Free Online Seismic Wave Simulator: Refraction and Reflection Live

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Click anywhere in the earth to fire a source there. The acoustic wave equation is solved on a grid live in your browser: reflections appear at each velocity boundary, transmitted fronts bend by Snell law, and the fast layers race ahead exactly as refraction surveys rely on. Change the velocities and fire again.

The wave equation, running live

This is not an animation of what seismic waves do; it is the acoustic wave equation being solved on a grid, thousands of cells per frame, in your browser. Click anywhere in the layered earth and a source fires: the wavefront expands, reflects at each velocity boundary, transmits and bends by Snell law, and in the fast layers the front races ahead to build the head waves that refraction surveying was invented to catch. Change the three layer velocities and the physics reorganizes instantly.

A seismic source firing circular wavefronts through three earth layers with the refracted front racing ahead in the faster rock below
Click to fire a source and watch the wavefront bend, bounce, and split at every layer.

Everything a first course in seismology asserts appears here because the mathematics produces it: the sharper the velocity contrast, the brighter the reflection; the faster the lower layer, the sooner its refracted energy overtakes the direct wave.

What to try

  • Fire at the surface and watch the second layer reflection climb back up: that arrival is what every seismic section is made of.
  • Set layer two slower than layer one and watch the refraction geometry invert.
  • Fire two shots side by side and watch the wavefields interfere like a tiny survey.
  • Fire deep in layer three and see energy trapped and leaking upward, the geometry of earthquake sources.

The numerics, honestly

A second order finite difference solver with a Ricker source, absorbing sponge edges, and a grid of 10 m cells: the same family of engine that industrial wavefield modeling uses, scaled to run at interactive speed. Grid dispersion and edge artifacts exist as they do in every such solver; spotting them is part of the education.

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