Fault structure and earthquake clustering in Aswan region (Egypt) revealed by high-accuracy earthquake location from 35 years of recorded natural and induced seismicity.

Here we study the structure and the triggering mechanisms of faults in Aswan region (South Egypt). The high-resolution locations of 2562 earthquakes (both natural and reservoir induced) collected in the study area from 1982 to 2016 highlight several fault segments, whose kinematics was estimated by focal mechanisms. We observe a time migration towards East and a gradual activation of several faults' strands, which may reveal the fluid migration in the Wadi Kalabsha embayment: the consequent pore-pressure increase would be considered the main triggering mechanism of the observed seismicity. Earthquake projections onto an E-W cross-section of the study area show a seismic gap localized on the Kalabsha Fault: it may be a locked fault patch, whose spatial extension (about 11 km) could be responsible for an up to $M_{w} = 5.9$ earthquake. The clustering analysis on the seismic catalog identifies many earthquake sequences, repeating earthquakes, and seismic swarms. Finally, the $b$-value decrease is correlated with higher seismic moment rates, whereas its increase up to 1.6 is temporally overlapped to a period in which earthquake swarms prevail.