Wireline Sonic Waveform Data
Science operator: Texas A&M University
Hole: U1456C
Expedition: 355
Location: Laxmi Basin (Arabian Sea)
Latitude: 16°37.293959' N
Longitude: 68°50.336604' E
Logging date: 17-18 April, 2015
Sea floor depth (driller's): 3649.2 m DRF
Sea floor depth (logger's): 3646 m WRF (FMS/DSI/GPIT/EDTC/HNGS Main run)
Total penetration: 4 m 114.4 DRF (465.2 m DSF)
Total core recovered: 215 m (78.1 % of cored section)
Oldest sediment recovered:
Lithology: Nannofossil ooze, silt, clay
ACOUSTIC TOOL USED: DSI
(Dipole Sonic Imager)
Recording mode: Monopole P&S, Upper and Lower Dipole and Stoneley mode in downlog and repeat run. Monopole, Stoneley and Cross Dipole modes in main run.
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.
CROSS-DIPOLE
MODE: uses alternate firings of upper and lower dipole transmitter, thus allowing
acquisition of orthogonally polarized data for anisotropy studies.
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 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: 2593 (downlog)
Number of rows: 2592 (main run)
The following
files have been loaded:
DSI from
FMS/DSI/GPIT/EDTC-B/HNGS (Downlog, drill pipe at ~ 80 m WSF)
355-U1456C_ldip_d.bin: 72-466.95 m WSF
355-U1456C_mono_d.bin: 72-466.95 m WSF
355-U1456C_st_d.bin: 72-466.95 m WSF
355-U1456C_udip_d.bin: 72-466.95 m WSF
DSI from FMS/DSI/GPIT/EDTC-B/HNGS(Main run, drill pipe at ~ 79 m WSF)
355-U1456C_cd_ldip_cl_main.bin: 74-468.8 m WSF
355-U1456C_cd_ldip_il_main.bin: 74-468.8 m WSF
355-U1456C_cd_udip_cl_main.bin: 74-468.8m WSF
355-U1456C_cd_udip_il_main.bin: 74-468.8 m WSF
355-U1456C_mono_main.bin: 74-468.8 m WSF
355-U1456C_st_main.bin: 74-468.8 m WSF
DSI from FMS/DSI/GPIT/EDTC-B/HNGS(Repeat run, recorded open hole)
355-U1456C_ldip_rep.bin: 126.12-467.8 m WSF
355-U1456C_mono_rep.bin: 126.12-467.8 m WSF
355-U1456C_st_rep.bin: 126.12-467.8 m WSF
355-U1456C_udip_rep.bin: 126.12-467.8 m 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 (3646-main run, 3647 m-repeat run, 3648 m-downlog). The downlog and repeat are not matche to the main pass, which was chosen as the reference run.
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 International Ocean Discovery Program, Expedition 355. 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