Seismic Wave Studio

ak135 · body-wave rayfronts

Earth cross-sectionTop-down view

1920 × 1080 canvas

Drag the red earthquake or the station marker around the rim

Calculating wavefronts…

00:00/ 30:00

PlaybackLoop

00:0005:0010:0015:0020:0025:0030:00

01 / ORIGIN

The earthquake begins

P and S waves spread from the focus. The faster P wave travels ahead, while both fronts bend as wave speed changes with depth.

Wavefronts

P wavesCompression · solids & liquids

S wavesShear · solid regions

Reflected wavesCore reflections & one surface bounce

Converted wavesSKS, SKIKS, ScP & PcS

Line opacity 70%

Earthquake

Position 0°

Focus depth 50 km

Position is measured clockwise from the top. Change depth to recalculate. Playback speeds compress physical time; the centre clock shows time since origin.

Seismic station

Station & seismogramSurface receiver A

From earthquake 90° left

Trace size 1.0×

Drag the station marker to move it. Time runs down the chart. Arrival times use ak135; pulse shapes and sizes are illustrative.

Calculating arrivals…

Composition

Layer labels

Central timer

410 & 660 km guides

Label size 32 px

Line thickness 1.6 px

Colour palette

MantleOuter coreInner coreBackgroundP wavesS waves

Physics & validation

This animation uses ak135, the published spherical Earth travel-time model of Kennett, Engdahl & Buland (1995). The embedded ANU velocity table is interpolated linearly in radius, preserving its crustal layers, mantle discontinuities and liquid outer core.

Earth radius: 6,371 km. Core–mantle boundary: 2,891.5 km depth. Inner-core boundary: 5,153.5 km depth.
Rays conserve spherical ray parameter p = r sin(i) / v. Travel time and angle are integrated through each velocity interval, with Snell refraction, turning and specular reflection.
Includes direct P/S families, PKP and PKIKP, PcP, ScS, PKiKP, ScP/PcS and SKS/SKIKS. The direct families continue through one surface reflection. Additional core branches stop on reaching the surface.
In SKS and SKIKS, the core legs are compression waves. No shear wave propagates in the liquid outer core. Colour follows the local wave type, including conversions.

Scope: these are equal-time fronts for selected body-wave ray families. Brightness and thickness are display settings. This does not calculate amplitudes, source radiation, interference, attenuation, surface waves, diffraction, head waves, all reflected/converted branches, or three-dimensional Earth structure. Fronts are sampled at 1-second intervals and 0.25° takeoff spacing; small gaps occur at branch boundaries. Ray theory is limited near caustics and shadow boundaries.

Station display: the receiver defaults to 90° counterclockwise from the epicentre. Surface arrivals are solved using the same ray families, including their permitted surface bounce. The two trace lanes group arrivals by their P or S wave type at the receiver; they are not physical sensor components. Time runs downward. Only arrivals already reached by the playback clock create pulses. Pulse shape, duration and amplitude are illustrative, with no ground-motion units, instrument response or measured noise. Visibility filters apply to both the globe and chart. Blank intervals mean no arrival from the included branches, not absence of all real seismic energy.

Travel-time checks: 16 selected arrivals at 50, 100 and 700 km source depths were checked against Kennett’s Seismological Tables: ak135 (2005). The largest difference is under 0.06 seconds. This measures agreement of the solver with that 1D model, not prediction uncertainty for a real earthquake.

Inspect and rerun the reference checks

Distance is the angle at Earth’s centre from epicentre to receiver. Times are seconds after origin. These checks use the same ray integrator as the animation.

Reference values are embedded; no internet connection is needed.

Phase	Depth km	Distance °	Reference s	Calculated s	Difference s

USGS: interpreting seismograms
ANU: ak135 travel-time velocity table
ANU: model description and phase tables
Kennett (2005): published travel-time tables