Transcript SAN FRANCISCO EARTHQUAKES

What is an Earthquake and how
does it occur?
• A sudden motion or trembling of the earth caused by the
abrupt release of energy that is stored in the rocks.
• Most movements occur by a slippage along an
established faults because the friction binding the two
sides of the faults is weaker than the rock itself.
• After the earthquake dies away, the stored potential
energy in the rock is released but the fault remains a
weakness in the rock.
How Earthquakes are Measured
• 1935 Charles Richter divised the richter scale to
measure the amount of energy released during
an earthquake.
• Richter magnitude is calculated from the height
of the largest earthquake body wave recorded
on a specific type of seismograph.
What’s a Tsunami?
• It’s a wave generated in a body of water
by a physical disturbance.
• Possibly produced by an earthquake or
volcanic eruption.
• Erroneously known as “tidal waves”
• “First the waters withdraw from the shore, leaving a seabed
exposed. Then the waters return as a breaker that may reach
heights of 40 feet. The wave carries away virtually everything in its
path and may travel a mile or more inland before returning to sea.”
SAN FRANCISCO
EARTHQUAKES
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How do Earthquakes Occur in San Francisco
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Earthquakes occur along plate boundaries,
like the one shown at right between the
Pacific Plate (to the west) and the North
American Plate (to the east).
The yellow dots represent earthquake
epicenters, which are aligned along faults.
As the plates move, stress builds up along
faults. When this stress is released, the
blocks or plates move and an earthquake
occurs. The distribution of epicenters
reveals that several fault zones -- on either
side of San Francisco Bay and Santa Clara
Valley -- take up portions of the movement
between the Pacific and North American
Plates.
One of these faults, the San Andreas, runs
through San Juan Bautista, the Santa Cruz
mountains, north through the San Francisco
Peninsula, off shore from the Golden Gate,
and then on-shore just east of the Pt. Reyes
Peninsula. The San Andreas Fault is
considered the main boundary between the
Pacific and North American Plates.
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Major Earthquakes seen in San Francisco:
THE EARTHQUAKE OF 1906
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The San Francisco earthquake of 1906 is perhaps the most discussed earthquake in history
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After this earthquake in San Francisco, subsequent fires destroyed almost the entire
city.
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First foreshock was registered at 5:12am on April 18, 1906.
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Casualty count: as many as 3000 people might have died, 225,000 people were left
homeless out of a population of 400,000.
The Earthquake itself occurred on the San Andreas Fault with an epicenter near San
Francisco which lasted for approximately 47 seconds and was felt from Oregon to Los
Angeles and inland as far as central Nevada.
The earthquake measured 7.9 on the magnitude scale and caused ruptures visible for 290
miles.
Fires burned out of control afterwards which destroyed a large amount of property
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These fires were fueled by natural gas minds breaking; as water mains were also broken.
During this time, the city fire department had much fewer resources to fight the fires with then
they do today.
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The fire ultimately destroyed over 500 city blocks of downtown core
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San Francisco’s City Hall after 1906 Earthquake
Sky view of
San Francisco
after the
destruction
Downtown San Francisco on April 19, 1906
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DAMAGE WAS
ESTIMATED AT
$500 MILLION
DOLLARS IN
1906
Major Earthquakes seen in San Francisco:
The Earthquake of March 22, 1957
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The worst Earthquake since 1906 struck at 11:45am
and registered 5.3 on the Richter scale.
– The quake started some fires, including a
blaze caused by spill in the chemistry lab at
old Lowell High School.
– Many buildings suffered damage in the
earthquake
• The top floor at St. Anne’s School at
13th and Irving was badly damaged but
children were safe.
• The McCrery Branch public library was
completely destroyed
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Major Earthquakes seen in San Francisco:
The Earthquake of October 17, 1989
“Ioma Prieta”
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A magnitude 7.1 Earthquake struck the Bay
Area just before the third game of the World
Series at Candlestick park; the worst
Earthquake since 1906
– The tremor collapsed a section of the
San Francisco-Oakland Bay Bridge.
– Damage was estimated at almost 3
billion dollars in San Francisco
• The earthquake knocked out
power for 3 full days.
• The quake killed 62 people
through Central California, injured
3757 and left more than 12,000
people homeless.
• The earthquake triggered a four
foot tsunami wave in Monterey
Bay as well as a huge undersea
landslide.
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RECENT EARTHQUAKES IN CALIFORNIA
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Other Significant Earthquake Occurrences in the 1900’s
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MARCH 10, 1933: Southern California struck by major 6.3 Earthquake.
Massive damage in Long Beach. Many school buildings collapsed. Fires
were started by the earthquake. 115 people were killed.
FEBRUARY 9, 1971: 6.4 Earthquake centered in Southern California and
caused major damage and knocked down freeways. At least 65 people
were killed. Damage exceeded $1 Billion dollars
APRIL 6, 1990: Exhibition game at Candlestick between the Giants and the
A’s was interrupted at 7:39 by a 4.5 earthquake. Regardless, they resumed
the game and the A’s later won 9-2.
APRIL 28, 1990: A swarm of earthquakes measuring 4.3 to 4.6 knocked out
electricity in homes of the Walnut Creek area.
JANUARY 17, 1994: Los Angeles was struck by a 6.7 Earthquake, the worst
tremor in that city’s recorded history. It was felt as a slight bump for the
people in San Francisco. Damage to the electric system caused power
failures in throughout California. 57 people died.
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Ka’u District, Island of Hawaii
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The History of Hawaii
• Each Year there are thousands of
earthquakes that occur in Hawaii
– Many of them are small
• Big island earthquakes have magnitude of
six or higher.
– Reoccur every ten to twelve years.
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The History of Hawaii
• Two major regions on
the Big Island that get
the most earthquakes
is East Kona and
South Kona
• Largest earthquake
was on Ka’u District
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Ka’u District Earthquake
• It was a major earthquake in 1868 on the
Southeast flank of Mauna Lua.
– It killed 77 people
• 31 by landslide
• 46 by tsunami
– destroyed several villages by this 15 meter tsunami
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General Facts
• Earthquakes occur in Hawaii
– Mass of the volcanic cone pushes down and
out on the plane of the Pacific tectonic plate
on which it sits.
• Pacific Plate pushes in a northwest
direction.
– Pressure builds up and the outer edge of the
earth crumbles and snaps as slippage occurs.
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New Madrid, Missouri
The Earthquake of 1811
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December 16, 1811
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Earthquake hits New Madrid Missouri.
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1st in a series of four. January 23, February 7
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Trees toppled, Old river channels slammed shut and new ones opened.
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One large lake had its water suddenly replaced by sand. Another lake,
Reelfoot, was created in a matter of moments.
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Over 150,000 acres destroyed/altered.
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Thousands of after shocks followed in-between the first and fourth quake.
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Effects
• Wide Spread.
• Damage was reported as far east as Charleston, South
Carolina and Washington, DC. In Boston,
Massachusetts, 1,000 miles away, church bells were
made to ring. The effects of the quake were felt as far
south as New Orleans and as far north as Canada.
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Facts
• Because of this sort of plate interaction it was recorded
as the largest earthquake the U.S had ever seen. (1811)
• No Richter Scale = estimated 8.0
• Still thought of as one of the
largest earthquakes ever to occur
In the U.S
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New Madrid Fault
• The New Madrid Fault extends from eastern Arkansas to
about the junction of the Mississippi and Ohio Rivers.
• Failed Rift: It is not located near one of the seven large
tectonic plates.
• Result: Ground is cold and brittle instead of hot and
elastic thus when friction occurs it is much more abrupt
and has the potential to escalate the magnitude of the
earthquake.
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Future for Missouri / Mid West
• 1811-1812 Marked the beginning of large amounts of earthquake
activity in Missouri.
• Although there has been relatively little earthquake activity in
Missouri since then scientists are predicting heavy quakes in the
coming years. 6.0 or higher
• Predicting earthquakes in the Mid-West rather then West Coast.
• New Madrid Fault- 2010, next 50 years, predictions vary.
• Disaster will hit the mid west again.
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Effects
• Wide Spread.
• Damage was reported as far east as Charleston, South
Carolina and Washington, DC. In Boston,
Massachusetts, 1,000 miles away, church bells were
made to ring. The effects of the quake were felt as far
south as New Orleans and as far north as Canada.
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The Good Friday
Earthquake
Alaska~ Friday March 27, 1964
5:36 PM
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• One of the most
damaging earthquakes in
the 20th century
• Lasted between 3-5
minutes
• Displacements up to 50 ft
along various faults
• Notable for the tsunami
that accompanied it.
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DAMAGES
• The earthquake, local tsunamis due to landslides,
and the regional tsunami were:
• Responsible for taking lives of more than 122 people
• Caused $106 million in damage
• Destroyed such things as :
2 saw mills
Union Oil Co. tank farm
Wharf and buildings
Alaska Railroad Depot
A boat harbor
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Affects in Alaska
• Estimated that 200,000
square kilometers of crust
were deformed.
• Greatest area of vertical
displacement ever
measured in earthquake
history.
• More than 2,000
landslides and
avalanches were
attributed to this
earthquake.
• Earthquake had dramatic
affects on lakes in Alaska.
• Movements of lakes cast
chunks of ice onto shore
and caused damage as
high as 30 ft to trees.
• Another result of serious
shaking was the
temporary change of soil
from the solid to liquid
state (liquefaction).
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Affects outside Alaska
• Traveled as far south
as Crescent City,
California.
• Coincided with
unusual observations
in other portions of
the US.
• For example, water
level in one well in
Dakota fluctuated
more than 20 feet.
• Similar fluctuations
were reported from
Puerto Rico and
Australia.
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Conclusion
• If you have any further questions about
earthquakes either refer to chapter 7 in the
text or the second exam or feel free to
contact the one and only brilliant Professor
Sandy.
LP