Seattle-based SEOmoz, the search engine optimization software provider headed by Rank Fishkin, said this morning that it has acquired Followerwonk, the Twitter analytics firm headed by Peter Bray. Financial terms of the buy were not disclosed. SEOmoz said it will use the buy to expand its current capabilities, and will make Followerwonk's tools free to its SEOMoz Pro Membership users. Fishkin said in the company's blog that it paid a "low 7 figures", between $1M and $4M for Followerwonk, including cash upfront, earnout, and SEOmoz stock. Followerwonk--which has been run out of Bray's home in Portland--will remain there, with possible plans for a full office in Portland. Followerwonk's software helps companies understand their Twitter followers and social relationships.