In a mine-shaft at Příbram he was able to differentiate between long-distance earthquakes and local microseismic activity with the use of seismometers. Also, he was the first scientist to solve the problem involving the refraction of seismic rays in spherical layers. The term Benndorfscher Satz (Benndorf's relationship) is used to describe the constancy of the ray parameter across the spherical layers.