Thread: Fw:Fwd: how to rotate R T comp into N E ?

Started: 2009-06-30 19:25:50
Last activity: 2009-06-30 19:25:50
Topics: SAC Help
Ning Liu
2009-06-30 19:25:50
Hi all,
Thank you for your letter.
In your letter, you have written how to rotate the N E comp to R T. But my problem is how to rotate the R T comp to N E. I did see the help of sac command "rotate", but there is no instruction abut it? So I wrote a letter again.


Best wishes,

Ning Liu and Weitao Wang








---------- Forwarded message ----------
From: Arthur Snoke<snoke<at>vt.edu>
Date: 2009/6/29
Subject: Re: [SAC-HELP] how to rotate R T comp into N E ?
To: weitao wang <wangwtustc<at>gmail.com>
Cc: sac-help<at>iris.washington.edu


In the help command for rotate, there are options for rotating "to" and "through" a fixed angle. It would be easy to write a macro that could give you back the N and E components. I would do test cases to make sure it works correctly for you.

Here is a macro I use to do the "normal" rotation:

r $1$.n $1$.e
rtr
rotate to gcp
write $1$.r $1$.t
r $1$.r
chnhdr kcmpnm "radial"
write over
r $1$.t
chnhdr kcmpnm "trnsvers"
write over

If it is named rotaate.m, one calls it for abc.n and abc.e using

SAC> m rotate.m abc


On Mon, 29 Jun 2009, weitao wang wrote:

Hi,All
I have a question while rotating horizontal component with sac. We can use "rotate to GCP" to rotate N E into R T comp,but how to rotate back into N E components? Is there an easy way to do this?






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  • Renate Hartog
    2009-06-30 05:09:15
    Hello,

    Below is a simple example to show how to use rotate to go from any
    orientation to another (orthogonal orientation). "rotate to number"
    changes the azimuth of the first listed component to "number" degrees
    clockwise from N. The second component will be number+90 from N.

    You can check the orientation of your two files by listing the value of
    the cmpaz header value (clockwise from N).

    -Renate

    SAC> r
    06100802482.D04A.BHE 06100802482.D04A.BHN
    SAC> lh cmpaz


    FILE: 06100802482.D04A.BHE - 1
    --------------------------

    cmpaz = 9.000000e+01

    FILE: 06100802482.D04A.BHN - 2
    --------------------------

    cmpaz = 0.000000e+00
    SAC> rotate to gcp
    SAC> lh


    FILE: 06100802482.D04A.BHE - 1
    --------------------------

    cmpaz = 2.871565e+02

    FILE: 06100802482.D04A.BHN - 2
    --------------------------

    cmpaz = 1.715649e+01
    SAC> rotate to 0.
    SAC> lh


    FILE: 06100802482.D04A.BHE - 1
    --------------------------

    cmpaz = 0.000000e+00

    FILE: 06100802482.D04A.BHN - 2
    --------------------------

    cmpaz = 9.000000e+01
    SAC>



    On Tue, 30 Jun 2009, bjlemon wrote:

    Hi all,
    Thank you for your letter.
    In your letter, you have written how to rotate the N E comp to R T. But my problem is how to rotate the R T comp to N E. I did see the help of sac command "rotate", but there is no instruction abut it? So I wrote a letter again.


    Best wishes,

    Ning Liu and Weitao Wang








    ---------- Forwarded message ----------
    From: Arthur Snoke<snoke<at>vt.edu>
    Date: 2009/6/29
    Subject: Re: [SAC-HELP] how to rotate R T comp into N E ?
    To: weitao wang <wangwtustc<at>gmail.com>
    Cc: sac-help<at>iris.washington.edu


    In the help command for rotate, there are options for rotating "to" and "through" a fixed angle. It would be easy to write a macro that could give you back the N and E components. I would do test cases to make sure it works correctly for you.

    Here is a macro I use to do the "normal" rotation:

    r $1$.n $1$.e
    rtr
    rotate to gcp
    write $1$.r $1$.t
    r $1$.r
    chnhdr kcmpnm "radial"
    write over
    r $1$.t
    chnhdr kcmpnm "trnsvers"
    write over

    If it is named rotaate.m, one calls it for abc.n and abc.e using

    SAC> m rotate.m abc


    On Mon, 29 Jun 2009, weitao wang wrote:

    Hi,All
    I have a question while rotating horizontal component with sac. We can use "rotate to GCP" to rotate N E into R T comp,but how to rotate back into N E components? Is there an easy way to do this?






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