Shear-wave velocity structure and Moho depth variation in northern Algeria from joint inversion of teleseismic P-wave receiver functions and Rayleigh wave dispersion from local earthquakes

Abstract

AbstractWe investigated the Moho depth and the velocity structure of the crust and upper mantle in northern Algeria. We used teleseismic P-wave receiver functions jointly inverted with Rayleigh wave dispersion curves obtained from local earthquakes. The events used are collected from the seismic broadband stations of the Algerian broadband seismic network. These stations are located in different geological settings including the Tell Atlas, High Plateaus, and the Saharan Atlas. The H–κ stacking method of receiver functions was applied to first obtain the crustal thickness and the Vp/Vs ratio. The inversion results show the variation in Moho depth in the different geological structures. The shallowest depths of the Moho (~20–30 km) are estimated along the Algerian continental margin and Tell Atlas. In the High Plateaus region, the Moho depths vary from 30–36 km, whereas the deepest Moho depths are found in the Saharan Atlas (36–44 km). The crust is divided in two layers in the whole study area. The upper crust, ~8 –14 km thick, presents an average shear velocity of ~3.0 km/s. The lower crust of about 12–30 km thick has an average shear-wave velocity that ranges between 3.4–3.8 km/s. The upper crust is thinner than the lower crust particularly in the Saharan Atlas. The upper mantle shear-wave velocity varies from 4.1 to 4.5 km/s maximum and is stable, generally, below ~60 km depth. We clearly observed two low-velocity zones particularly in the eastern part of the Tell Atlas and the High Plateaus. The obtained results are in accordance with the previous results found in the region, particularly those using land gravity and seismic data. As the first estimate of the Moho depth from earthquake data in northern Algeria, using the receiver function method, this study sheds new insights on the crustal structure and the Moho depth in this region of the world.