LWD Sonic Waveform Data

IODP-USIO logging contractor: LDEO-BRG

Hole: U1326A

Expedition: 311

Location: Cascadia Margin (NE Pacific)

Latitude: 48° 37.6350' N

Longitude: 127° 3.0289' W

Logging date: September 22-23, 2005

Water Depth (as seen on logs): 1838 mbrf

Total penetration: 300 mbsf

The LWD-SonicVision data were recorded by Schlumberger-Anadrill in DLIS format. Each of the four waveforms consists of 151 samples at depth intervals of 15.24 cm (6 inches) and 5.08 cm (2 inches). The DLIS format data is first loaded on a Sun system using GeoFrame software. The waveform data files are then converted into ASCII and finally binary format.

Each line of the binary files 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 case of 4 waveforms with 151 samples per waveform, this corresponds to 1 + 4x151 = 605 columns. In this hole, the specifications of the files are:

Number of columns: 605

Number of rows: 5592 (5.08 cm sampling rate)

Number of rows: 1865 (15.24 cm sampling rate)

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 binary files are available at Hole U1326A:

U1326A-2in.bin: 0-284.01 mbsf

U1326A-6in.bin: 0-284.01 mbsf

The binary files have been depth-shifted to the sea floor (-2203 m).

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 15 cm, 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)

z(k)=float(iz)/10

...

enddo

In such a case, the file dimensions will be ndepth rows by nwav*nsamples+1 columns

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