Geology Of Natural Disasters

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
Processes
 
internal and external
Process
 
ways in which events effect the earths surface
Hazzard
 
natural process that threatens human life or limb
risk
 
the probablu severity that a destructice event will occur mulitplied by the likelyhood of the event
mitigation
 
efforts to prepare for disasters and to minimize harmful effects
geological cycle has four parts which are
 
tectonic
rock
hydrologic
bigeochemical
tectonic cylce
 
large scale geological processes that deform the earths crust
outer most layer of the earth?
 
lithosphere
level below lithosphere
 
asthenosphere
plate boundary types
 
divergent
convergent
transorm
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
earthquakes
 
movement on faults
epicenter
 
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
 
atmosphere
hydrosphere
solid earth
life
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
physiology
 
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)
 
technical
ethical
economical
enviornmental
|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
 
intensity
duration
rate of change
managing population decline
 
immigration
raise retirment age
encourage women to have more children
managing population growth
 
regulations
education on birth control
provisions of contraception
eduactation of women
industrilization
more disasters because
 
population growth
land pressure
urbanization
inequality
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
Tusunami
 
generated by earthquake at sea
earthquake hazzard
 
ground faulting
earth shaking
afdtershock
material amplification
ground failure tsunami
fires
disruption of water
disease
dam construction
 
water changes stress regime on faults, water can lubricate faults
mining
 
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
radiation
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