International Federation of Digital Seismograph Networks

Thread: Ask for information on SEED manual.

Started: 2016-06-23 20:12:21
Last activity: 2016-06-23 20:12:21
2016-06-23 20:12:21
Hello Reinoud,

I hope you're always working on Seed norm in Fdsn and all goes fine for u.
Currently for the new french national seismological network Resif we are
discussing about a special topic from the SEED manual. The last one
edition seems to be from 2012 on Fdsn website.
It's dealing with the orientation codes for seismological sensors, and
more particularly when the orientation on some components are out of the 5°

From the page 134 out of the seed ref manual we read the followings:

/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./


thus above:

/"Orientation Code/

/Z N E Traditional (Vertical, North-South, East-West) (see 5 degree
convention above)///

/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///

/(see 5 degree convention above)///

/U V W Optional components///

/Dip/Azimuth: Ground motion vector (reverse dip/azimuth if signal
polarity incorrect)/

So as you can see it can exist an ambiguity. In the first part it seems
clear for me that if a sensor has its N and E components out of range
they have to be renamed resp. 1 and 2.
Thus the orientation code for the orientation of this unit become Z12
dealing with the association :

Bad orientation for N => 1
bad orientation fore E => 2

But, in the second part I can read "1 2 3 orthogonal components but not
traditional orientations", the ambiguity comes here, cause we can deal with:

Z=> 1, N=> 2 and E=> 3 ?
N=> 1, E=>2, Z=> 3 ?
or an other way ?

I thank you very much if you can give us an accurate reading from these
important pages for our current specif. work.

Best regards,

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