Standard Wireline Sonic Waveform Data (re-entry, Phase 1)

IODP-USIO logging contractor: LDEO-BRG

Hole: 1256D

Expedition: 309

Location: Guatemala Basin (NE equatorial Pacific)

Latitude: 6° 44.163' N

Longitude: 91° 56.061' W

Logging date: July 17-18, 2005

Sea floor depth (driller's): 3645.4 mbrf

Sea floor depth (logger's): 3643.5 mbrf

Total penetration: 752 mbsf (Leg 206)

Total core recovered: 227m (47.8%) (Leg 206)

Oldest sediment recovered: Calcareous nannofossil ooze (Middle Miocene) at Hole 1256B during the ODP

Lithologies: Clay-rich sediments and calcareous nannofossil ooze (sediments); basalt (basement)

TOOL USED: DSI (Dipole Sonic Imager)

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

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.

STONELEY MODE: measures low-frequency Stoneley wave slowness. The monopole transmitter, driven by a low-frequency pulse, generates the Stoneley wave.

Acoustic data are recorded in DLIS format. Each of the eight waveforms generally consists of 512 samples (256 in cross-dipole mode), each recorded every 10 (monopole P&S) and 40 microsec (all dipole modes), 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 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: 3248

All values are stored as 'signed short integers' (= 16 bits signed).

Each file can be viewed directly as an image with Spyglass transform or NIH image on MAcs and PCs, or Fortner transform or Khoros on UNIX) - where it has to be opened as either 'raw' or 'binary matrix'. Any image or signal-processing package should also allow viewing it.

The following files have been loaded (Phase 1):

DSI from FMS/DSI/GPIT/SGT (casing at ~ 3914.5 mbrf)

309-1256D_ph1_mono_up.bin: 3878.42-4373.27 mbrf

309-1256D_ph1_ldip_up.bin: 3878.42-4373.27 mbrf

309-1256D_ph1_st_up.bin: 3878.42-4373.27 mbrf

309-1256D_ph1_udip_up.bin: 3878.42-4373.27 mbrf

The sonic waveform files are not depth shifted to a reference run or to the seafloor. For depth shift to the sea floor, please refer to the DEPTH SHIFT section in the standard log documentation file.

NOTE: 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 = 2*(1+nwav*nsamples))

where nwav is the number of waveforms (4 or 8) and nsamples the number of samples per waveforms (see above).

If the total number of depths where waveforms have been recorded is ndepth (for a 150 m interval with data every 15cm, ndepth would be 1000), a generic loop to read the data would be

do k = 1, ndepth

...

read(1, rec=k) iz, (data(i), i = 1, nwav*nsamples)

z(k)=float(iz)/10

...

enddo

In such a case, the file dimensions will be ndepth rows by nwav*nsamples+1 columns

For further information about the logs please contact:

Cristina Broglia

Phone: 845-365-8343

Fax: 845-365-3182

E-mail: Cristina Broglia