"Omori's law" regarding the aftershock rate of earthquakes was developed by this pioneering Japanese seismologist, the second chairman of seismology at the Imperial University of Tokyo who conducted much critical early research on the cause and prediction of earthquakes and invented one of the first seismographs; he did much research in northern California after the 1906 San Francisco earthquake. Item #43270
Rare signature in Japanese, heavy stock 2¼" X 3" card, n.p., n.y. Very good. Lightly age toned. Three vertical lines in brown penned, of course, in Japanese characters, read (in translation: "Fusakichi Omori, Doctor of Physical Science / Professor, College of Science / Tokyo Imperial University." On the verso, an unknown hand explains: "F. Omori, Sc.D., / Professor of / Seismology, Tokyo / Imperial University." Although pure conjecture, as this item is not dated, it was most likely signed while he toured California for 80 days following the San Francisco earthquake in 1906. Omori died at age 55 and his signature is extremely scarce.