# Yanosuke Otsuka

Yanosuke Otsuka
Yanosuke Otsuka in c. 1940
Native name

Born11 July 1903
Died7 August 1950 (aged 47)
NationalityJapanese
Spouse(s)Chieko Otsuka (大塚千枝子)[1]
ChildrenYoshiyuki Otsuka (大塚義之)[1]
Natsuko Otsuka (大塚南津子)[1]
Scientific career
FieldsGeology
Yanosuke Otsuka
Japanese name
Hiraganaおおつかやのすけ
Kyūjitai大塚彌之助
Shinjitai大塚弥之助

Yanosuke Otsuka (Japanese: 大塚弥之助) (11 July 1903 – 7 August 1950) was a Japanese geologist and professor.[1][2]

Yanosuke Otsuka was born in Nihonbashi, Tokyo on 11 July 1903.[1][2] He went to the Junior High School attached to Tokyo Higher Normal School, and after that to Shizuoka High School.[2] For his undergraduate studies, he entered the Department of Geology, Faculty of Science, Imperial University of Tokyo, where he graduated in 1929.[2] While he was student, he learned the methods of historical geology from Yoshiaki Ozawa, topography from Taro Tsujimura (辻村太郎), and Cenozoic biological stratigraphy from Shigeyasu Tokunaga (徳永重康).[2] After graduation, he entered the Earthquake Research Institute as an assistant in 1930, becoming an associate professor in 1939 and a professor in 1943.[1] He made significant contributions in characterizing the surface faults in the circum-Pacific area, effects of tsunamis, tectonics of crustal movements, taxonomy of molluscs, paleoclimatology, mapping of Cenozoic strata, and the Tertiary history of the Japanese islands.[1][2] He died prematurely from pulmonary tuberculosis on 7 August 1950, at the age of 47, because effective antimicrobial therapy was not yet available in Japan at the time.[1]

In biology, he is known for the Otsuka similarity coefficient[3][4] (also known as Otsuka-Ochiai[5] or Ochiai coefficient[6]), which can be represented as:

${\displaystyle K={\frac {|A\cap B|}{\sqrt {|A|\times |B|}}}}$

Here, ${\displaystyle A}$ and ${\displaystyle B}$ are sets, and ${\displaystyle |A|}$ is the number of elements in ${\displaystyle A}$. If sets are represented as bit vectors, the Otsuka similarity coefficient can be seen to be the same as the cosine similarity.

## References

1. Sugimura, Arata (1992). "My two teachers: Katsumi Mochizuki and Yanosuke Otsuka" (PDF). Geology News (in Japanese). 455: 4–21.
2. Ōmori, Masae (2004). "Geological idea of Yanosuke Otuka, who built the foundation of neotectonics (geoscientist)". Earth Science (in Japanese). 58 (4): 256–259. doi:10.15080/agcjchikyukagaku.58.4_256.
3. ^ Otsuka, Yanosuke (1936). "The faunal character of the Japanese Pleistocene marine Mollusca, as evidence of the climate having become colder during the Pleistocene in Japan". Bulletin of the Biogeographical Society of Japan (in Japanese). 6 (16): 165–170.
4. ^ Hamai, Ikuso (1955). "Stratification of community by means of "community coefficient" (continued)". Japanese Journal of Ecology (in Japanese). 5 (1): 41–45. doi:10.18960/seitai.5.1_41.
5. ^ Ochiai, Akira (1957). "Zoogeographical studies on the soleoid fishes found in Japan and its neighhouring regions-II". Bulletin of the Japanese Society of Scientific Fisheries (in Japanese). 22 (9): 526–530. doi:10.2331/suisan.22.526.
6. ^ H. Charles Romesburg (1984). Cluster Analysis for Researchers. Belmont, California: Lifetime Learning Publications. p. 149.