Hazards BK 4 - Seismic Hazards Flashcards
what are 3 types of seismic hazards
earthquakes , tsunamis and aftershocks
what are 2 primary impacts of a seismic hazard
shaking of the ground
deformation
what is deformation
changing of the earths surface due to a seismic hazard
what are some secondary impacts of seismic hazards
mass movement
flooding
death/injury
evacuation
homelessness
fires
liquefaction
what is the definition of focus
the point where the pressure released from an earthquake occurs in the crust, where shockwaves radiate from
what is the definition of epicentre
the point immediately above the focus
which focus earthquake causes the most damage
shallow focus
what are the two main types of wave
body and surface
what are body waves
they transmit much of their energy deep underground
what are surface waves
waves that vibrate through the earths crust creating destructive surface waves
what are the two types of body waves
P waves and S waves
what are some factors of P waves
fast moving
cause rock to expand and contract
travel through liquids and solids, so can pass through the centre of the earth
cause little destruction
what are some factors of s waves
slower moving and can’t pass through liquid
exert force up and down
these waves can be destructive
what are the two types of surface waves
love waves
rayleigh waves
what are some factors of love waves
they cause the ground to shake from side to side
cause a lot of damage and destruction
what are some factors of rayleigh waves
very destructive
ground moves forwards and backwards and up and down too
how fast do P and S waves tend to travel
P= 6km per minute
S= 3km per minute
do the british isles still get earthquakes?
yes but they’re very small so mostly aren’t felt by anybody
what 3 ways are earthquakes measured
the richter scale
the moment magnitude scale
the mercalli scale
why are some scientists concerned about the richter scale
it was not developed to allow for accurate measurements of deeper focus quakes but it has been adapted.
what scale is now used by seismologists instead of the richter scale
the moment magnitude scale
whats the moment magnitude scale mkre reliable in measuring
measuring larger scale earthquakes more accurately
what scale does the richter scale measure to and from
1-9
what is the mercalli scale based on
the intensity of an earthquake as measured by the damage that it causes, in terms of the visual observation of effects
how many numbers does the mercalli scale go too
12
what are some impacts of seismic hazards
fires
shockwaves
tsunamis
soil liquefaction
mass movement
damage to infrastructure
what determines the severity of the ground shaking due to an earthquake
magnitude
depth
distance from epicentre
local geological conditions
what’s the definition of ground rupture
the visible breaking and displacement of the earths surface, usually along a line or fault
what two things does ground displacement involve
uplift and subsidence
what is liquefaction
when soil is shaken violently and takes on the properly of a liquid
what damage can liquefaction cause
infrastructure to collapse
uproot trees
damage to underground pipes
why do fires tend to follow earthquakes in urban areas more than rural ones
more gas pipes and electrical systems in urban areas
what is a tsunami
a giant sea wave generated by shallow focus underwater earthquakes, volcanic eruptions and large landslides into the sea
what are some factors of tsunamis
long wavelength
low wave height
height increases nearer the shore
what is the first warning of a tsunami
reduction in sea level at the shoreline
what are 8 techniques that can be used to manage seismic hazards
1)hazard resistant structures
2)education
3)fire preventation
4)emergency services
5)land use planning
6)insurance
7)aid
8)Building preparedness
how do hazard resistant structures work
1)large concrete weight ontop of building so it moves in opposite direction
2)large rubber shock absorbers in foundations
3)cross bracing to structure to hold it together when it shakes
how does education of seismic hazards work
authorities tend to give out instructions about how to prepare for these hazards , earthquake evacuation at school etc
how does fire preventation management work
smart meters that have been made will be cut off in event of a high magnitude earthquake
how does emergency services work in terms of the management of a seismic event
heavy lifting gear always available
first aid trained people
how does land use planning work in terms of managing a seismic event
help understand which areas are most and least at risk
areas can be grouped
how does insurance work in terms of managing a seismic hazard
more affluent areas see rich take out and invest in insurance to cover their losses
very expensive
how does aid work in terms of managing a seismic event
poorer countries tend to receive more aid e.g. medical support, tents etc
how does building preparedness work in terms of managing a seismic event
buildings and homes made using light walls, straw, bamboo to reinforce walls
better than having light roofs which can easily fall or collapse
