Geodetic and seismological evidence of triggered seismicity in Qarun oil field, west to Dahshour earthquake source, Cairo, Egypt

From 2000 to 2010, increased seismicity and surface deformation were observed approximately 50 km west of the 1992 Dahshour earthquake source (M_W5.8) within the Qarun oil field. The origin of this anomalous behavior is unknown, as are any links to the tectonically active Dahshour source region. In this study, we analyzed seismic data recorded by the local Dahshour network and Egyptian National Seismological Network (ENSN), as well as previously published data, to determine the origin of these earthquakes. The spatial and temporal distributions of events with magnitudes ≥3.0 were examined (e.g., b-values and moment tensor decomposition) to quantify the isotropic (ISO), compensated linear vector dipole (CLVD), and double-couple (DC) components. Persistent scatterer interferometry (PSI) using descending track scenes from Envisat (2004–2010) was applied to assess the ground deformation rates and evaluate potential induced seismicity. The results indicate that the seismicity in the Qarun oil field was predominantly shallow (2–5 km) and temporally correlated with oil production. Conversely, the Dahshour events were caused by deeper sources (~30 km) and reflect historical and ongoing tectonic activity, with b-values of 1.1 and 0.6, respectively. Moment tensor analyses suggest that the Qarun earthquakes were triggered by stress changes along local faults and pore-pressure variations caused by fluid injection and/or extraction, in contrast to the tectonically driven Dahshour earthquakes. The PSI analysis indicates that localized ground deformation occurred, with a central uplift rate of ~5 mm/a. Deformation fluctuated from ~−2 mm/a (subsidence) to 5 mm/a (uplift), and back to ~−1 mm/a (subsidence) over a distance of <50 km, which is consistent with hydrocarbon extraction and subsurface fluid injection.