nuclear test that has an extremely low yield, useless as a weapon but sufficient to test weapons technology. CTBT does not recognize the threshold principle and assumes all tests are detectable. The CTBTO will operate an International Monitoring System (IMS) of MASINT sensors for verification, which include seismic, acoustic, and radionuclide techniques. It is controversial if the IMS will be able to detect all events. Opponents are concerned that "Opponents of the CTBT are most concerned about one issue: in the absence of nuclear testing, U.S. nuclear weapons can be neither as safe nor as reliable as they should be. … While the treaty will constrain the United States from modernizing and developing weapons, it will be possible for other nations to cheat with little or no risk of being caught because the CTBT cannot be verified....The IMS of the CTBT is expected to provide the ability to detect, locate, and identify nonevasive nuclear testing of yields of 1 kiloton or greater. It will not be able to detect, with any significant degree of confidence, nuclear testing below 1 kiloton. If the test is evasively conducted, the system will not detect a test of several kilotons." Advocates of the CTBT argues "...there is recent demonstration that the IMS will be able to detect and identify non-evasive explosions of less than 1 kiloton in some strategically important areas." Initial indications, in August 1997, pointed to a seismic event in Novaya Zemlya, which is Russia's main test site. At first, it was believed to be a hidden nuclear test. IMS sensors, however, helped locate the event offshore, in the Kara Sea. IMS also established that it was an earthquake, not an explosion. "Had this been an underground nuclear test, its magnitude (3.3) would have corresponded to a yield of less than 100 tons (0.1 kilotons) in the absence of evasive measures. A nearby event identified as an earthquake in January 1996 was a factor of ten smaller (2.4), corresponding to a yield of about 10 tons." Opponents of the IMS had claimed the best that could be done was to recognize a 1 kt event, not concealed and of Richter magnitude 4.0. seems to assume that tests will still be in a plausible weapons range, and a 10-ton yield still might be useful in some tactical applications. There is a class of applied research testing, hydronuclear tests, that yield useful information but