SCGSN Nov96

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Session III.2 Instrumentation, Recording
systems Data transmission Archiving 8-10 May
2006 Jakarta, Indonesia
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Topics covered

• Types of seismic instruments
• Other equipment needed
• How sensors are installed
• Data transmission (telemetry)
• Data archiving (storage)

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A simple seismometer
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A large seismometer 1200kg, 2m
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Type of Seismometer

• Velocity type
• For small earthquakes
• Acceleration type
• For large earthquakes(generate displacement by
  double integration)
• Broadband type
• For mechanism analysis

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An observatory- class seismometer
Streckeisen STS-1 Very Broadband Seismometer
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A seismometer placed in a borehole.
Teledyne KS-54000-I Borehole Seismometer
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High frequency seismometers
Streckeisen STS-2
Guralp CMG-3T
Teledyne GS-13
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An insensitive (strong motion) seismometer
good for recording violent shaking
Kinemetrics FBA-23
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IRIS GSN SYSTEM
Why more than one kind of seismometer is used
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Other equipment needed

• Clock to time the data

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IDA MK8 DAS
Another popular model
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Vault of an observatory
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Other kinds of equipment needed

• Clock to time the data
• DAS to convert electric current to numbers for
  a computer to process
• A source of electric power

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Power Supply

• Commercial current gt Solar power
• Powerful
• Independent from weather condition

gt
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Thermoelectricity
Solar power
Power for an observatory
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Choice of Installation Point (3)

• Less human-activity noise
• Close to power supply and telephone line

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Remark for Installation (2)

• On bedrocks
• Bed should be big enough

Seismometer
N.G.
O.K.
Bed
Soft Ground
Hard Rock
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A regional station
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Vault of a regional seismic station
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Seismic vault under construction in Madagascar
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Seismic vault under construction in Madagascar
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Remark for Installation (3)

• Avoid rainfall, dust, high-humidity, big
  temperature change and cracking.(inside vault or
  small room is better)

Sensor Room
Inside
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Where is a good place to put a seismometer?

• Far from human-generated noise (roads and
  machinery)
• Far from the ocean
• On solid (competent) rock
• In a temperature-stable environment

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Recording room
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Vault of an observatory
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(No Transcript)
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When a vault or tunnel is not available, a
seismometer can be placed in a borehole to reduce
noise.
Pallekele, Sri Lanka
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At PALK, the wellhead and recording room are very
close.
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The wellhead cover protects the electronics
against damage.
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Types of circuits

• local area network (LAN)
• leased telephone lines
• VSATs
• local Internet service provider (ISP)

Mbarara, Uganda
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• For cut of power supply
• Ask electric power company
• For cut of telemeter
• Ask telephone carrier
• Trouble of seismometer
• Change with spares
• Regular maintenance
• Once a year or so

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Ocean Bottom Seismometer (1)

• Very effective for early detection of earthquakes
  in the sea.
• JMA has 2 sets of OBS (in 2008 another one will
  be installed)

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Ocean Bottom Seismometer (2)
Acceleration type
Velocity type
Seismometer
beryllium-copperalloyed cylinder hollowed out of
the column
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Ocean Bottom Seismometer (4)
Ground Earth
Terminal Station
Manhole
JMA Headquarters
Land Cable
Coastline
OBS-5
TG-3
OBS-4
OBS-3
TG-2
OBA
OBS-2
TG-1
OBS-1
Sea Earth
Submarine Optical Cable
OBSOcean-bottom Seismograph TG Tsunami
Gauge OBAOcean-bottom Optical Amplifier
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for your attention
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uplink circuit wire or radio
Recording Room
Seismometer Borehole
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Other equipment needed

• Clock to time the data
• DAS to convert electric current to numbers for
  a computer to process

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Ocean Bottom Seismometer (5)

• Selection of cable path
• Avoid steep slope
• Away from other cables
• Across perpendicular to other cables

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Ocean Bottom Seismometer (6)

• Set cable with sensors from sea to the coast
• Cut and buoy up the cable near the coast
• Pick-up buoy and draw to the coast
• Connect to the terminal station

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Seismometer

• An instrument to record seismic waves (vibrations
  caused by earthquakes or explosions)

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Todays seismometers use electromagnetic feedback
to hold the mass still. This allows seismometers
to be made and more compact and sensitive.
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Our eyes see only part of the light from the Sun.
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Data Telemetry
To transmit data, the following must be
considered

• Type of circuit to carry the data
• Format of the data
• The computer application(s) to manage the data
  transmission

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Data formats

• SEED (FDSN standard)
• Earthworm (US Geological Survey)
• SAC (Lawrence Livermore Laboratory)
• SEISAN (University of Bergen, Norway)
• Others

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Data archiving On-site recording media

• DAT tape
• CD-R

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In San Diego, comprehensive data analysis
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Data are then sent to the IRIS Data Management
Center in Seattle, USA where they are available
to anyone who requests copies. For more
information, see http//www.iris.edu.
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Ocean Bottom Seismometer (3)
Tsunami Gauge
beryllium-copperalloyed cylinder hollowed out of
the column
tsunami gauge
Thermometer