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Do nuclear bomb tests cause earthquakes?

Apart from escalating global fears about conflict, North Korea’s recent nuclear tests have raised questions about geological events caused by underground explosions.

Some media reports suggest the tests triggered earthquakes in South Korea. Others report the explosions may trigger a volcanic eruption at Paektu Mountain, about 100km from the test site.

So can an underground test cause an earthquake? The short answer is yes: a nuclear explosion can cause small earthquakes. But it is unlikely to affect the earth’s tectonic plates or cause a volcanic eruption.

Although a nuclear explosion releases a lot of energy in the immediate region, the amount of energy is small compared to other stresses on tectonic plates………

Earthquakes from nuclear testing

The 3 September 2017 North Korean nuclear test generated shock waves equivalent to a magnitude 6.3 earthquake. Eight minutes later, a magnitude 4.1 event was detected at the same site. This may have been linked to a collapse of a tunnel related to the blast.

Several small earthquakes measured since the event may have been induced by the nuclear test, but the largest is only a magnitude 3.6. An earthquake of this size would not be felt outside of the immediate area.

The largest induced earthquake ever measured from nuclear testing was a magnitude 4.9 in the Soviet Union. An earthquake of this size can cause damage locally but does not affect the full thickness of the earth’s crust. This means it would not have any effect on the movement of tectonic plates.

Historical data from nuclear testing (mostly in the USA) shows that earthquakes associated with nuclear testing typically occur when the explosion itself measures greater than magnitude 5, 10–70 days after the tests, at depths of less than 5km, and closer than around 15km to the explosion site. More recent studies have concluded that nuclear tests are unlikely to induce earthquakes more than about 50km from the test site……..

Monitoring nuclear tests

The Comprehensive Nuclear Test Ban Treaty Organisation (CTBTO) has a global monitoring system to detect nuclear tests, including seismometers to measure the shock waves from the blast and other technologies.

Seismologists can analyse the seismic data to determine if the shock waves were from a naturally occurring earthquake or a nuclear blast. Shock waves from nuclear blasts have different properties to those from naturally occurring earthquakes.

Testing was much more common before the CTBTO was formed: between 1945 and 1996 more than 2,000 nuclear tests were conducted worldwide, including 1,032 by the USA and 715 by the Soviet Union.

Since 1996 only three countries have tested nuclear devices: India, Pakistan and North Korea. North Korea has conducted six underground nuclear tests at the same site between 2006 and 2017. https://theconversation.com/ive-always-wondered-do-nuclear-tests-affect-tectonic-plates-and-cause-earthquakes-or-volcanic-eruptions-86915

November 8, 2017 - Posted by Christina Macpherson | 2 WORLD, environment, North Korea, safety