A note on the foreshock of the 1992 Roermond earthquake, the Netherlands

Abstract

Vertical components from 12 digital seismic stations which recorded the ML = 5.8 Roermond earthquake were used to determine the position and magnitude of a foreshock using relative methods. The small shock occurred 0.19 s before and 780 m away from the main shock on its SW-dipping fault plane. The local magnitude of the foreshock is ML = 4.0, which corresponds to a seismic moment of 2.8 x1014 Nm and to a seismic energy of 4.3 x109 J.