Earthquake Travel-time Curves: How they are created
Science
How Earthquake Travel-time Curves and How they are created
The time versus distance graph of P S and surface wave arrival times was constructed by analyzing thousands of earthquakes from hundreds of seismograph stations around the world. Here we shall an earthquake near the top of the globe and graft the arrival times to seismic stations at varying distances from the hypocenter. The Y axis shows the distance from the earthquake and the X axis shows the elapsed time since the event.
The seismograms record the arrivals of the compressional P, the shearing S and the rolling surface waves, seismic waves travel at different rates, so the farther a seismic station is from an earthquake, the farther apart the PS and surface wave arrival times are. Here we shall only the direct P and S wave paths through the mantle and crust, the final image of this animation will show more of the complexity within the earth as waves are reflected refracted and damped due to changes at depth.
Connecting the ways through a stack of seismograms creates a travel time curve, it can be used to locate earthquakes. Simply stated the time difference between the arrival of the P wave and the S wave can be used to measure the distance from seismometer to the epicenter.