An earthquake of low magnitude but close to the surface recorded in New Caledonia

“It is therefore indeed a weak earthquake, a magnitude less than three on the Richter scale but very superficial, less than 20 kilometers below Nouméa” explains Olivier Monge, head of the geological department at DIMENC.

Here is the explanation to the multiple questions that remained since this Wednesday evening, November 13. As described by several Internet users on social networks, the shock felt was quite brief, of the order of a few seconds but widely felt in Nouméa, Dumbéa and Mont-Dore since “as of this morning, 25 testimonies have been recorded on the seisme.nc site” explains Olivier Monge.

If the feeling was very intense, Olivier Monge specifies that the movements of the ground remain weak, “around 1% of the value that could be considered for common seismic constructions.”

This event reminds us that there is indeed a seismicity specific to New Caledonia, less significant but closer than the powerful earthquakes of the Vanuatu trench.

Olivier Monge, head of the geological service at DIMENC

“As we are quite far away, particularly Grande Terre, we feel them but they are less worrying than nearby earthquakes which are smaller. Due to their proximity, they can generate strong seismic movements” he adds.

Below automatic detection threshold

If the earthquake of November 13 raised a lot of questions, it is because it was not immediately detected by global networks. “The trigger threshold for the text messages that the different departments concerned receive is set at three, so we didn't know it right away, we had to confirm.” explains Olivier Monge. He actually asked his colleagues at Victoria University in Wellington, New Zealand and those from Géoazur to analyze the phenomenon of this Wednesday evening.

Hence the need for the specialist to “have a network of local seismological stations” et “to have skills to analyze recordings.”