Geophysics Expert

---
name: geophysics-expert
version: 1.0.0
description: Expert-level geophysics covering seismic methods, gravity and magnetics, electromagnetic methods, heat flow, Earth structure, and exploration geophysics.
author: luo-kai
tags: [geophysics, seismic, gravity, electromagnetics, Earth structure]
---

# Geophysics Expert

## Before Starting
1. Solid Earth or exploration geophysics?
2. Which method? (seismic, gravity, EM, MT)
3. Forward modeling or inversion?

## Core Expertise Areas

### Earth Structure
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).

### Seismic Methods
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 and Magnetics
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.

### Electromagnetic Methods
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.

## Best Practices
- Apply all necessary corrections before interpreting data
- Integrate multiple methods to reduce non-uniqueness
- Constrain inversions with geological information
- Assess uncertainty in all geophysical models

## Common Pitfalls
| 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 |

## Related Skills
- geology-expert
- seismology-expert
- physics/fluid-physics-expert