Download Earthquakes

What are Earthquakes?
•
•
•
The shaking or trembling caused by the sudden release of “pent-up”
energy after the shifting of tectonic plates
Usually associated with faulting or breaking of rocks
Continuing adjustment of position results in aftershocks. These are sometimes as
big as the initial quake
.
What is the Elastic Rebound Theory?
•
Explains how energy is
stored in rocks
– Rocks bend until the
strength of the rock
is exceeded
– Rupture occurs and
the rocks quickly
rebound to an
undeformed shape
– Energy is released in
waves that radiate
outward from the
fault
San Andreas Fault-L.A. a future San
Fran suburb?
The Focus and Epicenter of an Earthquake
• The point within
Earth where
faulting begins is
the focus
• The point directly
above the focus
on the surface is
the epicenter
Seismographs and
seismometers
record
earthquakes
Where Do Earthquakes Occur and How Often?
~80% of all earthquakes occur in the Pacific “Ring of Fire”
– most of these result from convergent margin activity
– ~15% occur in the Mediterranean-Asiatic belt (Turkey)
– remaining 5% occur in the interiors of plates and on
spreading ridge centers
– 150,000 quakes strong enough to be felt are recorded yearly
The Economics and Societal Impacts of EQs
• Buildings collapsehomelessness
• Fire from gas pipe bursts
• Tsunamis follow in coastal
areas
• Ground failure-slides
• Poor countries take longer
to rebuild and other
tragedies result (Haiti:
cholera, rapes in camps)
Damage in Oakland, CA, 1989
What are Seismic Waves?
• Response of solid/liquid rock
material to the arrival of energy
fronts released by rupture
• Two types:
– Body waves
• P and S-primary and secondary
– Surface waves
• R and L
Body Waves: P and S
waves • Body waves
– P or primary waves
• fastest waves
• travel through solids,
liquids, or gases
• compressional wave,
material movement is
in the same direction
as wave movement
– S or secondary waves
• slower than P waves
• travel through solids
only
• shear waves - move
material
perpendicular to
wave movement
Surface Waves: R and L waves
•
Surface Waves
– Travel just below or along the ground’s surface
– Slower than body waves; rolling and side-to-side
movement
– Especially damaging to buildings
How is an Earthquake’s Epicenter Located?
Seismic wave behavior
– P waves arrive first, then S waves, then L and R
– Average speeds for all these waves is known and put on a
chart
– After an earthquake, the difference in arrival times at a
seismograph station can be used to calculate the distance
from the seismograph to the epicenter.
How is an Earthquake’s Epicenter
Located?
• Time-distance graph
showing the average
travel times for P- and
S-waves.
• The farther away a
seismograph is from
the focus of an
earthquake, the longer
the interval between
the arrivals of the Pand S- waves
How is an Earthquake’s
Epicenter Located?
• Three seismograph
stations are needed to
locate the epicenter of an
earthquake
• A circle where the radius
equals the distance to the
epicenter is drawn
• The intersection of the
circles locates the
epicenter
• TRIANGULATION!
An Earthquake’s “Focus”
• The focus of an earthquake is the point
beneath Earth's surface where rock breaks
under stress and causes the earthquake
How are the Size and Strength of an Earthquake Measured?
•
Modified Mercalli Intensity Map
– subjective measure of the kind of damage
done and people’s reactions to it
– isoseismal lines identify areas of equal
intensity
– 1994 Northridge, CA earthquake,
magnitude 6.7
•
THE MERCALLI SCALE- based on observing effects from 1-12 not on a seismometer
•
I. Instrumental Not felt by many people unless in favourable conditions.
•
II. Feeble Felt only by a few people at best, especially on the upper floors of buildings. Delicately suspended objects
may swing.
•
III. Slight Felt quite noticeably by people indoors, especially on the upper floors of buildings. Many do not
recognize it as an earthquake. Standing motor cars may rock slightly. Vibration similar to the passing of a truck.
Duration estimated.
•
IV. Moderate Felt indoors by many people, outdoors by few people during the day. At night, some awakened.
Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing
motor cars rock noticeably. Dishes and windows rattle alarmingly.
•
V. Rather Strong Felt outside by most, may not be felt by some outside in non-favourable conditions. Dishes and
windows may break and large bells will ring. Vibrations like large train passing close to house.
•
VI. Strong Felt by all; many frightened and run outdoors, walk unsteadily. Windows, dishes, glassware broken;
books fall off shelves; some heavy furniture moved or overturned; a few instances of fallen plaster. Damage slight.
•
VII. Very Strong Difficult to stand; furniture broken; damage negligible in building 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. Noticed by people driving motor cars.
•
VIII. Destructive Damage slight in specially designed structures; considerable in ordinary substantial buildings with
partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments,
walls. Heavy furniture moved
.IX. Ruinous General panic; 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. Disastrous Some well built wooden structures destroyed; most masonry and frame structures destroyed with
foundation. Rails bent.
XI. Very Disastrous Few, if any masonry structures remain standing. Bridges destroyed. Rails bent greatly.
XII. Catastrophic Total damage - Everything is destroyed. Total destruction. Lines of sight and level distorted.
•
•
•
•
• What is LA's Most Earthquake-Proof
Building? – YouTube
• The Earthquake-Proof Tower in Japan Secret Revealed - YouTube
How are the Size and Strength of an Earthquake
• Magnitude up to 18
Measured?
– Richter scale
measures total
amount of energy
released by an
earthquake;
independent of
intensity
– Each increase is
equivalent to ten
times the previous
whole number; e.g.
an 8 is ten times
worse than a 7 and
100 times worse
than a 6.
Can Earthquakes be Predicted?
Earthquake Precursors
– changes in elevation or tilting of land surface, fluctuations in
groundwater levels, magnetic field, electrical resistance of the
ground. Animal behaviour
– seismic gaps
Can Earthquakes be Predicted?
Earthquake Prediction Programs
– include laboratory and field studies of rocks before, during,
and after earthquakes
– monitor activity along major faults
– produce risk assessments
Into the Quake Zone - The
National - CBC Player-B.C.
EARTHQUAKES?
IN NOVA SCOTIA?????
Can Earthquakes be
Controlled?
• Graph showing the
relationship between the
amount of waste injected
into wells per month and
the average number of
Denver earthquakes per
month
• Some have suggested
that pumping fluids into
seismic gaps will cause
small earthquakes while
preventing large ones
• Largest Earthquakes in the World Since
1900
• "12 of the Most Destructive Earthquakes“
• Mid-Plate Earthquakes: World of Earth
Science
Liquefaction
• YouTube - San Francisco Earthquake of 1906
• YouTube - 1989 San Francisco (Loma Prieta) Earthquake - World Series
footage
• NBC News on 1989 San Francisco Earthquake - Oct., 1989! - YouTube
• YouTube - Earthquake Destruction
• YouTube - MEGA QUAKE KOBE 1995
•
•
•
•
Haiti earthquake footage never seen before – YouTube
Haiti: 2 years after the earthquake – YouTube
YouTube - Port-au-Prince Before and After
http://www.theglobeandmail.com/news/world/project-jacmel/haiti-oneyear-later/haitis-baby-boom/article1864286/
• Pat Robertson - Haiti's Pact w/ Devil Created Earthquake - YouTube
• SHOCKING CCTV FOOTAGE: Inside a Costa Rican shop during the
MASSIVE EARTHQUAKE – YouTube
The result of an earthquake is
often a Tsunami. Tsunami is
Japanese for “Harbour Wave”
• The 2004 Indian Ocean earthquake was an undersea megathrust
earthquake that occurred at 00:58:53 on December 26, 2004, with an
epicentre off the west coast of Sumatra, Indonesia. The quake itself is
known by the scientific community as the Sumatra-Andaman
earthquake.
• The earthquake was caused by subduction and triggered a series of
devastating tsunamis along the coasts of most landmasses bordering
the Indian Ocean, killing nearly 230,000 people in fourteen countries,
and inundating coastal communities with waves up to 15 meters
(50 feet) high[5]. It was one of the deadliest natural disasters in
recorded history. Indonesia was the hardest hit, followed by Sri Lanka,
India, and Thailand.
• With a magnitude of between 9.1 and 9.3, it is the second largest
earthquake ever recorded on a seismograph. This earthquake had the
longest duration of faulting ever observed, between 8.3 and 10
minutes. It caused the entire planet to vibrate as much as 1 cm
(0.4 inches)and triggered other earthquakes as far away as Alaska.
• The plight of the many affected people and countries prompted a
widespread humanitarian response. In all, the worldwide community
donated more than $7 billion (2004 U.S. dollars) in humanitarian aid
•
•
•
EARTHQUAKE! - NOVA - Discovery/Science/History (documentary) YouTube
YouTube - 2004 Boxing Day Tsunami
They're All Right Here Weird fish found after tsunami - YouTube
YouTube - 2004 Boxing Day Tsunami
YouTube - Tsunami Footage - Penang Beach
[HD] Hereafter (2010) - Realistic Tsunami Scene – YouTube
The Impossible (2012)- Epic Tsunami Scene [HD] - YouTube
Petra Nemcova: Surviving the Tsunami – YouTube
Moment of Japan earthquake caught on cameras triggering 10m tsunami YouTube
Incredible HD Footage of Japan Tsunami – YouTube
Japan Tsunami: Nuclear crisis worsens - YouTube
•
Wave That Shook The World - tsunami documentary - YouTube
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
EARTHQUAKE! - NOVA - Discovery/Science/History (documentary) – YouTube
MegaQuake Could Hit North America - BBC (Full Documentary) - YouTube
YouTube - 2004 Boxing Day Tsunami
They're All Right Here Weird fish found after tsunami - YouTube
YouTube - 2004 Boxing Day Tsunami
YouTube - Tsunami Footage - Penang Beach
[HD] Hereafter (2010) - Realistic Tsunami Scene – YouTube
The Impossible (2012)- Epic Tsunami Scene [HD] - YouTube
Petra Nemcova: Surviving the Tsunami – YouTube
Moment of Japan earthquake caught on cameras triggering 10m tsunami - YouTube
Incredible HD Footage of Japan Tsunami – YouTube
Japan Tsunami: Nuclear crisis worsens - YouTube
•
Wave That Shook The World - tsunami documentary -
•
•
•
•
•
•
•
•
•
•
•
•
•
EARTHQUAKE! - NOVA - Discovery/Science/History (documentary) – YouTube
http://documentaryaddict.com/Naked+Science+Angry+Earth-11829-doc.html
MegaQuake Could Hit North America - BBC (Full Documentary) - YouTube
YouTube - 2004 Boxing Day Tsunami
They're All Right Here Weird fish found after tsunami - YouTube
YouTube - 2004 Boxing Day Tsunami
YouTube - Tsunami Footage - Penang Beach
[HD] Hereafter (2010) - Realistic Tsunami Scene – YouTube
The Impossible (2012)- Epic Tsunami Scene [HD] - YouTube
Petra Nemcova: Surviving the Tsunami – YouTube
Moment of Japan earthquake caught on cameras triggering 10m tsunami - YouTube
Incredible HD Footage of Japan Tsunami – YouTube
Japan Tsunami: Nuclear crisis worsens - YouTube
•
Wave That Shook The World - tsunami documentary -