Earth's Interior Flashcards
What is one of body waves characteristics that affect shaking
They reflect and/or refract through layers of rock
What does refraction mean?
The wave/ light BENDS
What type of waves do earthquakes generates?
ALL WAVE TYPES
What happens when a wave is reflected or refracted?
Some of the energy of one type is converted to waves of the other type
What do waves of different types have in common?
The velocity at which they travel DEPENDS ON THE MATERIAL (rocks) THAT THEY PASS THROUGH
P and S waves travel more rapidly through basalt than through granite
=seismic waves travel faster in a solid than a liquid
What does the velocity of seismic waves depend on?
Increase with depth
What path do seismic waves follow?
The paths through the interior are curved
DO NOT FOLLOW A STRAIGHT PATH
earth is layered and made of diff materials that conduct P and S waves at diff velocities
bend as they go through each layer
What is the basic data of seismology
Travel times
How many seismographs and clocks enable seismologists to measure the travel times of P, S, and surface waves precisely
Thousands
What do travel times depend on?
Their velocities
Which seismic waves reach a nearby seismograph first?
Waves traveling only in the crust
What is the crust-Mantle boundary called
Moho
Which seismic waves reach a distant seismograph first?
Waves traveling most of their path in the mantle
Is the outer core solid or liquid?
liquid
What do you need to know travel data?
Total travel time Speed limit (speed of seismic waves in rocks inside Earth)
How does path change?
The velocity changes with depth in the Earth
What is the p-wave shadow zone?
Earth has a core made of a material different from that of the overlying mantle
waves are bent downward
downward bending means that the waves travel more slowly in the core than in the mantle
P-waves move much more slowly in liquids than in solids
What is the s-wave shadow zone?
Other side of the core
Proved the outer core is liquid
when they hit the core, the fail to emerge from the other side
PP waves
P waves that bounce off the Earth’s surface back into Earth
SS
S waves that reflect back into Earth
ScS
S wave that reflected at the outer core/mantle boundary back to the surface
PcP
P waves that are reflected at the outer core/mantle boundary
PKP
P waves that penetrate the outer core
PKIKP
P waves that penetrate the inner core
How are PP, SS, PcP, ScS, PKP, PKIKP differentiated?
Differentiated from one another by their amplitude and frequency
What is geotherm
indicated the change in temperature as depth increases in the Earth
What is the melting curve
indicates the temperature at which materials melt as depth increases in the Earth
what is the geothermal gradient
the rate of change in temperature with depth e.g. 20 C/km
How to determine the p-wave velocity
sqrt ((K + (4/3u))/p)
K=the bulk modulus (the modulus incompressibility) of a material
u=the shear modulus (modulus of rigidity)
p=the density
travel speeds between 1 and 14 km/sec
the slower numbers
How to determine the s-wave velocity
sqrt (u/p)
u=the shear modulus (modulus of rigidity)
p=the density
What is seismic tomography
uses travel times to create 3-D images of Earth’s Interior
reveals features in the mantle clearly associated with mantle convection
hot and cold inside Earth
