EqLocate

The EqLocate program allows you to select P-wave arrivals of a number of seismograms for an earthquake and find its location.

The package contains several earthquakes which you can use for practice. To use you click on the P-wave arrival on each station and then guess at the epicenter. You will be shown lines toward each stations from the selected epicenter which will guide you toward your next pick. The RMS error is displayed in text at the top of the screen plus colored dots will record your past guesses.


Level: Novice

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Related Animations

Seismic waves travel through the earth to a single seismic station. Scale and movement of the seismic station are greatly exaggerated to depict the relative motion recorded by the seismogram as P, S, and surface waves arrive.

Animation Novice

We use exaggerated motion of a building (seismic station) to show how the ground moves during an earthquake, and why it is important to measure seismic waves using 3 components: vertical, N-S, and E-W. Before showing an actual distant earthquake, we break down the three axes of movement to clarify the 3 seismograms. 

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A cow and a tree in this narrated cartoon for fun and to emphasize that seismic waves traveling away from an earthquake occur everywhere, not just at seismic stations A, B, C, and D. A person would feel a large earthquake only at station A near the epicenter. Stations B, C, D, and the cow are too far from the earthquake to feel the seismic waves though sensitive equipment records their arrival.

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This companion to the animation "Four-Station Seismograph network"  shows the arrival of seismic waves through select wave paths through the Earth (P and S waves) and over the surface of the Earth. The movement at distant stations occurs at a microscopic scale. While that doesn't result in noticeable movements of the buildings, the arrivals are recorded on sensitive seismometers.

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A gridded sphere is used to show a single station recording five equidistant earthquakes.

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A gridded sphere is used to showt: 1) the seismic stations don't need to be lined up longitudinally to create travel-time curves, as they appear in the first animation, and 2) a single station records widely separated earthquakes that plot on the travel-time curves.

Animation Novice

A travel time curve is a graph of the time that it takes for seismic waves to travel from the epicenter of an earthquake to the hundreds of seismograph stations around the world. The arrival times of P, S, and Surface waves are shown to be predictable. This animates an IRIS poster linked to this animation.

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Related Videos

The arrival times of P and S waves are used to determine the distance to an earthquake using standard travel-time curves. 

Video Novice