Sonic Waveform Data

IODP-USIO logging contractor: LDEO-BRG

Hole: U1318B

Expedition: 307

Location: Porcupine Seabight (eastern N Atlantic)

Latitude: 51° 26.148' N

Longitude: 11° 33.019' W

Logging date: May 10, 2005

Sea floor depth (drillers'): 419.8 mbrf

Sea floor depth (step in GR log): 421 mbrf

Total penetration: 244.6 mbsf

Total core recovered: 213 m (87.08 % of cored section)

Oldest sediment cored: Siltstone (Miocene)

Lithologies: Silty clay, sand, conglomerate, siltstone and sandstone

TOOL USED: DSI (Dipole Sonic Imager)

Recording mode: Monopole P&S, Cross-Dipole, Upper and Lower Dipole, Stoneley mode.

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 (256 in cross-dipole mode), each recorded every 10 (monopole P&S) and 40 microsec (all dipole modes), 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 packed 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 value. In the general case of 8 receivers 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: 1247 (Pass 1)

Number of rows: 1848 (Pass 2)

All values are stored as 32 bits IEEE floating point.
Any image or signal-processing program should be able to import the files and display the data.

The following files have been loaded:

DSI from FMS/DSI/GPIT/NGT (Pass 1, BHA at ~488 mbrf)

U1318B-ldip_p1.bin: 477-666.9 mbrf

U1318B-udip_p1.bin: 477-666.9 mbrf

U1318B-st_p1.bin: 477-666.9 mbrf

U1318B-mono_p1.bin: 477-666.9 mbrf

DSI from FMS/DSI/GPIT/NGT (Pass 2, BHA at ~488 mbrf)

U1318B-ldip_p2.bin: 386.02-667.5 mbrf

U1318B-udip_p2.bin: 386.02-667.5 mbrf

U1318B-st_p2.bin: 386.02-667.5 mbrf

U1318B-mono_p2.bin: 386.02-667.5 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 log documentation file.

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

For any question about the data or about the LogDB database, please contact LogDB support: logdb@ldeo.columbia.edu.