understanding earthquakes Flashcards
(21 cards)
benioff zone
area of seismicity corresponding with slab being thrust down in the subduction zone (at destructive boundary
fault
fracture in rocks which make up the earths crust
locked fault
a slip due to built up strain (not friction between plates)
focus / hypocentre
point in crust where the seismic waves originated from
epicentre
point on earth’s surface above the hypocentre
seismic waves
type of wave which causes shaking
3 types of seismic waves
primary (compressional)
secondary (shear)
love (surface waves)
sequence of an earthquake
strain, pressure exceeded, release, rebound
2 primary hazards of an earthquake
ground shaking, crustal fracturing
ground shaking
movement of the ground due to the P,S and L waves in less than 60 seconds, causing buildings to be damaged if they are not aseismic
what does aseismic mean
earthquake proof
crustal fracturing
shockwaves in solid rock increases stress and causes rock fractures and faults - damaging building above
3 secondary hazards of earthquakes (physical)
soil liquefaction
landslides and avalanches
tsunami
soil liquefaction
loose rock and sediment causes buildings to settle/tilt/collapse worsened in river areas and sloping ground as building sink due to soil instability
landslides and avalanches
mag 4+, areas of land collapse due to shaking (often if land is saturated)
tsunamis
caused when plate rebounds and a water displacement is created, can devastate areas due to high amplitude, fast velocities
which causes more deaths, primary of secondary hazards
secondary -> 70% of all deaths are due to secondary earthquakes
P waves info
longitudinal, 8km/s and travel through solid and liquid
smaller wl, high frequency
S waves info
transverse, 4km/s only travel through solids and are slower but are very destructive
L waves 2 types
love = move side to side
raleign = like a roll (up,down,up etc)
L waves info
largest at the surface and decrease in amplitude at depth, are very destructive
