§ Mr. A. Hendersonasked the Minister of Education, as representing the Minister for Science, what estimate he has made of the smallest underground 114W nuclear explosion which could be distinguished from an earthquake; what seismographic reading would be recorded; and whether a seismographic reading of 4.75 equals an explosion of 19 kilotons.
§ Sir D. EcclesThe only underground nuclear explosions for which Her Majesty's Government have any data were in the United States. On the basis of these data it is calculated that small, and indeed quite large, underground explosions and earthquakes of equivalent magnitude could not in a large number of cases be distinguished from each other by the seismic network recommended by the Experts' Conference in 1958. The first and second parts of the Question do not admit of a precise answer and it is the general difficulty of this problem that causes us to insist, as did the experts in their Report, on the need to make on-site inspections a component part of any control system established to detect possible violations of an agreement on cessation of nuclear tests.
As regards the third part of the Question I have nothing to add to the reply given by my hon. Friend the Joint Under-Secretary of State for Foreign Affairs to the right hon. Member for Derby, South (Mr. P. Noel-Baker) on 22nd February.
I will send the hon. Member a copy of the Report of the technical working group which studied this question in November and December, 1959.