Analysis of the 8 September 2023 Al Haouz (Morocco) earthquake source using seismic and geodetic data

Abstract

This paper focuses on a study of the source of the Morocco September 8, 2023, earthquake (M w = 6.9) using seismic and geodetic data. We have used 46 P-wave and 11 S-wave teleseismic data to obtain a model of a kinematic extended seismic source. The rupture occurred on a near-vertical plane dipping 67° to the NNW and striking 247°, with a thrusting motion with a strike-slip component (rake=73°). The rupture was 10s, with the maximum energy released at the first 3, and the rupture occurred at 24 km depth, which doesn’t reach the surface, stopping approximately at 12 km depth. The slip distribution is an elliptical patch of an area of 568 km 2 , a maximum slip of 2.6 m and a scalar seismic moment of 2.5 x 10 19 Nm. The radiated seismic energy is 5.4 x 10 14 J, stress drop 4 MPa and apparent stress 0.98 MPa. Synthetic ground deformations obtained from the source model agree with DInSAR observed deformations, showing a maximum uplift of 16.4 cm and subsidence of 4.2 cm. This study enhances understanding of stress accumulation and release processes in the High Atlas and contributes to a better seismic risk assessment in the area, and highlighting that low seismicity zones are not immune to large, destructive earthquakes.

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