Wireline Sonic Waveform Data

IODP logging contractor: USIO/LDEO

Hole: U1414A

Expedition: 344

Location: Costa Rica Pacific Margin (Equatorial NE Pacific Ocean)

Latitude: 8° 30.2304' N

Longitude: 84° 13.5298' W

Sea floor depth (driller's): 2469.1 m DRF

Sea floor depth (logger's): 2469 m WRF

Total penetration: 2940.7 m DRF (471.6 m DSF)

Total core recovered: 383.95 m (81% of cored section)

Oldest sediment recovered: Miocene (~15 My)

Lithologies: Silty clay and sand, calcareous and siliceous ooze, calcareous and siliceous cemented siltstone and sandstone, basalt

TOOL USED: DSI (Dipole Sonic Imager)

Recording mode: Monopole P&S, and Upper and Lower Dipole.

Remarks about the recording: none.

MONOPOLE P&S MODE: measures compressional and hard-rock shear slowness. The monopole transmitter is excited by a high-frequency pulse, which reproduces conditions similar to previous sonic tools.

UPPER DIPOLE MODE: measures shear wave slowness using firings of the upper dipole transmitter.

LOWER DIPOLE MODE: measures shear wave slowness using firings of the lower dipole transmitter.

Acoustic data are recorded in DLIS format. Each of the eight waveforms geerally consists of 512 samples, each recorded every 10 (monopole P&S) and 40 microsec (dipolemodes), at depth intervals of 15.24 cm (6 inches).The original data in DLIS format is first loaded on a Sun system using GeoFrame software. The packed waveform data files are run through a GeoFrame module that applies a gain correction and then converted into ASCII and finally binary format.

Each line 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 general case of 8 waveforms with 512 samples per waveform, this corresponds to 1 + 4x512 = 4097 columns. In this hole, the specifications of the files are:

Number of columns: 4097

Number of rows: 2993 (downlog)

Number of rows: 751 (pass 1)

Number of rows: 2757 (pass 2)

The following files have been loaded:

DSI from FMS/DSI/GPIT/EDTC-B/HNGS (Downlog, pipe at  2560.5 m WRF)

344-U1414A_ldip_d.bin: 2412.87-2868.85 m WRF

344-U1414A_mono_d.bin:  2412.49-2868.47 m WRF

344-U1414A_udip_d.bin: 2412.79-2868.78 m WRF

DSI from FMS/DSI/GPIT/EDTC-B/HNGS (Recorded open hole)

344-U1414A_ldip_p1.bin:  2879.21-2764.91 m WRF

344-U1414A_mono_p1.bin: 2878.73-2764.53 m WRF

344-U1414A_udip_p1.bin:  2879.13-2764.83 m WRF

DSI from FMS/DSI/GPIT/EDTC-B/HNGS (Pass 2, pipe at  2563.5 m WRF)

344-U1414A_ldip_p1.bin: 2876.93-2456.92 m WRF

344-U1414A_mono_p1.bin: 2876.55-2456.54 m WRF

344-U1414A_udip_p1.bin: 2876.86-2456.84 m WRF

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 are NOT depth-shifted to the seafloor or depth-matched to a reference run. Please refer to the DEPTH SHIFT section in the standard data processing documentation file for further information about depth-shifting and depth-matching.

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 = 0 (DSI)
- mode (1 = Lower Dipole, 2 = Upper Dipole, 3 = Stoneley, 4 = Monopole)
- 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 Downhole Measurements sections of the expedition report, Proceedings of the Integrated Drilling Program, Expedition 344. For further questions please contact:

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