NO, earthquakes cannot be predicted!
It is currently not possible to predict earthquakes because they result from the combination of geological and physical factors that are unknown or poorly-known to scientists. Also, most earthquakes occur at significant depth (tens of kilometers) inside the Earth’s crust, so that their monitoring in situ is quasi-impossible, contrary to meteorological phenomena, for instance. The study of earthquakes must therefore rely on indirect observations from instruments placed at the surface of the Earth or on small-scale laboratory experiments.
Scientists can, however, assess the amount of shaking that may occur within seismic areas, with a given probability and over a given time interval. Such calculations require a good knowledge of history of past earthquakes, the current movements of tectonic plates, and the local geology. This leads to the production of so-called “seismic hazard maps“, such as the one below for Haiti, published in 2011. These products are highly technical, but provide invaluable information to architects and engineers for the design and dimensioning of buildings and infrastructures that are earthquake-safe.
In summary, the timing, location, and magnitude of earthquakes are unpredictable. Earthquakes can occur at any time, without warning, even in areas that have not had earthquakes for hundreds of years. The only useful protection measures to minimize human and economic losses are to (1) build properly, (2) be prepared, (3) have a contingency plan in place.
The emergence of “earthquake early warning”
The recent years have seen the emergence of early warning systems for earthquakes, currently implemented in places such as Japan, Mexico, or California. These systems use an array of seismometers to detect the primary waves (P-waves) emitted by an earthquake as it starts. The P-waves are faster, and milder, than the secondary waves (S-waves) that cause most of the shaking. By detecting these initial waves and analyzing their characteristics, early warning systems can detect earthquakes as soon as they occurs, and estimate their location and magnitude.
Once an earthquake is detected, the system sends out a warning to people in areas that are likely to be affected by the shaking, as the seismic waves – the shaking – propagate away from the epicenter. The warning information uses communication channels such as mobile phones, radios, and sirens. This can give people a few seconds to several minutes of warning before the shaking arrives, allowing them to take protective actions, such as drop, cover, and hold on, or evacuate buildings or areas.
While early warning systems can provide valuable time for people to prepare for earthquake shaking, they rely on an extremely reliable seismic arrays and communication systems, and have limitations in terms of accuracy and effectiveness. The warning time may be short in some cases, and the system may not be able to detect all earthquakes or predict the shaking accurately. Therefore, it is essential to combine early warning systems with other measures, such as preparedness planning and earthquake-safe infrastructure, to minimize the impact of earthquakes.
