Wireline Sonic Waveform Data
IODP logging contractor: USIO/LDEO
Location: Arctic Gateway (Bering Sea)
Latitude: 59° 3.0' N
Longitude: 179° 12.2' W
Logging date: August 18-19, 2009
Sea floor depth (driller's): 3183.4 m DRF
Sea floor depth (logger's): 3184.5 m WRF
Total penetration: 3928.4 m DRF (745 m DSF)
Total core recovered: 648.10 m (87 % of cored section)
Oldest sediment recovered: Early Pleistocene (~ 2 my)
Lithologies: dark greenish gray diatom-bearing silty clay to diatom-rich sandy silt, with occasional sandy layers, pebble size clasts, authigenic carbonate layers, and rare diatom ooze; moderately bioturbated.
TOOL USED: DSI (Dipole Sonic Imager)
Remarks about the recording. The dipole shear sonic imager (DSI) was operated in monopole mode (Pass 1 and downlog in standard frequency and pass 2 in lower frequency)), lower dipole (low frequency on all three passes), and upper dipole (standard frequency for downlog and pass 1, lower frequency for pass 2).
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 (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 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 + 4x512 = 4097 columns. In this hole, the specifications of the files are:
Number of columns: 4097
Number of rows: 4881 (Downhole)
Number of rows: 3902 (Pass 1)
Number of rows: 4264 (Pass 2)
All values are stored as 'IEEE floating point numbers' (= 4 bytes).
Any numerical software or programing language (matlab, python,...) can import the files for further analysis of the waveforms.
The following files were converted:
DSI from FMS/DSI/GPIT/HNGS (Downlog, pipe at 3277.5 m WRF)
323-U1344A_mono_d.bin: 3168.4-3912.11 m WRF
323-U1344A_ldip_d.bin: 3168.4-3912.11 m WRF
323-U1344A_udip_d.bin: 3168.4-3912.11 m WRF)
DSI from FMS/DSI/GPIT/HNGS (Pass 1, open hole)
323-U1344A_mono_p1.bin: 3918.2-3323.69 m WRF
323-U1344A_ldip_p1.bin: 3918.2-3323.69m WRF
323-U1344A_udip_p1.bin: 3918.2-3323.69m WRF
DSI from FMS/DSI/GPIT/HNGS (Pass 2, pipe at 3277.5 m WRF)
323-U1344A_mono_p2.bin: 3915.92-3266.24 m WRF
323-U1344A_ldip_p2.bin: 3915.92-3266.24 m WRF
323-U1344A_udip_p2.bin: 3915.92-3266.24 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 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
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)
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 323. For further questions about the logs, please contact:
E-mail: Cristina Broglia
E-mail: Tanzhuo Liu