LWD Sonic Waveform Data

IODP coring and logging operator: CDEX

Hole: C0012H

Expedition: 338

Location: Nankai Trough (NW Pacific Ocean)

Latitude: 32 ° 44.8783 ' N

Longitude: 136° 5.0351' E

Logging-while-drilling date: December 3-6, 2012

Sea floor depth (as seen on logs): 3538 m LRF

Total penetration: 4248 m LRF (710 m LSF)

TOOL USED: sonicVISION

The original LWD sonic data have been unpacked by Schlumberger Drilling and Measurements using GeoFrame's Preprocessor module, which also applies a gain correction. At LDEO-BRG the four waveforms have first been converted into ASCII and then binary format. Each of the four waveforms consists of 151 samples at depth intervals of 15.24 cm (6 inches). 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:  4496 (15.24 cm sampling rate)

The following files have been loaded:

338-C0012H_6in.bin: 0-713.35 m LSF

The binary files are depth-shifted to the sea floor (- 3538 m).

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 = 4*(1+nrec*nsamples))

where nrec is the number of receivers (8 in the case of the DSI) and nsamples the number of samples per waveforms.
If the total number of depths where waveforms were recorded is ndepth (for a 150 m interval with data every 15cm, ndepth would be 1001), a generic loop to read the data would be

do k = 1, ndepth
...
read(1, rec=1+k) depth(k), ((data(i,j,k), j=1,nsamples),i = 1,nrec))
...
enddo

the first record in each file is a header with some of the file specifications:
- number of depths
- number of samples /trace
- number of receivers
- tool number = 2 (sonicVISION / MP3)
- vertical sampling interval
- scaling factor for depth
- waveform sampling rate in microseconds

Additional information about the drilling and logging operations can be found in the Operations and Logging-while-drilling sections of the expedition report, Proceedings of the Integrated Drilling Program, Expedition 338.

For questions about the online database, please contact:

Cristina Broglia

Phone: 845-365-8343

Fax: 845-365-3182

E-mail: Cristina Broglia

For questions about the processing of the resistivity images please contract:

Tanzhuo Liu

Phone: 845-365-8630

Fax: 845-365-3182

E-mail: Tanzhuo Liu

For questions about the logs, please contact:

Yoshinori Sanada

E-mail: sanada@jamstec.go.jp

Yukari Kido

Email: ykido@jamstec.go.jp

Yuichu Shinmoto

Email: shinmoto@jamstec.go.jp