I don't think it's the overall number as much as the severity, and within a relatively short time (21 quakes over 6 in a little over 3 months):
Chile, 8.8, 6.9, 6.7, 6.4, 6.3, 6.2 (all different quakes)
Sumatra, 7.7 (April), 6.8 (March)
Indonesia, 7.7
Baja, 7.2
Solomon Islands, 7.1
Haiti, 7
Japan, 7, 6.5
China-Russia-N. Kora, 6.9
Papua New Guinea, 6.6
Andaman Islands, 6.6
California (Eureka, offshore), 6.5
Taiwan, 6.4
Argentina, 6.3
Turkey, 6.1
Like a bell that keeps ringing...
Sue