot Spot Volcanoes
• In geology, hotspots (or hot spots)
are volcanic locales thought to be fed by
underlying mantle that is anomalously hot
compared with the surrounding mantle.
Examples include the Hawaii, Iceland,
and Yellowstone hotspots.
SDC Map Color
Earthquake Hazard
Hazard Map
Seismic Design
Categories(SDC)
A Seismic Design
Categories will help us in
interpreting an earthquake
map. The following table
describes the hazard level
associated with each SDC
and the associated levels of
shaking.
Potential
effects of
shaking
A
White
Very small probability
of experiencing
damaging earthquake
effects
B
Gray
Could experience
shaking of
moderate intensity
Moderate
shaking-Felt by
all, many
frightened. Some
heavy furniture
moved; a few
instances of
fallen plaster.
Damage slight
C
Yellow
Could experience
strong shaking
Strong shakingDamage negligible
in buildings of good
design and
construction; slight
to moderate in well
built ordinary
structures;
considerable
damage in poorly
built structures
SDC
Map Color
D0
Light Brown
D1
Darker Brown
D2
Darkest Brown
E
Red
Earthquake Hazard
Potential effects of
shaking
Could experience very strong
shaking (the darker the color,
the stronger the shaking)
Very strong shaking-Damage
slight in specially designed
structures; considerable
damage in ordinary
substantial buildings with
partial collapse. Damage
great in poorly built
structures.
Near major active faults capable
of producing the most intense
shaking
Strongest shaking-Damage
considerable in specially
designed structures; frame
structures thrown out of
plumb. Damage great in
substantial buildings,with
partial
collapse. Buildings shifted
off foundations. Shaking
intense enough to
completely destroy
buildings.
Mt. Bayuso in San Enrique
Precautionary Safety
Measures for Volcanic
Eruptions
Objectives:
• identify the different
measures/interventions before a
volcanic eruption
• identify the different measures to take
during a volcanic eruption
• identify the different measures to take
after a volcanic eruption