There isn't a perfect antonym for "seismic wave" in the sense of a word with the exact opposite meaning. However, depending on the context, you might use words like:

For the concept of a wave:

* Static: This refers to something that is not moving or changing.

* Still: This implies a lack of movement or vibration.

* Constant: This refers to something that remains the same over time, without fluctuations.

For the cause of the wave:

* Non-earthquake: If you are talking about the cause of a seismic wave (an earthquake), you could use this phrase to indicate something else that didn't cause a seismic wave.

For the effect of the wave:

* Stable: This refers to something that is not being disrupted or shaken.

* Undetected: This means that the wave was not noticed or measured.

Ultimately, the best antonym will depend on the specific context in which you are using the word "seismic wave."