LWD Sonic Waveform Data



Science operator: Texas A&M University

Hole: U1518A

Expedition: 372

Location: Hikurangi Subduction Margin (SW Pacific Ocean)

Latitude: 38° 51.5368' S

Longitude: 178° 53.7606' E

Logging date: December 20, 2017

Sea floor depth (driller's): 2647.3 m DRF

Sea floor depth (logger's): 2642.4 LRF

Total penetration: 2747.4 m LRF (123 m LSF)



Recording mode: Monopole P&S, Low Frequency Monopole, Quadrupole.

Remarks about the recording: none.


MONOPOLE P&S MODE: measures compressional slowness in all formations and shear slowness in fast formations.

LOW FREQUENCY MONOPOLE: for stoneley waves analysis.

QUADRUPOLE MODE: measures shear slowness in slow formations.

Acoustic data are recorded in DLIS format. Each of the twelve waveforms consists of 256 samples, each sampled every 20 (monopole P&S) and 40 microsec (quadrupole and low frequency monopole modes), at depth intervals of 5.08 cm (2 inches) and 15.24 cm (6 inches).The original data in DLIS format were first loaded into the Techlog suite software. The packed waveform data were run through a module that applies a gain correction and the depths were converted to meters below seafloor. The waveforms data were then converted into binary format and gif images.

Each line of the binary file is composed of the entire waveform set recorded at each depth, preceded by the depth. In the general case of 12 waveforms with 256 samples per waveform, this corresponds to 1 + 12x256 = 3073 columns. In hole U1518A, the specifications of the files are:


Number of columns: 3073

Number of rows: 2452 (5.08 cm sampling interval)

Number of rows: 817 (15.24 cm sampling interval)

The following binary files are available at Hole U1518A:

372-U1518A_mono_2in.bin ( -0.952 to 123.559 mbsf)
372-U1518A_mono_6in.bin ( -0.952 to 123.559 mbsf)
372-U1518A_mono_lf_2in.bin ( -0.952 to 123.559 mbsf)
372-U1518A_mono_lf_6in.bin ( -0.952 to 123.559 mbsf)
372-U1518A_qp_2in.bin ( -0.952 to 123.559 mbsf)
372-U1518A_qp_6in.bin ( -0.952 to 123.559 mbsf)

All values are stored as '32 bits IEEE float'.

Any image or signal-processing program should allow to import the files and display the data.


The sonic waveform files were depth-shifted to the seafloor (-2642.4 m) . Please refer to the "DEPTH SHIFT" section in the standard processing notes for further information.


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 (12 in the case of the SonicScope) and nsamples the number of samples per waveforms.
If the total number of depths where waveforms were recorded is ndepth (here 1581), 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))


the first record in each file is a header with some of the file specifications:
- number of depths (4 bytes integer)
- number of samples /trace  (4 bytes integer)
- number of receivers  (4 bytes integer)
- tool number (0 = DSI; 1 = SonicVISION; 2 = SomicScope; 3 = Sonic Scanner)  (4 bytes integer)
- mode (1 = Lower Dipole, 2 = Upper Dipole, 3 = Stoneley, 4 = Monopole, 5 = Quadrupole)  (4 bytes integer)
- vertical sampling interval (4 bytes IEEE float)
- scaling factor for depth (4 bytes IEEE float)
- waveform sampling rate in microseconds (4 bytes IEEE float)

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 International Ocean Discovery Program, Expedition 372. For further questions about the logs, if the hole is still under moratorium please contact the staff scientist of the expedition.

After the moratorium period you may direct your questions to:

Cristina Broglia

Phone: 845-365-8343

Fax: 845-365-3182

E-mail: Cristina Broglia


Tanzhuo Liu

Phone: 845-365-8630

Fax: 845-365-3182

E-mail: Tanzhuo Liu