On 8/27/2012 at 4:37 UT( 12:37 AM EDT) a 7.3 magnitude quake occurred 75 miles (120km) off the west shore of Central America. No damage was reported. About 6 minutes later, after traveling 2,000 miles(3,2019 Km), station M49A caught the waves. Notice how the amplitude of all the other waves are reduced to compare the strengths? Otherwise, this one would “go off the charts” and be very difficult to measure. Also notice how the shock waves keep bouncing around for a couple of hours. Like the waves bouncing in a large pool before the surface finally calms down. As big as these waves are, we still feel nothing. This would be like a heavy train rumbling by for over an hour.
Look close…two “smaller” M5 earthquakes occurred in southern California the day before (8/26/2012), one just before 4 PM EDT(20:00 UTC) and a slightly bigger one after 5 PM EDT (21:00 UTC). No damage was reported.