Borehole Seismic Data
Science operator: Texas A&M University
Location: Maldives (Central Equatorial N Indian Ocean)
Latitude: 4° 51.0362' N
Longitude: 73°17.0197' E
Logging date: November 5-6, 2015
Sea floor depth (driller's): 499.5 m DRF
Sea floor depth (logger's): 499.5 m WRF (MSS/HRLA/APS/HLDS/EDTC-B/HNGS main run)
Total penetration: 1212.4 m DRF (712.9 m DSF)
Total core recovered: dedicated logging hole, no core recovered
Oldest sediment recovered: see Hole U1467C
Lithology: see Hole U1467C
SEISMIC TOOL USED: VSI (Versatile Seismic Imager)
The logging data was recorded by Schlumberger in LDF format. All processing, including first arrival picking and stacking, was performed by Schlumberger during Expedition 359. The data was then converted into SEGY format at USIO/LDEO, using code developed in house. Stacks are generally calculated with at least nine good traces.
In hole U1467E a total of 94 shots (13 stations) were recorded in the 155-683 m WSF interval. Overall the seismic data were of excellent quality. This was due to several factors such as the excellent weather conditions (no measurable heave), the positioning of the guns just 3 m below the sea surface (instead of the usual 5-7 m), and the use of a single GGun 250 to avoid excess power amd possible synchronization noise. Also, a lighter tool string than usual was used, which included the EDTC rather than the heavier HNGS; this was possible because of the lack of the lockable flapper valve (LFV) in the bottom hole assembly, which usually requires extra weight on the tool string to pass through it.
The depth of the original data was shifted 0.5 upward to match the reference depth on the MSS/HRLA/APS/HLDS/EDTC/HNGS main pass in real time; the data was shifted -499.5 m during the conversion from LDF to SEGY/ASCII at LDEO/BRG.
All the data in the SEGY files are sorted shot by shot (i.e. chronologically).
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 359. 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:
E-mail: Cristina Broglia
E-mail: Gilles Guerin