gel 1 - week 8

earthquakes

rocks sliding past each other

hypocenter (focus)

the exact underground point where rocks break

epicenter

the point on the surface directly above the hypocenter

fault traces

the line where a fault cuts the ground surface

fault scarp

a small cliff formed when one side steps upward

friction

the sticky force keeping rocks locked together

stress buildup

the stretching energy pushing rocks until they snap

normal fault

rocks pull apart, one side slides down

strike-slip fault

rocks slide horizontally past each other

thrust fault

rocks pushed together, one side shoves upward

foreshock

small earthquake that happens before the main quake

aftershock

smaller earthquakes that happen after the main quake

p-waves (primary)

fastest seismic waves, push and pull rocks

s-waves (secondary)

slower seismic waves, shake rocks side to side

love waves

surface waves that snake the ground side to side

rayleigh waves

surface waves that roll the ground like ocean waves

seismometer

machine that measures ground motion

seismogram

the paper or digital chart of squiggle lines recorded

s-p interval

the time gap between p-wave and s-wave arrivals

triangulation

using at least 3 seismometers to pinpoint a quake

richter scale

measures size based on wave height on seismograms

mercalli scale

measures size based on damage and human perception

moment scale

measures size based on total energy released

shallow earthquakes

happen at all boundary types: transform, divergent, convergent

deep earthquakes

only happen at convergent boundaries where plates sink

drop, cover, hold

the standard safety response during ground shaking

liquefaction

wet soil turning into mush during shaking

tsunami

giant ocean wave caused by underwater fault movement

secondary hazards

landslides, fires, and diseases triggered by quakes

cascadia subduction zone

fault capable of producing a massive magnitude 9+ quake

pnw earthquake types

deep, crustal, subduction megaquake, and volcanic

seismic hazard planning

designing stronger buildings to prevent structural collapse

earthquake early warning

systems that send alerts seconds before shaking hits