Wireline Sonic Waveform Data
IODP logging contractor: USIO/LDEO
Location: Gulf of Alaska
Latitude: 59° 30.4399' N
Longitude: 143°2.7395' W
Logging date: July 27, 2013
Sea floor depth (driller's): 729.7 m DRF
Sea floor depth (logger's): 729 m WRF (DIT/DSI/HLDS/EDTC-B main run)
Total penetration: 702.7 m DSF (1432.4 m DRF)
Core recovery: 20% of cored interval
Oldest sediment recovered: < 0.5 Ma (biostratigraphy)
Lithologies: mud with and without lonestones, diamict, drilled rock, diatom ooze
TOOL USED: DSI (Dipole Sonic Imager)
Recording mode: Monopole P&S and Upper and Lower Dipole (all passes).
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 + 8x512 = 4097 columns. In this hole, the specifications of the files are:
Number of columns: 4097
Number of rows: 5287 (downlog)
Number of rows: 5371 (main)
Number of rows: 2769 (repeat)
The following files have been loaded:
DIT/DSI/HLDS/EDTC-B (Downlog, drill pipe at ~92 m WSF)
341-U1417E_ldip_d.bin: -67.5-738 m WSF
341-U1417E_mono_d.bin: -67.5-738 m WSF
341-U1417E_udip_d.bin: -67.5-738 m WSF
DIT/DSI/HLDS/EDTC-B (Main, drill pipe at ~92 m WSF)
341-U1417E_ldip_main.bin: -122.45-695.94 m WSF
341-U1417E_mono_main.bin: -122.45-695.94 m WSF
DIT/DSI/HLDS/EDTC-B (Recorded open hole)
341-U1417E_ldip_rep.bin: 274.09-695.94 m WSF
341-U1417E_mono_rep.bin: 274.09-695.94 m WSF
341-U1417E_udip_rep.bin: 274.09-695.94m WSF
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 depth-shifted to the seafloor (-729 m) but they are not depth-matched to the reference run. Please refer to the 'depth_matches' folder in the hole index page for the depth-matching values and 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 (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))
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 341. For further questions please contact:
E-mail: Cristina Broglia
E-mail: Tanzhuo Liu