Anyone know what this anime is called?

Okay so I watched this anime a couple years ago, I don't remember where. Anyway the main characters were on like a spaceship but it was like earth. It had normal citizens living normal lives in this big city.
It was a romance I guess where the girl was a normal citizen and the guy was a programmer/maintenance guy for the ship (they were both teenagers).
The only scene I remember was that they were talking (I think it was on a balcony hoặc something). There was like an earthquake and the ground opened up in the đường phố, street below the balcony and people started falling into it. Somehow (I don't remember how) the girl and the guy got below and tried to help the people who had fallen into the hole.
There was an aftershock and the girl fell into the gorge the guy rushed to try and help her (she was still holding onto the side of the ravine) when he got a call from headquarters telling him that he was needed there
That's all I remember. Anyone know what it is called?