A former director of the Seismological Laboratory at Caltech, Hiroo Kanamori is widely known as a leading authority on earthquakes. He devised the moment magnitude scale for determining the magnitudes of very large earthquakes based on the amount of energy they release. The method accounted for the effect of seismic waves with very long periods that were not accounted for by the Richter magnitude scale. The improved method gave scientists a better means of studying and analyzing seismic events.

Kanamori has also studied tsunamis, exploring the relationship between ground motion and generation of giant sea waves. These tsunami earthquakes release most of their energy in very long-period seismic waves that do not necessarily cause precipitous shaking, but can nonetheless create huge-and potentially devastating-ocean waves.

Kanamori designs and advocates for automated early warning systems to protect people when a seismic event has occurred that could result in a tsunami or an urban disaster. He helped develop the algorithm used to predict the severity of an earthquake and trigger warning systems before shaking reaches urban centers at a distance from the epicenter. He is currently working on ways to estimate the magnitude of earthquakes based on P-wave signatures, which will improve earthquake early warning systems, as P-waves travel faster than the more damaging S-waves and Love waves.