LWD Sonic Waveform Data
Science operator: Texas A&M University
Hole: U1520A
Expedition: 372
Location: Hikurangi Subduction Margin (SW Pacific Ocean)
Latitude: 38° 68.1640' S
Longitude: 179° 7.9350' E
Logging date: December 27, 2017
Sea floor depth (driller's): 3538.3 m DRF
Sea floor depth (logger's): 3532.2 LRF
Total penetration: 3636.2 m LRF (104 m LSF)
ACOUSTIC TOOL USED: SonicScope
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, sampled every 20 microsecond (monopole P&S) and 40 microsecond (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 U1520A, the
specifications of the files are:
Number of columns: 3073
Number of rows: 2077 (5.08 cm sampling interval)
Number of rows: 692 (15.24 cm sampling interval)
The following files are avaialable at Hole U1520A:
372-U1520A_mono_2in.bin (-0.990-104.470 m LSF)
372-U1520A_mono_6in.bin (-0.939 -104.369 m LSF)
372-U1520A_mono_lf_2in.bin (-0.990-104.470 m LSF)
372-U1520A_mono_lf_6in.bin (-0.939-04.369 m LSF)
372-U1520A_qp_2in.bin (-0.990-104.470 m LSF)
372-U1520A_qp_6in.bin (-0.939-104.369 m LSF)
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 (-3532.2 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))
...
enddo
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