SEED Channel Naming

Source

SEED Manual Appendix A: Channel Naming
Contributed by Scott Halbert

Also see our interactive Time Series Data Channels tool

Band Code

The first letter specifies the general sampling rate and the response band of the instrument. (The A code is reserved for administrative functions such as miscellaneous state of health.)

Band code Band type Sample rate (Hz) Corner period (sec)
F ≥ 1000 to < 5000 ≥ 10 sec
G ≥ 1000 to < 5000 < 10 sec
D ≥ 250 to < 1000 < 10 sec
C ≥ 250 to < 1000 ≥ 10 sec
E Extremely Short Period ≥ 80 to < 250 < 10 sec
S Short Period ≥ 10 to < 80 < 10 sec
H High Broad Band ≥ 80 to < 250 ≥ 10 sec
B Broad Band ≥ 10 to < 80 ≥ 10 sec
M Mid Period > 1 to < 10
L Long Period ≈ 1
V Very Long Period ≈ 0.1
U Ultra Long Period ≈ 0.01
R Extremely Long Period ≥ 0.0001 to < 0.001
P On the order of 0.1 to 1 day 1 ≥ 0.00001 to < 0.0001
T On the order of 1 to 10 days 1 ≥ 0.000001 to < 0.00001
Q Greater than 10 days 1 < 0.000001
A Administrative Instrument Channel variable NA
O Opaque Instrument Channel variable NA

1. These are approximate values. The sample rate should be used for the correct Band Code.

Instrument Code and Orientation Code

The second letter specifies the family to which the sensor belongs. In essence, this identifies what is being measured. Each of these instrument types are detailed in this section.

The third letter in the channel name is the Orientation Code, which provides a way to indicate the directionality of the sensor measurement. This code is sometimes used for a purpose other than direction, which is instrument-specific. When orthogonal directions are used, there are traditional orientations of North (N), East (E), and Vertical (Z), as well as other orientations that can readily be converted to traditional ones. These options are detailed with each instrument type. Use N or E for the orientation when it is within 5 degrees of north or east. Use 1 or 2 when orientations are more than 5 degrees from north or east. Put the actual orientation of the sensor in the dip and azimuth fields of blockette 52.

Seismometer

Measures displacement/velocity/acceleration along a line defined by the dip and azimuth.

Instrument Code
H High Gain Seismometer
L Low Gain Seismometer
G Gravimeter
M Mass Position Seismometer
N * Accelerometer

* historically some channels from accelerometers have used instrumentation codes of L and G. The use of N is the FDSN convention as defined in August 2000.

Orientation Code
Z N E Traditional (Vertical, North-South, East-West)
A B C Triaxial (Along the edges of a cube turned up on a corner)
T R For formed beams (Transverse, Radial)
1 2 3 Orthogonal components but non traditional orientations
U V W Optional components
Dip/Azimuth: Ground motion vector (reverse dip/azimuth if signal polarity incorrect)
Signal Units: M, M/S, M/S**2, (for G & M) M/S**2 (usually)
Channel Flags: G

Tilt Meter

Measures tilt from the horizontal plane. Azimuth is typically N/S or E/W.

Instrument Code
A
Orientation Code
N E Traditional
Dip/Azimuth: Ground motion vector (reverse dip/azimuth if signal polarity incorrect)
Signal Units: Radians
Channel Flags: G

Creep Meter

Measures the absolute movement between two sides of a fault by means of fixing a metal beam on one side of the fault and measuring its position on the other side. This is also done with light beams.

The orientation and therefore the dip and azimuth would be perpendicular to the measuring beam (light or metal), which would be along the average travel vector for the fault. Positive/Negative travel would be arbitrary, but would be noted in the dip/azimuth. Another type of Creep Meter involves using a wire that is stretched across the fault. Changes in wire length are triangulated to form movement vector.

Instrument Code
B
Orientation Code
Unknown
Dip/Azimuth: Along the fault or wire vector
Signal Units: M
Channel Flags: G

Calibration Input

Usually only used for seismometers or other magnetic coil instruments. This signal monitors the input signal to the coil to be used in response evaluation. Usually tied to a specific instrument. Sometimes all instruments are calibrated together, sometimes horizontals are done separately from verticals.

Instrument Code
C
Orientation Code
A B C D For when there are only a few cal sources for many devices.
Blank if there is only one calibrator at a time or, Match Calibrated Channel (is. Z, N or E)

Pressure

A barometer, or microbarometer measures pressure. Used to measure the weather pressure or sometimes for state of health monitoring down hole. This includes infrasonic and hydrophone measurements.

Instrument Code
D
Orientation Code
O Outside
I Inside
D Down Hole
F Infrasound
H Hydrophone
U Underground
Dip/Azimuth: Not applicable – Should be zero.
Signal Units: Pa (Pascals)
Channel Flags: W or H

Electronic Test Point:

Used to monitor circuitry inside recording system, local power or seismometer. Usually for power supply voltages, or line voltages.

Instrument Code
E
Orientation Code
Designate as desired, make mnemonic as possible, use numbers for test points, etc.
Dip/Azimuth: Not applicable
Signal Units: V, A, Hz, Etc.
Channel Flags: H

Magnetometer

Measures the magnetic field where the instrument is sitting. They measure the part of the field vector that is aligned with the measurement coil. Many magnetometers are three axis. The instrument will typically be oriented to local magnetic north. The dip and azimuth should describe this in terms of the geographic north.

Example: Local magnetic north is 13 degrees east of north in Albuquerque. So if the magnetometer is pointed to magnetic north, the azimuth would be + 103 for the E channel. Some magnetometers do not record any vector quantity associated with the signal, but record the total intensity. So, these would not have any dip/azimuth.

Instrument Code
F
Orientation Code
Z N E Magnetic
Signal Units: T – Teslas
Channel Flags: G

Humidity

Absolute/Relative measurements of the humidity. Temperature recordings may also be essential for meaningful results.

Instrument Code
I
Orientation Code
O Outside Environment
I Inside Building
D Down Hole
1 2 3 4 Cabinet Sources
All other letters available for mnemonic source types.
Dip/Azimuth: Not applicable – Should be zero.
Signal Units: %
Channel Flags: W

Rotational Sensor

Measures solid-body rotations about an axis, commonly given in “displacement” (radians), velocity (radians/second) or acceleration (radians/second^2).

Instrument Code
J High Gain Seismometer
Orientation Code
Z N E Traditional (Vertical, North-South, East-West)
A B C Triaxial (Along the edges of a cube turned up on a corner)
T R For formed beams (Transverse, Radial)
1 2 3 Orthogonal components but non traditional orientations
U V W Optional components
Dip/Azimuth: Axis about which rotation is measured following right-handed rule.
Signal Units: rad, rad/s, rad/s^2 – following right-handed rule
Channel Flags: G

Temperature

Measurement of the temperature at some location.

Typically used for measuring:

  1. Weather – Outside Temperature
  2. State of Health
    1. Inside recording building
    2. Down hole
    3. Inside electronics
Instrument Code
K
Orientation Code
O Outside Environment
I Inside Building
D Down Hole
1 2 3 4 Cabinet sources
All other letters available for mnemonic types.
Dip Azimuth: Not applicable – Should be zero.
Signal Units: deg C or deg K
Channel Flags: W or H

Water Current

This measurement measures the velocity of water in a given direction. The measurement may be at depth, within a borehole, or a variety of other locations.

Instrument Code
O
Orientation Code
Unknown
Dip/Azimuth: Along current direction
Signal Units: M/S
Channel Flags: G

Geophone

Very short period seismometer, with natural frequency 5 – 10 Hz or higher.

Instrument Code
P
Orientation Code
Z N E Traditional
Dip/Azimuth: Ground Motion Vector (Reverse dip/azimuth if signal polarity incorrect)
Signal Units: M, M/S, M/S
Channel Flags: G

Electric Potential

Measures the Electric Potential between two points. This is normally done using a high impedance voltmeter connected to two electrodes driven into the ground. In the case of magnetotelleuric work, this is one parameter that must be measured.

Instrument Code
Q
Orientation Code
Unknown
Signal Units: V – Volts
Channel Flags: G

Rainfall

Measures total rainfall, or an amount per sampling interval.

Instrument Code
R
Orientation Code
Unknown
Dip/Azimuth: Not applicable – Should be zero.
Signal Units: M, M/S
Channel Flags: W

Linear Strain

One typical application is to build a very sensitive displacement measuring device, typically a long quartz rod. One end is affixed to a wall. On the free end, a pylon from the floor reaches up to the rod where something measures the position of the pylon on the rod (like a large LVDT).

There are also some interferometry projects that measure distance with lasers. Dip/Azimuth are the line of the movement being measured. Positive values are obtained when stress/distance increases, negative, when they decrease.

Instrument Code
S
Orientation Code
Z N E Vertical, North-South, East-West
Dip/Azimuth: Along axis of instrument
Signal Units: M/M
Channel Flags: G

Tide

Not to be confused with lunar tidal filters or gravimeter output. Tide instruments measure the depth of the water at the monitoring site.

Instrument Code
T
Orientation Code
Z Always vertical
Dip/Azimuth: Always vertical
Signal Units: M – Relative to sea level or local ocean depth
Channel Flags: G

Bolometer

Infrared instrument used to evaluate average cloud cover. Used in astronomy to determine observability of sky.

Instrument Code
U
Orientation Code
Unknown
Dip/Azimuth: Not applicable – Should be zero.
Signal Units: Unknown
Channel Flags: W

Volumetric Strain

Unknown

Instrument Code
V
Orientation Code
Unknown
Dip/Azimuth: Not Applicable – Should be zero.
Signal Units: M**3/M**3
Channel Flags: G

Wind

Measures the wind vector or velocity. Normal notion of dip and azimuth does not apply.

Instrument Code
W
Orientation Code
S Wind speed
D Wind Direction Vector – Relative to geographic North
Dip/Azimuth: Not Applicable – Should be zero.
Channel Flags: W

Derived or Generated Channel

Time series derived from observational data or entirely generated by a computer aseismograms.

Instrument Code
X
Orientation Code
Similar to the observable data that was modified or the observable equivalent for generated time series (synthetics). See Orientation Codes for the corresponding observed channel.

Further Usage:
In order to document the provenance of the data, SEED header information must be available that documents the algorithms, processes, or systems that modified or generated the time series. A Channel Comment Blockette (059), providing a Uniform Resource Locator (URL), must be included. The information available at the URL must identify the processes that were applied to modify or generate the time series. This information must reference the FDSN web site (http://www.fdsn.org/synthetic).

In addition to the requirement to include a B059, it is required to put a short description of the process/instrument in the 30 character channel comment (field 7 of B052).

Non-specific Instruments

The instrument code in SEED format covers most commonly used instruments that generate time series. For instruments not specifically covered by an existing instrument code the Y instrument code can be used.

Instrument Code
Y
Orientation Code
Instrument Specific. Should be documented in the URL referenced below.

Further Usage:
In order to document the instrument type and provenance of the data, SEED header information must be available that documents the instrument that was used to generate the time series. A Channel Comment Blockette (059) must be provided in the SEED metadata. The Channel Comment Blockette should provide a short description of the instrument, the type of measurement it makes and provide a Uniform Resource Locator (URL) referencing the FDSN web site (http://www.fdsn.org/) that fully describes the instrumentation.

In addition to the requirement to include a B059, it is required to put a short description of the process/instrument in the 30 character channel comment (field 7 of B052).

Synthesized Beams

This is used when forming beams from individual elements of an array. Refer to blockettes 35, 400, & 405.

Instrument Code
Z
Orientation Code
I Incoherent Beam
C Coherent Beam
F FK Beam
O Origin Beam
Dip/Azimuth: Ground motion vector (reverse dip/azimuth if signal polarity incorrect)
Signal Units: M, M/S, M/S**2, (for G & M) M/S**2 (usually)
Channel Flags: G

Channel Code

We suggest that two sequences be reserved for special channels: the LOG channel for the console log, and the SOH channel for the main state of health channel. Subsidiary logs and state of health channels should begin with the A code; the source and orientation fields can then be used in any way.

Here are some typical channel arrangements used by a GSN system:

Channel Description
EHZ/EHN/EHE Short Period 100 sps
BHZ/BHN/BHE Broad Band 20 sps
LHZ/LHN/LHE Long Period 1 sps
VHZ/VHN/VHE Very Long Period 0.1 sps
BCI Broad Band Calibration Signal
ECI Short Period Cal
LOG Console Log
ACE Administrative Clock Error
LCQ 1hz Clock Quality
OCF Opaque Configuration File

Note

Log Records: Log records has a channel identifier code of LOG and a sample rate of zero. The number of samples field is the number of characters in the record (including the carriage return and line feed that terminates each line). Log messages are packed into records until a message falls into a new minute. Log records have no blockettes, so the strings start at offset 48. For examples of Log Records, ACE, and OCF channels, refer to the end of Appendix E.