[Gideon7]

1.3 KT seems pretty low for a successful test.

[JPX2011]

I looked at that scale. I think it’s off. According to this 5.3 = 90KT

http://www.english.ucla.edu/all-faculty/335-kelly-kiloton-index-of-earthquake-moment-magnitudes

[Robert A Cook PE]

How many truck bombs is that 1300 KILOTONS of explosive equal to?

1.300 x 1000 = 1,300 TONS of explosives.
1300 x 2200 lbs/ton = 2,860,000 pounds of explosives ... = 72 tractor trailer rigs.

[Karl Spooner]

1.3 KT seems pretty low for a successful test.

I bet it doesn't seem that way to Japan. The North Koreans have been firing off missiles their way recently too.