LWD Sonic Waveform Data
Science operator: CDEX-JAMSTEC
Hole: C0002Q
Expedition: 358
Location: Nankai Trough (NW Pacific Ocean)
Latitude: 33° 18.050' N
Longitude: 136°38.2029 ' E
Logging-while-drilling date: November 17-December 14, 2018
Total
penetration: 5225.38 m LRF (3257.88 m LSF)
ACOUSTIC TOOL USED: SonicScope
Recording Modes:
LOW FREQUENCY MONOPOLE: for Stoneley wave analysis.
QUADRUPOLE: measures shear slowness in slow formations.
Number of
columns: 3073
Number of
rows: 1555 (2-in, 5.08-cm sampling rate)
Number of rows: 519 (6-in, 15.24-cm sampling rate)
The following
files have been loaded:
358-C0002Q_mono_2in.bin: 2861.49-2908.59 m LSF
358-C0002Q_mono_lf_2in.bin: 2861.49-2908.59 m LSF
358-C0002Q_qp_2in.bin: 2861.49-2908.59 m LSF
358-C0002Q_mono_6in.bin: 2861.49-2908.59 m LSF
358-C0002Q_qp_6in.bin: 2861.49-2908.59 m LSF
No sonic waveforms with 2-in (5.08-cm) sampling rate were found on the JAMSTEC web site. Gilles Guerin, one of the logging specialists on expedition 358, provided them. The dataset did not include 6-in (5.8-cm) low-frequency waveforms.
All values are stored as '32 bits IEEE float'.
Any numerical software or programing language (matlab, python,...) can import the files for further analysis of the waveforms.
The sonic waveform files were depth-shifted to the seafloor (-1967.5 m).
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 × ns × 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 Site Expedition Report and in the Methods section, Proceedings of the International Ocean Discovery Program, Expedition 358.
For questions about the logging operations and the processing performed onboard, please contact:
Yukari Kido
E-mail: ykido@jamstec.go.jp
For database-related questions you may contact:
Cristina Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Cristina Broglia
Tanzhuo Liu
Phone: 845-365-8630
Fax: 845-365-3182
E-mail: Tanzhuo Liu