An important observation was made possible by his serendipitous observation of the 1994 Bolivia earthquake during a field campaign in the region : the data recorded by his broadband seismograph array showed that the source region of this event , which is the largest deep quake on record ( as of November 2009 ) , is in conflict with the generally accepted view that such quakes are caused by phase transformations of mantle minerals
1994 Bolivia earthquake
1994 Bolivia earthquake
Paul Silver