Seismic Intensity, Seismic Scale
The earthquake degrees is how you measure an earthquake. The 震度 is the earthquake intensity, AKA earthquake magnitude, seismic intensity, or seismic scale.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
The seismic intensity was three, but it felt quite strong.
What’s the difference between magnitude and seismic scale?
They say the aftershocks from the 2011 Tohoku Earthquake hit a magnitude of seven, and that they'll continue for the next hundred years, even the big ones.