Borehole Seismic Data

 

Science operator: Texas A&M University

Hole: U1503A

Expedition: 368X

Location: South China Sea Rifted Margin (South China Sea)

Latitude: 18° 8.6300' N

Longitude: 116° 18.8456' E

Logging date: December 6, 2018

Sea floor depth (driller's): 3878.7 m DRF

Sea floor depth (logger's): 3879.1 m WRF

Total penetration: 5589.7 m DRF 1710 (m DSF)

Total core recovered: 175.73 m (24.6 % of cored section)

Oldest sediment recovered: n/a

Lithology: solidified sandstone, siltstone, and claystone, nannofossil-rich; phyric basalts with sparse 

SEISMIC TOOL USED: VSI (Versatile Seismic Imager)

The logging data was recorded by Schlumberger in LDF/DLIS format. Expedition 368X objectives were to revisit the site, drilling and coring in the basement, and logging with the Vertical Sesismic Imager tool. The recording took place in the cased hole section of hole U1503A that had been installed during expedition 368. The hole conditions in the open hole section were highly adverse, therefore only the cased section was logged. A continuous GR log was recorded with the EDTC-B tool from the bottom of the hole to just above the sea floor, while simultanerously shooting the required stations. A total of 104 shots were fired in 18 stations. All processing, including first arrival picking and stacking, was performed by Schlumberger during Expedition 368. The data was then converted into SEGY format at LDEO, using code developed in house.

Stacks are generally calculated with at least nine good traces. A summary figure with the depth expressed in mbsf has been produced.

All the data in the SEGY files are sorted shot by shot (i.e. chronologically).

The gamma ray and any non-VSI data were shifted to meters below the sea floor. The amount of the shift was 3879.1 m, corresponding to the sea floor depth as observed on the logs. This amount differs 0.4 m from the driller's water depth (see above).

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 368X.

For any question about the data or about the LogDB database, please contact LogDB support: logdb@ldeo.columbia.edu.