Seismic Signal Discrimination Between Natural Earthquakes and Mining Explosions Using Moroccan Seismic Network

Abstract

Some regions of Morocco are characterized by relatively moderate active seismicity and mining. The seismic activity in Morocco is related to the African and Eurasian plate’s convergence. In this work, we examined several diagnostic techniques to identify and distinguish between earthquakes as natural events and explosions as artificial events in the northern part of Morocco. The methods used are based on seismic spectral amplitude ratio, moment magnitudes (M_w), the time duration of signals, and focal mechanisms. The discrimination has been checked regarding monitoring of local seismicity and chemical explosion using the data recorded from more than 80 seismic stations in the framework of several projects; PICASSO, Topo Iberia, Morocco-Array, SIMA, RIFSIS for the period from 2010 to 2012. It comes out that using the distribution of Amplitude/Frequency methods between 0.1 and 25 Hz frequency band, the separation appears clearly for the earthquakes in the range 1–3 Hz and explosions in the range 9–12 Hz. Therefore, the moment magnitude of natural earthquakes is greater than that of artificial explosions. The detectability of the local earthquake and chemical explosion is estimated by the near station to the mine. The magnitude of explosions and earthquakes is between 2 and 4. Our approach is to apply these methods to better separate the populations of earthquakes and explosions to help calibrate local discriminants, especially in the phosphate areas where explosions rich database is available. This may shed light on the seismicity pattern of the region.