Kansai International Airport Osaka Japan: A sinking airport

Just arrived at Kansai International Airport from KLIA. A journey took 6 1/2 hours from KLIA, departed at 12am and reached osaka at 7am. Surprised to see a hairline crack on the floor of the airport due to 2 main reasons; i.e. settlement of the airport because the airport was built on the reclamation land; or possibly due to an earthquake. Japan island is an island arc that is a product of subduction zone between two lithospheric plates that collide with each other.