Final answer:
The first earthquake waves to arrive at a seismograph station are P-waves (longitudinal waves), which will do so a (B)short time after the earthquake occurs. They are followed by S-waves (transverse waves). The time interval between their arrivals can be used to determine the distance to the earthquake's epicenter.
Step-by-step explanation:
The first earthquake waves will arrive at a seismograph station a short time after the earthquake occurs. Earthquakes produce both longitudinal waves (also known as P-waves) and transverse waves (S-waves), which travel at different speeds depending on the rigidity of the medium they're traveling through.
The P-waves, being faster, reach the recording equipment first, followed by the slower S-waves. The interval between the arrival of these two wave types can be used to estimate the distance from the seismograph station to the earthquake's epicenter.
This sequence of wave arrival is due to the nature of seismic wave propagation, as waves are released once an earthquake occurs and then travel through the various layers of Earth until they reach the seismograph station that detects and records them.
Learn more about Seismic Waves