A B727 CREW; DSNDING INTO SEA OVERSHOT A STAR RESTR.

Narrative

FLT WAS CLRED TO 'DSND VIA THE OLM3 ARR;' BTG TRANSITION. APPROX 10 NM S OF THE OLM VOR; ATC ISSUED A VECTOR FOR US TO LEAVE THE ARR FOR TFC SEPARATION. ATC GAVE NO FURTHER ALT CLRNC WITH VECTOR INSTRUCTIONS. ATC THEN RECLRED US TO FLY DIRECT OLM VOR; OLM3 ARR; AND TO 'DSND VIA THE OLM3 ARR.' WE CROSSED ABEAM THE OLM VOR (THROUGH THE VOR'S 'ZONE OF CONFUSION') IN A NORMAL DSCNT PROFILE TO CROSS ARVAD INTXN AT 12000 FT MSL. CREW NOTED THAT WHILE TURNING ABEAM OLM VOR; WHILE REJOINING THE OLM3; THAT THE ACFT WAS BELOW THE XING ALT FOR A S LNDG AT SEA; OUR DEST; BUT WAS ON A DSCNT PROFILE TO CROSS ARVAD AT 12000 FT MSL. FLT CONTINUED FOR A NORMAL LNDG AT SEA. THIS OCCURRENCE SEEMED TO BE CAUSED BY A COORD PROB BTWN OURSELVES AND ATC IN REGARDS TO THE ALT CLRNC; COMPOUNDED BY THE TIMING OF THE VECTOR; INITIALIZATION OF THE DSCNT; AND THE PROX OF THE VOR. TO PREVENT A REOCCURRENCE: 1) WHEN BEING VECTORED OFF ANY STAR WITH NO SUBSEQUENT ALT CLRNC; FLC MUST QUERY ATC IMMEDIATELY FOR CLARIFICATION. 2) WHEN ISSUING A VECTOR TO AN AIRPLANE THAT IS FLYING A STAR AND IS CLRED TO 'DSND VIA THE...ARR;' ATC SHOULD ISSUE A NEW ALT CLRNC.