►
From YouTube: EOSC 350 Lecture 5: Magnetics 3. Doug Oldenburg
Description
3rd lecture on the use of magnetics in geophysics.
Slides are available at:
https://github.com/ubcgif/eosc350website/raw/master/assets/2_Magnetics/3_Magnetics.pdf
The Jupyter Notebook demonstrated is available through binders: http://mybinder.org/repo/ubcgif/gpgLabs/notebooks/Mag/InducedMag2D.ipynb and on github: https://github.com/ubcgif/gpgLabs/blob/master/Mag/InducedMag2D.ipynb
A
B
A
A
Have
you
got
well
we'll
just
just
hold
still,
because
if
the
collective
power
of
class
is
so
strong
that
they
really
wanted
to
slap,
it'll
be
sunny,
and
so
we're
gonna
do
a
lot
all
right
here
we
go
so
I
want
to
do
a
couple
things
today,
the
last
time.
At
the
end
of
the
day,
we
had
this
exercise
where
you
hit
Barrett
some
magnets
and
you've
gone
around
and
found
some
of
them.
I
want
to
be
talked
I
want
to
revisit
that.
A
I
would
also
like
to
talk
about
remnant
magnetization,
and
I
also
want
to
talk
to
you
about
total
feels
magnetometers
and
total
field.
Normally,
those
are
all
things
that
have
relevance
to
exactly
slab.
So
to
see
what
sir,
we
can
go
with
that.
So
here
we
are
we're
in
magnetics,
we've
got
energy
source
in
got
magnetic
susceptibility
and
we've
got
data
coming
out
and
the
thing
that
we
didn't
talk
about
yesterday,
because
we
just
kind
of
read
a
little
bit
of
time.
A
Okay,
there's
a
number
of
magnetometers
we're
going
to
talk
about,
feel
them.
The
the
one
that
you're
going
to
use
in
the
beach
this
afternoon
is
a
proton
procession
magnetometer.
So
the
the
sensor
is
up
at
the
at
the
head.
I'll
tell
you
a
little
bit
more
about
how
that
actually
works
later
on,
but
basically
it's
going
to
be
on
a
pole
that
is
sort
of
one
just
left
two
meters
high
and
it
measures
the
total
magnetic
field.
A
So
whenever
we're
in
a
situation
where
we've
got
the
Earth's
field
coming
in
like
this
and
we've
got
an
object
here,
that
is
magnetized
and
it
gives
its
own
magnetic
field,
which
we
call
be
a
then
the
magnetic
fields
that
we
measure
is
the
son
of
those
is
V
naught,
plus
the
a
and
the
total
magnetic
field.
That
measures
is
the
absolute
value
of
that
effective.
So
that's
the
vector
sum.
So
that's
just
not
going
to
scalar.
A
That's
what
most
of
these
instruments
are
measuring
these
guys
here,
they're
just
all
measuring
the
total
magnetic
field,
and
you
can
see
that
they
can
be
yo
down.
You
know
you
can
put
them
kind
of
on
the
ground.
You
can
help
them
up
this
guy.
Here
is
there's
one
here
and
one
here,
so
you
can
measure
the
total
field
at
two
locations
and
then
find
out
how
much
it's
changing
as
a
function
of
height.
So
that's
where
term
radiometer
comes
in.
It's
measuring
the
gradient.
You
can
put
these
into
space.
A
There's
been
a
number
of
vectors
that
are
in
space
and
in
fact,
there's
some
three
component
magnetometers
that
were
built
by
a
guy
being
very
near
odd.
Who
was
in
the
geophysics
department.
He
probably
builds
the
best
magnetometers
in
the
world
and
he
a
lot
of
those
guys
are
flying
in
various
satellites
and
in
space.
You
can
put
them
in
an
array
on
the
back
of
an
aircraft,
this
one's
actually
for
a
you,
XO
survey,
they're
trying
to
do
a
whole
bunch
of
these
and
fly
low.
A
You
can
have
them
in
various
parts
like
this
on
this
here
we've
got
two
on
wingtips,
so
it's
looking
at
the
change
in
the
field
as
you
go
from
one
side
edge.
So
that's
another
gradient
irate.
Sometimes
you
can
carry
them
just
on
a
boom.
So
here's
the
helicopter
you're
trying
to
get
this
magnetometer
away
from
all
of
them.
Medellin.
You
remember
when
you
get
the
exercise
it
is
in
the
lab.
A
They
ask
you
to
take
away
all
your
keys
and
stuff
like
that,
because
that
all
affects
the
fields
you're,
trying
to
get
those
guys
away
from
them
and
the
one
that
you
used
in
your
phone
are
three
component:
fluxgate
magnetometer,
so
there's
three
of
these
little
sensors
and
there,
but
just
in
well
different
phones,
have
them
in
different
places,
but
they're
often
sort
of
up
in
this.
This
pot
left
hand
corner.
So
that's
your
your
magnetic
field,
sensors.
We
used
this
one
when
we
did
the
survey
in
class
yesterday.
A
A
They
kind
of
had
a
diameter,
maybe
about
six
millimeters
that
was
the
largest
month
and
it's
kind
of
interesting
to
take
that
little
magnet,
which
has
forgot
to
bring
up
which
had
a
particular
scale,
its
associated
with
it
just
a
couple
of
millimeters
and
scale
that
up
to
something
that's
a
little
bit
bigger.
So
the
thing
that
was
going
to
fail
to
was
an
unexploded
ordinance,
which
is
you
know
these
guys
are
around.
You
know
the
big
ones
are
assured
of,
like
20
centimeters
in
diameter,
in
there
sort
of
that
long.
A
The
table
that
we
used
to
use
these
are
a
little
bit.
Smaller
was
one
meter
by
three
meters.
So
it's
it's
a
little
bit
more.
This
size,
this
size
of
the
table,
and
now
you
can
imagine
this
little
magnet
kind
of
sitting
on
this
table
and
then
you're
trying
to
find
it
and
so
you're
going
over
it
with
a
little
magnetometer.
A
A
That
would
be
significant
achievement
for
an
afternoon
if
you
could
find
something
like
that,
and
if
you
took
the
scale
of
that
little
magnet
and
you
try
to
up
it
to
trying
to
find
a
copper
deposit
that
was
a
billion
dollars.
Then
you
kind
of
have
to
go
through
this
scenario.
Again
we're
going
to
use
the
table
size
as
a
scale,
the
magnets
going
to
be
six
millimeters
in
diameter,
a
couple
of
millimeters
thickness,
and
so
it's
got
a
volume
of
about
10
to
minus
8
cubic
meters.
A
A
So
if
we
have
a
need
four
billion
dollars,
then
you
know
besides
okay,
how
many
kilograms
of
this
do
you
need?
So
you
can
try
to
figure
that
out:
okay,
divide
1
billion
by
684.
That
would
give
me
something
and
then
the
density
of
actually
maybe
I'll,
just
I
used
to
have
people
do
this
as
an
exercise,
but
I
don't
think
we
need
to
do
that,
so
that
would
in
order
to
do
the
billion
dollars,
you
need
about
a
million
kilograms
to
to
really
make
it
worthwhile.
A
A
A
A
So
if
we
scaled
up
the
you
know
the
size
of
the
of
the
table,
if
we
now
come
to
about
10
kilometers
by
30
kilometers,
so
if
you're
going
to
put
that
in
perspective,
so
here's
here's
the
idea
with
the
mineral
deposit,
so
we've
got
this
area,
so
this
is
about
10
x,
30,
kilometers,
so
you're,
going
from
where
we
are
here
over
beyond
Surrey
and
10
kilometers.
This
way,
and
now
we've
got
an
object.
That's
thirty!
A
Eight
meters
cubed
sitting
someplace
here
and
is
a
dot
on
any
of
any
of
these
areas,
is
in
so
the
the
point
I
wanted
to
make
about
that,
and
that
should
have
come
back
with
respect
to
what
you
get
in
the
exam
here.
Is
that
if,
if
you're
going
to
try
to
find
something
like
that-
and
you
thought
okay
well,
I'm
just
going
to
drill
and
try
to
hit
that
by
kind
of
direct
sampling,
your
chances
are
really
really
small.
A
A
So
I
think
with
this.
If
you
think
about
it
and
then
also
this
afternoon,
what
we're
going
to
do
is
give
you
the
opportunity
to
try
to
find
something
that
first
instrument
that
I
showed
you
that
proton
procession
magnetometer,
and
you
also
can
have
the
opportunity
to
try
to
dig
it
by
hand.
If
you
like
so
see
what
your
success
or
not
is
at
them.
A
A
A
A
Okay,
I
encourage
everybody
to
get
give
this
a
shot,
so
maybe
I
guess
the
thing
I
want
to
do
now.
I
will
kind
of
go
through
a
couple
of
things
that
we
did
just
at
the
end
of
last
day,
just
to
kind
of
highlight
the
but
I
don't
want
to
spend
a
lot
of
time,
just
kind
of
working
through
particular
examples.
The
the
informative
thing
for
you
will
come
when
you
actually
try
to
work
with
the
applet
and
try
to
see
what
the
responses
are
so
again
are.
A
Our
goal
here
is
the
following:
so
we're
going
to
bury
something
at
some
point
on
the
earth
and
for
now
I'm
just
going
to
bury
something
right
at
the
North
Pole
so
that
the
magnetic
field
is
coming
in
and
then,
if
I
come
over
here-
and
I
put
my
object
down
here
so
here's
my
so
this
is
the
Earth's
field.
Now
we
just
kind
of
want
to
be
a
little
bit
local
and.
A
A
B
A
As
we
come
out
over
here,
it's
going
to
kind
of
come
back
to
20
and
then
actually
maybe
a
little
bit
positive,
and
so
it's
going
to
be
something
then
but
basically
looks
like
this
and
if
I,
so
that's
a
profile
across
here
if
I
plot
it
in
plan
view.
So
if
I
look
down
on
it,
then
I'm
going
to
see
something
that
that
looks
like
this.
A
So
my
just
tune
it
up
a
bit.
You
notice
how
it's
kind
of
like
a
little
bit
lumpy
here,
it's
a
little
bit
lumpy,
because
we
were
looking
at
the
digitizing.
What
the
full
signal
is
respect
to
these
number
of
points.
That's
the
number
of
points
and
we've
got
20
hear
from
this
section
to
this
section.
So
that's
actually
not
very
many.
You
can
see
this
because
effects
there.
If
I
come
back
and
increase
that
to
let's
say
50.
A
So
like,
if
I
increase
it
to
50,
you
can
see
how
much
smoother
it's
going
to
be,
and
now,
if
you
look
to
see
what
the
character
of
this
field,
is
you
see
that
it's
it's
negative
over
here?
So
here's
our
peers
are
sitting,
that's
completely
negative
and
it
goes
back
20
or
just
a
little
bit
positive.
Let
me
explain
the
positive
part
so
when
it's
coming
down
like
that,
it's
clearly
in
this
direction
and-
and
you
might
say
but
wait
a
minute
what.
A
A
Right,
that's
right!
So
it's
exactly
something
that
we
haven't
explicitly
talked
about
for
for
this,
but
the.
If
I
have
it.
If
I
have
a
little
magnet
here.
Okay,
then,
if
I'm
sitting
right
up
host
the
magnet
the
feels
pretty
strong,
but
the
farther
I
go
away
from
this
mega,
the
weaker
the
field
becomes
and
I
go
long
ways
away.
It's
actually
goes
almost
to
zero
and
does
anybody
know
if
I
have
that
if
I
have
a
magnet,
how
they
magnetic
field
full
off
with
distance
from
the
magnet.
A
B
A
Have
you
looked
at
gravity?
Okay,
so
you
had
a
little
mass
particle,
so
you
got
a
little
mass
particle
and
then
the
gravitational
field-
okay,
was
G-
am
fell
off
his
GM
over
R
squared,
so
the
magnetic
field
are.
The
gravitational
field
falls
off
as
one
over
R
clear
and
that
was
effectively
dears
due
to
a
single
element
of
a
mass
which
is
kind
of
like
a
pole
in,
I
think,
is
impossible
and
a
minus
pole,
and
the
effect
of
that
is
that
the
magnetic
field
falls
off
as
one
over
R
cubed.
A
You
know
what
the
directions
are
these
fields,
but
we
haven't
factored
in
this
business
of
the
magnitude,
so
the
farther
that
you
go
away
from
here.
The
magnitude
is
going
to
fall
off
as
one
over
R
cube.
So
even
though
the
magnetic
field
vectors
are
coming
up
like
this,
the
the
attitude
of
that
becomes
very
small.
The
result
of
that
is
that
this
profile
across
here
here
has
got
something:
that's
just
a
little
bit
positive
and
then
it's
really
affected
only
by
what
good
is
going
on
here
and
the
negative.
A
That
you
also
have
to
remember
for
the
zakim,
because
one
of
the
stations
that
you're
going
to
do
is
we're
going
to
set
something
up
and
you're
going
to
have
to
think
about.
Okay,
where
this
thing
is
a
placed
effective
in
the
Earth's
field.
So
the
magnetic
field
of
the
earth
is
coming
in
a
particular
direction
and
then
you're
actually
going
to
you
know,
face
stickers
and
kind
of
sketch
out
what
this
profile
is.
This
might
be,
just
too
can
help
you
figure
out
what
our
experience
actually
from
past
years
ago.
A
That
was
one
of
the
most
instructive
of
things
that
people
have
done.
It
came
back
to
it.
Oh
yeah,
really
kind
of
helped.
Me
sit
solidified,
okay,
so
what
we
got,
we've
got
some
P,
it's
magnetized,
we've
got
the
anomalous
fields
and
that
you
know
as
we
sketch
them.
That
tells
you
what
the
what
the
geometry
is
and
then
as
you're
trying
to
figure
out.
Okay,
what's
really
going
to
be
big
and
small,
and
you
have
to
factor
in
that
bit:
okay,
as
I
go
further
away
from
here.
Things
are
just
going
to
get
and.
A
Also
on
this
case
here,
if
we
have
the
same
magnetization,
but
we
look
at
a
different,
a
different
feel,
for
instance,
if
we
look,
that
was
the
set
for
the
field.
If
you
looked
at
the
X
component
of
the
field
now,
of
course,
we
get
something.
That's
really
quite
different
right,
because
over
here
the
X
component
is
is
pointing
this
way
over
here.
The
X
component
is
pointing
this
way,
so
that
means
there
must
be
a
zero
crossing
place
on
this
side,
it's
pointing
in
the
negative
x
direction.
A
A
If
we
look
at
it
in
2d,
we
see
that
we've
got
something
that
looks
like
like
this,
so
this
is
negative
over
here.
This
is
positive
over
here
and
here's.
What
the
problem
is
you
take
the
same
object
put
in
the
ground
measure,
different
components,
see
a
different
signature,
see
a
different
front
profile.
A
The
another
thing
that's
said
that
I
won't
want
it
to
stress
here,
which
again
will
play
a
role
in
in
the
left.
We've
got.
You
have
to
figure
out
where
your
sensor
is
with
respect
to
the
object
that
you're
that
you're
looking
at
so
the
object
is,
is
here
so
it's
buried
at
a
certain
distance,
the
underneath
the
surface
of
the
earth
and
that
distance
is
given
by
this
quantity
here
the
depth.
So
at
this
point
the
object
is
sitting
right
at
the
surface
of
the
of
the
earth.
A
But
the
sensor
is
this:
so
this
is
the
receiver
height,
so
very
aqua
mutants
are
experts
even
and
the
height
at
1.2
meters.
So
basically
the
object
to
city
right
at
the
table
level
and
you're
measuring
up
about
like
this
and
the
characteristic
signature
that
you
have
looks
like
we're
going
to
be
doing
something
that
there's
an
important
aspect
of
this
curve.
That's
that's
really
useful
and
that's
something
called
the
half
width
of
the.
A
B
A
A
A
So
the
half-width
will
get
dinner,
Lucy
Furr
anybody
else.
What
else
might
we
see?
Okay?
So
let's
try
that
so
let
us
take
this,
and
instead
of
at
zero
depth
will
make
it
deeper,
so
just
go.
Take
we're
going
to
take
the
same
object.
Nothing
else
changing
and
we're
going
to
make
in
deeper,
though
we'll
put
them
down
two
and
a
half
meters
and
then
oh,
what
happened
to
run
this.
B
A
A
A
A
A
A
B
A
A
A
A
So
how
cool
is
that?
Ok,
so
we
come
along,
we
got
something
very
sure
we
get
this
feel.
Well,
we
get
a
sick
integer
over
top
of
it,
and
now
we
know
where
is
very
right.
It's
gonna
be
buried
right
underneath
the
maximum,
that's
good.
So
now
we
know
where
your
day
when
it's
the
harder
we
eat
today.
Well,
we
can
actually
use
the
characteristics
of
this
of
this
curve.
We
look
at
the
half
width
of
this
curve
and
we
say
at
4
metres.
A
We're
gonna
have
to
dig
four
meters
down
to
find
this
guy.
So
with
this
with
it,
with
this
image,
we
not
only
find
a
character
or
something
that
we're
looking
for.
We
can
localize
the
horizontality
usually
fairly,
even
if
it's
just
simple
so
but
but
the
other
thing
is
that
I'm
looking
at
some
aspect
of
the
curve,
so
you
get
some
information
about
that,
so
we
kind
of
go
back
here
again.
You
can
see
how
the
character
changes.
A
A
Depth
is
it
one
yeah
about
2.3
right,
so
we
think,
okay
to
pop
on
commuters.
If
everything
is
going
according
to
rule
and
the
half-width
should
be,
you
know,
sort
of
Route
2
over
2
meters,
and
if
we
look
at
this,
so
this
is
not
out
at
6.5,
so
it's
3.2,
so
here's
the
half
with
and
that's
four
that's
eight!
So
that's
about
two
years,
so
the
rule
holes
yeah.
The
other
thing
is
if
we.
B
A
A
All
right
so
so
easiest
number
is
one,
so,
let's
make
the
receiver
height
be
one
and
let's
make
the
gap,
be
zero.
B
A
A
A
A
And
we've
yet
yeah
close
to
host
three.
A
A
A
A
A
Okay,
is
a
total
field,
magnetometer
and,
as
I
said,
it
measures
the
magnitude
of
the
field
which
is
equal
to
the
magnitude
earth.
Steel
plus
the
night.
Soon
of
the
anomalous
deal,
hey
you're,
going
to
do.
What
you're
going
to
do
is
to
generate
a
total
field.
Anomaly
you,
your
shield
is
big
right.
It's
certain,
like
50,000
nano
teslas
the
object
that
you're
going
to
be
dealing
with
yeah,
there's
their
small
guys.
Wait.
You
have
the
altitudes!
A
In
order
to
work
with
justy
anomalous,
Earth's
feel
or
mama
field
object,
what
we're
going
to
do
is
generate
a
magnetic
field
anomaly
in
this
app
here,
it's
actually
listed
as
t/f
total
feel
you
could
say
list
about
that.
Tf
khufia
is
the
measured
aptitude,
though-
aptitude
of
the
turf
field,
so
that
is
going
to
be
a
number
that
that
you
measure
and
then
it's
a
question.
Okay.
How
do
we
and
interpret
that?
A
A
Like
it
suppose,
we
have
the
Earth's
field
this
way,
so
it's
just
spokes
you're,
not
and
now
so
this
is
like
50,000,
nano
teslas
and
now
we've
got
at
any
particular
point.
We've
got
at
the
anomalous
field
of
the
target
coming
in
so
here
is
VA
y,
sometimes
at
points
1
way.
Sometimes
it's
points
another
way,
it's
kind
of
all
over
the
map,
and
so
we
think
about
another
vector
here,
which
is
the
anomalous
field.
So
at
something
take
a
point.
We
got
a
little
bit
of
a
nominal
Hilda,
that's
coming
up
in
a
ditch.
A
What
to
what
the
magnetometer
measured,
actually
the
length
of
this
guy
right.
So
this
is
this
is
B
dot.
That's
ba!
That's
B,
naught,
plus
B
a
is
going
to
measure
the
length
of
it.
If
we
look
at
this
length-
and
we
say
oh
well
I'd
like
to
subtract
this
this
amount
from
from
here-
then
what
do
we
have
if
it's
effectively?
So
imagine
this
imagine
this
vector
here
and
we
just
fed-
you
know,
swing
it
around
on
this
on
this
art.
So
this
is
everything
here.
A
Everything
on
this
is
a
magnitude
V
naught
plus
ba.
If
I
subtract
from
this
effort
that
I've
got
a
vector,
that
is
a
length
flip
right.
So
this
is
the
Delta
B
that
I'm
going
to
mention
or
okay,
but
the
question
is:
how
do
I
think
about
it?
And
what
you
see
here
is
that
this
you
know
this
vector
here
is
coming
here-
is
pretty
much
the
same
as
if
I
just
took
that
anomalous
feel
and
just
I
projected
it
onto
this
x-axis
or
onto
the
axes
in
the
university.
A
So
that
means
that
this
difference
here
is
approximately
equal
to
the
direction
of
yours
field
and
the
projection
of
this
anomalous
field.
On
to
that,
so
by
the
way
is
he
I'm
almost
feel
rejected
on
dot
product
number,
be
my
tab,
so
be
not
happy
talked
about
that's
the
unit
vector
for
when
you
deal
ba.
A
So
that
is
the
total
field
anomaly
that
you're
going
to
get
so
you
could
take
the
proton
procession,
magnetron
you're,
going
to
go
to
a
base
station
measure.
The
total
feel
right
and
you're
going
to
come
over
the
anomaly
you're
going
to
measure
this
total
field
you're
going
to
subtract,
though
those
numbers
you're,
going
to
get
some
number
right
37
and
then
how
do
I
think
about
that
number?
A
Well,
you're
going
to
think
about
that
number
as
being
the
projection
of
the
true
anomalous
feel
on
to
a
particular
direction,
and
that
direction
is
the
Earth's
field,
so
why
this
is
going
to
be
easy,
for
you
is
because
you
spent
all
weekend
working
with
the
app
thinking
about
taking
these
anomalous
scales,
projecting
them
on
to
x,
y
and
z.
Now
you're
going
to
do
exactly
this
anything,
except
instead
of
projecting
them
out
to
XYZ
you're,
just
going
to
project
them
onto
another
vector.
That's.
A
If
we're
sitting
up
here,
so
let's
do
the
example
that
we
were
working
with.
We've
got
magnetic
field,
that's
coming
in
so
here's
when
young
love,
yes,
okay,
and
so
it
gets
magnetized
in
this
direction
and
not
I've
got
a
magnetic
field.
It's
coming
in
like
this,
and
now
we're
going
to
measure
so
here's
the
anomalous
feel
and
we're
going
to
measure
the
total
field,
and
not
only
so
that
is
actually
then
going
to
be
equal
to
the
same
as
one
of
these
previous
component.
A
So
V
naught
is
lining
up
with
the
vertical
component
here.
So
when
we,
when
we
do
this,
we're
actually
going
to
get
we're
going
to
take
the
projection
of
this
anomalous
field
on
to
that
particular
direction,
and
then
that
is
going
to
be
so
if
we
look
at
this
example
and
if
we
think
about
projecting
it
onto
this
direction
here
now,
what
do
what's
going
to
be
human?
I
get
it
feels
coming
in
like
this,
you
know
skill.
A
A
A
A
toad
feel
is
going
to
be
Lee
a
dot,
B,
naught
hat
right
and
now
I'm
going
to
plot
this
thing
with
the
same
height
confections
that
we
always
do.
It
almost
feel
it
is
in
the
direction
of
the
this
in
the
Earth's
field,
because
here
now
my
unit
vector
I'm
thinking
about
is
this
guy
going
down
them
is
I'm
going
to
get
this
number
out
here
is
going
to
be
positive,
so
now
my
magnetic
field,
not
only
for
the
total
field,
is
actually
going
to
be
something.
Then
that
looks,
looks
like
this.
A
So
if
I
plot
this
guy
here
so
I
get
something
that
looked
just
like
what
does
that
feel?
You
speak.
But
now,
my
because
my
sign
convention
is
that
I'm
looking
for
a
good
positive
anything
that
is
projected
onto
diverse
deal,
then
I've
got
a
positive
value,
so
what
the
procedure
will
be
in
the
sand.
This
is
fault.
You'll,
be
asked
to
put
an
object,
someplace,
you're
kind
of
thinking
about
make
some
place
on
the
earth
and
the
magnetic
field
lines
are
going
to
come
in,
like
that.