Observation and research of deep underground multi-physical fields-Huainan -848 m deep experiment

Area of Science:

• Geophysics
• Earth Science
• Geoscience

Background:

• The deep subsurface offers a 'super-quiet and ultra-clean' environment for geophysical observation, minimizing vibration noise and electromagnetic interference.
• This environment is ideal for long-term, high-precision monitoring of multi-physical fields, crucial for solving complex geoscience problems.

Purpose of the Study:

• To conduct the first deep-underground geophysical observations in an extensive coal mine.
• To assess the feasibility and benefits of utilizing deep underground environments for geophysical field observations.
• To identify challenges and requirements for deep geophysical observation technology and data processing.

Main Methods:

• Conducted comprehensive geophysical observations at 848 m depth in the Panyidong Coal Mine.
• Measurements included radioactivity, gravity, magnetic, magnetotelluric, background vibration, and six-component seismic data.
• Compared deep underground data with surface observation environments.

Main Results:

• Deep subsurface gravity noise (< 2 Hz) is nearly two orders of magnitude lower than at the surface.
• Underground electric fields are significantly weaker, especially at higher frequencies (> 1 Hz).
• North-south magnetic fields (< 10 Hz) are at least one order of magnitude lower, indicating a cleaner electromagnetic environment.
• Background vibration noise is substantially lower, aiding detection of weak signals, though ferromagnetic supports interfere with the geomagnetic field.

Conclusions:

• Deep underground environments provide superior conditions for geophysical observations due to reduced noise.
• Existing geophysical equipment and data processing techniques require adaptation and improvement for deep observation.
• Interpreting and utilizing high-precision multi-physics data from deep environments is an urgent research priority.