Several simultaneous multicar crashes occurred Monday morning inside the northbound side of the Thomas P. O’Neill Jr. Tunnel, injuring one person and causing significant traffic delays. State Police responded to three crashes, involving 15 cars, inside the Interstate 93 tunnel at 7:52 a.m. One person involved in the first crash was taken to Massachusetts General Hospital with injuries not considered life-threatening, said State Trooper Todd Nolan. No other injuries were reported. The first crash involved nine cars in the left lane just inside the tunnel. Another four-car collision in the same lane occurred immediately after, followed by another two-car crash.