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Seismic Wave Travel Time Calculator

Work out seismic wave travel time instantly with clear inputs, formula shown and shareable results.

About Seismic Wave Travel Time Calculator

P waves are compressional and travel at about 6 km/s in the crust; S waves are shear and manage about 3.5 km/s. At 400 km the P arrives in 66.7 s and the S in 114.3 s, a 47.6 second gap. That interval is what earthquake early warning systems exploit, and it also lets a single station estimate distance.

Formulas

Travel time

t = distance / wave speed

Distance from the S-P interval

distance = (S - P interval) / (1/vs - 1/vp)

Worked example

With the default values below, Seismic Wave Travel Time Calculator returns S Minus P Arrival Interval of 47.62. Change any input above and every figure here is recalculated in your browser.

Inputs used

Distance to the epicentreminimum 0 km
400 km
P wave speedminimum 0 km/s
6 km/s
S wave speedminimum 0 km/s
3.5 km/s

Results

S Minus P Arrival Interval
47.62 s
P Wave Travel Time
66.67 s
S Wave Travel Time
114.29 s
Warning Time After Detection And Processing
42.62 s

Step by step

  1. 1Values used
  2. 2Travel time
  3. 3Distance from the S-P interval
  4. 4S Minus P Arrival Interval= 47.62 s
  5. 5P Wave Travel Time= 66.67 s
  6. 6S Wave Travel Time= 114.29 s
  7. 7Warning Time After Detection And Processing= 42.62 s

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How does one station locate an earthquake?

The S minus P interval gives distance, so three stations' distance circles intersect at the epicentre - the classic triangulation method.

Why do S waves not travel through the liquid core?

Because shear waves need a medium that resists shear, and liquids do not. The S wave shadow zone is how the liquid outer core was discovered.

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