When an earthquake of magnitude 9.0 (Mw) occurred some 70 kilometres off the coast of Tohoku, Japan, in March 2011, it took the resulting mega tsunami less than 30 minutes to reach the mainland and cause mass destruction. Such was the force of the earthquake that the planet is estimated to have shifted on its axis by as much as 25cm. Here’s a rundown of how best to detect a mega-tsunami on the rise.
Deploy seismometers
“Tsunami warning systems typically rely on a network of seismographs to assess earthquake location, magnitude, depth and focal mechanism,” says Stuart Fraser, a tsunami and tsunami-evacuation researcher at Massey University, New Zealand. These systems notify local tsunami warning centres on registering an earthquake’s seismic vibrations. The centres then issue alerts.
Back these up with GPS
As well as a network of 200 seismographs and 600 of its own seismic intensity meters, the Japanese Meteorological Agency has an extensive network of over 1,000 GPS systems deployed across the Japan Trench. Seismographs can identify the main source of a quake’s origins and estimate its strength, but they are unable to produce rapid data sets for multiple plate ruptures — although GPS systems can.
Use local knowledge
“Warning systems are mostly triggered by detection of source quakes,” explains Simon Day, senior research associate of UCL’s Institute for Risk and Disaster Reduction. Should you feel a seismic shake, head inland and uphill. It’s advice reinforced by Fraser: “Feeling strong ground tremors when at the coast is your tsunami warning, and immediate evacuation is the best method of self-preservation.”
Condé Nast UK 2013