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:
mass wasting (landslide)
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?
intraplte seismicity also common
explain intraplate earthquakes
soft weak area of plate interior
occur near pre existing plate boundaries
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
go through solid and liquid
pushes and pulls
go through solid
side to side
what are the two surface waves and explain
go through earth surface
move up, down, forward and back
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 ?
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?