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Seismic Impedance Calculator

Resistance to seismic wave propagation.

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Impedance

Formula first

Overview

Seismic impedance is a physical property of medium that represents the resistance to seismic wave propagation. It is defined as the product of the rock density and the seismic wave velocity traveling through that medium.

Symbols

Variables

Z = Impedance, = Density, V = Velocity

Impedance
Density
kg/m³
Velocity
m/s

Apply it well

When To Use

When to use: This equation is used when analyzing seismic reflection data to determine the acoustic properties of subsurface layers. It is essential for calculating the reflection coefficient at an interface between two different rock types or fluids.

Why it matters: Understanding impedance allows geologists to map the structure of the Earth's crust and identify potential oil or gas reservoirs. Differences in impedance at boundaries are what cause seismic waves to bounce back, creating the images used in mineral exploration.

Avoid these traps

Common Mistakes

  • Confusing with velocity alone.
  • Convert units and scales before substituting, especially when the inputs mix kg/(m²·s), kg/m³, m/s.
  • Interpret the answer with its unit and context; a percentage, rate, ratio, and physical quantity do not mean the same thing.

One free problem

Practice Problem

A sandstone layer in a potential oil field has a bulk density of 2350 kg/m³ and a seismic wave velocity of 3200 m/s. Calculate the seismic impedance for this layer.

Density2350 kg/m³
Velocity3200 m/s

Solve for:

Hint: Multiply the density by the velocity to find the impedance (Z = ρ ×V).

The full worked solution stays in the interactive walkthrough.

References

Sources

  1. An Introduction to Seismology, Earthquakes, and Earth Structure by Peter M. Shearer
  2. Wikipedia: Seismic impedance
  3. Seismic Data Analysis, Volume 1: Processing, Inversion, and Interpretation of Seismic Data by Öz Yilmaz, 2001
  4. An Introduction to Geophysical Exploration, 3rd Edition by Keary, Brooks, Hill, 2002
  5. Fundamentals of Geophysics, 2nd Edition by William Lowrie, 2007
  6. Stein, S., & Wysession, M. (2003). An Introduction to Seismology, Earthquakes, and Earth Structure. Blackwell Publishing.
  7. Lowrie, W. (2007). Fundamentals of Geophysics (2nd ed.). Cambridge University Press.
  8. University Geophysics — Seismic Methods