It is not often that science can answer questions with an easy "yes" or "no". Usually, it is a kind of "evidence suggests" or "this correlation proposes" a kind of situation, even if the general public's understanding is a little less nuanced. Then the USGS seismologist Susan Hough found the right question.
Image: Dean Hochman / Flickr
"Are large global earthquakes (magnitude ≥ 8) occurring on preferred days of the calendar year or lunar cycle?"
And his summary, recently published in Seismological Investigation Letters reflected it:
Image: Susan Hough, SRL (2018)
This was not the first time that a research question was answered related to an earthquake with a single word. Another article from 1974 posed a similar question, basically, if earthquakes happen at random in time, and they answered "yes". In this case, the evidence suggests something similar: earthquakes do not occur on the preferred days of the year, solar or lunar.
"That was the point of the exercise, in fact: to boil the lunar / tidal shot to the questions that most people think of," Hough told Gizmodo in an email. "Once it became clear that there is no evidence of a significant correlation, the summary wrote to itself =)"
However, the work itself has more nuances than a simple yes or no. Hough does not really refute a relationship between the moon, the tides and the great earthquakes. She refers to some rigorous studies that, in fact, have shown a link between the moon and the powerful tremors with specific failures or different data sets.
Instead, she's looking to do something more useful for the general public: ease concerns that the moon phase is something you need to worry about when it comes to earthquakes (as we suggested).
So she analyzed the world catalog of earthquakes from 1600 until now, recording the day and the lunar phase of large earthquakes to see if there were groups of earthquakes around certain dates or phases. There was not.
Work is not cut and dried alone, and still leaves the possibility that large earthquake rates "fluctuate systematically but weakly with the lunar date". It's just that there's not enough earthquake data to show a link. "What we really have to do is wait 4,000 years and do the exercise again." Lacking that, there are more sophisticated statistical tests than one could do, but in the end, the catalog is the catalog, and smart statistics are not going to overcome that limitation. "
Hough's summary is not the first delineator. There has been one with respect to neutrinos faster than light (which do not exist, as far as we can tell), a completely empty summary for a 1974 article on the writer's block, and the 1974 article by Gardner and Knopoff that I mentioned earlier. Many people are talking about these documents now in social networks.
So, science can come with yes or no answers, but this requires asking the right question. There may be some link between tides and large earthquakes, but there is definitely no correlation between calendar dates and large earthquakes today, based only on the last 400 years of data, given the correct restrictions.
In the final reflection, Hough said Gizmodo says that when science intersects with public concern, it can lead to a disconnection. "Scientists today ask complex questions and often get complex answers," he wrote. "The documents I referred to were careful in saying that the modulation of the tides is subtle and of no practical use for prediction, but I think we should do a better job explaining science, focusing on the things that people do. it matters. "
[SRLvia Twitter of Alexandra Witze ]