Exploring Seismic Travel Times and Speeds
in a Layered Medium

Seismic pressure waves or 'P-waves' are expansions and contractions of a medium similar to sound waves. As the density of a rock layer changes, the speed of these P-waves also changes. This calculator lets you simulate a stack of four different rock types and calculate the speed and travel times of P-waves.

The program examines a 300-meter long section of rock split into four different materials, as shown in the figure. A darker rock layer color represents a higher density. Each rock layer displays its density (kg/m3), horizontal width (km), P-wave speed (km/s), and P-wave travel time (s).

The text below the figure shows the total time it takes for the P-wave to travel horizontally across all four rock layers.

Click-drag a rock boundary (orange) to set its location. Click at different points within a rock layer (or click-drag) to change its density.

Total travel time =

Computation code

GitHub source

More Space Math modules

This web page is adapted from Space Math @ NASA ILabs.

Information about estimated Mars rock surface densities from https://solarsystem.nasa.gov/docs/p370.pdf.

Background image of North Polar layered region taken by Mars Reconnaissance Orbiter HiRiSE Camera