Variations

Askew

Many of us live in the areas undergoing weak but frequent earthquakes, which can be detected only with seismographs. We are not sure which animal species are able to feel these events. As for us, we can only notice that a picture in our room gets askew. It is said that over 1,000,000 earthquakes of a small magnitude around 2 to 3 occurs every year. Earthquakes of different types and magnitude result from sudden release of energy in the Earth’s crust. The cause of it may be geological faults of several types resulting in earth movement or rupture, volcanic activity, a landslide, or other processes. Human activity such as nuclear tests or mine blasts may also cause an earthquake. Apart from damages caused by storms, volcanic activity, coastal waves, and wild fires, earthquakes may produce disastrous impacts on humans caused by avalanches, landslides, fires, soil liquefaction, tsunami, and floods; they result in damages of dams, architectural structures, bridges, and roads. Seismic waves propagate with velocity ranging from 3 km/s up to 13 km/s. Some seismic activities cannot be seen or sensed but can be detected by their results or recordings; sensors such as seismometers are necessary for this purpose. Results of earthquakes, registered in form of seismic waves’ measurements, can be found online.