Sonic Waveform Data

Science operator: Texas A&M University

Hole: U1502B

Expedition: 368

Location: China Sea Rifted Margin (South China Sea)

Latitude: 18° 27.8798' N

Longitude: 116° 13.8409' E

Logging date: May 13, 2017

Sea floor depth (driller's): 3774.7 m DRF

Sea floor depth (logger's): 3774.7 m WRF

Total penetration: 4695.5 m DRF (920.8 m DSF)

Total core recovered: 303.75 m (52.7 % of cored section)

Oldest sediment recovered: Late Oligocene

Lithology: Claystone, sand, clay

ACOUSTIC TOOL USED: DSI (Dipole Sonic Imager)

Recording mode: Monopole P&S and Upper and Lower Dipole (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.

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 (dipolemodes), 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 run through a GeoFrame module that applies a gain correction and then converted into ASCII and finally binary format.

Each row 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: 633 (downlog)

Number of rows: 591 (repeat)

Number of rows: 859 (main)

The following files have been loaded:

DSI from DSI/HLDS/EDTC-B/HNGS (Downlog, drill pipe at 745.3 m WSF)

368-U1502B_ldip_d.bin: 745-840 m WSF

368-U1502B_mono_d.bin: 745-840 m WSF

368-U1502B_udip_d.bin: 745-840 m WSF

DSI from DSI/HLDS/EDTC-B/HNGS (Repeat run, drill recorded open hole)

368-U1502B_ldip_rep.bin: 786-876 m WSF

368-U1502B_mono_rep.bin: 786-876 m WSF

368-U1502B_udip_rep.bin: 786-876 m WSF

DSI from DSI/HLDS/EDTC-B/HNGS (Main run, drill pipe at 745.3 m WSF)

368-U1502B_ldip_main.bin: 745-876 m WSF

368-U1502B_mono_main.bin: 745-876 m WSF

368-U1502B_udip_main.bin: 745-876 m WSF

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 sonic waveform files are depth-shifted to the seafloor (3774.7 m) but they are not depth-matched to the reference run. 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 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 Operations and Downhole Measurements sections of the expedition report, Proceedings of the International Ocean Discovery Program, Expedition 368.

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