Wireline Sonic Waveform Data

 

IODP logging contractor: USIO/LDEO

Hole: U1395B

Expedition: 340

Location: Lesser Antilles, off Montserrat (Caribbean Sea)

Latitude: 16° 29.5985' N

Longitude: 61° 57.0751' W

Logging date: March 16, 2012

Sea floor depth (driller's): 1211.6 m DRF

Sea floor depth (logger's): 1209 m WRF (HRLA/MSS/HLDS/EDTC-B/HNGS main)

Total penetration: 1414.9 m DRF (203.3 m DSF)

Total core recovered: 139.54 m ( 68.6 % of cored section)

Oldest sediment recovered: ~ 1.5 - 2 Ma

Lithologies: Volcaniclastic material, turbidites, hemipelagic sediments, ash layers, some pumice-rich units.  Recovery was very poor below 125 m DRF ('chaotic' unit identified from seismic at ~125-175 m DRF). Some semi-lithified material recovered below 150 m DRF.

 

TOOL USED: DSI (Dipole Sonic Imager)

Recording mode: Monopole P&S, Upper and Lower Dipole modes (DSI).

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: 1664 (Downlog)

Number of rows: 1540 (Main run)

Number of rows: 580 (Main run)

 

The following files have been loaded:

DSI from FMS/DSI/GPIT/EDTC-B (Downlog, pipe at  ~1287 m WRF)

340-U1395B_udip_d.bin: 1154.27-1407.71 m WRF

340-U1395B_ldip_d.bin: 1154.35-1407.79 m WRF

340-U1395B_mono_d.bin: 1153.97-1407.41 m WRF

DSI from FMS/DSI/GPIT/EDTC-B (Main run, pipe at ~1286m WRF)

340-U1395B_udip_main.bin: 1407.25-1172.71 m WRF

340-U1395B_ldip_main.bin: 1407.33-1172.79 m WRF

340-U1395B_mono_main.bin: 1406.95-1172.41 m WRF

 

DSI from FMS/DSI/GPIT/EDTC-B (Repeat run, recorded open hole)

340-U1395B_udip_rep.bin:1407.25-1319.01 m WRF

340-U1395B_ldip_rep.bin: 1407.33-1319.09 m WRF

340-U1395B_mono_rep.bin: 1406.95-1318.71 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 340. 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