We present the 3D seismic model of crustal structure and the distribution of seismicity in the El Asnam region (Algeria) where a strong earthquake (M7.3) occurred in 1980. We apply the local earthquake tomography inversion for the data of temporary networks which recorded the aftershocks of the 1980 event. The results of the tomography inversion have been rigorously tested using a number of different tests. The velocity anomalies from the inversion show pronounced low-velocity anomalies in the surface rupture zone associated with El Asnam fault, which are consistent with the finding of the previous studies (Philip and Meghraoui Tectonics 2:17–49, 1983), Ouyed et al. (Nature 292:26–31, 1981). Moreover, we have also reported the high velocities that exist at shallow crustal depths in the El Asnam zone. We have associated this feature to tectonic, geomorphological, and structural settings in the study area. Finally, we hope that the main features of the interpretation summarized in this article will be the basis for further integrated geophysical and tectonic analyses.