Assignment 1
Great 1964 Alaska Earthquake
Xiao Li 7677527
1. Introduction
On March 27, 1964, at 5:36 p.m. ADT (03:36 3/28 UTC) a great earthquake of magnitude 9.2
(moment magnitude) occurred in Prince William Sound region of Alaska. The earthquake
rupture started approximately 25 km beneath the surface, with its epicenter about 6 miles (10
km) east of the mouth of College Fiord, 56 miles (90 km) west of Valdez and 75 miles (120 km)
east of Anchorage. The earthquake damage the area covered about 130,000 square kilometers.
The area in which it was felt was about 1,300,000 square kilometers (all of Alaska, parts of
Canada, and south to Washington). The seismic wave traveled around the earth. The earthquake
lasted approximately 4.5 minutes and is the most powerful recorded earthquake in U.S. history.
This earthquake changed our thought about tsunami and we learned many lessons from the
disastrous Alaskan earthquake. A scientific understanding of the events that occurred may make
it possible to anticipate future earthquakes. This report will introductory many characteristic for
1964 great Alaska Earthquake, like the cause for the earthquake, the significance of theory of
Plate Tectonics for the Alaska earthquake, precursor activities, impacts on local communities,
and what can do to prepare the earthquake in the future.
2. Cause for the Great Alaska Earthquake
Background knowledge: Theory of Plate Tectonics
At start, geologists did not know how such a huge earthquake could have happened,
because, the theories of the day could not explain the movement of earthquake. Then people
come up a new theory, plate tectonics, which describe the large scale motion of Earth’s
lithosphere. The theory broken up lithosphere into seven or eight major plate and many minor
plates, these plates call tectonic plates, the moments of those plates was derived by mantle
convection force move away from mid ocean ridge. When these plates meet with each other
will create different type of boundary; convergent, divergent, or transform. These plates
boundary help geologists to explain many of the landforms and processes that we observe on
Earth.
Figure 1: The map shows the epicenter of the 1964 Great Alaska Earthquake (red star), caused when the Pacific
Plate lurched northward underneath the North American Plate. (U.S. Department of the Interior, 2014)
From the Figure 1, the location of epicenter is just between the Pacific plate and the North
American plate, and they are converge toward each other , Pacific plate is being overridden by
the North American plate, then Pacific plate subduct into the Earth’s mantle generating
subduction zone. Because the Pacific Plate moving towards the mantle, there is a force applying
to the plate boundary towards the mantle, so the North American Plate is dragged by that force,
the rock layer will deform elastically under low stress, exhibit plastic deformation at higher
stresses, after hundreds years that huge strain energy suddenly releases in few minutes, that’s
why earthquake has such big magnitude.
3. Precursor activities
An earthquake precursor is a phenomenon that might give effective warning of an
impending earthquake. But this kind of precursor activities generally recognized as such only
after the event.
Responses in water wells
Water-level fluctuations caused by the 1964 Alaska earthquake were recorded in 716 wells
in the United States. This response also was registered on water level recorders in many other
countries. The common type of ground water response is an instantaneous water level offset,
The water level will be recovery after earthquake.
4. Impacts on local communities after the Great Alaska
Earthquake
Primary impact
Primary impact includes seismic waves damage directly generates by earthquake Focus.
Body waves include two parts, P waves and S waves. P wave are series of compressions and
expansions waves. S waves are shear waves move up and down motion after the P waves. These
body waves travel through the interior of the Earth. The surface waves include Rayleigh waves
and Love waves, these particle motion waves has several times higher amplitude than body
waves, that’s why surface tend to have greater damage for manmade building structure.
According to dates from USGS, About 120 kilometers northwest of the epicenter, sustained
the most severe damage to property. About 30 blocks of dwellings and commercial buildings
were damaged or destroyed in the downtown area. The J.C. Penney Company building was
damaged beyond repair; the Four Seasons apartment building, a new six-story structure,
collapsed; and many other multistory buildings were damaged heavily. The schools in Anchorage
were almost devastated.
Secondary impact
Secondary impacts are the disaster trigger by earthquake, such like landslide, tsunamis and
aftershocks. As a mass wasting process, landslide is rapid mass movement cause by gravitational
transfer of earth materials down a slope. Conditions favoring mass wasting may exist for long
periods of time without movement; it usually requires an additional ingredient to initiate
movement. At this cause 1964 great Alaska earthquake is main factor to trigger landslides
disaster in Anchorage. Huge slides occurred in the downtown business section, at Government
Hill, and at Turnagain Heights. The largest and most devastating landslide occurred at Turnagain
Heights. An area of about 130 acres was devastated by displacements that broke the ground
into many deranged blocks that were collapsed and tilted at all angles. This slide destroyed
about 75 private houses. Water mains and gas, sewer, telephone, and electrical systems were
disrupted throughout the area.
Tsunami is other secondary impacts is relate to earthquake, generated by large-scale motion
of the sea floor. During the 1964 great Alaska earthquake, huge energy release by sea floor
motion transit to ocean, this energy raise the water level above the original level, when water
waves go through the sea, because the ocean is deep, huge potential energy keep inside the
huge mass of water, so the change of height of water wave are not distinct. When the tsunami
wave move to shallow area or approaching the shore, as water mass decreasing, the height of
tsunami wave will increasing. The 1964 Alaska tsunami was the second largest ever recorded,
maximum height reported for these waves were 70 meters in Valdez Arm. Tsunami hazard
generally can spread in very large area, the 1964 Alaska tsunami engulfed towns along the Gulf
of Alaska and caused serious damage in Canada, the west coast of the United States, Hawaii,
and even Japan.
Usually, an earthquake event will include several main shock and thousands of aftershocks.
Generally the aftershocks are much weaker than main shock, but aftershocks can exist very long
period of time. The aftershocks in 1964 Alaska earthquake was about 250 km wide and
extended about 800 km from Prince William Sound to the southwestern end of Kodiak Island.
Thousands of aftershocks were recorded in the months following the main shock.
5. The significance of Great Alaska Earthquake
Recognizing Hazards due to Movement on Secondary Faults
The geologists recognize the uplifts and tsunamis produced by the 1964 great Alaska
earthquake were greater than those generated by displacement in the subduction zone itself.
This demonstrated that splay upward from the main rupture plane can accommodate
movement associated with the sudden plate motion. These splay faults were commonly located
closer to shore, and can locally uplift the seafloor, causing the water above to be displaced and
increasing height or creating tsunami. After the 1964 earthquake, there are some uplifts
displacement along splay faults found at Montague Island, and Kodiak Island.
Increased Understanding of Liquefaction
Liquefaction refers to the process by which water saturated, unconsolidated sediments are
transformed into a substance that acts like a liquid, causing them to flow out to other place and
to lose material to support subsurface or manmade structures. Liquefaction can cause
substance and manmade structures collapse make huge damage. The 1964 great Alaska
earthquake provided a new insight that liquefaction caused by earthquake threat to the stability
of engineered structures. Many railroad bridges were destroyed when their pilings and piers
sank or spread apart because the underlying support soils material flowed out. This make the
government was funded some research after the 1964 earthquake, the research has developed
some methods to determine liquefaction potential of coarse grained soils; these methods are
used around the world by engineers to help ensure the safety of manmade structures.
Increased Understanding of Earthquake Hazards in Alaska
Geologists have improved understanding of the characteristics of subduction zones, and the
earthquakes and tsunamis after the 1964 Great Alaska Earthquake. The global scientists include
USGS are able to use GPS to measure the rate at which the Pacific Plate is converging with
southern Alaska, the data shows that Pacific Plate is sliding beneath southern Alaska at about
2.3inches per year.
Tsunami Hazard Assessments and Warnings
After the 1964 Great Alaska Earthquake, geologists recognizes that Tsunami hazard is great
threat can damage much more widespread than shaking damage. The tsunami caused by 1964
Great Alaska Earthquake southeastward toward the Washington, Oregon, and California
coastline, tsunami caused extensive flooding and damaged harbors. Because huge destruction
caused by faraway tsunami motion, the National Tsunami Warning Center operated by the
National Oceanic and Atmospheric Administration now can send alerts within minutes of an
earthquake that has the potential for generating a tsunami. At the U.S west coast, there are lot
of protective action has completed for mitigated Tsunami damage, such as planning evacuation
routes, educating coastal communities and their visitors, constructing tsunami-resistant
infrastructure, and creating earthquake monitoring and tsunami warning systems and centers.
6. The regional situation today
The 1964 Alaska earthquake has changed people thinking about the earthquake and
tsunamis. Basic understanding of tectonic tsunami generation was also improved following the
1964 event. But there are a lot of unknown for the earthquake and tsunami, like when is the
next big earthquake? How big is the potential greatest magnitude of earthquakes these ruptures
will produce? People find several ways to protect our self from earthquake.
The USGS Science Application for Risk Reduction (SAFRR) project
This project helps build resilience many natural hazards, like earthquakes, floods, wildfires,
landslides, tsunamis, and coastal erosion by improve decision making and emergency response
efforts across the nation. SAFRR project also point a direction for scientific researcher to
producing innovative products, improve vulnerability and connecting experts with users of their
science.
The “Alaska Shield” component of FEMA’s National Exercise Program
Capstone Exercise 2014
The “Alaska Shield” component of FEMA’s National Exercise Program Capstone Exercise
2014 is a complex emergency preparedness exercise designed for Alaska to test response plans
and capabilities during the great natural hazard.
Earthquake Early Warning System
Earthquake Early Warning System can alert people the expect time of earthquake wave to
arrive at their location. Not like weather forecast, Earthquake Early Warning System only can
provide a few minutes or few seconds warning before the earthquake wave arrive, time is less
but does matter, it will great help people to enable much of protective actions.
7. Conclusions
The 1964 great Alaska earthquake is one of largest magnitude and mean to human in the
history. Because 1964 Alaska earthquake people start to recognizing Hazards due to Movement
on Secondary Faults, Increased Understanding of Liquefaction, Increased Understanding of
Earthquake Hazards in Alaska and Tsunami Hazard Assessments and Warnings. And people start
to come up many project to prepare the future great hazard, such like the USGS Science
Application for Risk Reduction (SAFRR) project, FEMA’s National Exercise Program and
Earthquake Early Warning System. But those protective preparations still cannot stop the deaths
from earthquake hazard, there are lots of unknowns for earthquake, such like how to improve
the efficiency of predicting earthquake, people still need to develop understanding of
earthquake.
8. Reference
Alaska Earthquake Information Center. (2002, November). The Great Alaska Earthquake of 1964.
Retrieved from AEIC:
http://www.aeic.alaska.edu/quakes/Alaska_1964_earthquake.html
Federal Emergency Management Agency. (2014, July 24). National Exercise Program (NEP) Capstone Exercise 2014. Retrieved from FEMA: http://www.fema.gov/national-exerciseprogram-nep-capstone-exercise-2014
U.S. Department of the Interior. (2014, September 11). Earthquake Early Warning. Retrieved
from USGS: http://earthquake.usgs.gov/research/earlywarning/
U.S. Department of the Interior. (2014, July 22). SAFRR - Science Application for Risk Reduction.
Retrieved from USGS: http://www.usgs.gov/natural_hazards/safrr/
U.S. Department of the Interior. (2014, March 25). The 1964 Great Alaska Earthquake &
Tsunami. Retrieved from USGS:
http://www.usgs.gov/blogs/features/usgs_top_story/the-1964-great-alaskaearthquake-tsunami/
U.S. Department of the Interior. (2014, MAY 28). The Great Alaska Earthquake and Tsunami of
March 27, 1964. Retrieved from USGS:
http://earthquake.usgs.gov/earthquakes/events/alaska1964/
U.S. Department of the Interior. Michelle Sneed, Devin L. Galloway and William L. Cunningham.
(2014, February 18). Earthquakes—Rattling the Earth’s Plumbing System. Retrieved
from USGS: http://pubs.usgs.gov/fs/fs-096-03/
U.S. Department of the Interior.Thomas M. Brocher, John R. Filson, Gary S. Fuis, Peter J.
Haeussler, Thomas L. Holzer, George Plafker, and J. Luke Blair. (2014, March 11). The
1964 Great Alaska Earthquake and Tsunamis—A Modern Perspective and Enduring
Legacies. Retrieved from USGS: http://pubs.usgs.gov/fs/2014/3018/
U.S. Department of the Interior.Wallace R. Hansen, Edwin B. Eckel, William E. Schaem, Robert E.
Lyle, Warren George, and Genie Chance. (2011, November 4). Professional Paper 541,
The Alaska Earthquake of March 27, 1964. Retrieved from USGS:
http://pubs.usgs.gov/pp/0541/