Well, according to Google Earth's real-time earthquake application, the Mariana Islands just had a magnitude 6 and a magnitude 5 a couple of hours ago.
On average, around the world, every year you can expect:
Descriptor ....... Magnitude ......... Annual average
Great .............. 8 or higher ........ 1
Major .............. 7–7.9 ................ 17
Strong ............. 6–6.9 ............... 134
Moderate ......... 5–5.9 ............... 1,319
Light ............... 4–4.9 ............ c. 13,000
Minor .............. 3–3.9 ............ c. 130,000
Very minor ...... 2–2.9 ............. c. 1,300,000
Of which none are accurately predictable.