Results of seismic observations in Germany on the Heligoland explosion of April 18, 1947

Abstract

Seismic recording of the Heligoland explosion of April 18, 1947, provided important evidence on the structure of the continental shield, especially so since the region of the German bay around which most of the stations were located is well defined geologically. The depths and velocities of the three layers are discussed and comparisons are made with the interpretations of others. The velocities of the seismic waves inferred from the summarized observations are 5.4 km/sec in the upper layer (granitic), 6.18 and 6.6 km/sec in the middle layer (gabbroic), and 8.32 and 8.19 km/sec in the lowest one (peridotitic). The observational data indicate the discontinuous character of the stratification of the crust; that the granitic and gabbroic layers are not horizontal but variable in depth. When consideration is taken of possible factors involved, such as non-uniform elastic properties of the sedimentary layer and inclination along profiles, a more uniform depth is found.