Seismic sensor

Tutorial about Seismic Sensor Network

Vinayak Naik, Martin Lukac, and Deborah Estrin

Information Processing in Sensor Networks
(IPSN’07), Cambridge, MA

April 24, 2007
Acknowledgments to Igor Stubailo, Derek Skolnik, Joey Degges, and Mike Allen for lending us
equipments and time.

Special demands of seismic and acoustic applications

• Seismic
– Large-scale deployment spanning hundreds of kilometers
– It’s not easy
• Highly varying links with frequent disconnections results in
challenged networks
• Remote monitoring and fixing of nodes demands services such
as reliable broadcast, sink-based data collection, and
maintenance of a global state
• Developing these services become non-trivial due to challenged
networks
• Acoustic localization
– Sampling rate of the order few KHz
– Lew will summarize the challenges

Outline

• Using the seismic array out-of-the-box

• A few words about seismology

• Remotely managing and configuring array
after the deployment

• Assembling the array in 30 minutes

• Adapting the software to fit your needs

What’s in the box?

• 1 PC
• 3 Cens Data Communication Controller
(CDCCs)
• 1 Q330 (a combined ADC and data logger)
• Ubuntu live CD, which contains
– Emstar source code
– Emstar code compiled for the i366 and stargate
architectures
– TFTP server and minicom to reflash the nodes (to
be used while assembling the array)
– You may also use the CD to install all the required
software on your PC or run it in an emulator such
as qemu!

Using the CD

• Prerequisites:
– A computer that can be booted using a CD and has wired
ethernet connection
– A basic knowledge of Linux, such as use of ssh, scp, and
ifconfig
• Procedure:
– Boot your computer using the CD
– Set password for ubuntu: "sudo passwd ubuntu”
– setup IP address for the ubutu: “ifconfig eth0 131.179.145.X
netmask 255.255.255.0 broadcast 131.179.145.255”
– If using a virtual machine, unload USB-to-serial driver if
alread loaded

The seismic activities before the start of the tutorial

• Stop the data collection process (Duiker)
• Transfer data to the base station (PC)
• Strip the DTS header from the packet
• Uncompress the data
• Convert the data from miniseed to ascii format
• Transfer data to your laptop
• Plot the data using gnuplot

Wait, the theory about seismology is coming up.

In situ data collection and presentation

• Start Duiker and let it run for 4 minutes
• Stop Duiker
• Strip the header
• Uncompress the data
Same as the
• Convert the data from miniseed to previous slide
ascii format
• Transfer data to my laptop
• Plot the data using gnuplot

Seismology 101

Wikipedia: An earthquake is a phenomenon that results
from the sudden release of stored energy in the Earth’s
crust that creates seismic waves.

There are two types of seismic wave, 'body wave' and
'surface wave'. There are two kinds of body waves:
primary (P-waves), travel fastest through any type of matter
and secondary (S-waves), shear, the most destructive.

Body waves travel through the Earth’s interior:

P-wave speed: 1.5-8 Km/s
S-wave speed: 60-70% of the speed of P-wave

Seismic wave energy

Richter TNT for Seismic Example
Magnitude Energy Yield (approximate)
-1.5 6 ounces Breaking a rock on a lab table
1.0 30 pounds Large Blast at a Construction Site
2.0 1 ton Large Quarry or Mine Blast
4.0 1,000 tons Small Nuclear Weapon
4.5 5,100 tons Average Tornado (total energy)
6.5 5 million tons Northridge, CA Quake, 1994
7.0 32 million tons Japan Quake,1995;Largest Thermonuclear Bomb
8.0 1 billion tons San Francisco, CA Quake, 1906
9.0 32 billion tons Chilean Quake, 1960
12.0 160 trillion tons Fault Earth in half through center

160 trillion tons of dynamite is a frightening yield of energy. Consider, however, that
the Earth receives that amount in sunlight every day.

Because of this huge amount of energy released the seismic waves travel large
distances and make possible to capture them with different kinds of seismic
sensors (seismometers).

Seismic sensors

Most signals are composites of many frequencies.

Analog with light and sound:
Seismic Light Sound Typical seismogram
Short-period Blue Treble
Long-period Red Bass

The long-period and short period instruments are called
"narrow" band used for volcano experiment by Harvard. They
sense frequencies near 1/15 s and 1 hertz respectively.
The yellow region is the low end of the frequency range
audible to most humans, 20 hertz to 20,000 hertz.

A broadband instrument senses most frequencies equally well.
For our data collection we use the best in its class CMG-3T
broadband sensor, made by Guralp Systems.
Its standard frequency response is 120 s – 50 Hz what Frequency responses
results in high quality seismic data. of seismometers

About Middle America Subduction Experiment (MASE)

• We have a seismic deployment to study the
structure of the mantle in Mexico
• The deployment consists of wireless stations
covering large distances
• We developed software to:
– Handle collection the seismic data
– Manage the seismic system
• This tutorial presents this software and how to
use it

Seismic deployment application requirements
50 standalone Caltech sites • Extensive: 500 Km from Acapulco through Mexico
62 wirelessly connected UCLA sites
City to Tampico
• Dense: 1 sensor every 5-10 Km
• High bandwidth: Data acquisition rate: 3 - 24 bit
channels at 100Hz each
• Online and Reliable: Semi real-time (on the order
of days), reliable data delivery to UCLA for
analysis
• Online system management
– Query state, change configuration, update binaries
– Can not interfere with data delivery
• Application driven topology: application
determines sensor placement
– Infrastructure does not (Can’t rely on pre-existing cell
or power infrastructure)

MASE: Given these
requirements, we
deployed solar powered
seismic stations equipped
with 802.11b

MASE wireless seismic station

15 dBi YAGI or 24 dBi Parabolic 2.4GHz antenna

70 watt solar panel, GPS

mast and guy wires

Quanterra Q330 24-bit digitizer

sensor controller

2.4GHz amp

car battery

CDCC (CENS Data
Communication Controller)

Guralp 3T seismometer

A block diagram of the system’s architecture

DTS & file_mover Duiker

TCP/IP, UDP CDCC

WiFi ethernet

Q330 (ADC)
Replace with
your own
Sensor

Pakistan earthquake

Our network:
•Achieves almost 10 times better resolution than the previous network as of
Oct. 2005 (with 50 sites total). Now it is 20 times better (100 sites)

•Provides visualization of the upper mantle and the subduction process,
coast to coast across Mexico.

Google video

• The data was used to analyze the structure of
the earth underneath Mexico
• Results are being submitted to the Science
journal

Networking support needed for both
data acquisition and system management

• Data delivery – Bandwidth driven
– Bandwidth: 20-40 of MB per day per station
– Latency: get the data eventually, but reliably
– Many to one routing

• System Management – Latency driven
– Bandwidth: usually less than 10’s of KB’s
– Latency: as fast as possible
– One to all routing and back

Use of wireless network for remote operation

• Demonstrate use of Delay Tolerant Shell (DTS)
– Start dtsh
– Issue a ps command Configuration
– See result of the ps command utilities
• Demonstrate the use file transfer
– Xfer a file from /opt/test
• Demonstrate the use of file mover Data collection
– Create a file on a stargate
utility
– Show the same file on the PC
• Xfers
– Shows the active transfers
• Links Adjunct
– Shows existing links on a node utilities
• Sink_status
– Shows the upstream route to the sink

Challenges handled by DTS, file transfer, and file mover

• Frequent unpredictable
disconnections
– Rainy season: sites flood (some
24x7), trees grow
– Wind: misaligned antennas
– Equipment malfunction: amps
burn, voltage regulators break
• Poor and unstable links
– Connectivity secondary concern
for site selection
– Stretched links highly
susceptible to weather and
environment
• Useful tools for operating
wireless sensor networks under
harsh wireless settings

System management

• Existing management tool: remote df –h
ls /opt/dts/file_mover | wc
shell (ssh) A
• Modified management tool:
Disruption Tolerant Shell
E
B
– Asynchronous remote shell to all
nodes in network simultaneously
– Provides node management C D
capabilities when end-to-end
connections are unavailable or fail
F
– Ensures that commands will succeed:
as long as there is eventually a
connection between a node and any
other node that already has the
command

Commands
Responses

Data delivery using DTN techniques

• Buffer data into hour long bundles (1-3 MB) A

• Deliberate one hop bundle transfer
• Path to sink determined by best ETX B

• Improvement over end-to-end
– Not affected by path disconnections C

– Keeps retrying on single link instead of full path
– Continual ‘progress’ being made towards sink
F
– More efficient use of bandwidth in face of
disconnections and bottlenecks
end-to-end
hop-by-hop

Extra fun features of DTS

• Guaranteed in order execution from
source node
• Reboot and crash safe
• Implicit feed back on nodes and
links: spot bottlenecks, dead nodes
• Execute a command on individual
nodes
• Push a file to all nodes
– Distribute new script or component

Handling sessions in DTS

• A sequence number is assigned per source node per session
• Each node publishes a ‘starting sequence number’ across the
network
– It identifies the oldest command issued by a node that should be in
the network
– Any commands and responses with sequence numbers below the
value (for that particular node) are discarded and not propagated
• User controls the starting sequence number
– To remove commands from the network, user increments the
commands source node starting sequence number
– Can choose to do this after all the nodes have reported responses
or sooner
• Giving control of seqno to user is simple, easy to understand,
and efficient
• Utilities to handle seqno
– Use seqno command to see all the nodes starting sequence
numbers
– Use incr command to increment the starting sequence number on
the current node

Ingredients

• 3 stargates to form a 1-hop network
• 1 computer
• 1 serial cable
• 1 ethernet hub and 1 ethernet cable

Assembling a seismic node

• Connect an episensor to the Q330

• Connect Q330 to the wired ethernet hub

• Connect a stargate to the wired ethernet

• Connect wireless antenna to the stargate

• Note that you can substitute Q330 with your

choice of data logger

Reprogramming the stargates

• Connect PC to the wired ethernet
• Connect a serial cable from PC to a stargate
• Configure minicom profile called “stargate0”
• In stargate-install.exp, change the IP address of the
TFTP server to PC’s IP address
• Flash the kernel and the root file system
– The kernel and the root file system comes with all the
seismic software!
– Screenshot of the flashing in progress

Configuring a gateway node (base station)

• Designate a stargate as a gateway

• Restart DTS

Index

• Episensor
– Measures movement across multiple axes
• Q330
– Data logger, GPS, accurate maintenance of time
• PDA
– Reports status and configures Q330 via infra-red
• Williard
– A closed-source software to retrieve the data from Q330
• Duiker
– An open source software to retrieve the data from Q330
– A comparison with Antelope (supports network, open
source, and inexpensive)
• DTS
– An open source software for the remote management of
stargates

Use of the software for other wireless sensor networks

• Replace Q330 with ADC of your choice
• Install a driver that collects data from the ADC
and creates files on the stargate at
/opt/dts/xfer
• file_mover will transfer files to the gateway
node
• No change in DTS and other utilities

Convert existing 7.2/7.3 stargates into seismic nodes

• Download dts-whole-system.tar.gz and
dts-whole-system-install.tar.gz to /opt on the
stargate
• Make sure that the script dts-whole-system-
install.tar.gz is executable
• Execute the script

Adapting the DTS code for your needs

• Change code in
emstar/devel/dts/dts/dts_status.c
• Compile code for stargate architecture
• Stop DTS if it is running
• Copy the new code to the right place on a
stargate
• Start DTS and see the change

Convert other platforms into seismic arrays

• Portable to Linux-based platforms

• Instructions to port EmStar to other platforms

Seismology of the future at CENS

• Deploy the CDCCs in Peru
• Use of low power LEAP-II nodes instead of
stargate
• Use of low power and inexpensive ADC
boards from Reftek Corp. instead of Q330
• Deploy combination of the LEAP-II and the
new ADC
– For GeoNet to study aftershocks
– For structural health monitoring of tall buildings in
Los Angeles

A few upcoming features of DTS

• Provide visualization of the data
movement
– Using a coarse grained global time (one
second), recreate ‘movie’ of file
movement for entire network
– Can help spot network problems and
bottlenecks
• Upload data to SensorBase.org
– Makes it easy to visualize and browse
data collection status
– RSS feed can provide access to anyone
who wants to monitor problems or
generic status of network
• Web interface to simplify operation
– Command line interface is nice for Linux
pros
– Web interface more intuitive for
asynchronous model

Thank you

• Resources for users and developers
– Emstar web-page
– Emstar mailing list
– Disruption Tolerant Shell in the Proceedings of the
2006 SIGCOMM workshop on Challenged Networks

Wish you happy seismography!

Use of seismic sensing

• The similarity between the Mexico and LA
region
• P and S waves
• How is the seismic array different from the
Harvard's volcano motes?
• What is the sampling frequency

Need for DTS, file transfer, and file mover

• Unreliable links
• Need to broadcast commands to the nodes
and get responses from the all the nodes
• Need to broadcast files to the nodes
• Hop-by-hop data movement

%18 - A
%152 - B
13 Node Cuernavaca Line L K
%69 - C
%77 - D Data paths A
%107 - E B
• Network
%42 - F topology does not reflect
%81 - G linear physical topology
the mostly
%202 - H A – sink
%76 - I F
Direct inet
%106 - J G connection
%95 - K
D
%53 - L C
%157 - M
E

M H

I

J N

Seismic sensor

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