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what is an earthquake?
sudden shaking of earth crust
what are earthquakes sually associated with?
rupture of a fault
accumulated stress energy is released as _______
when seismic waves radiate through the earths interior and surface what does it cause?
why do subduction zones have extreme earthquakes?
two plates touching build up stress
how many major cities lie on on near unstable regions of the earths crust?
ground shaking produces:
- sediment liquefaction
- mass wasting (landslide)
- building collapse
explain elastic rebound theory:
- crust at rest- no strain
- crust deformed- strain build up
- ruptured crust causing earthquake-elastic rebound
- fractured crust, fault zone- strain released
where do most earthquakes occur?
- plate boundaires
- intraplte seismicity also common
explain intraplate earthquakes
- shallow foci
- soft weak area of plate interior
- occur near pre existing plate boundaries
- ex appalachian
what are the sites of frequent earthquake activity?
divergent, convergent and transform margins
what is the epicenter and and focus point?
epicenter is point on ground above focus and and focus is where earthquake occurred
explain transform seismicity
Most earthquakes along transform plate boundaries tend to occur at shallow to moderate depths in the crust
explain convergent seismicity:
steep diping plane called wadati benioff zone
explain divergent seismicity:
- transform fault- strike slip faulting
- divergent boundary-normal fault
- shallow low magnitude earthquakes
what are difference between body waves and surface waves?
- body waves move through interior of the earth
- surface waves confined to earth crust
what are the two body waves and explain
- p wave-fast
- go through solid and liquid
- pushes and pulls
- s wave- second fastest
- go through solid
- side to side
what are the two surface waves and explain
- rayleigh wave- third fastest
- go through earth surface
- move up, down, forward and back
- love wave-slowest
- go through earth surface
- move side to side
which type of waves do liquids absorb
wht is a seismogram made by?
what are the order of the waves ?
- p wave
- s-p interval
- s wave
- surface wave is last
what are seismometers?
measure and help locate earthquakes
how do geologists determine richter magnitude of earthquakes?
- measure amplitude of largest wave
- time interval b/w P and S wave
- plot two measurement on graph and connect points
what is the study of seismic waves in order to improve understanding of earths interior?
wave refraction is used to identify a _________
seismic data confirm the existence of _________ in the earths interior
what is a mohorovicic discontinuity?
about 8 km beneath ocean basin and 20-70 km beneath continents
what uses seismic data to make cross sections of earth interior?