The Comprehensive Nuclear Test Ban Treaty Technical Issues for the United States (2012) / Chapter Skim
Currently Skimming:
APPENDIX D Monitoring Areas of High Interest
APPENDIX D Monitoring Areas of High Interest
Pages 139-160
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 139... ...
Seismic sensitivity to nuclear explosions has improved significantly due to increased deployment of seismometers and improved data analysis. For locations of interest, this allows regional monitoring at distances less than about 1,600 km (1,000 miles)
|
From page 140... ...
Particularly important is the availability today of data from seismic stations throughout the Middle East, North Africa, Russia, Kazakhstan, Mongolia, China and South Korea. Access to these regions permits countries of special concern to the United States to be monitored at much closer distances and thus down to events of much smaller size.
|
From page 141... ...
From 1949 to 1989, at which time the Semipalatinsk test site was closed (Adushkin and Leith, 2001) , eastern Kazakhstan was the primary location for Soviet nuclear tests.
|
From page 142... ...
Overlapping red stars show the locations of past nuclear tests since 1977, including the last test on October 24, 1990. Seismic events from 1999 to 2009 with magnitude greater than 2.0 from the Norwegian organization NORSAR reviewed regional bulletin are shown as blue circles.2 IMS primary stations (triangles)
|
From page 143... ...
. Noise levels and spikes of energy received from earthquakes during that day (in the azimuthal beam focused on the test site at Novaya Zemlya)
|
From page 144... ...
monitoring for seismic events from Novaya Zemlya for 24 hours on February 9, 1998. SOURCE: Kværna et al., 2002 For well-coupled nuclear explosions at the main Russian test site at Novaya Zemlya, magnitude = 4.3 + B log Y (where Y is yield in kilotons)
|
From page 145... ...
The 90 percent confidence limit for location of one of these, a magnitude 2.7 earthquake in 1992, included the test site. This event, events in the Kara Sea in 1986 and 1997, and two on the north island of Novaya Zemlya in 1995 and 1996 were claimed in the media to be either Russian nuclear tests or possible tests.
|
From page 146... ...
Monitoring the Chinese Test Site at Lop Nor China conducted all of its nuclear tests near Lop Nor in the sparsely populated northwestern part of the country. China stopped testing in 1996 just prior to signing the CTBT.
|
From page 147... ...
Many other seismic stations at greater distances also recorded past Chinese nuclear explosions. Lop Nor is located near the southeastern side of the Tien Shan, a region of moderate earthquake activity and contemporary horizontal compressive stress in the earth's crust, which proves to be of significance in the discrimination of earthquakes from nuclear explosions in that region.
|
From page 148... ...
of Lop Nor test site. Known nuclear explosions (triangles, with full amplitude range marked in pink)
|
From page 149... ...
SOURCE: Adapted from Sykes and Nettles, 2009 Figure D-8 shows seismic events located near the Lop Nor test site in the Reviewed Event Bulletin of the CTBTO IDC in Vienna. The four CMT solutions, shown as colored "beach balls," indicate that those events were earthquakes.
|
From page 150... ...
Summary Seismic monitoring of the Chinese test site at Lop Nor during the past decade has improved greatly with the availability of data from stations and seismic arrays in many surrounding and nearby countries. This has permitted smaller events to be located and highfrequency techniques to be used for identification of an event as being either an earthquake or an underground explosion.
|
From page 151... ...
On average, North Korea has a natural earthquake over magnitude 4 only once every few years, so the nuclear tests stood out as unusual, just because of their location and size. There are several IMS primary and auxiliary seismic stations within 1,200 km (750 mi)
|
From page 152... ...
and stations in the vicinity of North Korea. The seismic locations of the 2006 and 2009 North Korean declared nuclear tests are shown by overlapping red stars.
|
From page 153... ...
FIGURE D-10: Example showing how ratios of P-wave to S-wave amplitudes discriminate the 2006 and 2009 nuclear tests in North Korea (red seismogram represents data from the 2006 test, and stars on the right indicate 2006 and 2009 test data) from earthquakes in the region (blue seismograms and symbols)
|
From page 154... ...
. One result the two North Korean tests made very clear is that if multiple nuclear tests occur in the same region, then relative methods of detection, location, discrimination, and yield estimation can be brought to bear on the verification problem.
|
From page 155... ...
Compared with the North Korean region shown in Figure D-9, the broad Middle East and Southwest Asia region shown below has about twenty times as many earthquakes per year. Whereas North Korea has a magnitude 4 earthquake only every few years, Iran has a magnitude 4 earthquake on average once a week.
|
From page 156... ...
The structural complications also degrade the location accuracy of seismic events and explosion identification unless they are accounted for. For these reasons, the Middle East has been the focus of much seismic research and development effort aimed at using the large number of earthquakes to calibrate the region.
|
From page 157... ...
Identification of explosions in the Middle East and Southwest Asia can be accomplished by the usual methods of Ms-mb, depth, moment tensor analysis, and regional high frequency P/S ratios. For example in Figure D-12, the May 11, 1998, Indian nuclear test (shown in red)
|
From page 158... ...
for many earthquakes all over the region are compared and after correcting for the path effects, the explosion (red star) stands out and is discriminated from all the earthquakes (blue circles)
|
From page 159... ...
By taking advantage of the many previous earthquakes recorded at the many tens of available seismic stations deployed for earthquake hazard purposes, we can map out these path effects and correct for them using tomographic methods. The result, as shown in Figure D-12, is the ability to quickly identify explosions using their individual regional seismic signals in a large and tectonically complex area, without the necessity of having a good nearby reference event in each case.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.