SEED Channel Naming

Source ¶

SEED Manual Appendix A: Channel Naming
Contributed by Scott Halbert

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.)

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.

* 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.

Tilt Meter ¶

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

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.

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.

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.

Electronic Test Point: ¶

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

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.

Humidity ¶

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

Rotational Sensor ¶

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

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

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.

Geophone ¶

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

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.

Rainfall ¶

Measures total rainfall, or an amount per sampling interval.

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.

Tide ¶

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

Bolometer ¶

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

Volumetric Strain ¶

Unknown

Wind ¶

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

Derived or Generated Channel ¶

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

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.

Synthesized Beams ¶

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

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:

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.

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