Hammer plate seismic on the Shackleton Ice Shelf - 2023-24

Full description

Raw active source seismic data collected using the hammer and plate method at two sites on the margin of the Shackleton Ice shelf, close to the Denman Glacier Tongue. The data were collected in conjunction with radar data (metadata record) to optimally locate a hot water drilled borehole by providing a measure of the ice shelf thickness and the depth to the ocean floor beneath the ice shelf.

The survey involved laying out an array of 48 geophones along a line 470 m long with geophones spaced every 10m. The geophones were pushed into the snow surface to the same level. The source of seismic energy is simply a thick plastic plate struck by a sledgehammer which is located at the survey line mid-point. Two point measurements were collected, HWD_01 and HWD_02.

HWD_01
Date:16/12/2023
Timing: 1300 - 1700
Location: Shackleton Ice Shelf close to the Denman Glacier margin
Coordinates: -66.230357, 98.735936
Team: Sarah Thompson, Katie Miles, Nick Morgan
Weather: Some high cloud, low wind, good visibility
Site notes: Very soft snow.
Equipment: 48 channel Geometrics Geode Seismograph communicating with a laptop via ethernet cable using Geometrics Seismodule Controller Software Version 11.1.69.0 (Geometrics Inc., 2014).
Sampling interval: 62.5 microseconds
Window length: 2 seconds
Survey layout: 2 x 235 m cables (10 m spacing), geophones all set into surface by pushing into the snow.
Bearing of seismic line: 266 degrees
Geophones: 1-24 to East and 24-28 to West of centre point
Shot point: Midpoint of survey line.
Survey collected in two halves due to software issues, ~20 hammer blows per half, all hammer blows carried out by Nick Morgan.

Files included
*.dat - raw data files each containing seismic record from single shot
Geophones 1-24: 1000.dat – 1021.dat
Geophones 25-48: 1022.dat – 1042.dat

HWD_02 -
Date: 26/12/2023
Timing: 1530 - 1800
Location: Shackleton Ice Shelf close to the Denman Glacier margin
Coordinates: -66.232110, 98.738019
Team: Sarah Thompson, Katie Miles, Madi Rosevear, Nick Morgan
Weather: Some high cloud, low wind, good visibility
Site notes: Very soft snow.
Equipment: 48 channel Geometrics Geode Seismograph communicating with a laptop via ethernet cable using Geometrics Seismodule Controller Software Version 11.1.69.0 (Geometrics Inc., 2014).
Sampling interval: 62.5 micro seconds
Window length: 2 seconds
Survey layout: 2 x 235 m cables (10 m spacing), geophones all set into surface by pushing into the snow.
Bearing of seismic line: 296 degrees
Geophones: 1-24 to East and 24-28 to West of midpoint
Shot point: Midpoint of survey line.
Survey collected in two halves due to software issues, 20 hammer blows per half, all hammer blows carried out by Nick Morgan.

Files included
*.dat - raw data files each containing seismic record from single shot
Geophones 1-24: 1000.dat – 1001.dat
Geophones 25-48: 2000.dat – 2018.dat and 2020.dat - 2021.dat

Lineage

Progress Code: onGoing

Statement: The data is of reasonable quality however very soft snow at the surface necessitated the plate be dug out and repositioned every 5 hammer blows. Due to a problem with the seismic software each of the datasets were collected in two halves i.e. 24 electrodes located to one side of the survey mid-point in one data set and the 24 electrodes to other side in a second data set.

Notes

Purpose
The purpose of the data was to optimally locate a hot water drilled borehole by providing an indication of ice thickness, and the thickness of the water column underneath the ice shelf. The aim was to locate the borehole with greater than 500 m water column beneath the ice shelf to allow identification of different ocean water masses. Ground penetrating radar data was collected at the same site to give an accurate measure of ice thickness and improve the measurement of ocean depth from seismic data.