Volcano City by Grace Bridges

SPFBO9

New Zealand's largest city. Forty-nine volcanoes. What's one more? Auckland is built on volcanoes and has more ocean coastline than any other city in the world. For Anira, a reluctant and forgetful superhero, it's home. Away from the thermal springs and legendary creatures of Rotorua, Anira's supernatural brainpower and memory have faded. She's forgotten the events of summer and even the friends who became the Earthcore team. Tiger, Graeme and Bethany come to the big city too, each unsettled in their own way.

But their maniacal opponent has arrived in Auckland, wielding mind control and bent on revenge, terrorism and profit. When the earth becomes restless from his meddling, Anira must fight to remember her gifts, to bring the team together again, figure out shenanigans at sea, and to call the ancient taniwha to help protect her hometown from a disastrous eruption.

In the Earthcore series, every book is a self-contained adventure and can be read as a standalone.

Earthcore Book 3: Aftershocks by Grace Bridges

SPFBO6

They saved a town with the help of the creatures that command the geysers. They saved a city from volcanic eruption. Surely they've earned a break? Tell that to the Titanosaur. Now the faultline network is active, threatening all of central New Zealand with aftershocks that might be bigger than the initial event. Amateur geologist Anira Fraser is in Picton, facing her final high school athletics competition. Along with her friend Tiger McRae, she realises their presence is disturbing the area's guardian spirits. Soon other Earthcore members arrive in town and discover an old enemy stirring up fresh trouble, while the locals hint at the legend of a mysterious taniwha war that could worsen the series of quakes. It's up to Anira and the Earthcore team to find the cause of the war and end it--otherwise they themselves could be responsible for a cataclysmic natural disaster.