Animals can detect the P-wave or ultrasonic wave generated by a big underground explosion or the rupture of an earthquake, even if the waves are too small for humans' senses. These waves travel faster than the S-wave earthquake wave that most strongly shakes the ground and causes the most damage. When this happens, animals can detect the incoming earthquake wave, and start behaving agitatedly or nervously, the same way a human would behave if they heard a loud explosion right outside their house.
Others postulate that the animal behavior is simply their response to an increase in low-frequency electromagnetic signals.[6] The University of Colorado has demonstrated that electromagnetic activity can be generated by the fracturing of crystalline rock. Such activity occurs in fault lines before earthquakes. According to recent research, electromagnetic sensors yield statistically valid results in predicting earthquakes - modern science's answer to centuries of human observation of animals.[7]
Some people believe that in these ways, animals sense the immediate onset of earthquakes. In support of this claim, instances are cited when people have witnessed flight of animals just before an earthquake disaster. In fact, according to the Chief conservator of forests for the Indian state of Tamil Nadu, a few minutes before the killer tsunami waves generated by an underwater earthquake hit the Indian coastline in December 2004, a 500-strong herd of blackbucks rushed away from the coastal areas to the safety of a nearby hilltop. Since the beginning of recorded history, observations of unusual animal behavior before earthquakes have been recorded by people from almost all civilizations. The Chinese began a systematic study of this unusual animal behavior and in December 1974 predicted a major earthquake that did, in fact, occur in February 1975. But skeptics claim to debunk nearly all such observations. In fact, the 1975 prediction relied most heavily on a series of strong foreshocks. The animal behavior reports are often ambiguous and not consistently observed. There is little evidence for animals being able to sense impending earthquakes, although it is likely they can sense the initial, weaker P-waves before people. Seismometers remain much more sensitive than even the animals, however.
.
