Transcript Earthquake Notes - Science at East Lee Campus

Need:
“music” CD of eq sounds
Stick to break
Slinky
Smithsonian CD
THE STORY OF AN EYEWITNESS
By Jack London, Collier's special
Correspondent
(First published in Collier's, May 5, 1906)
http://london.sonoma.edu/Writings/Journalism/sfearthquake.html
http://www.youtube.com/watch?v=4Xebwzb3dDE
Japan, subduction zone earthquake
RECORDS OF EARTHQUAKE WAVES
Three sets of waves recorded for each EQ, P, S, and surface waves.
TIME-DISTANCE GRAPHS
LOCATING EARTHQUAKES
Seismic Wave Propagation
M9.0_Earthquake_Japan 110308.mov
http://www.youtube.com/watch?v=R8dsrBf16pc
INTERPRETING EARTHQUAKES
WORLDWIDE STANDARD SEISMOGRAPH NETWORK
EARTHQUAKE INTENSITY
EQ effects classified in terms degrees of intensity.
Modified by Mercalli in 1902
12 degrees of intensity.
Michigan’s Largest Earthquake
1947
Intensity VI
M=4,6
VI. Felt by all, many frightened. Some heavy furniture moved; a few instances
of fallen plaster. Damage slight.
Magnitude 9.0 NEAR THE EAST COAST OF HONSHU, JAPAN
Friday, March 11, 2011 at 05:46:23 UTC
Shaking intensity scales were developed to standardize the measurements and ease
comparison of different earthquakes. The Modified-Mercalli Intensity scale
is a twelve-stage scale, numbered
from I to XII. The lower numbers
represent imperceptible shaking
levels, XII represents total
destruction. A value of IV indicates a
level of shaking that is felt by most
people.
Modified Mercalli Intensity
Perceived
Shaking
Extreme
Violent
Severe
Very Strong
Strong
Moderate
Light
Weak
Not Felt
Image courtesy of the US Geological Survey
USGS Estimated shaking Intensity from M 9.0 Earthquake
Magnitude - an index to the energy released by an EQ as reflected by
the amplitude of seismic waves.
Ex: M 2.5, felt by most people in vicinity
M 4.5, some damage
M 6, potentially destructive
>M 7, major EQ
Note: scale is logarithmic.
Ex: M6 to M8 = 100 times as large amplitude
Note: An increase in one magnitude equals a 40 times increase in released energy.
Ex: M6 to M8 = 1,600 times more energy released.
Magnitude 9.0 NEAR THE EAST COAST OF HONSHU, JAPAN
Friday, March 11, 2011 at 05:46:23 UTC
Globally, this is the 4th largest earthquake since 1900.
Great (M > 8) Earthquakes Since 1900
9.6
Chile 1960
9.4
Alaska 1964
9.2
Magnitude
Sumatra 2004
Russia 1952
9
8.8
Japan 2011
Ecuador 1906
Chile 2010
Alaska 1965
8.6
8.4
8.2
8
7.8
1900
1920
1940
1960
Year
1980
2000
2020
Magnitude 9.0 NEAR THE EAST COAST OF HONSHU, JAPAN
Friday, March 11, 2011 at 05:46:23 UTC
The moment magnitude
scale is designed to give
an accurate
characterization of the
true size of an earthquake,
but be tied to the original
description of magnitude
that was developed by
Charles Richter. Moment
magnitude accounts for
earthquake size by looking
at all the energy released.
It is striking that only 6
earthquakes over the last
106 years account for over
half of the energy released
during that time.
New Mexico Institute of Mining and Technology
Magnitude 7.0 HAITI
Tuesday, January 12, 2010 at 21:53:09 UTC
The earthquake occurred about 10 miles west of the capital of
Haiti, Port-au-Prince, and caused extreme shaking.
USGS Shaking Intensity
Mike Blanpied of the US
Geological Survey said that,
based on the location and size of
the quake, about three million
people would have been
severely shaken by its impact.
Modified Mercalli Intensity
Perceived
Shaking
Extreme
Violent
Severe
Very Strong
Strong
Moderate
Light
Weak
Not Felt
Lower magnitude EQs can be more hazardous
if in populated areas or
in areas of poor construction.
1. Most EQs in circum-pacific, area of active volcanism (80% of energy).
2. Burma, Himalayas, Iran, Europe (15% of energy).
3. MORs and the other locations.
Number of
Earthquakes 1974-2003
 1. Alaska 57.2 %
 2. California 23.2 %
 3. Hawaii 7.3 %
 4. Nevada 3.7 % 5. Washington 2.0 % 6. Idaho
1.9 % 7. Wyoming 1.0 % 8. Montana 0.9 % 9.
Utah 0.7 % 10. Oregon 0.3 %
Magnitude 9.0 NEAR THE EAST COAST OF HONSHU, JAPAN
Friday, March 11, 2011 at 05:46:23 UTC
The map on the right shows historic
earthquake activity near the epicenter
(star) from 1990 to present.
As shown on the cross section,
earthquakes are shallow (orange dots) at
the Japan Trench and increase to 300 km
depth (blue dots) towards the west as
the Pacific Plate dives deeper beneath
Japan.
Seismicity Cross Section across the subduction zone
showing the relationship between color and
earthquake depth.
Images courtesy of the US Geological Survey
Draw layers of the Earth
Layers of the Earth
Chemical = crust, mantle, core
Physical = lithosphere, asthenosphere, lower mantle, outer core,
and inner core
STRUCTURE OF THE EARTH
A.CRUST
Base of the crust, the Moho, first detected in 1909.
Crust of the Continents
Thickness varies: greater in mountains than lowlands.
Crust Under Oceans
Average about 5km. Mafic, rich in magnesium and iron (basalt).
B. MANTLE
Mantle extends down to 2,900 km.
Both P and S-waves travel through. Must be solid.
C. LITHOSPHERE AND ASTHENOSPHERE
Lithosphere - rigid crust and uppermost mantle
Asthenosphere - plastic mantle
Top of the asthenosphere has a low-velocity zone, where body
waves decrease in velocity.
Rocks close to their melting temperature, less elastic, and more plastic.
Less efficient at transmitting wave.
D. CORE
Extends from 2,900 km to center of the Earth at a depth of 6,370 km.
No S-waves observed from 103-142 degrees from the source S-wave seismic shadow.
Interpretation: liquid outer core. Size determined by size of shadow.
P-waves reflect off of denser layer within the core.
Interpretation: solid inner core of same composition.
EFFECTS OF EARTHQUAKES
A. FIRE
B. DAMAGE TO STRUCTURES
C. SEISMIC SEA WAVES (Tsunami)
D. LANDSLIDES
E. LIQUEFACTION
Japan earthquake: Footage of moment tsunami hit
http://www.bbc.co.uk/news/world-asia-pacific-12725646
Tsunami
Fire
Kobe 1995
Damage to Structures
Kobe 1995
Northridge, 1994
Tsunami
Making Waves, Saving Lives
http://www.youtube.com/watch?v=ZXxDUkGMNLs&feature=autoplay&list=PL01AC183B464BAC05&index=29&playnext=2
Landslide