<P> Ordinarily, subduction earthquakes under magnitude 7.5 on the Richter magnitude scale do not cause tsunamis, although some instances of this have been recorded . Most destructive tsunamis are caused by earthquakes of magnitude 7.5 or more . </P> <P> A flood is an overflow of any amount of water that reaches land . Floods occur usually when the volume of water within a body of water, such as a river or lake, exceeds the total capacity of the formation, and as a result some of the water flows or sits outside of the normal perimeter of the body . However, floods may be secondary effects of earthquakes, if dams are damaged . Earthquakes may cause landslips to dam rivers, which collapse and cause floods . </P> <P> The terrain below the Sarez Lake in Tajikistan is in danger of catastrophic flood if the landslide dam formed by the earthquake, known as the Usoi Dam, were to fail during a future earthquake . Impact projections suggest the flood could affect roughly 5 million people . </P> <P> An earthquake may cause injury and loss of life, road and bridge damage, general property damage, and collapse or destabilization (potentially leading to future collapse) of buildings . The aftermath may bring disease, lack of basic necessities, mental consequences such as panic attacks, depression to survivors, and higher insurance premiums . </P>

Who was the first person to explain the mechanism by which most earthquakes are generated