A B737 PLT RPTS WAKE TURBULENCE AT FL230 10 NM IN TRAIL OF A B757.

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WE WERE HELD IN POSITION FOR TAKEOFF ON RWY 7L BEHIND A DEPARTING B757 DUE TO WAKE TURB. AFTER APPROPRIATE DELAY WE RECEIVED TKOF CLRNC AND DEPARTED. INITIAL CLB WAS NORMAL; HOWEVER CLBING THROUGH APPROX 23000 FT WE ENCOUNTERED WAKE TURBULENCE OF MODERATE INTENSITY. ACFT ROLLED TO THE R AND I DISCONNECTED THE AUTOPLT AND AUTOTHROTTLE AND PITCHED DOWN AND CONTINUED THE TURN TO THE R IN AN ATTEMPT TO EXIT THE VORTEX. ENCOUNTER LASTED APPROX 3 SECONDS. AFTER WE CLEARED THE TURB WE INFORMED ATC OF THE ENCOUNTER AND ASKED FOR THE POSITION OF THE B757. THEY RPTED HE WAS 10 MILES AHEAD OF US. WE SPOKE WITH THE CABIN CREW TO ENSURE THERE WERE NO INJURIES AND THEY RPTED ALL IN CABIN WERE OK. I MADE AN ANNOUNCEMENT TO THE PAX AND WE PROCEEDED UNEVENTFULLY. ATC DID NOT PROVIDE ADEQUATE SPACING OR INFORM US OF THE B757'S POSITION. I BELIEVE IN TRAIL SPACING SHOULD BE RE-EVALUATED FOR WAKE TURBULENCE BEHIND HEAVY/LARGER ACFT. THIS IS THE THIRD TIME I HAVE ENCOUNTERED WAKE TURB BEHIND A B757 DURING CLB AND ON ONE OCCASION WE WERE 17 MILES IN TRAIL AND INJURIES TO A CABIN CREW MEMBER RESULTED. THESE ENCOUNTERS ALWAYS PRESENT A RISK OF INJURY.