With the present knowledge of geophysics it is possible to discriminate between nukes and normal earthquakes.
https://www2.usgs.gov/faq/categories/9839/3338
http://seismo.berkeley.edu/blog/seismoblog.php/2009/05/25/of-nuclear-bombs-and-earthquakes
Let us see if this works:
South Korea, US to simulate attack on nuclear facility
http://edition.cnn.com/2016/09/20/asia/south-korea-us-nuclear-drills/
if not this http://www.freerepublic.com/focus/news/3467457/posts?page=15#15 will make it