Why do all seismograph around the world detect P waves about me some seismographs around the world detect S waves?

Seismographs around the world detect P waves because these primary waves, or compressional waves, travel faster than S waves (secondary waves) and can move through both solid and liquid layers of the Earth. In contrast, S waves can only travel through solids, which is why some seismographs may not detect them if they are located in areas where the waves encounter liquid layers, such as the Earth's outer core. This difference in wave propagation explains why P waves are universally detected, while S waves are only recorded in specific locations.