Earthquakes emit two types of body waves: primary waves (p-waves) and secondary waves (s-waves). Both waves originate at the epicenter of an earthquake.
Primary waves, so named because they are the first wave to be emitted during en earthquake, travel through rock and liquid. These waves are the first to reach seismic stations, which alert seismologists of tectonic activity. Following the primary waves are s-waves, which travel through rock like p-waves, but cannot travel through...
Earthquakes emit two types of body waves: primary waves (p-waves) and secondary waves (s-waves). Both waves originate at the epicenter of an earthquake.
Primary waves, so named because they are the first wave to be emitted during en earthquake, travel through rock and liquid. These waves are the first to reach seismic stations, which alert seismologists of tectonic activity. Following the primary waves are s-waves, which travel through rock like p-waves, but cannot travel through liquid. The speeds of p-waves and s-waves depend on many factors, but most importantly depend on Earth's surface material.
The speed of an s-wave ranges from 1 km/sec to 8 km/sec and is mostly determined by Earth's surface material. In loose, unconsolidated sediments, an s-wave may only travel 1 km/sec, whereas deeper beneath the surface, s-waves can move as fast as 8 km/sec.
Because the speeds of p-waves and s-waves are dependent on their environment, it is impossible to assign an exact speed to p-waves and s-waves. However, by looking at material, it is possible to estimate body wave speed and determine how long it would take for a wave to reach a specific distance.
This question asks how long it will take for an s-wave to travel 2000km in an earthquake. Depending on the forcing factors, an earthquake's s-wave could reach this distance in anywhere from approximately 4 minutes (at a speed of 8km/s) to 33 minutes (at a speed of 1km/s).
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