►
From YouTube: EOSC 350 Lecture 9: Seismic 1. Doug Oldenburg
Description
First lecture on seismic. Body waves and surface waves. Waves and rays. The app used in this lecture is available at https://www.3ptscience.com/app/SeismicRefraction
A
A
A
This
is
now
the
kind
of
problem
that
we're
going
to
deal
with,
so
it's
going
to
be
an
entirely
different
kind
of
physical
property.
So
now
we're
going
to
go
into
something
called
seismology
and
we're
going
to
do
three
different
things
in
here,
but
they're
going
to
all
be
kind
of
tied
together.
What
is
going
to
be
refraction?
It
was
going
to
be
reflection
and
the
other
one
is
called
MA.
A
A
Here's
an
example
where
these
guys
are
kind
of
doing
a
pile
driving
for
a
bridge
some
place
in
Napa
Valley
and
the
goal
to
try
to
kind
of
figure
out.
Okay,
where
is
the
you
know?
The
bedrock
in
this
case
can
be
attacked
by
the
thing
I've
just
put
out
on
the
board.
We've
got
an
earth
that
might
look
like
this.
You
got
maybe
an
unsaturated
soil,
water,
saturated
soils
in
a
bedrock,
and
the
goal
is
somehow
to
do
a
geophysical
experiment,
which
is
the
seismic
experiment.
A
Where
we're
going
to
put
some
energy
off
into
the
ground
and
we're
we're
going
to
record
some
signal
at
various
detectors,
so
our
generic
types
of
plots
is
like
this:
we've
got,
you've
got
sores
and
input.
Some
energy
I've
got
a
subsurface
with
some
physical
properties
and
we're
going
to
measure
a
response.
A
A
Sizing
velocities
are
something
that
you
usually
geological
engineers
are
not
you
know
particularly
connected
with,
although
you
can
see
in
the
in
the
first
lab.
You
have
this
little
experiment
right
where
you
did
the
V,
P
and
V
s,
so
actually
those
those
words
are
already
familiar
to
you,
but
there's
a
whole
bunch
of
ways
to
describe
the
elastic
properties
of
materials.
A
Perhaps
the
one
that
you're
most
familiar
with
I
would
guess
is
maybe
Young's
modulus
and
poissons
ratio,
but
you
could
also
do
bulk,
modulus
and
shear
modulus.
That's
what
was
you
saw
in
that
first
lab
their
shear
modulus
and
lambie's
first
parameters
or
just
P
and
S
wave
velocities,
so
there's
a
whole
bunch
of
descriptions
and
because
the
you
know,
different
people
and
different
walks
of
life
tends
to
use
different
words.
A
A
Think
from
our
particular
point
of
view,
and
given
that
your
geological
engineers,
the
thing
that's
most
important,
is
your
shear
modulus
and
that
is
related
to
the
density
as
well
as
the
shear
velocity.
So
we
can.
We
got
V
s
squared
times,
Rho
that
gives
you
this.
The
shear,
modulus
and
Young's
modulus
depends
both
upon
the
peel
aid
and
es
what
velocity,
as
well
as
the
density.
A
So
there's
the
connection
if
you're
interested
in
knew
and
E
and
if
we
do
a
head
and
we
do
some
experiments
that
give
you
the
P
wave
and
the
S
wave
velocity,
then
okay,
you're
you're
back
connected
with
stuff.
That's
really
intrinsically
interesting
to
your
that
you're
used
to
so
III.
Don't
really
want
to
go
through
a
lot
of
details
here
in
the
course
with
respect
to
stresses
and
strains
and
the
definition
of
these
things.
A
A
A
So
we
start
with
shear
normal
stress,
tensile,
stress,
shear,
stress,
there's
the
bulk
and
the
shear
modulus,
which
you've
seen
Young's
modulus
poissons
ratio,
and
then
it's
going
to
get
into
different
types
of
velocities,
so
just
to
kind
of
I'm
going
to
hit
that
in
a
second,
but
just
to
kind
of
give
you
an
idea
of
materials
and
the
p-wave
and
s-wave
velocities.
This
gives
you
a
bit
of
a
kind
of
a
kind
of
an
overview.
If
you
have
air
and
air
can
still
transmit
a
p-wave
velocity.
A
So
we'll
talk
a
bit
more
about
that,
but
a
p-wave
is
it
is
a
pressure
wave.
So
it's
just
exactly
the
same
way
that
we
have
when
we're
when
we're
speaking
right.
So
you
can't
all
know
how
that
works,
but
I
got
I
got
some
vocal
cords
here
and
there
goes
through
and
vibrates
the
bulk
of
cords,
and
you
know
there's
always
this
compression
that
goes
out
of
prescience
rarefactions
and
you
pick
that
up
vocal
cords
start
to
forget
your
life
start
to
vibrate,
and
then
that
gets
transmitted
as
a
signal.
A
A
Then
the
shear
wave
velocities
have
a
table.
Also.
That
looks
like
that.
You'll
notice
that
shear
wave
velocity
is
always
less
than
the
feet
come
back
to
that.
But
anyway,
so
there
you
have
it:
the
elastic
properties,
p-wave
and
s-wave
velocities.
For
what
we're
going
to
do
it,
you
can
connect
it
to
engineering
properties
and
there's
a
table
and
some
background
about.
What's
going
on.
A
A
A
A
Write
a
particular
I'm
going
to
ask
them
to
do
one
more
thing.
Instead
of
holding
your
really
step,
nothing,
that's
really
rigid
material.
We're
going
to
do
I'm
going
to
ask
me
just
to
not
be
be
super
relaxed,
but
just
less
a
little
bit
more
more
relaxed
and
I'm
gonna
push
on
here
and
I.
Want
you
to
watch
two
things.
I
want
you
to
watch
the
speed
of
the
way.
A
A
A
A
A
A
So
you
can
see
what's
happening
here,
so
this
is
what's
called
the
P
wave
or
the
compressional
wave,
and
it's
doing
exactly
what
we
just
did
right.
So
it's
it's
being
pushed
this
way
and
you
can
see
the
compressions
and
then
the
rarefactions,
as
as
that
goes
so
the
energy
propagates
down
this
way
particle
motion
is
back
and
forth,
and
this
little
box
that
we've
got
here
kind
of
squeezes
in
and
then
expands
out
as
as
things
go
through.
Okay,
that's
the
P
wave.
A
That
was
the
first
one
that
we
did
and
the
velocity
of
that
P
wave
depends
upon
the
compressional
bulk
modulus,
as
well
as
the
shear
modulus
and
the
density.
So
that
was
the
expression.
This
is
called
a
body
wave
because
it
travels
inside
the
earth
or
maybe
because
it
had
a
whole
bunch
of
bodies.
But
it's
we're
going
to
refer
to
this
guy
as
a
body
wave,
something
that
really
travels
inside
you.
A
The
motion
was
transferred,
so
it's
a
shearing
motion
and
you
can
see
what
it's
done
it's
so
you
can
see
how
it's
changing
the
shape.
This
is
not
changing
volume.
These
little
cells
I'll
keep
their
same
volume
but
they're
they're,
shared
they're
twisted
in
shape.
You
can
see
how
I'll
do
that
and
again
that
particle
motion
is
transverse
to
the
direction
of
propagation.
A
A
A
A
A
A
Tell
me
the
fight.
It's
really
and
Coover
a
good
place
to
could
be
considered
about
that.
Okay,
so
we've
got
some
kind
of
source
ground
motion.
Maybe
it's
an
earthquake,
maybe
it's
an
explosive
source.
There's
there's
waves
that
come
down
into
the
earth.
Okay,
so
those
were
the
body
waves.
You
know
the
P
wave
velocity
or
the
P
wave
S
wave,
but
we
can
also
get
waves
that
travel
along
the
surface
and
reasonably
not
those
are
called
surface
waves.
A
The
wave
travels
along
the
surface.
The
amplitude
decreases
as
you
go
down
in
depth
and
the
particle
motion
is
a
retrograde
ellipse,
so
the
particle,
if
you
looked
at
any
particular
particle,
it's
actually
going
around
like
that.
If
you
had
a
little
sometimes
they
show
examples
where
you've
got
a
little
cork,
that's
sitting
on
water
or
something
like
that,
and
you
look
it
to
see
what
that
didn't.
A
Let's
see,
if
that
just
sort
of
going
like
that,
so
that's
the
Rayleigh
wave,
velocity,
really
wave
and
particle
motion
and
then
there's
also
something
called
a
maguey
and
again
this
is
much
more
related
to
the
to
the
tissue.
So
the
energy
is
moving
this
way
and
the
part
of
the
motion
is
moving
back
and
forth,
but
it's
confined
to
a
surface
and
the
amplitude
decreases
as
you
as
you
go
down
again,
so
we
can
ask
you
not
to
check
stirred
it's
like
that.
Well,
we're
doing
so.
A
Those
are
the
four
waves.
Two
body
waves,
two
surface
waves,
these
guys
here
from
point
of
view
of
earthquake
hazard
are
generally
the
ones
that
caused
a
lot
of
damage
if
they
just
they
have
a
long.
They
stand
around
for
a
long
time
and
they
have
a
big
amplitude
and
yeah.
They
tend
to
cause
the
problem.
A
A
How
the
energy
actually
propagates,
we
kind
of,
did
it,
as
you
know,
like
you
know,
a
big
force
that
was
coming
in
and
everything
was
was
kind
of
moving,
but
in
reality
a
lot
of
sources
are
very
kind
of
highly
localized
and
a
good
example
of
that
would
be.
You
know
a
rock
coming
down
into
a
water
pool
right.
So
if
we
did,
that
I
mean
you've
all
done
this
right,
rock
you
dumped
it
in
and
then
you
get
these
waves
and
they
propagate.
Oh,
so
now
we've
got
got
waves.
You've
all
seen
this.
A
A
A
One
of
them
is
the
wave
fronts
and
the
other
is
when
we
try
to
think
about
a
wave
and
how
it's
coming
so
here's
the
source
and
we're
out
here
and
we
think,
okay,
how
is
the
energy
travel?
The
energy
travel
has
travel
along
a
particular
path,
we're
going
to
call
that
the
rate
path-
and
this
would
be
if
I'm
sitting
here
and
here
is
the
source-
that's
how
the
energy
got
there.
Okay,
so
that's
the
rate
at
and
the
rate
path.
A
A
But
I'd
now
like
to
do
is
to
show
you
a
little
movie
clip
that
has
got
it's
going
to
show
you
how
things
propagate
as
a
function
of
time.
So
what's
going
to
happen
here,
so
we're
looking
at
a
cross-section.
So
this
is
getting
into
the
earth
right,
and
this
is
distance
along
here
and
there's
going
to
be
a
source
that
goes
off
here
and
initially
there's
nothing.
Source
goes
off.
Things
start
to
move
outward
and
just
the
same
as
they
get
with
the
students.
A
You
know
one
pushes
on
another
and
then
gradually
this
wave
propagates
outward
so
we're
going
to
watch
that
as
a
function
of
time
and
initially
what's
going
to
happen,
is
that
it's
going
to
be
very
simple.
It's
going
to
be
just
like
that
rock
that
went
into
the
water
and
the
waves
go
out,
but
you
know
also,
if
you
had
like,
if
you
have
this
system
here
and
then
you
you
put
up
a
you,
know
a
barrier
or
a
boundary,
or
something
like
this-
that
it
would
really
change
things.
A
A
A
I've
been
quick
with
the
fingers
okay,
so
what
I've
done
is
I've
stopped
this
movie
before
anything,
really
serious
has
happened.
So
what
what
started
here
was
that
the
energy
started
right
here
and
then
it's
expanding
outward
so
that
the
velocity
in
this
region
up
here,
okay,
is
a
constant.
That's
just
at
a
velocity
v1.
A
These
arrows
that
you
have
here.
Okay,
this
guy
that's
coming
in
here-
that
is
the
normal
to
the
weight
to
that
wave
front,
and
that
is
the
Ray
path
for
energy.
That's
travelling
along
this
line
and
arrow
here,
that's
good!
That's
the
way
path,
let's
go!
So
what
we're
now
going
to
do
is
to
start
this
up
again
and
we're
going
to
look
at
what
happens
here,
because
now
we've
got
energy,
that's
coming
into
a
boundary,
and
things
are
changing
right.
I
got
I
got
a
different
velocity
here
than
I
have
here.
A
A
Again,
it's
pretty
fast.
You
could
play
with
this
yourself,
we'll
go
through
things
a
little
bit
more
slowly,
but
as
this
Scot
as
this
impinged
on
here,
there
was
something
that
happened.
First
of
all
the
energy
that
went
in
here
now
it
started
to
to
travel
out
and,
after
a
certain
length
of
time,
it's
already
traveled
out
to
this
distance
out
here.
So
the
energy
came
down
here,
get
this
and
now
some
of
it
actually
got
transmitted
and
I've
got
it
here,
but
this
velocity
is
really
fast.
This
is
faster
than
up
here.
A
A
So
that
is
the
transmitted
wave
that
we
saw
here
then
there's
also
a
wave
that
is
reflected
and
that's
what
this
guy
is
here.
So
the
wave
has
come
down
and
now
it's
got
reflected
and
it
starts
to
come
back
up,
and
that
gives
us-
and
in
addition
to
that
we
also
have
a
direct
wave.
That
is
just
simply
traveling
it's
along
the
very
surface
here
at
this
speed
of
the
one-
and
here
is
this
direct
wave.
That's.
A
A
A
That's
going
to
be
the
saving
grace
for
the
geological
engineers
there's
going
to
be
a
wave
that
comes
along
this
interface,
it's
called
a
refracted
wave,
the
wings
going
to
travel
along
here
and
give
energy
up
to
the
surface
and
we're
actually
going
to
be
able
to
measure
them.
So
let
me
see
if
we
can
see
that.
A
A
Yeah,
it's
pretty
big.
Okay,
soon,
I
know
it's
a
it's
right
here.
It's
a
straight
line
and
as
time
goes
on
and
this
wave
front
is
here,
this
wave
is
going
to
travel
up.
Plea
arrive
at
the
surface,
so
that
is
refracted
in
Turkey.
That's
coming
in
it's
going
to
come
in,
like
a
regular
arrival,
you're
going
to
be
able
to
find
that
guy
and
he's
going
to
tell
you
some
information
about
what
this
lower
velocity
so
he's,
really
critical.
A
A
This
works,
one
of
the
things
that
you'll
be
doing
is
playing
with
a
well
you've
got
your
gonna
have
for
seismic
apps.
This
was
one
that
this
is
going
to
be
the
first
one
that
you
use.
Let
me
try
to
explain
what's
going
to
happen
here.
This
is
this:
is
gonna,
be
your
simulated
earth
model.
So
this
is
depth,
and
this
is
most
listed
is
offset
that's
a
distance,
so
this
is
in
meters
and
there's
a
couple
of
horizontal
line
here.
So
there's
one
here
at
five
meters
depth
and
there's
one
here
at
15
meters.
A
So
that's
your
layer
dirt!
You
got
layer,
1
layer,
2
over
here.
You've
got
two
velocities,
so
velocity
one
two
and
three.
The
default
values
on
this
is
that
velocity
one
is
400
meters
per
second
velocity
2
is
the
thousand,
and
velocity
3
is
1500
okay.
So
what
we're
going
to
do
is
to
look
at
the
energy,
but
now
just
using
ray
paths
right.
So
we're
just
we're
just
going
to
use
Ray's.
But
you're
always
going
to
remember
that.
A
Oh
my
gosh
there's
all
kinds
of
waves
that
are
traveling,
but
now
we're
just
going
to
kind
of
think
about
energy
that
has
managed
to
get
to
a
particular
location
and
we're
just
going
to
look
at
how
that
energy
traveled
and
we're
going
to
describe
that
by
a
ray
pack.
So
we're
going
to
set
off
an
explosion
and
we're
going
to
look
at
various
types
of
energy.
That
I
pointed
out
to
you
in
that
in
the
movie,
and
the
very
first
thing
that
we're
going
to
look
at
is
what's
called
the
direct
arrival.
A
And
as
a
function
of
distance,
so
here's
here's
how
the
path,
here's,
how
the
ray
or
energy
travels
it
travels
right
along
the
surface
as
a
companion
plot
to
this
guy,
we've
got
what's
called
a
travel
time
curve
or
a
travel
time
plot.
A
travel
time
plot
is
something
that's
got
a
horizontal
distance
on
it
connected
in
this
case
with
the
the
offset
and
time
so
here's
zero
time.
This
is
point
two
four
seconds,
and
this
is
distance
along
here.
A
A
A
A
Time,
sorry,
but
we
want
foot
size
each
place
so
we're
sitting
at
one
particular:
here's
our
experiment,
here's
our
here's,
our
shot.
Here's
our
receiver
and
the
energy
goes
off,
nothing
happens,
nothing
happens,
nothing
happens
and
then
suddenly,
there's
some
energy
that
comes
in
and
that's
going
to
come
in
at
the
time
in
this
case
put
one
two
five
seconds
and
this
is
going
to
be
our
director
Vic,
but
there
was
also
other
waves
that
that
could
travel
in
particular.
We
have,
we
could
have
a
reflection
event,
all
right,
so
I
could
have
a
wave.
A
A
A
Oh
this
guy,
here
sorry,
oh
there
we
go
right,
so
you
can
see
that
this
length
here
is
almost
the
same
as
the
red
so
that
these
guys
are
coming
here.
So
what
have
we
got
here?
We've
got.
First
of
all,
we've
got
two
two
types
of
energy
paths:
one
that's
going
right
along
the
surface,
that's
the
direct
way
and
then
we've
got
another
one
that
is
reflected
and
if
we
plotted
the
travel
time
curves
for
the
direct
ray
or
the
reflected
ray,
we
see
it's
got
this
kind
of
shape.
A
Okay,
the
next
thing
and
we'll
pick
this
up
again
next
time,
but
I
want
to
just
show
you
what
happens
is
that
we
can
actually
have
a
refracted
wave
that
goes
down
to
this
interface
draws
and
comes
back
up.
So
that's
that
little
faint
line
that
I
was
talking
about
that
you
could
hardly
hardly
see,
but
that
is
going
to
be
the
the
path
that
the
energy
takes
and
that
is
actually
going
to
be
the
refracted
arrival.
A
So
what
we're
going
to
do
on
Monday
and
and
actually
what
I'd
like
you
to
do
over
the
weekend,
is
to
go
to
the
fill
to
the
DPD.
Read
this
section
on
the
elastic
properties
and
the
basics.
Okay,
so
there's
two
sections
and
then
use
this
so
mode
the
news
finders
to
explore
the
app
just
so
then
you
come
a
bit
more
familiar
with
things
and
then
yeah
just
kind
of
play
around
and
and
see
what
intuition
you
can
get
and
then
on
Monday.
A
We're
gonna
pick
it
up
from
here
and
we're
going
to
go
through
some
more
of
the
you
know
the
details
about
Snell's
law
and
refraction,
and
really
try
to
kind
of
nail
this
down
and
see
what
the
travel-time
curves
are
light.
And
then
you
can
actually
go
ahead
and
use
those
two
five
things
like
layers
that
can
sleep.