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Seismic Methods

Seismic waves travel at speeds set by the elastic moduli and density of the material they cross, so travel times carry structural information. Near-surface work leans on the refraction method: head waves from faster layers below overtake direct arrivals and reveal layer depths and velocities.

Learning Objectives

Undergraduate Core: By the end of this module, you will be able to:

  • Relate stress, strain, elastic moduli, density, and P- and S-wave velocity.
  • Read slopes, intercept time, and crossover distance from a refraction travel-time plot.
  • Recover a two-layer velocity model and interface depth under the planar-layer assumption.
  • Recognize low-velocity-layer blindness, lateral variation, and first-break picking uncertainty.
Graduate Extension

Compare intercept-time interpretation with refraction tomography, reciprocal acquisition, regularization, resolution, and uncertainty analysis.

Practice this module Teach with active-learning slides

Topic Apps

Demo

  • ⚡ Refraction Travel-Time Curve Builder

    Adjust layer velocities and thickness in a two-layer earth and see the direct wave, head wave, crossover distance, and intercept time update live.

Classroom Lab

🧰 Foundation refraction and aquitard reflection — fit a three-segment T–X plot, estimate a layered model, test pick uncertainty, and diagnose a low-velocity hidden layer.

Research Code: PyHydroGeophysX

Seismic refraction and joint inversion

The travel-time picking and interpretation you practice here scale up to full seismic refraction tomography (SRT). PyHydroGeophysX provides SRT forward modeling and inversion, rock-physics velocity models (Hertz-Mindlin, differential effective medium), and joint ERT plus seismic inversion so the two methods constrain one shared subsurface model.

Data and Notebooks