A series of powerful earthquakes which struck Asia and South America in the past week could be followed by a 'mega' quake in the near future, a scientist has claimed. On Thursday and yesterday, two earthquakes struck Japan, killing at least 41 people, causing landslides and widespread damage to buildings and infrastructure. Today, a 6.1 magnitude quake struck southeast of the Pacific island nation of Tonga, with no immediate reports of damage. And at the other end of the infamous Ring of Fire, Ecuador was also struggling after a major 7.8 quake which hit last night, killing at least 77. Roger Bilham, a seismologist at the University of Colorado, told The Daily Express: 'The current conditions might trigger at least four earthquakes greater than 8.0 in magnitude. 'And if they delay, the strain accumulated during the centuries provokes more catastrophic mega earthquakes.' In addition to the four major earthquakes to have struck since Thursday, last week there were also shakes in the