Geology Of Natural Disasters

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Geology Of Natural Disasters

Geology Of Natural Hazzards 

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Tsunamis are triggered by?
subduction zones
what is a subduction zone?
long narrow srip of lithosphere where one tectonic plate move benith the other
internal and external
ways in which events effect the earths surface 
natural process that threatens human life or limb
the probablu severity that a destructice event will occur mulitplied by the likelyhood of the event
efforts to prepare for disasters and to minimize harmful effects
geological cycle has four parts which are
tectonic cylce
large scale geological processes that deform the earths crust
outer most layer of the earth?
level below lithosphere
plate boundary types
reasons damage from natural disasters are increasing
population growth
magnitude and frequency of events
befits of natural disaster
floods=new sediment
volcano= new land
earthquake=mountain range
movement on faults
point on the surface of the earth directly above the fault rupture or focus
fault types
strike slip

dip slip
ice age caused by
tilt, precission, ecentricity
4 reservoirs of earth system
solid earth
Galia theory
all life and all the material parts of the earths surface make up a single system a kind of meta organism and a living planet
brach of bio that deals with activitiesd of life and the physical chemical phenonmeon involved
father of geology
james hutton
Thomas Midgely
greatest impact on the earth, leaded gasoline and fist chloroflurocarbins
Managing earth requires (4)
|Risk Analysis
1) understand the hazzard

2) acess the risk from the hazzard in a particular area
Risk Managment
minimize risk by reducing probablility and severity of hazzards
cost benifit anaysis
main factors that conrol how severe an event is 
rate of change
managing population decline
raise retirment age
encourage women to have more children
managing population growth
education on birth control
provisions of contraception
eduactation of women
more disasters because
population growth
land pressure
climate change
political change
economic growth
technological innovation
local expectations
global interdependence
Understanding the hazzard
what causes earthquakes
where do they occur
what energy to they release
what causes damage
Elastic rebound theory
rigid part of the earth can store elastic energy. when you apply stress it bounces back when you apply too much to breaks
 seismometers allow
detect energy from a quake
measure distnace to a quake
measure energy releases
first seismometer
april 17, 1889
san francuscio sit on what fault
san andreas fault
two types of surface waves
love waves
reyleigh waves
Body waves
p waves: primanry push and pull
s waves: secondary shear
the more elastic the material
higher the sesmic velocity
more dense a material
lower the sesimic velocity
s waves travel at 
3.3 km per sec
p waves travel at 
5.6 km per sec
why do earthquakes only occur in the outer 10% of the earth 
only part that is rigid enough to experience brittle failure
how do we estimat energy from a quake
measure intensity based on obsrved damage: modified mercalli scale
richter magnitude
Modified Mercalli Scale
based on observed damange, subjective, depends on how close people are, varies based on distance to epiceter
Richter Magnitude
quantitative measure of energy released determined frim the maximum amplitude (surface waves) on seismogram  
damage is a direct consequence of 
surface wave motion
amount of damage is proportional to 
distnace from quake (inversly)
magnitude of quake (directly)
surface faulting 
fault will be disrupted by the tearing motion
Ground shaking
greatest threat to buildings and people
Material Amplification
sesimic velocity changes when going from one medium to another 
after shock
smaller earthquakes that occur soon after the main shock with epicenters in the same area as the main shock
Ground Failure
land slides and liquefaction of soils
generated by earthquake at sea
earthquake hazzard
ground faulting
earth shaking
material amplification
ground failure tsunami
disruption of water
dam construction
water changes stress regime on faults, water can lubricate faults
underground blasting can destabilize rocks which can lead to earthquakes
Assess seismic risk of area
locate and determine nature of faults in the area
determine what type of fault
study history of quakes
set up seismometers
deterimne reccurence interval
Law of Superposition 
for sediment layers the oldest aare on the bottom and the youngest on top
Law of Cross-cutting relationship
fault cuts across the layers there for the fault is younger then the layers
carbon 14 data 
can be used to deterimine when the fault last move
Preventative measures
appply land planning and zoning
apply building codes
set up emergency response plans
what causes faults
stress on rock in earth
what causes stress in earth 
release of earths internal heat
how is heat released to the surface
conduction and convection