Wireline Sonic Waveform Data
IODP logging contractor: USIO/LDEO
Location: Wilkes Land Margin (antarctic Ocean)
Latitude: 64° 24.5733 ' S
Longitude: 143° 53.2001' E
Logging date: March 1-2, 2010
Sea floor depth (driller's): 3465.5 DRF
Sea floor depth (logger's): 3469.5 m WRF
Total penetration: 3853.5 m DRF 388 (m DSF)
Total core recovered: 338.86 m ( 87.1 % of cored section)
Oldest sediment recovered: Late Miocene
Lithology: Diatomaceous silty claystones and finely-laminated claystones
TOOL USED: DSI (Dipole Sonic Imager)
Recording mode: Monopole P&S and Upper Dipole modes.
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.
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 and Stoneley 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 (multiplied by 10 to be stored as an integer). In the general case of 8 waveforms 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: 1640 (pass 1)
Number of rows: 2821 (pass 2)
All values are stored as 'signed short integers' (= 16 bits signed).
Each file can be viewed directly as an image with Spyglass transform or NIH image on MAcs and PCs, or Fortner transform or Khoros on UNIX) - where it has to be opened as either 'raw' or 'binary matrix'. Any image or signal-processing package should also allow viewing it.
The following files have been loaded:
DSI from FMS/DSI/GPIT/HNGS (Pass 1, recorded open hole)
318-U1361A_mono_p1.bin: 3613.55-3863.34 m WRF
318-U1361A_udip_p1.bin: 3613.55-3863.34 m WRF
DSI from FMS/DSI/GPIT/HNGS (Pass 2, pipe at 3572 m WRF)
318-U1361A_mono_p2.bin: 3433.572-3863.34 m WRF
318-U1361A_udip_p2.bin: 3433.572-3863.34 m WRF
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 data processing documentation file.
NOTE: For users interested in reading and converting the data to a format more suitable for their own purpose, the fortran declaration used to open the file *.bin would be:
open (1, file = *.bin,access = 'direct', recl = 2*(1+nwav*nsamples))
where nwav is the number of waveforms (4 or 8) and nsamples the number of samples per waveforms (see above).
If the total number of depths where waveforms have been recorded is ndepth (for a 150 m interval with data every 15cm, ndepth would be 1000), a generic loop to read the data would be
do k = 1, ndepth
read(1, rec=k) iz, (data(i), i = 1, nwav*nsamples)
In such a case, the file dimensions will be ndepth rows by nwav*nsamples+1 columns
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 318. For further questions about the logs, please contact:
E-mail: Cristina Broglia
E-mail: Tanzhuo Liu