Wednesday, May 27, 2009

North Korea nuclear test, like m=4.7 earthquake

Underground nuclear tests generate seismic waves like earthquake. Properties of the seismic waves generated by these two mechanisms allow these types of events to be distinguished.

The seismogram of this event to the right is from the BBC.

According to the U.S. Geological Survey:

The shallow, magnitude 4.7 seismic event that occurred on 25 May 2009 at 00:54:43 UTC is linked to the claim of a nuclear test by North Korean officials. While the USGS cannot positively identify the seismic event as a nuclear test, it was shallow and located in the vicinity of the 9 October 2006 North Korean nuclear test (magnitude 4.3). Moreover, comparison of the seismograms of the 9 October 2006 and 25 May 2009 events at individual seismic stations shows similar features, suggesting that the two events are in close spatial proximity and are the same type of source, although the more recent event is larger.

Location41.306°N, 129.029°E
Depth0 km (~0 mile) set by location program
Distances70 km (45 miles) NNW of Kimchaek, North Korea
95 km (60 miles) SW of Chongjin, North Korea
180 km (115 miles) SSW of Yanji, Jilin, China
375 km (235 miles) NE of PYONGYANG, North Korea
Location Uncertaintyhorizontal +/- 3.8 km (2.4 miles); depth fixed by location program
ParametersNST= 75, Nph= 75, Dmin=371.4 km, Rmss=0.57 sec, Gp= 72°,
M-type=body wave magnitude (Mb), Version=A

More on nuclear tests and seismic waves to come.

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