IODP Expedition 340, Hole U1395B - Wireline Sonic Waveform Data

Wireline Sonic Waveform Data

IODP logging contractor: USIO/LDEO

Hole: U1395B

Expedition: 340

Location: Lesser Antilles, off Montserrat (Caribbean Sea)

Latitude: 16° 29.5985' N

Longitude: 61° 57.0751' W

Logging date: March 16, 2012

Sea floor depth (driller's): 1211.6 m DRF

Sea floor depth (logger's): 1209 m WRF (HRLA/MSS/HLDS/EDTC-B/HNGS main)

Total penetration: 1414.9 m DRF (203.3 m DSF)

Total core recovered: 139.54 m ( 68.6 % of cored section)

Oldest sediment recovered: ~ 1.5 - 2 Ma

Lithologies: Volcaniclastic material, turbidites, hemipelagic sediments, ash layers, some pumice-rich units. Recovery was very poor below 125 m DRF ('chaotic' unit identified from seismic at ~125-175 m DRF). Some semi-lithified material recovered below 150 m DRF.

TOOL USED: DSI (Dipole Sonic Imager)

Recording mode: Monopole P&S, Upper and Lower Dipole modes (DSI).

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 geerally 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 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: 1664 (Downlog)

Number of rows: 1540 (Main run)

Number of rows: 580 (Repeat run)

The following files have been loaded:

DSI from FMS/DSI/GPIT/EDTC-B (Downlog, pipe at ~1287 m WRF)

340-U1395B_udip_d.bin: 1405.509-1152.068 m WRF

340-U1395B_ldip_d.bin: 1405.509-1152.068 m WRF

340-U1395B_mono_d.bin: 1405.509-1152.068 m WRF

DSI from FMS/DSI/GPIT/EDTC-B (Main run, pipe at ~1286m WRF)

340-U1395B_udip_main.bin: 1405.049-1170.506 m WRF

340-U1395B_ldip_main.bin: 1405.049-1170.506 m WRF

340-U1395B_mono_main.bin: 1405.049-1170.506 m WRF

DSI from FMS/DSI/GPIT/EDTC-B (Repeat run, recorded open hole)

340-U1395B_udip_rep.bin: 1405.049-1316.810 m WRF

340-U1395B_ldip_rep.bin: 1405.049-1316.810 m WRF

340-U1395B_mono_rep.bin: 1405.049-1316.810 m WRF

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 NOT depth-shifted to the seafloor or 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 × 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 Integrated Drilling Program, Expedition 340.

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