A C172 PLT RPTS LNDG ON THE PARALLEL TXWY AT MBL WHICH WAS THE ORIGINAL RWY.

Narrative

MY INITIAL INSTRUCTIONS WERE TO FLY TO MBL AND PICK UP AN OBSERVER TO ASSIST WITH FOREST FIRE DETECTION. HOWEVER; WHILE ENRTE I WAS DIVERTED TO A FIRE IN PROGRESS; WHICH I COVERED FOR ABOUT 30 MINS UNTIL RELIEVED BY ANOTHER ACFT; TO PICK MY OBSERVER. I FLEW TO MBL ENTERED A NORMAL L HAND PATTERN FOR RWY 9; LANDED AND TAXIED TO PICK UP MY OBSERVER. WHILE TAXIING OUT I NOTICED THAT I HAD TO CROSS THE 'RWY' I HAD LANDED ON TO GET TO THE REAL RWY WHICH PARALLELED THE TXWY. AT THE TIME OF THE INCIDENT THE ARPT HAD NO MOVING TFC AND FOR THE MOST PART MY ERROR WENT UNNOTICED. AFTER FLYING SEVERAL HOURS I RETURNED TO MBL AGAIN ENTERED THE SAME PATTERN AND TRIED TO FIGURE WHERE I WENT WRONG. THIS IS WHAT I NOTICED THAT MAY HAVE CONTRIBUTED TO THE PROB. THE TXWY WAS FORMERLY THE PRIMARY RWY FOR MBL; BUT HAD BEEN REPLACED WITH A NEW ONE WHICH NOW PARALLELS IT. ON THE APCH TO THE TXWY THERE IS AN OLD OVERRUN THAT EXTENDS TO THE W END OF THE TXWY WELL PAST THE BEGINNING OF THE NEW PRIMARY RWY. THE TXWY PREVIOUSLY SERVING AS A RWY ACTUALLY LOOKED LIKE A RWY ALTHOUGH THE WHITE MARKING HAD BEEN PAINTED BLACK. CONSIDERING THE VISIBILITY; TIME OF DAY (EARLY IN MY SHIFT) AND THE FACT THAT I HAVE BEEN TO THAT PARTICULAR ARPT MANY TIMES BEFORE; ALTHOUGH NONE RECENTLY; I CANNOT THINK OF A 'GOOD' EXCUSE FOR THIS TO HAPPEN. I AM SURE THE OVERRUN REACHED OUT AND GRABBED MY ATTENTION AND I JUST FOLLOWED IT IN. WHILE ADVISING MY SUPERIOR OF THE INCIDENT; HE INDICATED THAT HE RECENTLY LINED UP ON THE TXWY HIMSELF NOT TO LONG AGO; BUT DISCOVERED THE MISTAKE PRIOR TO LNDG. I AM THINKING THAT THE VISUAL CUES FOR THAT END OF THE APCH MAY BE CONFUSING. OBVIOUSLY; COMPLACENCY PAID A PART IN THE SIT AS WELL AS THAT I WAS LATE TO PICK UP MY OBSERVER.