(San Francisco Chronicle) A huge earthquake that struck beneath the Indian Ocean in April triggered an extraordinary burst of large quakes around the world that alerted scientists to new seismic hazards everywhere.
Seismologists have known for more than 20 years that major earthquakes can trigger small seismic slips thousands of miles away. But the one on April 11 caused what scientists termed an astonishing increase in dangerous quake activity across five continents for at least six days, with temblors in, among other places, Japan, Alaska, Mexico and off the coast of Oregon.
It was a highly unusual event: At least four seismic faults deep underground off the island of Sumatra ruptured within 100 seconds to create a single giant quake with a combined magnitude of 8.7. No major problems occurred anywhere on land, but its effects worldwide call for a new assessment of global dangers, said scientists reporting in the current issue of Nature.
