Joint inversion of local, regional and teleseismic data for crustal thickness in the Eurasia-Africa plate boundary region

Abstract

SUMMARY A new map for the Moho discontinuity (EAM02) in the Eurasia–Africa plate boundary region is presented. Reliable results have also been obtained for the southern and eastern Mediterranean Basin, the northern African coasts and the eastern Atlantic Ocean, regions only occasionally considered in studies on the Mediterranean region. The Moho topography model is derived from two independent sets of constraints. Information contained in the fundamental and higher‐mode Rayleigh waves obtained from waveform modelling is used to constrain the Moho depth between estimates of crustal thickness taken from published reflection and refraction surveys, gravity studies and receiver function analysis. Strong lateral variations in the Moho topography have been observed in the Mediterranean Sea, confirming the complex evolution of this plate boundary region. In the west, the Moho discontinuity has been found at 15–20 km depth, suggesting extended and, at least in some locations, oceanic crust, while in the east the crust is on average 25–30 km thick. There it is interpreted either as Mesozoic oceanic or thinned Precambrian continental crust covered by thick sedimentary deposits. Standard continental crust (30–35 km) is observed along the eastern part of the northern African coast, while to the west a rapid change from a relatively deep Moho (down to 42 km) below the Atlas Mountain Range to the thin crust of the southwestern Mediterranean Sea has been found. The crust beneath the eastern North Atlantic Ocean can be up to 5 km thicker compared with standard oceanic crust (6 km). The crust has been interpreted to be heterogeneous as a consequence of irregular magma supply at the Mid‐Atlantic ridge. In addition, serpentinization of the sub‐Moho mantle could contribute to the imaging of apparently anomalous thick oceanic crust. In Europe, the presence of crustal roots (>45 km) beneath the major mountain belts has been confirmed, while thin crust (<25 km) has been found beneath extensional basins. Comparing the obtained Moho topography and Moho depth computed assuming isostatic compensation at 60 km depth shows that most of the Mediterranean and eastern Atlantic region appears to be in isostatic equilibrium. The large positive residuals observed for the eastern Mediterranean are likely to be due to overestimating crustal thickness, owing to the thick sediment deposits present.

Deformation and stress regimes in the Hellenic subduction zone from focal Mechanisms

“…The dip of each segment was adjusted following structural models of the forearc region that were derived from wide angle seismics (Bohnhoff et al, 2001;Brönner, 2003), surface wave and receiver function analysis (Li et al, 2003;Meier et al, 2004a;Endrun et al, 2004) and moving source profiles (Truffert et al, 1993). Furthermore, we implement data from a Moho map of the Eastern Mediterranean (Marone et al, 2003). We defined all events above the contact zone as brittle failure within the upper Aegean plate and all events below as earthquakes within the dipping African lithosphere.…”

Estimation of the crustal structure in Central Anatolia (Turkey) using receiver functions

“…The global maximum of the H-K stack for KSLM is at 37.4 km in thickness and 1.80 Vp/Vs ratio with 0.6 km (~1.6%) and 0.02 (~1.11%) uncertainties while the local maximum is at 31.8 km in thickness and 2.0 Vp/Vs ratio. While the study results of Marone et al (2003) showed that the crustal thickness near the KSLM station is almost 32 km, most previous studies (e.g., Arslan et al, 2010;Molinari and Morelli, 2011;Laske et al, 2013;Tezel et al, 2013;Vanacore et al, 2013;Uluocak et al, 2016) agreed with the crustal thickness at the global maximum. The H-K stack for SERE shows a significantly shallower Moho depth (31.4 km) and higher Vp/Vs ratio (1.87) at the local maximum than the findings of previous studies (e.g., Marone et al, 2003;Arslan et al, 2010;Molinari and Morelli, 2011;Laske et al, 2013;Tezel et al, 2013;Vanacore et al, 2013;Uluocak et al, 2016).…”

“…Some of them assert that the crustal thickness of the Anatolian plate gets thinner from east to west (e.g., Marone et al, 2003;Angus et al, 2005;Luccio and Pasyanos, 2007;Maden et al, 2008). Marone et al (2003) determined that the mean crustal thickness in Central Anatolia varies between 36 and 40 km. Arslan et al (2010) studied the crustal structure of Turkey using gravity data and found results very similar to those of Marone et al (2003).…”

“…Marone et al (2003) determined that the mean crustal thickness in Central Anatolia varies between 36 and 40 km. Arslan et al (2010) studied the crustal structure of Turkey using gravity data and found results very similar to those of Marone et al (2003). They declared that the crust gets thinner towards the northwest as a result of their study.…”

Deep-rooted “thick skinned” model for the High Atlas Mountains (Morocco). Implications for the seismic Eurasia-Africa plate boundary region

“…This is supported by the relative low Pn velocity of 7.7-7.9 km/s. Additional information has been recently obtained by receiver function studies of Sandvol et al (1998) and Van der Meijde et al (2003). The results of Van der Meijde et al (2003) show that the Mohorovicic (Moho) discontinuity under Midelt (in the plains north of the High Atlas) is located at 39 km.…”