Source: Nature

A recent study published in the respected scientific journal Nature has been covered by some news media outlets as a prediction of an earthquake that rattled Guanacaste and all of Costa Rica in 2012. The September 5^th earthquake will always be remembered as a significant event with regard to earthquake preparedness and anticipation, but it is important to note the difference between forecasts and predictions.

Earthquake prediction is not exactly a pseudo science, but it is a problematic field of study. In the immortal words of seismologist Charles Francis Richter, creator of the widely used magnitude scale for seismic events:

“Bah, no one but fools and charlatans try to predict earthquakes!”

It may be a matter of semantics, and Wikipedia has a reasonable explanation:

The prediction of earthquakes is plagued from the outset by two problems: the definition of “prediction”, and the definition of “earthquake”. This might seem trivial, especially of the latter: it would seem that the ground shakes, or it doesn’t. But in seismically active areas the ground frequently shakes. Just not hard enough for most people to notice.

[…] such a constant drumbeat of earthquakes various kinds of chicanery can be used to deceptively claim “predictions” that appear more successful than is truly the case.

With the foregoing in mind, the Nature Geoscience Letter that has been reported in some media circles as an earthquake prediction (although it can be hardly called a prediction more than a year after the fact) actually provides an interesting look at the clever geodesic analysis performed by the Costa Rica Observatory of Seismology and Volcanology (Spanish acronym: OVSICORI):

Land-based Global Positioning System (GPS) and seismic measurements revealed a region where the plate interface was locked and hence accumulated seismic strain that could be released in future earthquakes.

Over the last few years, people in Costa Rica have grown accustomed to seeing OVSICORI scientists in the news describe how Nicoya was due for a major release of tectonic energy (the accumulated seismic strain described above). They never issued any predictions, they merely stated that their observations indicated that Guanacaste was due for the big one.

Based on the OVSICORI models, officials in Costa Rica took adequate measures. The seismic building code was enforced across Guanacaste and disaster management and recovery efforts were strengthened. After the 7.6 magnitude earthquake, observers were amazed at how little damage was experienced in the region. Once again, the scientific method triumphed in Costa Rica, and research in this field will continue:

By pairing observations of the spatial extent of interseismic locking and subsequent coseismic rupture, we demonstrate the use of detailed near-field geodetic investigations during the late interseismic period for identifying future earthquake potential.