WEBVTT
Kind: captions
Language: en-US

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Greetings.

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The USGS Earthquake Science Center
has a new nodal seismometer facility.

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I’ll describe a little bit about
what we have and what’s available

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if anyone wants to use it.

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Nodes, for anyone who’s not familiar
with them, are a new generation of

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seismometers that were really originally
developed for the oil industry.

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They’re small, portable, wireless,
and they have an onboard GPS

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and solid state storage. They have
an internal rechargeable battery.

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They can record ground motion, timing,
and location all in the same package.

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They can record for days, weeks,
or even months in some situations.

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They can record both below the ground
surface or above the ground surface.

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The ESC nodal seismometers are more
research-oriented seismometers than

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the oil industry type, which
are a typical vertical component.

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The ESC seismometers are three-
component. We have 500 of them.

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We have four 16-slot portable
charging systems and comparable

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harvesting systems. We have
multiple field deployment tools –

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which I’ll explain later,
several laptop servers,

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gigabytes of portable storage,
and auxiliary equipment.

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The ESC nodal seismometers, again,
are three-component seismometers

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with the internal battery that lasts
about 30 to 40 days per charge.

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Now, that battery is changeable,
as you can see here on the right.

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The sensor, recorder, and GPS is
the top part of the unit, and the

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bottom part is the battery with the
spike on it for securing it to the ground.

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Now, because it has internal GPS
timing and location, you can –

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it is recorded automatically, even
if it’s buried up to a meter deep.

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Now, they also have quite a wide
recording range for frequencies,

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from seconds up to about
1,000 hertz, and I’ll show

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some slides on that
in the next couple slides.

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You can select a choice of gains from
zero to 36 dB in 6-dB increments.

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You can change the sampling rate from
0.25 milliseconds to 4 milliseconds.

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It can be deployed in one to two
minutes once you’re on site,

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so they’re really fast for deployment.
And they’re IP67 water- and dust-proof.

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So, if you bury them in a marsh,
still you can be assured

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you’re going to
get good data.

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Now, as I mentioned, the frequency
range is quite wide, and to examine that,

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we did a study with UC-Berkeley,
which was led by Taka’aki Taira.

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And what we did was we put a
node outside the UC-Berkeley vault,

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one inside the vault with
two broadband seismometers.

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And here is the – here are the recordings
from a magnitude 6.7 teleseismic event.

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And the data are filtered from about
20 seconds to about 2 hertz.

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And, as you can see,
the data are very comparable,

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particularly the in-vault node and
the STS-1. It looks very similar.

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But overall, all of the recordings
look similar in that recording range.

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And this is for the body waves.
If you look at the S waves, again, this –

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going down to about 33 seconds
in frequency, you can see, again,

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we have very comparable recordings
for both the nodes and the broadbands.

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So this shows us that we can get
very good low-frequency data,

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which is generally what you
want for earthquake recordings.

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But the nodes also go very
high on the frequency scale,

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up to about 1,000 hertz,
which the broadbands do not do.

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Broadbands typically top out
at about 25 to 50 hertz.

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So it makes the nodes
a very flexible instrument.

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Now, that makes them ideal
for aftershock recordings,

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short-term earthquake monitoring,
noise studies, reflection and refraction

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site characterization,
guided wave recordings –

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a whole series of the type of
recordings that you might want to do.

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And they are very simple to deploy.
Basically, you need two things.

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You need a node,
and you need a simple magnet.

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And that will start it – will record it.
However, if you’re deploying

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a lot of instruments, it’s good to
have something called a field

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deployment tool. And that’s the
thing that looks like a calculator here.

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It will – if you don’t have that
field deployment tool, a compass

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is probably another thing that
you need when you go out.

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Now, they’re very simple to turn on,
and I’ll show just an example of this.

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With that magnet – you put that
magnet in a strategic location.

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It’s turning on. You’re done.
It’s going to record.

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Now, if you’re deploying a lot
of these things, as I mentioned,

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you probably want to use
this field deployment tool.

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It uses RFID technology
to identify the node.

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It records wirelessly the lat, the lon,
the serial numbers of the battery

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and of the node, the line number, etc. –
most of the information you need

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in order to process the
data in order to keep track.

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So you don’t need pencil and paper to
decipher what instrument went where.

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So, it’s as simple as
pushing a button,

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like you show here, and all that data
are recorded from the instrument itself.

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Once you have that information when
you deploy, when you come back to

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pick up, it’s also a very simple process.
You can be 1,000 miles away and

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simply put in that you want to go to
that site, and it will tell you the

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directions you need to go
in order to get there.

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So locating the instrument is very
difficult after it’s been out for

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a month or two or three,
and there’s been rain or wind,

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and it’s very hard to locate the
instrument. This FDT will help you

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do that very easily. We also
have chargers and harvesters.

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They look like a small rolling
suitcase. They’re portable.

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They can plug into any 110 outlet.
The chargers will charge batteries

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in about four to six hours for
a completely drained battery.

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And the harvesters will download
16 nodes at 20 megabytes

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per second per node. So they’re
very efficient and very fast.

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So, because we have four harvesters
and four chargers, that means that

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there can actually be four separate site
investigations going on in different

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locations by different PIs at the same
time with a subset of the nodes.

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This is what they look like –
the harvester is on the left –

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when you open it up.
The charger is on the right.

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So having these inside of a hotel room,
you can do quick downloading and

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recharging, get your instruments
back out in the field very quickly.

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The nodes are available to ESC
scientists and collaborators to use.

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Whereby, they can use just
a few nodes, or they can use

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all the nodes at the same time.
And, again, we have about 500 of them.

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The availability can be seen at this
website shown here on the right bottom.

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Now, one of the problems with
portable seismometers in the past

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has been that they’re
notoriously unreliable.

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Sometimes we have as much as 20%
failure rate on the old seismometers.

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But these nodes are incredibly
durable, as you can see from this –

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this is a video
by SmartSolo.

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[banging sounds]

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Now, this is the tumble test.
So, when they are thrown in

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and tumbled around, 200 rotations,
you’ll see, when they come out,

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if they’re blinking green, that means
they’re recording as they should be.

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They’re also – this drop test,
where you see the same thing.

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If it blinks green, you’ve still got
a good, functioning instrument.

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[silence]

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And, in this case,
it blinks green.

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There are also optional
external batteries.

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Like I said, the typical node will
record for about a month to –

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about 30 days to 40 days in the
field, just on the internal battery.

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But if you want to record for, say,
three or four months, you can buy

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these external batteries that are
attached – they can buried

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with the node, or they can
be set on the ground surface.

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very convenient for a little
bit longer-term recording.

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I’m going to show an example
of a passive and an active study

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that we’ve done using the nodes.
Here is from Ridgecrest,

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where deployed 461 nodes
occupying 575 sites.

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We got them out the day after
the major earthquake – the 7.1,

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and they recorded
for about two months.

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We have 12 linear fault-crossing
arrays and 2 two-dimensional arrays –

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one across the Garlock, one across
the major seismicity, which you can

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see here. Here’s the major
seismicity shown in white.

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We recorded about 14 terabytes
of data during that time, and again,

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we recorded – at least
the network reported

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30,000 earthquakes shown here.
And we were able to record that.

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Here is an example of
a single station and a linear array.

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And for the three components of
those from the Ridgecrest nodal data.

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We also conducted some
studies whereby we conducted

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guided wave studies.

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On the right shown here is our
linear array across the fault trace.

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These yellow dots show where
geologists mapped the faults.

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And the red lines
show those as well.

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And, when we project those
locations onto a plot of PGV versus

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the station locations,
we see we get these

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prominent peaks where
the two faults were met.

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We also get a small peak in between,
suggesting that there’s another fault

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in the shallow subsurface that
didn’t make it to the surface.

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So we found, from many studies,
that this is a very convenient way

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to precisely map exactly
where the faults are located.

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Another study that was done using
the nodal data was by White et al.

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And here, using the nodal data –
remember I said the network

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located 30,000 earthquakes.
Well, we were able to re-locate

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approximately 95,000 earthquakes in
this area, and much more precisely.

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And, from that, we were able to
develop a 3D tomography model

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for the – both P and S for the region.
Just an example to look, here is

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a slice at 12 kilometers’ depth
comparing the new model with the

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SCEC Community Velocity Model,
and you see there’s much more

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resolution on the new
model using the nodal data.

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We’ve also conducted a number
of active-source surveys,

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mainly for site characterization
and guided wave studies,

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but also some noise
studies using the nodes.

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So, in summary, ESC has a new
nodal seismometer facility.

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We have about 500 three-component
nodes and auxiliary equipment.

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The nodes are available to ESC
scientists and their collaborators.

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And the node schedule is available
at the website shown here.

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If you want to use any of the nodes,
you should contact someone from

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the Nodal Committee, and those
people are shown here below.

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Thank you
very much.

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[silence]