Daniel Griscom
Dear Sirs/Madams,
I'm the author of a free IRIS-supported Macintosh program called
SeisMac, which uses Mac laptops' built in accelerometers to convert
the laptops into (not very accurate) seismographs. You can find more
about it at http://www.suitable.com/tools/seismac.html.
I'm finishing off an update which will let you export selected data
as a binary SAC or ascii SACA file. I think I've got it right (Global
Earthquake Explorer successfully reads the SAC files), but I'd love
to have further confirmation. Would any of you be able to review
example files and tell me if I've made any format errors? Or, point
me to other tools which will read/validate SAC/SACA files?
I've uploaded the same set of data in three ways:
- Comma-separated values (all three axis):
http://www.suitable.com/temp/SeisMacData.CSV
- Binary SAC file (Z axis only): http://www.suitable.com/temp/SeisMacData.SAC
- Ascii SACA file (Z axis only):
http://www.suitable.com/temp/SeisMacData.SACA
(If you have a Mac laptop and would like to play with exporting data
yourself, the latest binary is at
http://www.suitable.com/temp/SeisMac30b2.zip)
Thanks,
Dan
--
Daniel T. Griscom griscom<at>suitable.com
Suitable Systems http://www.suitable.com/
1 Centre Street, Suite 204 (781) 665-0053
Wakefield, MA 01880-2400
I'm the author of a free IRIS-supported Macintosh program called
SeisMac, which uses Mac laptops' built in accelerometers to convert
the laptops into (not very accurate) seismographs. You can find more
about it at http://www.suitable.com/tools/seismac.html.
I'm finishing off an update which will let you export selected data
as a binary SAC or ascii SACA file. I think I've got it right (Global
Earthquake Explorer successfully reads the SAC files), but I'd love
to have further confirmation. Would any of you be able to review
example files and tell me if I've made any format errors? Or, point
me to other tools which will read/validate SAC/SACA files?
I've uploaded the same set of data in three ways:
- Comma-separated values (all three axis):
http://www.suitable.com/temp/SeisMacData.CSV
- Binary SAC file (Z axis only): http://www.suitable.com/temp/SeisMacData.SAC
- Ascii SACA file (Z axis only):
http://www.suitable.com/temp/SeisMacData.SACA
(If you have a Mac laptop and would like to play with exporting data
yourself, the latest binary is at
http://www.suitable.com/temp/SeisMac30b2.zip)
Thanks,
Dan
--
Daniel T. Griscom griscom<at>suitable.com
Suitable Systems http://www.suitable.com/
1 Centre Street, Suite 204 (781) 665-0053
Wakefield, MA 01880-2400
-
Hi Dan,
Very cool stuff. The binary file seems to work fine in sac (the
reference application), the PQL waveform viewer and my sac2mseed
converter.
The ASCII/ALPHA file has a small problem. The recognized NULL value
is "-12345.00", as you can see from the snippet below from
SeisMacData.SACA the null value seems to have "61" in place of "00"
which causes minor havoc with the interpretation.
Chad
-- top of SeisMacData.SACA --
0.020000 -12345.61 -12345.61 -12345.61
-12345.61
0.000000 21.34106 -12345.61 -12345.61
-12345.61
-12345.61 -12345.61 -12345.61 -12345.61
-12345.61
-12345.61 -12345.61 -12345.61 -12345.61
-12345.61
-12345.61 -12345.61 -12345.61 -12345.61
-12345.61
-12345.61 -12345.61 -12345.61 -12345.61
-12345.61
-12345.61 -12345.61 -12345.61 -12345.61
-12345.61
On Mar 27, 2009, at 6:44 PM, Daniel Griscom wrote:
Dear Sirs/Madams,
I'm the author of a free IRIS-supported Macintosh program called
SeisMac, which uses Mac laptops' built in accelerometers to convert
the laptops into (not very accurate) seismographs. You can find more
about it at http://www.suitable.com/tools/seismac.html.
I'm finishing off an update which will let you export selected data
as a binary SAC or ascii SACA file. I think I've got it right
(Global Earthquake Explorer successfully reads the SAC files), but
I'd love to have further confirmation. Would any of you be able to
review example files and tell me if I've made any format errors? Or,
point me to other tools which will read/validate SAC/SACA files?
I've uploaded the same set of data in three ways:
- Comma-separated values (all three axis): http://www.suitable.com/temp/SeisMacData.CSV
- Binary SAC file (Z axis only): http://www.suitable.com/temp/SeisMacData.SAC
- Ascii SACA file (Z axis only): http://www.suitable.com/temp/SeisMacData.SACA
(If you have a Mac laptop and would like to play with exporting data
yourself, the latest binary is at http://www.suitable.com/temp/SeisMac30b2.zip
)
Thanks,
Dan
--
Daniel T. Griscom griscom<at>suitable.com
Suitable Systems http://www.suitable.com/
1 Centre Street, Suite 204 (781) 665-0053
Wakefield, MA 01880-2400
_______________________________________________
sac-help mailing list
sac-help<at>iris.washington.edu
http://www.iris.washington.edu/mailman/listinfo/sac-help
-
Dear Chad and George,
Many thanks: this is exactly the help I was looking for. In detail:
At 9:36 PM -0700 3/27/09, Chad Trabant wrote:
The ASCII/ALPHA file has a small problem. The recognized NULL value
Hello, Chad. Ooops, missed that. I fixed a rounding issue and broke
is "-12345.00", as you can see from the snippet below from
SeisMacData.SACA the null value seems to have "61" in place of "00"
which causes minor havoc with the interpretation.
something else. I'll try again.
At 10:39 AM +0000 3/28/09, George Helffrich wrote:
1) Undefined character values in the binary file should be
Are you sure? The SACA example I have uses trailing nulls (which surprised me).
padded with blanks, not trailing zero characters, to their field
lengths (8 or 16 characters, as appropriate);
2) Undefined values should numerically be -12345.00 in the
I'll fix this.
alphanumeric file.
3) I think that you can safely set IDEP to IACC (integer
The values in the data section are in m/s/s, not nm/s/s; would you
number 8) to signify that the dependent variable is acceleration.
still suggest IACC ("Acceleration in nm/sec/sec")?
4) The component naming fields KCMPNM for the traces don't
Ah, hadn't seen that reference. Excellent. Letter by letter:
follow FDSN standards. (See Appendix A of the SEED manual). My
reading of the manual suggests that, for the sample rate shown, the
channels should be named with three-letter codes BNx, where x is the
orientation letter. N (middle character) is the code for an
accelerometer. ZNE aren't useful because orientation can't be
guaranteed. XYZ are probably OK for consistent usage with your
program documentation, though they aren't FDSN-endorsed. FDSN would
prescribe them to be 123 (orthogonal but orientation not guaranteed).
1: The band code letter. My sample rates can be from 20Hz to 500Hz
(user selected). Should I change based on the sample rate? If so then
I'd switch between S, E or D, assuming that for accelerometers
"corner period" means the native resonance of the detector, which in
this case is extremely high.
2: Instrument code: pretty clearly "N".
3: Orientation code. I want the vertical samples to be marked
vertical, but don't want to imply specific directions for the two
horizontal vectors. I'm using "1", "2" and "Z" right now; should I
switch to "X", "Y" and "Z"? Or perhaps even "2", "3" and "Z" (with
vertical being the primary component of interest)?
Thanks again,
Dan
P.S. For all you Mac-owning seismologists, I'd also be interested in
any feedback you may have about the data export process. Right now
you choose the axis and name and then save, which means to save all
three axes you have to enter three different names. I'm considering
going to saving a folder instead of a file, with the folder
containing three axis files. Thoughts?
--
Daniel T. Griscom griscom<at>suitable.com
Suitable Systems http://www.suitable.com/
1 Centre Street, Suite 204 (781) 665-0053
Wakefield, MA 01880-2400
-
Dear Dan -
Some responses to your queries:
On 28 Mar 2009, at 12:28, Daniel Griscom wrote:
...
At 10:39 AM +0000 3/28/09, George Helffrich wrote:
Positive. The binary format is defined by Fortran behavior. Character
1) Undefined character values in the binary file should be padded
Are you sure? The SACA example I have uses trailing nulls (which
with blanks, not trailing zero characters, to their field lengths (8
or 16 characters, as appropriate);
surprised me).
fields are blank-filled; trailing nulls have no significance in
Fortran.
...
I'm not particularly bothered by the units discrepancy, but you could
3) I think that you can safely set IDEP to IACC (integer number 8)
The values in the data section are in m/s/s, not nm/s/s; would you
to signify that the dependent variable is acceleration.
still suggest IACC ("Acceleration in nm/sec/sec")?
fix it either by 1) multiplying samples by 10**9; 2) setting SCALE to
be 10**-9 with unchanged samples; 3) go back to setting IDEP to IUNKN
(but you *do* know, after all).
Hmmm. The first character choice depends on the idea of a4) The component naming fields KCMPNM for the traces don't follow
Ah, hadn't seen that reference. Excellent. Letter by letter:
FDSN standards. (See Appendix A of the SEED manual). My reading of
the manual suggests that, for the sample rate shown, the channels
should be named with three-letter codes BNx, where x is the
orientation letter. N (middle character) is the code for an
accelerometer. ZNE aren't useful because orientation can't be
guaranteed. XYZ are probably OK for consistent usage with your
program documentation, though they aren't FDSN-endorsed. FDSN would
prescribe them to be 123 (orthogonal but orientation not guaranteed).
1: The band code letter. My sample rates can be from 20Hz to 500Hz
(user selected). Should I change based on the sample rate? If so then
I'd switch between S, E or D, assuming that for accelerometers "corner
period" means the native resonance of the detector, which in this case
is extremely high.
2: Instrument code: pretty clearly "N".
3: Orientation code. I want the vertical samples to be marked
vertical, but don't want to imply specific directions for the two
horizontal vectors. I'm using "1", "2" and "Z" right now; should I
switch to "X", "Y" and "Z"? Or perhaps even "2", "3" and "Z" (with
vertical being the primary component of interest)?
seismometer's corner period, where its response to velocity turns flat.
Accelerometers aren't built to be flat to velocity anywhere. Their
response is broad band, however, because they are flat to acceleration
from DC to a very high frequency. In that spirit, I'd use either B or
H as appropriate to the sample rate.
My vote for the last character is XYZ, since you'll never be
FDSN-compliant if you want to use Z (but a laptop on my lap isn't
guaranteed to have Z up, either). At least there will be a clear link
between the trace names and the computer-fixed coordinate system.
...
Only this: Folders don't seem to have any benefit other than reducing
P.S. For all you Mac-owning seismologists, I'd also be interested in
any feedback you may have about the data export process. Right now you
choose the axis and name and then save, which means to save all three
axes you have to enter three different names. I'm considering going to
saving a folder instead of a file, with the folder containing three
axis files. Thoughts?
file name typing. In the save dialog just provide a choice of a file
prefix and whether to save X, Y, Z, or all components. Then generate
the suffixes like the component names. Trying to encode too much
information in a file name leads to quite cumbersome names like what
rdseed writes!
George Helffrich
george<at>geology.bristol.ac.uk
-
-
-
Dear Dan -
This will be a very useful SeisMac feature. There are two minor
problems with the specimens that you provided:
1) Undefined character values in the binary file should be padded with
blanks, not trailing zero characters, to their field lengths (8 or 16
characters, as appropriate);
2) Undefined values should numerically be -12345.00 in the
alphanumeric file.
Something else you might think about are:
3) I think that you can safely set IDEP to IACC (integer number 8) to
signify that the dependent variable is acceleration.
4) The component naming fields KCMPNM for the traces don't follow FDSN
standards. (See Appendix A of the SEED manual). My reading of the
manual suggests that, for the sample rate shown, the channels should be
named with three-letter codes BNx, where x is the orientation letter.
N (middle character) is the code for an accelerometer. ZNE aren't
useful because orientation can't be guaranteed. XYZ are probably OK
for consistent usage with your program documentation, though they
aren't FDSN-endorsed. FDSN would prescribe them to be 123 (orthogonal
but orientation not guaranteed).
On 28 Mar 2009, at 01:44, Daniel Griscom wrote:
Dear Sirs/Madams,
George Helffrich
I'm the author of a free IRIS-supported Macintosh program called
SeisMac, which uses Mac laptops' built in accelerometers to convert
the laptops into (not very accurate) seismographs. You can find more
about it at http://www.suitable.com/tools/seismac.html.
I'm finishing off an update which will let you export selected data as
a binary SAC or ascii SACA file. I think I've got it right (Global
Earthquake Explorer successfully reads the SAC files), but I'd love to
have further confirmation. Would any of you be able to review example
files and tell me if I've made any format errors? Or, point me to
other tools which will read/validate SAC/SACA files?
I've uploaded the same set of data in three ways:
- Comma-separated values (all three axis):
http://www.suitable.com/temp/SeisMacData.CSV
- Binary SAC file (Z axis only):
http://www.suitable.com/temp/SeisMacData.SAC
- Ascii SACA file (Z axis only):
http://www.suitable.com/temp/SeisMacData.SACA
(If you have a Mac laptop and would like to play with exporting data
yourself, the latest binary is at
http://www.suitable.com/temp/SeisMac30b2.zip)
Thanks,
Dan
--
Daniel T. Griscom griscom<at>suitable.com
Suitable Systems http://www.suitable.com/
1 Centre Street, Suite 204 (781) 665-0053
Wakefield, MA 01880-2400
_______________________________________________
sac-help mailing list
sac-help<at>iris.washington.edu
http://www.iris.washington.edu/mailman/listinfo/sac-help
george<at>geology.bristol.ac.uk
Chad Trabant
George Helffrich
