The propagation characteristics of the regional Sn shear waves have been mapped to provide insight into the lithospheric structure of the Anatolian and Iranian plateau and the surrounding regions. Thousands of regional earthquakes within the distance range of 2-15 degrees were recorded by broadband and short period stations located in Turkey and nearby regions, especially new data recorded by 29 broadband stations in the Eastern Turkey Seismic Experiment network. The propagation efficiencies of Sn were determined visually using their amplitude and fre-quency content. Attenuation maps were then tomographically constructed using the observed propagation efficiencies. Our results confirm that Sn propagates efficiently in the uppermost mantle beneath the Mediterranean Sea, the Black Sea, and the Caspian Sea and along the Zagros fold and thrust belt. Sn is not observed in eastern Turkey, northwestern Iran, or central Anatolia. In contrast to previous available studies, this study considerably improved the mapped location of the boundaries between the zones of efficient and attenuated Sn. Our results are best explained by an absence of lithospheric mantle, or the presence of thin and hot lithospheric mantle beneath most of the Anatolian and Iranian plateau.

Sn attenuation in the Anatolian and Iranian plateau and surrounding regions : The Turkey seismic experiment: The study of a young continent-continent collision

Although many different mechanisms for subduction initiation have been proposed, only few of them are viable in terms of consistency with observations and reproducibility in numerical experiments. In particular, it has recently been demonstrated that intra-oceanic subduction triggered by an upwelling mantle plume could greatly contribute to the onset and operation of plate tectonics in the early and, to a lesser degree, modern Earth. On the contrary, the initiation of intra-continental subduction still remains underappreciated. Here we provide an overview of 1) observational evidence for upwelling of hot mantle material flanked by downgoing proto-slabs of sinking continental mantle lithosphere, and 2) previously published and new numerical models of plume-induced subduction initiation. Numerical modeling shows that under the condition of a sufficiently thick (>100 km) continental plate, incipient downthrusting at the level of the lowermost lithospheric mantle can be triggered by plume anomalies of moderate temperatures and without significant strain- and/or melt-related weakening of overlying rocks. This finding is in contrast with the requirements for plume-induced subduction initiation within oceanic or thinner continental lithosphere. As a result, plume-lithosphere interactions within continental interiors of Paleozoic-Proterozoic-(Archean) platforms are the least demanding (and thus potentially very common) mechanism for initiation of subduction-like foundering in the Phanerozoic Earth. Our findings are supported by a growing body of new geophysical data collected in various intra-continental areas. A better understanding of the role of intra-continental mantle downthrusting and foundering in global plate tectonics and, particularly, in the initiation of “classic” ocean-continent subduction will benefit from more detailed follow-up investigations.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020GC009482

Plume‐Induced Sinking of Intracontinental Lithospheric Mantle: An Overlooked Mechanism of Subduction Initiation?

Accessibility is an important property of geoheritage sites (geosites), which is commonly considered in their assessment. A new method, which refers partly to previous developments, is proposed to assess this property semiquantitatively. Inner (on-site) and outer accessibility are distinguished, and each is measured depending on the opportunities to reach unique geological features. Distant visibility and entrance fees/required permissions are also taken into account. On the basis of the scores, three grades of geosite accessibility (excellent, moderate, and low) are delineated. The proposed method is applied to 15 geosites of Mountainous Adygeya (southwestern Russia), and the outcomes prove its efficacy. This application also helps to establish within-site and territorial spatial heterogeneity of geosite accessibility and to propose some managerial implications.

https://www.mdpi.com/2571-9408/4/3/60/pdf

Accessibility of Geoheritage Sites—A Methodological Proposal

The ‘pargasosphere’ hypothesis: Looking at global plate tectonics from a new perspective

Approaches to Solving the Maximum Possible Earthquake Magnitude (Mmax) Problem

/pdf/geodynamics-seismicity-and-seismic-hazards-of-the-caucasus-o4fjwivsjf.pdf

Jemal Kiria

Papers

Geodynamics, seismicity, and seismic hazards of the Caucasus