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North Korea conducted its sixth and the largest nuclear test to date on September 3rd, 2017. The U.S. Geological Survey (USGS) reported it as a magnitude 6.3 explosion at the Punggye-ri test site, a mountainous region in the northeastern part of the country. The USGS preliminary epicenter location was (41.343N, 129.036E), at a substantial distance (~8 km) away from the tunnel entrance reportedly used for the nuclear tests (www.38north.org). Using seismic waves recorded at regional distances and by modeling waves scattered by surface topography, we determined the epicenter location at (41.309N, 129.067E), with an estimated uncertainty - approximated as one-standard deviation - of (0.4 km, 0.6 km, 0.53 km) in the longitude, latitude, and depth directions.
An one-page summary of the results can be downloaded here as a pdf file.