Seismic Wave Arrival Calculator

Estimate when P-waves and S-waves may arrive at a location after an earthquake, based on distance from the epicenter and average wave speeds.

This calculator uses simplified average speeds: P-waves travel faster, while S-waves arrive later and often cause stronger shaking.

Seismic Wave Arrival Result

P-Wave Arrival-
S-Wave Arrival-
Warning Gap-
Wave Pattern-
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P-Wave and S-Wave Timeline

Earthquake starts P-wave first S-wave later

Understanding Your Seismic Wave Arrival Results

Earthquakes release energy through seismic waves that travel through Earth’s crust and interior. These waves move at different speeds, which is why some earthquake vibrations arrive earlier than others.

The seismic wave arrival calculator estimates when P-waves and S-waves may reach a location based on distance from the earthquake source and average wave speeds.

P-waves are the fastest seismic waves and arrive first. S-waves travel more slowly but often produce stronger ground shaking.

What the Calculator Results Mean

Result Meaning
P-Wave Arrival Time The estimated arrival time of the first fast-moving seismic waves.
S-Wave Arrival Time The estimated arrival time of slower but usually stronger seismic waves.
P-S Time Gap The time difference between P-wave and S-wave arrival.
Wave Pattern An educational interpretation of how close or far the earthquake may be.

What Are P-Waves?

P-waves, also called primary waves, are compression waves that travel fastest through Earth. They move by pushing and pulling particles in the same direction as the wave travels.

These waves usually arrive first and may feel like a quick vibration, small jolt, or subtle rumble before stronger shaking begins.

What Are S-Waves?

S-waves, or secondary waves, move more slowly than P-waves. Instead of compressing material, they move particles side-to-side or up-and-down.

S-waves often cause stronger shaking and are responsible for much of the structural damage during earthquakes.

S-waves cannot travel through liquid outer layers inside Earth, while P-waves can move through both solids and liquids.

Why the P-S Time Gap Matters

The difference between P-wave and S-wave arrival times helps scientists estimate how far a seismic station is from the earthquake epicenter.

A short time gap usually means the earthquake happened nearby. A longer gap often indicates the earthquake occurred farther away.

Typical Seismic Wave Speeds

Wave Type Average Speed Characteristics
P-Waves 5–8 km/s Fastest waves, arrive first, travel through solids and liquids.
S-Waves 3–4.5 km/s Slower waves, stronger shaking, travel only through solids.
Surface Waves 2–3 km/s Slowest waves but often responsible for severe surface damage.

Why Seismic Speeds Change Underground

Seismic wave speeds depend on rock density, temperature, pressure, and underground structure. Waves travel faster through solid bedrock and more slowly through loose sediment.

Scientists study seismic wave behavior to understand Earth’s interior structure, including the crust, mantle, and core.

Earthquake early warning systems use the difference between fast P-wave arrival and slower damaging waves to send alerts before strong shaking arrives.

Real-World Seismic Wave Examples

2011 Japan Earthquake

Japan’s earthquake warning system detected fast-moving P-waves and sent alerts before stronger shaking reached many cities.

San Andreas Fault Earthquakes

California uses seismic sensors to measure P-wave and S-wave arrival times for earthquake monitoring and warning systems.

Global Seismology Networks

Scientists worldwide use seismic wave arrival times to locate earthquakes and study Earth’s internal structure.

Deep Earthquake Research

Variations in seismic wave speed help researchers map Earth’s mantle and identify hidden underground structures.

Seismic Wave Arrival Calculator FAQ

What is a seismic wave arrival calculator?

It estimates when P-waves and S-waves may arrive at a location after an earthquake, based on distance and wave speed.

What is a P-wave?

A P-wave is the fastest seismic wave. It usually arrives first and may feel like a quick jolt or vibration.

What is an S-wave?

An S-wave travels slower than a P-wave but often produces stronger side-to-side or up-and-down shaking.

Why do P-waves arrive before S-waves?

P-waves travel faster through Earth materials, so they reach seismic stations and nearby locations before S-waves.

What does the P-S time gap mean?

The time gap between P-wave and S-wave arrival can help estimate how far a location is from the earthquake source.

Are wave speeds always the same?

No. Seismic wave speeds change depending on rock type, depth, temperature, and underground structure.

Is this calculator an official earthquake warning tool?

No. It is an educational calculator only. Official warning systems use real-time seismic instruments and advanced models.