Why can the tremor of the ground from a distant explosion be felt before the sound of the explosion can be heard?

The sound travels faster through the stiffer material of the ground than is does through the air.

Explanation:

Sound is a mechanical, longitudinal wave that is caused by the vibration of molecules.

A mechanical wave is a wave that requires a medium through which to travel, as opposed to electromagnetic waves which do not require mediums.

Ground being solid has a very tight arrangement of particles. Due to less spacing sound or vibrations can easily be passed on to the next particle where as in gases due to lower density and larger distance of particles with the gas , the vibrations are not passed on easily to the next particle as in solids.

Hence sound actually travels around four times faster in solid such as ground than in gases such as air. Speed of sound in air is 343 meters per second.  Speed of sound in solids has a wide range depending on the density of the solid.

The tremor of the ground can be felt because sound travel faster on ground, underground than sound travels in air.

Explanation:

If we consider the components of the of the earth or sold ground, we can see that the element or components are tightly packed together, thus allowing sound to travel swiftly through these particles. Sound travels through these solid particles at an average of 6000 meters per second.

While

If we consider the elements of the air, we can clearly see that its components are mostly gaseous based and are very space or less compacted due to the fact that they are free to air. Thus, making sound unable to travel through the components ate a slower speed. Sound travels in are at an approximate figure of 343 meters per second  due to the fact that we the gasses are scattered.

well clustered together.

points close on a scatter diagram