This simulator launches a P wave and an S wave from a source along two particle chains toward a recording station. Set the distance and the wave speeds, switch to a liquid medium, and compare how the particles move with the direction the wave travels.
• A real-time 3D scene with 4 inspectable parts (Seismic source, Compressional P chain, Shear S chain and Recording station), with home view, focus-selected-part, auto-rotate, expand, instrument-cover and hide-labels scene tools, plus a model response curve beneath the scene. • Experiment controls: Source–station distance (30-180 km); P-wave speed (5-8 km/s); S-wave speed in solid (2-4.5 km/s); use liquid medium; Displacement magnification (0.1-0.5); show explanatory motion markers; pause/resume, 0.1 s and 1 s single-step buttons, four playback speeds and a restart button. • A Curves & measurements tab with a parameter-comparison chart, a live-measurements chart, the model equations and snapshot readouts (Elapsed model travel time; P arrival; S arrival in solid; S−P time in solid; P front distance). • An Experiments tab with 2 guided presets (solid medium and liquid medium) and a Model verification bench that runs independent fresh models, plus a timestamped event log and a copyable trial report. • A Learn & assess tab with guided lessons, a knowledge-check quiz with reset and a written model-scope statement linking to a technical reference.
P waves are compressional: particles move parallel to the direction of travel, so compressions and dilations pass along the chain. S waves are shear waves: particles move perpendicular to it. The lab reports P arrival time, S arrival time in a solid, the S-minus-P time, the elapsed travel time and the P front distance.
Arrival times follow t = L / v, and the S-minus-P interval is L (1/vS - 1/vP), which grows with distance - the basis of locating earthquakes from a single station's arrival gap.
Shear waves require nonzero shear rigidity, so ordinary S waves do not propagate through a liquid bulk medium. Switching on the liquid medium removes the S wave from the scene while the S metrics remain labeled as solid-reference values.
The model is homogeneous and one-dimensional with no attenuation, refraction or reflection. Distances are compressed and displacements enlarged for visibility, although animation time equals modeled travel time.
Parallel to the direction the wave travels, in alternating compressions and dilations. In the S chain they move perpendicular to the direction of travel.
Not as ordinary shear waves in a bulk liquid, because liquids have no static shear rigidity. The liquid-medium option in the lab removes the S wave to show this.
It equals the distance multiplied by the difference of the reciprocal speeds, L times (1/vS - 1/vP). The larger the distance, the larger the gap between the two arrivals.
The speed ranges are representative of crustal values, but the model is homogeneous, one-dimensional and without attenuation, refraction or reflection, and distances are compressed for display.