Multichannel Sonic Data Processing

ODP logging contractor: LDEO-BRG

Well name: 639D

Leg: 103

Location: Galicia Bank (NE Atlantic)

Latitude: 42° 8.6' N

Longitude: 12° 15.3' W

Logging date: May, 1985

Bottom felt: 4753 mbrf (used for depth shift to sea floor)

Total penetration: 293.1 mbsf

Total core recovered: 24.1 m (21 %)

TOOL USED: MCS (Multichannel Sonic Tool)

Recording mode: 1 transmitter and 12 receivers, each spaced 15 cm apart.

Remarks about the recording: none.

The Multichannel Sonic data were originally acquired with acquisition software produced in-house, residing on a Masscomp computer.

Each of the 12 waveforms consists of 2000 samples, each recorded at a sampling rate of 5 microsec, at depth intervals of 0.3 m. The original data has been loaded on a Sun system and then converted into binary format.

Each line is composed of the entire waveform set recorded at each depth, preceded by the depth. In the general case of 12 waveforms with 2000 samples per waveform, this corresponds to 1 + 12x2000 = 24001 columns. In this hole, the specifications of the files are:

Number of columns: 24001

Number of rows: 110 (downlog)

Number of rows: 91 (upper section)

Number of rows: 226 (lower section)

(

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:

103-639D_mcsd.bin: 4965-4997.7 mbrf

103-639D_mscl.bin: 4940-4999 mbrf

103-639D_mscu.bin: 4914-4940 mbrf

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 log 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 (12) 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)

...

enddo

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

For further information about the logs please contact:

Cristina Broglia

phone: 845-365-8343

fax: 845-365-3182

email: Cristina Broglia

Gilles Guerin

phone: 845-365-8671

fax: 845-365-3182

email: Gilles Guerin