On the Linear Relation Between mb And Ms for Discrimination Between Explosions and Earthquakes

Summary. The statistical capability of the mb :Ms, discriminant for the discrimination of earthquake and explosion populations is examined by application of discriminant functions to a group of 83 explosions and 72 earthquakes in Eurasia. Equations are derived for the probability that an event is an earthquake or an explosion. The positive sign of DIS in the decision index equation, DIS, = 34.3383 - 11.9569 mbi, + 7.1 161 Msi, indicates that the event i is an earthquake. Its negative sign indicates that event i is an explosion. The probability of correct classification for an event, Pi, is reiated to its DISi, value, by Pi = [l t exp (DISi,)]-1, where a large, positive DIS indicates a high probability that an event is an earthquake and a large, negative DIS indicates a high probability that an event is an explosion. The discrimination line Ms = 1.680 mb ~ 4.825, or rnb = 0.595 Ms + 2.872 very successfully separates the explosion population from the earthquake population. The points on this line have an equal chance of being an earthquake or an explosion; moreover, for any event, the distance parallel to the Ms,-axis from the point representing that event in the mb:Ms, plane to this line is a measure of the probability for the correct classification of that event