Earthquake
noun
An earth earthquake is just another way to say earthquake.
じしん
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. Notice that 地 is read as じ instead of ち. You've seen this happen a few times before, so just try to remember that this is the case here.
最近、地震、多いよね。昨日もでしょ？
There have been a lot of earthquakes lately, haven't there? Yesterday too, right?
人工地震って、本当にあると思いますか？
Do you think man-made earthquakes really exist?
東日本大震災はでは、マグニチュード9の大地震が起こりました。
The Great East Japan Earthquake was a massive magnitude 9.0 earthquake.