Sonic Waveform Data

Science operator: Texas A&M University

Hole: U167B

Expedition: 402

Location: Tyrrhenian Basin

Latitude: 40° 0.0317' N

Longitude: 13° 24.4662' E

Logging date: March 30, 2024

Sea floor depth (driller's): 2833.6 m DRF

Sea floor depth (logger's): 2833.6 m WRF

Total penetration: 3204.0 m DRF (370.4 m DSF)

Total core recovered: 68.9 m (57.2 % of cored section)

Oldest sediment recovered: Late Miocene (Messinian)

Lithology: Nannofossil ooze; tephra; sapropel; organic-rich mud; anhydrite; gypsum; halite; black shale

ACOUSTIC TOOL USED: DSI (Dipole Sonic Imager)

Recording mode: Monopole P&S, Upper and Lower Dipole, Stoneley (all passes).

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, sampled every 10 microseconds (monopole P&S) and 40 microseconds (dipole modes), at depth intervals of 15.24 cm (6 inches). The original waveforms in DLIS format are first loaded into Schlumberger's Techlog log analysis package. The packed waveform data files are run through a module that applies tool gain and offset correction. After being exported from Techlog, they are converted into binary and GIF format (images) using in-house software. 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 + 8×512 = 4097 columns.

In this hole, the specifications of the files are:

Number of columns: 4097

Number of rows: 2098 (downlog)

Number of rows: 2093 (uplog)

The following files have been loaded:

DSI from DSI/HNGS/EDTC-B/LEHPT (Downlog, in open hole below ~277 m WMSF)
402-U167B_mono_down.bin: -0.994 - 318.589 m WMSF
402-U167B_udip_down.bin: -0.994 - 318.589 m WMSF
402-U167B_ldip_down.bin: -0.994 - 318.589 m WMSF
402-U167B_st_down.bin: -0.994 - 318.589 m WMSF

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-matched to the reference run and depth-shifted to the seafloor (- 2833.6m). Please refer to the 'depth_matches' folder in the hole index page for the depth-matching values and to the "DEPTH SHIFT" section in the standard processing notes for further information.

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 just 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

  enddo