In an earthquake, the initial seismic energy wave is called a primary wave. It compresses the material ahead of it; other types of subsequent waves travel in sideways and up-and-down motions. A primary wave travels at different speeds depending on what type of substance it is traveling through. In order to determine how long it will take to travel 2,000 km we have to do the math, using the speed in km/sec and setting up proportions. In a solid such as rock, the primary wave can travel at 5 km/sec; it would take 400 seconds, or about 6.7 minutes to travel 2,000 km. If traveling through water, the wave travels at about 1.45 km/sec and would need 1,379 seconds (23 minutes) to travel 2,000 km. Primary waves traveling through air travel at the speed of sound (.34 km/sec), and would take 5,882 secondsĀ (98 minutes) to travel 2,000 km.

Speeds are usually expressed in m/s, as they are in the link I have attached. I converted to km, as your question was phrased that way.