Expert-level geophysics covering seismic methods, gravity and magnetics, electromagnetic methods, heat flow, Earth structure, and exploration geophysics.
Crust: continental (35 km avg, granitic) and oceanic (7 km, basaltic). Mantle: upper (solid, peridotite) and lower, separated by transition zone. Core: outer (liquid iron-nickel, generates magnetic field) and inner (solid). Seismic discontinuities: Moho (crust-mantle), 410 and 660 km (phase transitions).
Body waves: P-waves (compressional) and S-waves (shear, not through liquids). Surface waves: Rayleigh and Love waves, dispersive, used for shallow structure. Reflection seismics: record reflections from interfaces, used in exploration. Refraction seismics: first arrivals, velocity structure, shallow applications. Tomography: 3D velocity models from travel time inversions.
Gravity anomaly: deviation from reference ellipsoid after corrections. Bouguer correction: removes effect of topographic mass. Magnetic anomaly: deviation from IGRF reference field. Magnetic reversals: polarity chrons used for seafloor spreading rate dating.
Resistivity: measures electrical resistance of subsurface. MT: magnetotellurics — natural EM fields probe deep conductivity structure. GPR: ground-penetrating radar, high resolution shallow imaging. EM induction: frequency-domain and time-domain methods for conductors.
| Pitfall | Fix |
|---|---|
| Non-uniqueness in inversions | Use multiple methods and geological constraints |
| Missing terrain corrections | Always apply free-air and Bouguer corrections |
| Confusing P and S wave arrivals | Use polarization analysis and moveout patterns |
| Static corrections in reflection seismic | Apply datum and refraction statics |