Enter any two values (distance, average P-wave velocity, or travel time) into the calculator to estimate the missing value. Results are approximate because real P-wave speeds vary with depth and geology, and seismic rays can follow curved paths; this calculator assumes a constant average velocity along a straight path.

P Wave Travel Time Calculator

Travel time from distance
Distance from S−P lag

Enter the distance; we assume a typical P-wave speed.

Related Calculators

P Wave Travel Time Formula

The following formula is used to calculate an approximate P wave travel time (assuming a straight path and a constant average P-wave velocity).

TT = D / V

Variables:

  • TT is the P wave travel time (seconds, if using km and km/s)
  • D is the source-to-station distance along the assumed path (often approximated using the station-to-epicenter distance for shallow/local events)
  • V is the average P wave velocity along the path (kilometers per second, km/s)

To calculate the P wave travel time, divide the distance by the P wave velocity using consistent units (for example, km divided by km/s gives seconds).

What is P Wave Travel Time?

P wave travel time is the duration it takes for primary waves (P waves)—the fastest common seismic body waves generated by an earthquake—to travel from the earthquake source (hypocenter) to a specific point, usually a seismic station. In practice, measured P-wave arrival times are combined with Earth velocity models (travel-time curves/tables) to locate earthquakes and to study the Earth's internal structure.

How to Calculate P Wave Travel Time?

The following steps outline how to calculate the P Wave Travel Time.

  1. First, estimate the source-to-station distance (D) in kilometers (often approximated by epicentral distance for shallow/local events).
  2. Next, choose an average P wave velocity (V) in kilometers per second that is appropriate for the path/material.
  3. Next, gather the formula from above: TT = D / V.
  4. Finally, calculate the P Wave Travel Time (TT) in seconds.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Distance to the epicenter (D) = 300 kilometers

P wave velocity (V) = 6 km/s → TT = 300 km ÷ 6 km/s = 50 seconds