3-2- Geophysical Data
The distributions of seismic b-values from the entire eastern Anatolia, and the major high-wave number magnetic anomaly values favor high-density rocks under the Neogene successions matching the density of an ophiolite association (Bektaş et al. 2007; Bektaş 2013; Mahatsente et al.; 2018; Cırmık et al. 2018). The seismic waves down to 5-6 km at depths display a relatively uniform pattern (Figs 10 A and B) without abrupt vertical changes to infer a lower density layer under the ophiolitic rocks.
Maden and Öztürk (2015), examining rich data derived from the entire eastern Anatolia and the surrounding areas, concluded that the eastern Anatolian crust is thick, where the large negative gravity anomalies and low b-values are observed.
Fowler (2004) calculated a Bouguer gravity anomaly of -300 mgal in the case of 100% isostatic equilibrium (roc=2.85 gr/cm3, rum=3.3 gr/cm3) in a region with a topographic height of 1 km. The eastern Anatolia region has an average topography of 2 km. Therefore, it would be expected to yield gravity values lower than -300 mgal. However, the values observed in eastern Anatolia range between -100 and -200 mgal. This may be explained by the rapid uplift of the eastern Anatolian region due to delamination of the mantle lithosphere (see the discussion in the following paragraphs), insufficient immersion of the root of the lithosphere in the mantle, and the consequent isostatic disequilibrium.