That's the translation of her name into Chinese..
浜 is the Japanese simplification of the Chinese character 濱.
http://en.wikipedia.org/wiki/Kanji#O...lists_of_kanji
The 歩 character has not been changed from the Chinese original but Ayu uses the hiragana for her given name in Japan, in China/Taiwan/Hong Kong they use the Kanji.
The pronouncation of 濱崎歩 can be heard here
binxiu boo (not the correct pinyin but you should be able to point it out)