A 5.3 magnitude seismic event, likely a nuclear test, has been detected approximately 10km from North Korea’s nuclear test site.

The event was recorded as taking place at a depth of zero kilometers by USGS and took place at 9.30AM Korean time, on the DPRK’s National Foundation Day, a public holiday.

“We detected a 5.0 magnitude man-made earthquake near North’s Punggye-ri … As a result of the investigation, we judge that the North conducted a nuclear test. But we are still investigating the material of nuclear test and success or failure. The yield of the test is 10 kilotons,” South Korea’s Ministry of National Defense said.

South Korean Prime Minister Hwang Kyo-ahn called for an emergency session of the National Security Council to discuss the probable test, South Korea’s Yonhap News Agency reported.

USGS classified the event as a possible explosion, but has not yet verified whether it the cause was a nuclear detonation.

Other geological and meteorological services reported the event at a magnitude of 5.3, including the European-Mediterranean Seismological Centre (EMSC), the Geophysical Survey of the Russian Academy of Sciences, and GEOFON of Germany.

South Korea’s Ministry of National Defense estimated the yield of the test at 10 kilotons and said it is the largest scale nuclear test the North has conducted so far, Yonhap reported.

North Korea has previously conducted nuclear tests in 2006, 2009, 2013, and 2016, with explosive yields of less than one kiloton, 2-4 kilotons, 6-9 kilotons, and 7-9 kilotons respectively.

Seismogram of today’s M5.3 explosion in North Korea compared to their nuclear test from 8 months ago. pic.twitter.com/SgtngDQ3Za — Andy Frassetto (@drrocks1982) September 9, 2016

South Korean President Park Geun-hye held an emergency phone call with U.S. President Obama, Yonhap News Agency reported. The two leaders were both attending the Asean Summit in Laos, however Park has now cut short the diplomatic visit and is returning to Seoul.

PREPARATIONS

Satellite imagery from August 27 analyzed by the 38 North website detected notable activity at all three portals of the Punggye-ri nuclear test site. The site said it wasn’t sure if the activity was related to maintenance of preparations for a fifth nuclear test.

News of the development comes after the North conducted a salvo of three Rodong mid-range ballistic missile launches on Monday.

North Korea last conducted a nuclear test on January 6, 2016, much to the surprise of international observers. Pyongyang made no warning of that test.

The last time more than one test took place in a year was in 1998, when Pakistan and India conducted a number of tests.

The United States government acknowledged the event and indicated they are evaluating the relevant information.

“We are aware of seismic activity on the Korean Peninsula in the vicinity of a known North Korean nuclear test site. We are monitoring and continuing to assess the situation in close coordination with our regional partners,” U.S. National Security Council spokesman Ned Price said.

Park Hyeong-jung, Senior Fellow from Korea Institute for National Unification (KINU), told NK News Friday that the North’s fifth nuclear test most was likely conducted with the nuclear warhead the North presented in state media in March.

During a recent conference held in Seoul, Park warned that “Pyongyang would have already decided on when to detonate their next nuclear bomb.”

“In March, Kim Jong Un ordered to perform the test with this warhead. The North has recently done a variety of missile launch tests, and it is most likely they have tested the warhead that can be loaded with the missiles.”

DETERMINED

The second test inside the span of a year indicates North Korea will press ahead with its nuclear programme in the face of international condemnation and a stricter sanctions regime.

“North Korea is determined to possess a nuclear deterrent that it believes, contrary to our sense of reality, is necessary to fend off US-directed regime change,” said Mark Fitzpatrick of the International Institute for Strategic Studies. “The irony is that the nuclear and missile tests give North Korea’s antagonists all the more reason to seek the end of the regime.”

“China, however, will continue to undermine sanctions that it sees as potentially contributing to such an outcome,” Fitzpatrick told NK News. “So the US and South Korea have no good options. They may begin to consider military options, which is just what the tests are designed to prevent.”

Fitzpatrick said that despite the national holiday, the test was likely not primarily for the domestic audience.

“I don’t think the fissures in the regime are so great that nuclear tests are necessary to overcome internal divisions,” said Fitzpatrick. “So I come back to the main purpose being deterrence-driven.”

The possible test could also be a way of signalling that the North Korean government are no longer sensitive to external political or sanctions considerations.

“North Korea is celebrating their national holiday and sending a message that the regime is strong and their weapons are not affected by outside pressure. (It is also telling) the world that development is proceeding and they have the capacity and the capability,” Chun In-bum, Lieutenant General (retired) in the ROK army told NK News.

The most recent test will once again place the spotlight on neighboring China. Many observers saw some movement from Beijing following the January test, but more recently doubts have arisen as to how far Chinese authorities were enforcing the newest UN Resolutions.

“While chagrined by the North’s action, the manner in which the Chinese express displeasure will be determined in part by their calculation of steps necessary to appease the feisty Americans. China’s emphasis on regional stability trumps U.S. and ROK calls for denuclearization of North Korea,” Keith Luse, Executive Director National Committee on North Korea said, speaking in a personal capacity.