A technique that applies inversion theory to tsunamis has led to a new branch of seismology and a tool for studying earthquakes that have left records on tide gauges but not on seismographs.

For many years seismic waves have been used to piece together the complex tectonic motions of faults that create earthquakes. Now a Japanese seismologist has shown that the same methodology can be applied to tsunamis (Japanese for harbor wave), the powerful, sometimes catastrophic ocean waves that can result from submarine earthquakes. The method is potentially important because it is independent of seismic analysis and can be used to look at past earthquakes for which no seismic data are available.