Actually, Percy doesn't do earthquakes, interestingly enough. Earthquakes are mentioned throughout the books, but Percy isn't creating them. Annabeth mentions Poseidon being god of earthquakes in the Lightning thief, and in the Son of Neptune, Hazel tells Percy, that supposedly a son of Neptune destroyed the old Camp Jupiter, by earthquake in 1906.

And Oh yeah. House of Hades, abducting women since 400BC

"Earth-Shaker"

The reactions were very different across the room. Percy, Calypso, Piper and Hazel looked curious. Will and Leo looked exited. Reyna, Jason, Annabeth and Frank all looked horrified.

"She can't stay here!" Reyna announced. "She's putting the entire camp at risk! We're right on top of the San Andreas faultline!"

"Reyna, would I bring someone here, if they were a threat?" Nico pointed out.

Reyna looked between him and Hermione, noting how close they were standing.

"If you cared about them enough, yeah." Reyna countered.

Everyone looked uncomfortable at that.

"Look, Reyna," Hermione interjected "I can only make small localized quakes at the moment. In time, with training, I could be a threat, but I purposely haven't tried to build up strength. It would be too dangerous to attempt, in case I lost control and couldn't contain it. Honestly though, I think I could still be of benefit. I can't just provoke earthquakes, I can also hold them at bay. Plus, I have a lot of practice with protection- and concealment spells. I could probably cast them to cover the entire Camp, and New Rome."

Annabeth looked skeptical.

"Can you really do that?"

Hermione sighed. "I've had a lot of practice over this past year. I haven't done it on quite this scale before, but I'm confident in my abilities."

"I've been searching for her for a long time. Not even Hades could locate her!" Nico boasted.

"And the earthquakes? Can you really contain them?" Annabeth continued.

"Yes. About as well as I can create them."

"Could you do it better with training?"

"Probably. But you have to understand, that training this ability is dangerous. Earthquakes can destroy buildings, kill people, and cause tsunamis. Especially on top of a faultline. If I had to train, it would have to be somewhere remote, uninhabited and without risk of causing a tsunami, that could destroy a second location."

Calypso smirked. "I may, or may not know a location like that. Do you think we could find it again, Leo?"

Leo grinned maniacally. "I think Festus misses the air"

"The - the air?" Hermione blanched "but isn't the air, what got us in trouble in the first place?"

"Yeah! That just means it can't get any worse! Besides, Festus is a dragon made from Celestial Bronze. It perfectly safe. Well, almost safe."

Hermione looked about ready to throw up.

"Oh, come on, Hermione." Nico coaxed. "Didn't you tell me earlier that you flew on a real dragon? Leo is at least somewhat in control of Festus"

"That was different! I was escaping after a bank robbery. It was a life and death situation!" Hermione hissed.

"Wait a minute, you robbed a bank?" Percy and Leo asked simultaneously, Percy looking worried, Leo looking awed.

"Yes. But that's a story for another time. I'm just really not good with heights"

"We'll do everything to make sure that you're safe." Nico softly said, taking her hand. "I won't let anything happen to you."

Percy was feeling very uncomfortable. He still hadn't accepted her existence fully, but he was pretty sure, that Nico di Angelo was hitting on his little sister. That thought made him queasy.

"But what about Zeus?" Hermione tried.

"Well, that concealment-thingy, couldn't you just do that on Festus?" Leo pointed out.

Hermione sighed. "Fine." She caved in the end. "But not right away. I need to process a lot of stuff, and also, you, Blondie, I need that flyer. There's a telephone number on it, yes? Can anyone show me where to find a phone? I know it's a no-no, but I really need one. I'm sure they can't receive Iris-messages because of magical interference, but if this was distributed in muggle areas, they must have a hotline or something."

"Sorry, but we'll need to go outside for that. It's too risky attracting monsters here. We have protective barriers, sure, but it wouldn't be good if new campers got stuck in a traffic jam of monsters."

"Actually, I have something" Leo interrupted "It's just a prototype, but I've been working on this gadget with Harley. It's based off a beacon he made with Apollo a couple of years ago. It can be used as a cell-phone. Try it out"

Leo threw her a beat up old Nokia 3310. She looked at it skeptically. "It was the only model that could take the abuse." He explained sheepishly.

"Um. I'll just go outside then. You should probably go get some rest Ghost King. You look dead on your feet!" She yelled over her shoulder as she walked out.

Nico rolled his eyes exasperatedly "Ha ha." But his mouth twitched.

"You should listen to her." Will said with a smirk.

Nico hung his head and went out, looking for a place to sleep. This left ten very confused demigods in the principia, trying to process what was going on.

"We still didn't discuss what we're actually going to do." Jason said, shaking his head.

"Who cares," Leo replied. "Watching those two is great entertainment!" Leo replied.

Percy just looked nauseous.