Sonic Waveform Data
IODP logging contractor: USIO/LDEO
Hole: U0080A
Expedition: 344S
Location: Baffin Bay (Labrador Sea)
Latitude: 75° 35.9015' N
TOOL USED: DSI (Dipole Sonic Imager)
Recording mode: Monopole P&S, Stoneley and
Upper and Lower Dipole.
Remarks about the recording: none.
MONOPOLE P&S MODE: measures compressional and
hard-rock shear slowness. The monopole transmitter is excited
by a high-frequency pulse, which reproduces conditions similar
to previous sonic tools.
UPPER DIPOLE MODE: measures shear wave slowness
using firings of the upper dipole transmitter.
LOWER DIPOLE MODE: measures shear wave slowness
using firings of the lower dipole transmitter.
STONELEY MODE: measures low-frequency Stoneley
wave slowness. The monopole transmitter, driven by a
low-frequency pulse, generates the Stoneley wave.
Acoustic data are recorded in DLIS format. Each of the eight waveforms generally consists of 512 samples, each recorded every 10 (monopole P&S) and 40 microsec (dipole modes), at depth intervals of 15.24 cm (6 inches). The original data in DLIS format was loaded on a Linux system using the techlog software. The packed waveform data files are run through a module that applies a gain correction and then converted into ASCII and finally binary format.
Each row of
the binary file is composed of the entire waveform set
recorded at each depth, preceded by the depth. In the general
case of 8 waveforms with 512 samples per waveform, this
corresponds to 1 + 4x512 = 4097 columns. In this hole, the
specifications of the files are:
Number of columns: 4097
Number of rows: 2257
(downlog)
Number of rows: 2254 (uplog)
The following files were converted:
DSI from HRLA/DSI/MSS/EDTC-B/HNGS (Downlog, pipe
at 30.5 m WSF)
344S-U0080A_ldip_down.bin: -0.919 - 342.896 WSF
344S-U0080A_mono_down.bin: -0.919 - 342.896 WSF
344S-U0080A_st_down.bin: -0.919 - 342.896 WSF
344S-U0080A_udip_down.bin: -0.919 - 342.896 WSF
DSI from HRLA/DSI/MSS/EDTC-B/HNGS
(Uplog, pipe at 30.5 m WSF)
344S-U0080A_ldip_up.bin: 2.129 - 345.486 WSF
344S-U0080A_mono_up.bin: 2.129 - 345.486 WSF
344S-U0080A_st_up.bin: 2.129 - 345.486 WSF
344S-U0080A_udip_up.bin: 2.129 - 345.486 WSF
All values are stored as '32 bits IEEE float'.
Any image or signal-processing program should allow to import the files and display the data.
The sonic waveform files are depth-shifted to the
seafloor but not depth-matched to a reference run. Please
refer to the DEPTH SHIFT section in the standard data
processing documentation file for further information about
depth-shifting and depth-matching.
NOTE: For users interested in converting the data to a format more suitable for their own purpose, a simple routine to read the binary files would include a couple of basic steps (here in old fashioned fortran 77, but would be similar in matlab or other languages):
The first step is to extract the files dimensions and specification from the header, which is the first record in each file:
open (1, file = *.bin,access = 'direct', recl = 50) <-- NB:50 is enough to real all fields
read (1, rec = 1)nz, ns, nrec, ntool, mode, dz, scale, dt
close (1)
The various fields in the header are:
- number of depths
- number of samples per
waveform and per receiver
- number of receivers
- tool number (0 = DSI; 1 =
SonicVISION; 2 = SonicScope; 3 = Sonic Scanner; 4 = XBAT; 5 =
MCS; 6 = SDT; 7 = LSS; 8 = SST; 9 = BHC; 10 = QL40; 11 = 2PSA)
- mode (1 = Lower Dipole, 2
= Upper Dipole, 3 = Stoneley, 4 = Monopole)
- vertical sampling interval
*
- scaling factor for depth
(1.0 = meters; 0.3048 = feet) *
- waveform sampling rate in
microseconds *
All those values are stored as 4 bytes integers, except for the ones marked by an asterisk, stored as 4 bytes IEEE floating point numbers.
Then, if the number of depths, samples per waveform/receiver, and receivers are nz, ns, and nrec, respectively, a command to open the file would be:
open (1, file = *.bin, access = 'direct', recl = 4*(1 + nrec*ns))
Finally, a generic loop to read the data and store them in an array of dimension nrec x ns x nz would be:
do k = 1, nz
read (1, rec = 1+k) depth(k), ((data(i,j,k), j = 1,ns), i = 1,nrec)
enddo
Additional information about the drilling and
logging operations can be found in the Operations and Downhole
Measurements sections of the expedition report.
For further questions please contact:
Tanzhuo Liu
Phone: 845-365-8630
Fax: 845-365-3182
E-mail: tanzhuo@ldeo.columbia.edu
Gilles Guérin
Phone: 845-365-8671
E-mail: guerin@ldeo.columbia.edu