Wireline Sonic Waveform Data
IODP-MSP
drilling and logging contractor: ESO
Hole: M0004B
Expedition: 302
Location: Lomonosov Ridge (
Latitude: 87° 52.018' N
Longitude: 136° 10.475' E
Logging
date: September 4,
2004
Sea floor
depth (driller's): 1289.70 mbrf
Sea
floor depth (logger's): 1291.00 mbrf
Total
penetration: 218.00 mbsf
Total
core recovered:
7.31 m (66.50 % of cored section)
Oldest
sediment recovered: Middle Eocene
Lithologies: Clays to silty muds
TOOL USED: BHC (Borehole Compensated Sonic Tool)
Remarks about the
recording: The velocity
data show no indication for cycle skipping and so no corrections have been
applied.
Acoustic data are recorded in DLIS
format. Each of the four waveforms consists of 120 samples, each recorded at
depth intervals of 15.24 cm (6 inches). The original data in DLIS format is
first loaded on a Sun system using GeoFrame software.
The waveform data files are then converted into ASCII and finally binary
format.
Each line is composed of the entire
waveform set recorded at each depth, preceded by the depth (multiplied by 10 to
be stored as an integer). In the general case of 4 waveforms with 400 samples
per waveform, this corresponds to 1 + 4x500 = 2001 columns. In this hole, the
specifications of the files are:
Number of columns: 481
Number of rows: 3441 (Pass 1)
Number of rows: 4881 (Pass 2)
All values are stored as 'signed short integers' (= 16
bits signed).
Each file can be viewed directly as an image with
Spyglass transform or NIH image on Macs and PCs, or Fortner transform or Khoros
on UNIX) - where it has to be opened as either 'raw' or 'binary matrix'. Any
image or signal-processing package should also allow viewing it.
The following files have been loaded:
BHC from FMS/BHC/GPIT/NGT/SGT (Pass 1, pipe at ~1357 mbrf)
302-M0004B_p1.bin: 1333.25-1508 mbrf
BHC from FMS/BHC/GPIT/NGT/SGT (Pass 2, pipe at ~1357 mbrf)
302-M0004B_p2.bin: 1262.79-1510.74 mbrf
The sonic waveform files are not depth shifted to a
reference run or to the seafloor. For depth shift to the sea floor, please
refer to the DEPTH SHIFT section in the standard data processing documentation file.
NOTE: For users interested in reading and
converting the data to a format more suitable for their own purpose, the fortran declaration used to open
the file *.bin would be:
open (1, file = *.bin,access
= 'direct', recl = 2*(1+nwav*nsamples))
where nwav is
the number of waveforms (4 or 8) and nsamples the
number of samples per waveforms (see above).
If the total number of depths where waveforms have
been recorded is ndepth (for a 150 m interval with
data every 15cm, ndepth would be 1000), a generic loop
to read the data would be
do k = 1, ndepth
...
read(1, rec=k) iz, (data(i), i
= 1, nwav*nsamples)
z(k)=float(iz)/10
...
enddo
In such a case, the file dimensions will be ndepth rows by nwav*nsamples+1 columns .
Additional information about the drilling and logging
operations can be found in the Operations and Downhole
Measurements sections of the expedition report, Proceedings of the Integrated
Drilling Program, Volume 302.
For further questions about the logs, please contact:
Jennifer Inwood
Phone:
011-44-116-252-3327
Fax:
011-44--116-252-3918
E-mail: iodp@le.ac.uk
For any web
site-related problem please contact:
E-mail: logdb@ldeo.columbia.edu