Foreign Relations of the United States, 1961–1963, Volume VII, Arms Control and Disarmament

159. Telegram From the Department of State to the Delegation to the Eighteen-Nation Disarmament Committee⁰

Washington, March 18, 1962, 4:17 p.m.

Todis 57. Verbatim text. Following is text of agreed conclusions of US-UK technical meeting on nuclear test detection held here March 17-18:

Begin verbatim text

1. That Western unilateral detection systems can currently detect seismic events in the USSR of magnitude 4.75 or slightly less. This will lead on the average to detection of about 125 shallow seismic events per year within the USSR.

2. That the proposed Geneva system is predicted to detect seismic events down to 3.75 magnitude, which implies detection of about 1,000 shallow events per year in the USSR. This system could not be available much before 1965.

3. That improvements of detection by unilateral systems to perhaps magnitude 4.2 in the USSR is a reasonable technical goal for 1965. This we now believe implies detection of 300 shallow seismic events per year within the USSR. Among the research areas of particular promise are use of deep hole detection systems and correlation of data from phased arrays.

4. That a unilateral system can currently locate detected seismic events to within a radius of from 10 to 20 km.

5. That, with utilization of data from an improved internal USSR seismic detection system for the purpose of calibrating the external system, the location capability of an external unilateral system might improve to the point where location to within a radius of ten km. or less in seismic areas would be feasible. This conclusion is predicated on the assumption that the USSR data are not falsified.

6. That at present it is impossible unilaterally to identify shallow seismic events in the USSR as earthquakes, excepting at large magnitudes but that future improvements, in particular ones involving processing of data from large arrays, offer hope of reducing the magnitude at which identification of some earthquakes is possible down to about magnitude five. There does not appear to be any prospect of identifying a given event as an explosion by seismic means alone.

7. That if a unilateral system (for example a non-Soviet system for detecting events within the USSR) is to be used as a basis for initiating inspections, it will be necessary to agree on objective criteria which will determine eligibility for inspection and to establish a mechanism for certifying the eligibility of a given event. Although these problems were discussed no specific proposals have been formulated.¹ End verbatim text.

Ball

0. Source: Department of State, Central Files, 700.5611/3-1862. Secret. Drafted by Goodby (ACDA) and cleared by Long (ACDA). Repeated to London.
1. In responding to a query from the delegation in Geneva about specific paragraphs in these agreed conclusions, transmitted in Disto 48 from Geneva, March 19 (ibid., 700.5611/3-1962), the Department concluded: “UK may attempt use joint report to reinforce their views on unilateral control systems. However, agreed conclusions indicate no significant changes in capabilities of unilateral detection systems as previously understood by both US and UK.” The telegram concluded: “in short, we believe US-UK agreed conclusions indicate no reason for making change in previously agreed view of need for international control system for monitoring underground tests.” (Todis 61 to Geneva, March 19; ibid., 700.5611/3-1862)