Narrative:

We were cleared from 9000 ft to 6000 ft by sfo approach control. Upon leveling at 6000 ft, we received a 'terrain, terrain' warning on the GPWS. We immediately climbed back up to 9000 ft and advised approach control of the warning we received and our intentions. Approach control advised us that we were overwater and there was no reason for the GPWS warning we had received. We continued to the airport and landed uneventfully. Supplemental information from acn 393061: after exiting the hold, we had descended from 9000 ft to 6000 ft given a west vector. On that westerly heading, we received 2 GPWS warnings for terrain. Captain called for an immediate climb/go around thrust. I simultaneously notified ATC.

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Original NASA ASRS Text

Title: A B757 DSNDING FROM 9000 FT TO 6000 FT RECEIVES A GPWS ALERT AND CLBS IMMEDIATELY BACK TO 9000 FT. ACFT WAS FLYING OVER THE OCEAN AT THE TIME AND TERRAIN WAS NOT A THREAT. ALL OF THIS UNDER CTL OF OAK, CA, TRACON.

Narrative: WE WERE CLRED FROM 9000 FT TO 6000 FT BY SFO APCH CTL. UPON LEVELING AT 6000 FT, WE RECEIVED A 'TERRAIN, TERRAIN' WARNING ON THE GPWS. WE IMMEDIATELY CLBED BACK UP TO 9000 FT AND ADVISED APCH CTL OF THE WARNING WE RECEIVED AND OUR INTENTIONS. APCH CTL ADVISED US THAT WE WERE OVERWATER AND THERE WAS NO REASON FOR THE GPWS WARNING WE HAD RECEIVED. WE CONTINUED TO THE ARPT AND LANDED UNEVENTFULLY. SUPPLEMENTAL INFO FROM ACN 393061: AFTER EXITING THE HOLD, WE HAD DSNDED FROM 9000 FT TO 6000 FT GIVEN A W VECTOR. ON THAT WESTERLY HEADING, WE RECEIVED 2 GPWS WARNINGS FOR TERRAIN. CAPT CALLED FOR AN IMMEDIATE CLB/GAR THRUST. I SIMULTANEOUSLY NOTIFIED ATC.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.