[2] Omori became chair of seismology at the university and secretary of the Imperial Earthquake Investigation Committee following Sekya's death on 9 January 1896.

[6] On 28 October 1891 Mino and Owari provinces were devastated by earthquakes; their fault lines were traced by Bunjiro Koto (1856–1935), another professor at Imperial University.

He ascribed the high number of casualties due to structure collapse of the dominant local building type: sun-dried brick walls loosely cemented with mud and overlaid by heavy roof beams.

[10] Previously, in 1889 Omori had worked with John Milne to record experiments carried out at the Engineering college at the University of Tokyo to investigate the overturning and fracturing of brick and other columns by horizontally applied motion.

For many years the modernization of Japan during the Meiji Restoration, through replacement of traditional light wooden structures resting on boulders, with red brick buildings and iron bridges, had been a major source of concern or Milne.

[19] At least two authors state that Omori and colleagues were attacked on Mission Street, San Francisco by a gang of men and youths who were later hailed by the local press for their anti-Japanese racist stoning and slugging of random Japanese men,[20][21] however contemporary sources indicate that one boy involved in the stoning of Dr. Omori worked for the Post Office as a messenger was fired by Postmaster Fisk of San Francisco when the Japanese Association of America protested.

[22] Other incidents alleged in a letter to the newspaper[23] are unreferenced by any other sources, and Omori himself chose to forgive writing, "referring to some trouble I had with hoodlums in San Francisco.

[16] Omori seismographs were rapidly installed all over northern California, and a list of aftershocks to the San Francisco earthquake was compiled and published.

[1] After meeting Thomas Jaggar of the Massachusetts Institute of Technology who was planning a volcanic observatory on the Big Island of Hawaii, Omori designed the foundations and seismograph emplacement for the Whitney Laboratory of Seismology, building 29 near Volcano House, now part of the Hawaiian Volcano Observatory,[30] state historic site 10-52-5506 and National Register of Historic Places site 74000292, added 24 July 1974.

[33] In fall 1923 Omori attended the Second Pan-Pacific Science Congress in Australia, where he and Edward Pigot, the director of the observatory at Riverview College in Sydney, Australia observed a seismograph recording the major great Kantō earthquake which destroyed Yokohama and Tokyo on 1 September 1923, killing about 140,000 and leaving 1.9 million people homeless.

Shortly thereafter, he was diagnosed with a brain tumor[35] and entered the university hospital where he received the Order of the Sacred Treasure from the Imperial Court a few days before his death at age 55 on 8 November 1923.