Keiiti Aki (安芸 敬一, Aki Keiichi, March 3, 1930 – May 17, 2005) was a Japanese-American professor of Geophysics at the Massachusetts Institute of Technology (MIT), and then at the University of Southern California (USC), seismologist, author and mentor.

He then did post-doctoral research at the Caltech Seismological Laboratory, where he worked with Frank Press.

This second visit to the United States coincided with the 1966 Parkfield earthquake, noteworthy for its so-called coda waves, reverberations of seismic energy due to multiple scattering from subsurface inhomogeneities.

In 1995, Aki moved to the seismically active island Réunion, east of Madagascar in the Indian Ocean, where he continued to work until his death there in 2005.

[3] He sustained an injury to his brain from a fall while walking in the street on May 13; he fell into a coma and died on May 17.