Land Degradation Due to Agriculture:
Part 3 Impacts of Deforestationand Soil ErosionFall 2012 , Lecture 7
Earth ObservatoryImage
• On March 19, 2012, MODIS, on NASA’s Terra satellite, captured this natural-color image of a storm sweeping across Iran, Afghanistan, and Pakistan
• Some source points are visible in southern Afghanistan, and the dust blew in southeast-northeast arcs
• Most of the dust plumes in this storm were thick enough to completely obscure the land and water surfaces below
2
Soil Loss• Deforestation often leads to soil erosion• Agricultural use of land can also produce soil
erosion Modern methods used in advanced countries have
greatly cut these losses In developing countries, agricultural soil loss is still a
major problem3
On-site Impacts of Soil Erosion• Reduction in soil quality resulting from
Loss of the nutrient-rich upper layers of the soil Reduced water-holding capacity of many eroded soils
• Increased use of artificial fertilizers can mitigate the first problem in developed countries
• Not an option in most developing countries
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Time-Scale of Problems• On-site impacts of soil erosion are a present-day
problem for many of the developing nations• For developed nations, on-site impacts will be a
problem only in the long term future because they are outside the relatively short time horizon within which their policy makers work
5
Off-site Impacts of Soil Erosion• Water erosion’s main
off-site effect is the movement of sediment and agricultural pollutants into watercourses
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• China's Yangtze River at the Three Gorges, in Hubei province. Note the sediment-rich water
Watercourse Sedimentation
• Sediment in watercourses can lead to the silting-up of dams, disruption of the ecosystems of lakes, and contamination of drinking water
7
• Satellite view of the delta of the Yangtze River as it discharges into the East China Sea. The sediment plume is clearly visible. (Image: NOAA)
Down-stream Flooding• Increased downstream flooding may also
occur due to the reduced capacity of eroded soil to absorb water, and to the reduced capacity of streams and lakes to hold water
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Time-Scale of Off-Site Problems• Short-term effects of erosion's off-site effects can be
a notable problem for developed nations• Policy change in developed countries may be driven
by off-site impacts• For less developed nations, there may be less
incentive for short-term policy change
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Examples of Soil Erosion • We will examine soil loss in several areas
Indonesia Madagascar Haiti
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Kalimantan, Borneo, Indonesia • In less than 25 years, three-
quarters of Kalimantan, which occupies a large part of the Island of Borneo in Indonesia, half of the thick forests have been cut by loggers for agricultural land, including oil palm plantations
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Agricultural Land Clearing• Kalimantan locals have
long burned forestland to create plots for farming
• Formerly small, controlled fires were used
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“A” is Borneo, in relation to SE Asia
Drying the Land• As deforestation has progressed, the island has
become drier• The small fires have changed to
conflagrations • The cause is burning peat
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Loss of Swamp Land• Peat has formed over thousands of years from decomposed
trees, grass and scrub • It contains huge quantities of carbon dioxide• Formerly, that was safely sequestered in the ground• Deforestation has caused drying, and the peat is disintegrating• Once-soggy swamps are shorn of trees and drained by canals• When peat burns, carbon dioxide gushes into the atmosphere
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Indonesian Photo Gallery• Washington Post Photo Gallery – Indonesia• The link is from a story “A climate threat,
rising from the soil”, by Andrew Higgins, which appeared in the Washington Post on November 19, 2009
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CO2 from Peat Burning• Wetlands International, a Dutch research and lobbying group, estimated
Indonesia's peatlands released roughly 1.9 billion metric tons of carbon dioxide in 2006
• This was equal to the combined emissions that year of Germany, Britain and Canada, and more than U.S. emissions from road and air travel.
• In 1997, particularly bad fires raged across Kalimantan and, according to a study led by a British scientist, the amount was up to four times as high -- more than the total emissions by the United States in that period
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Economics versus the Environment• Logging and palm oil companies deploy
formidable resources across Kalimantan• These are both economic, and physical forces,
used against environmental activists trying to protect the fragile peat
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Palm Oil Operations• At the PT Globalindo Agung Lestari, an oil palm
estate, a wooden barrier separated a dozen or so out-of-town environmental activists with a bullhorn
• On the other side, company security guards, local police officers and Indonesian soldiers, armed with automatic weapons, stood ready
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Supporting the Company• Villagers were angry at the plantation, but had to stay
away• They couldn’t afford to lose their jobs tending oil palm• The pay is about $3 a day and the work is backbreaking• Budi, a 21 year old worker, said "when you don't have
anything, you have to support the company"
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Ethics vs. Economics
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This video, from Time movies, shows the ethical problems faced by indigenous peoples, when choosing to exploit the environment or be unemployed
Erosion in Action• Video clip shows
erosive rainfall in a region of steep topography in Indonesia
• The effect of vegetation removal is evident
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Kuala Cenaku, Riau Province,
Indonesia
• Riau is a province of Indonesia, located in the center and eastern coast of Sumatra along the Strait of Malacca
• Extensive logging has led to a massive decline in forest cover from 78% in 1982 to only 33% in 2005
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WWF Information• Riau Province is the home of two of the world’s largest pulp mills,
produces more than two thirds of Indonesia’s pulp, and is covered with more timber plantations and more oil palm concessions than any other province in Indonesia
• Between 1988 and 2005, half of Riau’s forests disappeared at an average rate of 170,000 hectares per year or 460 hectares per day
• The loss of some of the most diverse forests on earth is accelerating rapidly - the annual rate of forest cover loss was 2.2% in 2002, 4.2% in 2004 and 6.8% in 2005
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Peat Depth• According to Indonesian law, it is illegal to
clear forest where peat exceeds 3 meters in depth
• The law is largely ignored, with disastrous consequences
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Greasy Palms: The Impact of
Indonesia’s Palm Oil
Plantations• Video from
the Paradigm Shift Project
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Air Pollution• A final problem caused by fires in the thick peat
deposits is severe air pollution• The haze can travel hundreds of miles in SE Asia• The following video shows the effects in Malaysia• The video also some of the products palm oil is used
for
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Malaysian Haze Video
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Madagascar• Fourth largest island in the world• Madagascar split from India around 88 million
years ago, allowing plants and animals on the island to evolve in relative isolation
• Isolated areas often see less evolution than other regions
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Restricted Evolution• In Madagascar, there are no woodpeckers or
ungulates (hooved animals) present• Instead, animals like lemurs dominate rare
ecosystems, present no where else on earth• More than 200,000 known species are found on
Madagascar, and about 150,000 exist nowhere else
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Madagascar History• Beginning in the early 19th century, most of the island was
united and ruled as the Kingdom of Madagascar by a series of Merina nobles (Merina is the largest cultural sub-group)
• Collapse of the monarchy occurred in 1896 when the island was conquered and absorbed into the French colonial empire, from which the island gained independence in 1960
• The autonomous state of Madagascar has since undergone four major constitutional periods, termed Republics
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Coup d'état• Since 1992 the nation has officially been governed as a
constitutional democracy from its capital at Antananarivo• However, in a popular uprising in 2009 the last elected
president Marc Ravalomanana was made to resign and presidential power was transferred in March 2009 to Andry Rajoelina in a move widely viewed by the international community as a coup d'état
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Patricia Wright• Before Rajoelina came to power, the state of
Madagascar's ecological health was actually improving, according to Patricia Wright, professor of anthropology at the State University of New York at Stony Brook, executive director for the Institute for the Conservation of Tropical Environments, and a recipient of a MacArthur Foundation "genius award"
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Wright’s Opinion• “It's one of the success stories in all of the conservation
world. Because of big inputs from conservation agencies — U.S. AID [Agency for International Development], the European Union — the infrastructure of the country improved. The protected areas were being protected. Everything looked really optimistic for keeping the island's forests in place.”
33
Effects of the Coup d'état• The problem with the coup d'état, according to Wright,
“Everyone assumes they can literally take anything they want. So we have major rosewood being extracted from the beautiful forests in the north. We have a certain amount of lawlessness that's going on, also in the north. Inside protected areas, the National Park Service [rangers] abandoned their posts because they were afraid. They've since returned, but it's been a very difficult year for protecting wildlife.
34
Tavy• “Tavy” is a Malagasy word for the slash and burn agriculture practiced
in Madagascar• An acre or two of forest is cut, burned, and then planted with rice• After a year or two of production the field is left fallow for 4-6 years,
then the process is repeated• After 2-3 such cycles the soil is exhausted of nutrients and the land is
likely colonized by scrub vegetation or alien grasses• On slopes, the new vegetation is often insufficient to anchor soils,
making erosion and landslides a problem
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Economic Necessity• Madagascar is among the world's poorest countries• As such, people's day to day survival is dependent upon
natural resource use• Where day-to-day subsistence is a question, people show little
concern for the long-term consequences of their actions• As long as there is more forest land freely available for
clearing, you might as well use the land before a neighbor does.
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Erosion in Madagascar
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Seen from the air
Erosion in Madagascar
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• Betsiboka River, Madagascar, running like liquid chocolate, January 2012
• Astronauts have remarked that it looks as if Madagascar is bleeding to death, with its rivers running blood red and staining the surrounding Indian Ocean
Image from Space
• Nearly a century of extensive logging of Madagascar’s rainforests and coastal mangroves has resulted in nearly complete clearing of the land and fantastic rates of erosion
• After every heavy rain, the bright red soils are washed from the hillsides into the streams and rivers to the coast
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This image of the Betsiboka Estuary on the northwest coast of Madagascar reveals the mouth of the country’s largest river and one of the world’s fast-changing coastlines
NASA Description• Astronauts describe their view of Madagascar as 'bleeding into
the ocean' • One impact of the extensive 20th century erosion is the filling
and clogging of coastal waterways with sediment - a process that is well illustrated in the Betsiboka estuary
• In fact, ocean-going ships were once able to travel up the Betsiboka estuary, but must now berth at the coast
40
Malagasy Agriculture• Agriculture is the mainstay of the Malagasy economy, using
80% of the labor force • Deforestation, unsustainable farming methods, low
productivity and insecure land tenure are all fuelling diminishing soil yields and threatening the island's food security, putting the agriculture section at risk
41
Agroecological Techniques• The Agence française de développement (AFD) is developing,
the use of agroecological techniques with Malagasy farmers• This approach involves protecting the soil with a green cover
crop, as a way of avoiding plowing, and restricting the use of fertilizers
• Soil fertility is restored, watershed erosion is reduced and as are CO2 emissions
• The video on the next slide explains the use of agroecology
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Agroecology in Madagascar
43
Haiti• Haiti occupies the western
third of the island of Hispaniola, which is situated in the Caribbean between Cuba and Puerto Rico
• The Dominican Republic occupies the remainder of the island
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• The Atlantic Ocean borders Haiti’s northern shores, while the Caribbean Sea is to the west and south
Haitian Topography• Haiti occupies the mountainous portion
of the island of Hispaniola• Five mountain ranges dominate Haiti’s
landscape and divide the country into three regions northern, central, and ⎯southern
• Slopes of more than a 20 percent grade cover nearly two-thirds of the country
• Plains constitute only about 20 percent of Haiti’s land, making cultivation difficult
45
Haitian Deforestation• Haiti faces a severe deforestation problem• In 1923, forests covered nearly 60 percent of the
country; today they cover less than 2 percent• Wood and charcoal are the primary fuel source
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Beginnings of Deforestation• At the onset of colonialism, Haiti began to suffer deforestation• Around 1730, coffee was introduced, producing a monoculture
agriculture• Within 50 years upland forest clearing resulted in 25% of the
land being under coffee• Other crops included indigo, tobacco, and sugarcane• Clean cultivation between row crops exhausted nutrients and
lead to erosion
47
Nineteenth Century• Throughout much of the 19th century, the
government was forced to export timber to repay a large debt to France
• Peasants were restricted to hillside farms, where often steep slopes lead to severe erosion
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Poverty• Lack of economic capital make farming difficult• Average per capita income is less than one-seventh
of the average for Latin America and the Caribbean• With inheritance, land is subdivided, and plots grow
increasing smaller• One estimate claims the average peasant has less the
one-quarter of a hectare49
Leased Land• Many families lease or sharecrop additional
land• Farmers on leased or share-cropped land have
little incentive to take care of the land• In addition, most agricultural work is by hand,
with no mechanical equipment
50
Lack of Government Aid• The government has been controlled by a
string of dictators for many years• They are much more intent on enriching
themselves, not using the few resources they have to improve conditions
51
Effects of Deforestation• Deforestation has a number of effects
Soil erosion• Soil erosion has decreased agricultural yields• Soil erosion into the ocean also blankets coral reefs with sediment, killing
the reefs
Floods due to disruption of the natural hydrologic cycle Landslides
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Flooding• When vegetative cover is removed from the
land, the rate of infiltration decreases dramatically
• Since water has to go somewhere, if it can’t infiltrate, it runs off
• Rapid runoff leads to flooding
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Haiti’s Unnatural Floods
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Landslides• Landslides have also been a frequent cause of
death in Haiti• For example, there was a landslide in late
March of 2012 in which six people in Port-au-Prince were killed by a landslide
55
Tropical Storm Hanna, 2008• As Hurricane Hanna approached Haiti in September
2008, Dave Petley (Wilson Professor of Hazard and Risk in the Department of Geography at Durham University in the United Kingdom) blogged on an American Geophysical Union site that 136 people have been killed in flash floods and landslides as a result of Hanna, but time might reveal more casualties
56
Haiti-Dominican Republic Border• The river in the photo is the
border between Haiti (left) and the Dominican Republic (right)
• The lack of vegetation in Haiti has made landsliding a tremendous problem
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Aftereffects of Gustav/Hanna• On August 26, 2008 Hurricane Gustav brought strong
winds and heavy flooding to Haiti• On 1 September 2008, only days after Gustav hit
Haiti, Tropical Storm Hanna surprised the country, worsening the effects of Gustav and leaving more people affected, especially in the city of Gonaives
58
Post Storm Damage Estimates• According to Haitian government statistics:
A total of 793 people lost their lives 310 were declared missing 548 were injured Damage to homes and infrastructure affected 165,337 families
• It is estimated that 22,702 families’ homes were completely destroyed • Another 84,625 families’ homes were damaged
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Aftereffects of Haitian Storms, 2008• This is a series of
still photos showing the aftereffects of the 2008 Haitian storms
• Note especially the extent of the flooding
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Video Interview• The following video interview by Amy
Goodman, the host of Democracy Now!, an independent global news program broadcast daily on radio, television and the Internet, with Dr. Paul Farmer
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Paul Farmer, M.D.• Paul Farmer is an American anthropologist and physician• Named chairman of Harvard Medical School's Department of
Global Health and Social Medicine in May 2009• In December, 2010, Harvard University's President, Drew
Gilpin Faust, and the President and Fellows of Harvard College, named him a Kolokotrones University Professor of Harvard University, the highest honor that the University can bestow on one of its faculty members
62
Partners in Health• This video conveys the magnitude of the problems that Haiti
faces, much of which has been caused by deforestation• Dr. Farmer co-founded Partners In Health, which began in
Cange in the Central Plateau of Haiti and has developed into a worldwide health organization
• His extensive experience in Haiti and other third world countries give him a perspective most commentators do not have
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Farmer Interview
64
Haitian Earthquake• On January 12, 2010 Haiti suffered a magnitude 7.0
earthquake, which caused the death of more than 200,000 people, the injury of about 300,000 people, and left about two million people homeless
• A year and a half prior to the earthquake, Haiti was subjected to another severe disaster, flooding induced by two hurricanes and two tropical storms (Fay, Gustav, Hanna and Ike)
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Hurricane-Earthquake Connection?• Both natural disasters results in death and
destruction, but because their origins are very different, they are generally considered to be unrelated phenomena
• A pr by Shimon Wdowinski et al. suggested there may be a connection
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Earthquake Location• The earthquake was thought
to have occurred along the Enriquillo-Plantain Garden Fault, part of the fault system that separates the North American plate to the north from the Caribbean plate
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Previous Tectonics• In 1770, there had been a large earthquake to
the west of Port-au-Prince• GPS measurements suggest that the underlying
tectonics are a left lateral shear at 8 mm per year and shortening (convergence) at about 5 mm per year
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Strike and Dip
The strike-dip symbol, used on geologic maps, is shown - the long direction points in the horizontal direction, and the shorter side
shows dip direction
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Strike-slip Direction
• Strike-slip faults are further described as "right-lateral" or "left-lateral" depending if the block opposite the viewer moved to the right or left, respectively
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Left-Lateral Strike Slip• Block is displaced to the
left, looking across the fault
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Strike Slip Faults - Left Lateral
Near Lillooet, British Columbia
Westward Movement• So the previous work indicated that the area
north of the fault was moving west relative to the area south of the fault
• The earthquake showed westward movement on the Enriquillo fault, but there was no evidence of surface rupture on that fault
73
Discovery of a New Fault• Post earthquake investigations suggest shortening as well as
strike slip movement• The data suggest a different fault, not the Enriquillo fault, was
responsible for the earthquake• This new fault, which is orientated sub-parallel to the
Enriquillo Fault, is now known as the Leogane Fault, with a combination of strike slip and dip slip movement
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Dip-slip Faults
• Dip direction is always perpendicular to the strike line
• Combination of dip and strike slip produces oblique-slip
Fault Models• From remote sensing data it was evident there was no surface
rupture• There was evidence of coastal uplift• Measurement of the uplift suggested movement of about 64
cm over a distance of 50 km of coast• Two fault models have been proposed to explain this, one with
movement along two faults, the other with movement along three faults
76
Movement on a Blind Fault• Both models suggest that most slip was on
south dipping blind fault.• A blind fault is one which does not reach the
surface• The presence of blind faults is often unknown
until an earthquake reveals their presence
77
Haitian Scientific Effort• Jean Altidor, from the Haiti Bureau of Mines and
Energy, working with the USGS and the Canadian natural resource bureau, deployed seismometers in March 2010 to measure aftershocks
• Worked with various other groups to undertake geological and geodetic measurements
78
Earthquake Amplification• Found that downtown Port-au-Prince is
underlain by soft sediments• Soft sediment behaves like a bowl of jello
during an earthquake and will amplify shaking, causing much greater destruction
79
Sediment Unloading• Wdowinski et al. suggest that the hurricanes trigger surface
unloading due to rapid erosion, which then triggers the earthquake
• Unloading may decrease pressure perpendicular to the ground’s surface
• In the case of the earthquake, movement on the fault was atypical (dip slip)
80
Leogane River and
Delta
81
Google Earth Image
• “Google Earth image of Haiti taken November 8, 2010, showing the capital of Port-Au-Prince and the mountainous region to its west where the epicenter of the 2010 earthquake was. Note the brown color of the mountains, where all the vegetation has been stripped off, leaving bare slopes subject to extreme erosion. Heavy rains in recent years have washed huge amounts of sediment into the Leogane Delta to the north.”
82(From figure caption on Dr. Jeff Masters blog)
Leogane Delta• Zoom-in view of the Leogane Delta region of previous figure, showing the large expansion in the Delta's area between 2002 and 2010. High amounts of sediments have been eroded from Haiti's deforested mountains and deposited in the Delta. Recent expansion of the river channel due to runoff from Hurricane Tomas' rains is apparent in the 2010 image. Image credit: Google Earth, Digital Globe, GeoEye.
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(From figure caption on Dr. Jeff Masters blog)
Rapid Erosion as Earthquake Trigger• Hurricane induced rapid erosion in the mountains
would release downward pressure, allowing vertical movement
• Previous movements were estimated at 5 mm per year of convergence, which would produce vertical uplift
• Reducing load might act as a trigger, allowing movement to initiate
84
Sediment Deposition in Delta• The calculated sediment deposition in the
delta of the river draining the mountains gives an erosion rate of 6 mm per year
• This is much higher than expected, and is due to deforestation
85
Digitial Elevation Model• A (DEM) was used to calculate stress change at the earthquake
focus due to sediment unloading• Wdowinski et al. modeled resultant stress change on the fault• The model shows that unloading promotes fault movement on
a south dipping fault and that the magnitude of change is at least hypothetically able to trigger the earthquake
86
Delay Between Hurricane and Earthquake• Why was there a delay between the hurricane and the
earthquake? • Possibly the increased soil moisture help to keep normal
stress high, due to the increased mass of the water in the soil• Once the soil dries out, mass is reduced, causing a reduction
in normal stress• Fault movement may have resulted
87
Hypothesis, not Theory• This is a very interesting speculation• However, it is a hypothesis• The paper was presented at a meeting of the
American Geophysical Union in the Fall of 2010, but has yet to appear in the scientific literature, possibly due to peer review comments
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