Geophysics

The method should match both the investigation objective and the physical properties of the target. An expert may examine expected target depth, required resolution, geology, groundwater conditions, surface access, anticipated contrasts in electrical or seismic properties, equipment configuration, survey spacing, and data quality. Ground-penetrating radar, electrical resistivity, electromagnetic methods, and seismic techniques do not respond to subsurface conditions in the same way, so method selection can materially affect what a survey is capable of detecting.

Geophysical measurements generally record a physical response rather than directly displaying the subsurface feature responsible for it. Differences can arise from processing choices, assumptions used in modeling or inversion, noise removal, survey geometry, calibration, geological assumptions, or the use of different supporting information. Comparing the raw data, processing history, model parameters, and independent site evidence can help identify where competing interpretations diverge.

Geophysical information can help characterize subsurface materials and site conditions that influence how earthquake ground motion behaves at a particular location. The analysis may involve seismic velocities, sediment thickness, bedrock conditions, or other properties relevant to site response. A geophysics expert should not automatically attribute structural damage to earthquake shaking; structural performance and building damage may require separate engineering expertise.