The future big ones

[The_Magical_Unicorn]

Hello eveyone,

I heard several times that majors earthquakes will probably hit big cities in the following decades, such as Los Angeles, Istanbul or Tokyo
Do you have scientific information on these? And are they other citites/countries that might be heavily struck in the following decades?
Just so I know if I ever want to live in these places!

Is there, to your knowledge, a program in these places to raise awareness among the population on the seismic risk?

Best

[SismoLaure]

That’s a lot of a great questions !
Yes we’ve all heard about “big ones”. The most famous is probably “the Big One” that is expected in California, and which inspired the movie San Andreas.
To date, seismologists cannot predict earthquakes, so we’re not able to say when exactly and how strongly these earthquakes will occur. However, scientists can estimate the probability of experiencing a seismic event in a specific area within a time window. This is what seismologists call a probabilistic earthquake forecast.
Indeed, in Los Angeles for instance seismologists working at the USGS have estimated that the risk of a big earthquake is high… but we don’t know enough to be able to say when precisely it will occur.

This is why it’s so important to get prepared !!

[Laurosaurus]

And in these areas, people should also beware of small earthquakes according to this last piece in tremblor : The Central San Andreas creeps along without a major earthquake - Temblor.net

[Laurent_88]

I found an example of “big one” research related to earthquakes in Haiti.
After the devastating January 12th 2012 earthquake, many asked if that was “the Big One”… and if so, if that meant a smaller risk of big earthquake in the following years.

Eric Calais, researcher specialised in Seismic risk in Haiti brings the following answer:

Citation Le séisme du 12 janvier 2010 a libéré peu d’énergie sismique — ce n’était pas le “big one”, qui est toujours attendu en Haiti…

Un des questions que l’on pose souvent — avec raison — concernant le séisme du 12 janvier 2010 est si son occurrence nous permet maintenant de “dormir sur nos deux oreilles” pendant un certain temps. En effet, si un séisme libère l’énergie élastique qui s’accumule au voisinage d’une faille, on pourrait alors penser qu’il faut des dizaines d’années pour accumuler à nouveau cette énergie “perdue”. Pendant ce temps, sommes-nous à l’abri?
Ce raisonnement simple n’est cependant pas tout à fait exact. En effet, les failles de la Presqu’Ile du Sud d’Haiti — celles qui la traversent et celles qui la jalonnent en mer au sud et surtout au nord — représentent plusieurs centaines de kilomètres de rupture potentielle. Or seulement 20 kilomètres ont rompu le 12 janvier 2010 — il reste donc des longueurs de faille importantes qui ont toujours, aujourd’hui, la capacité de générer des séismes de magnitude 7 ou plus. En d’autres termes, le séisme du 12 janvier 2010 avait une magnitude relativement modérée, insuffisante pour libérer l’énergie élastique accumulée depuis le 18ème siècle sur l’ensemble des failles de la Presqu’Ile du Sud.

Par ailleurs, la faille responsable du séisme du 12 janvier 2010 n’était pas celle bien connue de la Presqu’Ile du Sud (dite aussi d’Enriquillo), mais une faille jusqu’alors inconnue, la faille de Léogâne. Il est fréquent qu’un séisme ait lieu sur une faille “secondaire” comme celle de Léogâne. Un bon exemple en est le séisme de Loma Prieta qui frappa le sud de San Francisco en 1989 et dont la source était une faille proche — mais différente — de la grande faille de San Andréas qui marque pourtant la frontière entre les grandes plaques tectoniques Pacifique et Amérique du Nord.

Enfin, même si l’on parle beaucoup de la faille de la Presqu’Ile du Sud (ou d’Enriquillo) car elle apparait clairement dans la topographie depuis Tiburon à l’ouest jusqu’à Pétionville à l’est, de nombreuses autres failles ont été identifiées dont le potentiel sismique est avéré. C’est par exemple le cas de la faille des Trois Baies, qui se trouve en mer au large de Petit Goave. D’autres failles sous-marines sont connues qui longent la côte nord de la presqu’Ile du Sud. Des recherches en cours visent à déterminer leur capacité à générer des séismes futurs

On retient donc que de nombreuses failles capables de générer des séismes équivalents à celui du 12 janvier 2010 existent dans le sud du pays. La faille de la Presqu’Ile du sud (ou d’Enriquillo) est un candidat sérieux à des séismes futurs — peut-être à un “big one” — mais d’autres plus petites existent qui sont elles aussi capables de séismes importants.”

@The_Magical_Unicorn in case you wanted to live in Haiti I hope this helps !

(source;Le risque sismique en Haiti, expliquez-moi! | Sismologie Citoyenne en Haiti)

[Laurent_88]

And for the translation:
One of the questions often asked - and rightly - about the January 12, 2010 earthquake is whether its occurrence now allows us to “sleep soundly” for a period of time. Indeed, if an earthquake releases the elastic energy that accumulates in the vicinity of a fault, then one might think that it takes tens of years to accumulate this “lost” energy again. Meanwhile, are we safe?
This simple reasoning is not entirely correct, however. Indeed, the faults of the Southern Peninsula of Haiti - those which cross it and those which mark it out at sea to the south and especially to the north - represent several hundred kilometers of potential rupture. However, only 20 kilometers broke on January 12, 2010 - so there are still significant fault lengths which still have the capacity to generate earthquakes of magnitude 7 or greater today. In other words, the earthquake of January 12, 2010 was of a relatively moderate magnitude, insufficient to release the elastic energy accumulated since the 18th century on all of the faults of the Southern Peninsula.

Furthermore, the fault responsible for the earthquake of January 12, 2010 was not the well-known one in the Southern Peninsula (also known as Enriquillo), but a hitherto unknown fault, the Léogâne fault. It is common for an earthquake to occur on a “secondary” fault such as the Léogâne one. A good example of this is the Loma Prieta earthquake which struck southern San Francisco in 1989 and whose source was a fault close to - but different - from the great San Andréas fault which nevertheless marks the border between the large Pacific and Pacific tectonic plates. North America.

Finally, even if we talk a lot about the fault of the Southern Peninsula (or Enriquillo) because it appears clearly in the topography from Tiburon in the west to Pétionville in the east, many others faults have been identified with proven seismic potential. This is the case, for example, with the Trois Baies fault, which is located at sea off Petit Goave. Other submarine faults are known to run along the northern coast of the Southern Peninsula. Ongoing research aims to determine their ability to generate future earthquakes

We therefore retain that many faults capable of generating earthquakes equivalent to that of January 12, 2010 exist in the south of the country. The Southern Peninsula (or Enriquillo) fault is a serious candidate for future earthquakes - perhaps a “big one” - but other smaller ones exist which are also capable of large earthquakes. ”