The propagation speed of seismic waves is 5-6 kilometers per second.
Seismic waves can cause the ground to jump up and down, while transverse waves propagate slowly, 3-4 kilometers per second, and can cause the ground to shake horizontally. Since longitudinal waves attenuate quickly, only horizontal shaking is felt in places far away from the epicenter. Under normal circumstances, during an earthquake, the ground always jumps up and down first, and then shakes horizontally. There is a time interval between the two, which can be judged based on the length of the interval. The distance of the epicenter.
There are three main types of seismic waves inside the earth: longitudinal waves (P waves), transverse waves (S waves) and surface waves (including Rayleigh waves and Love waves). These seismic waves travel at different speeds within the Earth because they travel in different media and are affected by different physical properties.
Longitudinal waves are compressive waves that push rock particles to vibrate back and forth along the direction of propagation. Because they can spread through liquids and solids, they spread relatively quickly. In the earth's crust, the propagation speed of P waves is about 5-8 kilometers per second. A shear wave is a shear wave that causes rock particles to vibrate perpendicular to the direction of propagation.
Compared to longitudinal waves, they can only propagate through solids and therefore propagate slower. In the earth's crust, the propagation speed of S waves is about 3-5 kilometers per second. Surface waves are the slowest type of seismic waves that travel along the Earth's surface. Rayleigh waves are surface waves in which particles move in elliptical trajectories, while Love waves are transverse waves that propagate only on solid surfaces. These waves generally travel slower than longitudinal and transverse waves.
Hazards of earthquakes
1. Casualties and life dangers: Earthquakes may cause buildings and structures to collapse, and people may be buried under the rubble, resulting in serious casualties and life dangers. . Especially in the case of a strong earthquake, the risks of falling, being crushed and being buried are more serious.
2. Destroy infrastructure: Ground vibrations and crustal movements caused by earthquakes may damage infrastructure, such as roads, bridges, pipelines, and power lines. Such damage will cause traffic interruptions, water supply and power supply interruptions, causing serious trouble to the daily lives of residents in the disaster area.
3. Subsequent disasters and secondary risks: Earthquakes often cause secondary disasters, such as ground collapse, landslides, mudslides and floods. Additionally, earthquakes can cause fires and explosions due to damage to gas lines and electrical lines.