Basin architecture and lithosphere structures of Western Central Asia – Uzbekistan: from geophysical studies

This paper presents an integrated geophysical study of the Western Central Asia (WCA) in the Uzbekistan area. It presents new interpretations of deep seismic sounding (DSS) data and new analyses of potential fields data. An integrated model of the physical properties and lithosphere structures displays distinct features that are related to tectonic history of the study WCA-Darius area. Task-oriented complex geological and geophysical research revealed in the lithosphere of western Uzbekistan series of crust blocks with abnormal petrophysical characteristics and established some correlation dependences between the distribution and placement of these objects (in plan) with deposits of minerals.

Landslide hazard zones determination on open pit mine edge by circular seismic sounding method

Herein there is an algorithm and method of processing the experimental data obtained by a circular seismic sounding method that makes it possible to increase accuracy in determining an anisotropy coefficient of the ground mechanical properties. The coefficient value is mutually related to the deformation processes at the initial stages of landslide formation. There are results of data processing of the field seismic studies of the adjacent ground at the Angrenskiy coal mine that allow establishing boundaries for the potentially landslide-prone zones, as well as a numerical criterion to predict rock stability under the given conditions.

Ufa mantle ridge fault – main tectonic, geological and minerogenic consequences

Relevance of the work. The data on the structure and properties of the subsoil, obtained on the basis of geophysical studies, make it possible to significantly revise the ideas about the structure and patterns of formation of mineral deposits within the Ufimsky ridge fault and its zone of influence (55º–56º north latitude in the Urals). Purpose of the work: constructing a model of the formation of the Ufa mantle ridge fault and identifying its mineragenic features using the example of deposits of ferruginous quartzite, kyanites and rare earth mineralization. The methodology of the research. The published databases and their summarizing materials on deep seismic sounding of the Urals with the allocation of a mineragenic load characteristic of the Ufa mantle ridge fault and its influence zone were used as a factual basis for the research. Research results. The Ufa ridge fault is a structure formed by the uplift of the upper mantle, presumably at the intersection of intramantle shear faults. The transverse asymmetry of the mantle ridge fault and the later rift-collisional processes are reflected in the overlying complexes and lead to a distortion of the lines of the outcropping of deep faults at the level of the modern erosional section. Horst formation was complicated by rifting-collisional tectonic events with accompanying magmatic, metamorphic, metasomatic, and dislocation processes, accompanied by various types of numerous manifestations and mineral deposits exposed by erosional processes. Schemes of the location of deposits and manifestations of ferruginous quartzites, kyanites and rare earth mineralization in its more eroded part are given as examples confirming the confinement of various types of minerals to the structure of the Ufa mantle ridge fault. Conclusions. The cropping of deposits and occurrences of ferruginous quartzites, kyanite, rare earth mineralization and other minerals is closely related to the development of the Ufa mantle ridge fault.

Anatomy of a crustal-scale accretionary complex: Insights from deep seismic sounding of the onshore western Makran subduction zone, Iran

The Makran subduction zone has produced M 8+ earthquakes and subsequent tsunamis in historic times, hence indicating high risk for the coastal regions of southern Iran, Pakistan, and neighboring countries. Besides this, the Makran subduction zone is an end-member subduction zone featuring extreme properties, with one of the largest sediment inputs and the widest accretionary wedge on Earth. While surface geology and shallow structure of the offshore wedge have been relatively well studied, primary information on the deeper structure of the onshore part is largely absent. We present three crustal-scale, trench-perpendicular, deep seismic sounding profiles crossing the subaerial part of the accretionary wedge of the western Makran subduction zone in Iran. P-wave travel-time tomography based on a Monte Carlo Markov chain algorithm as well as the migration of automatic line drawings of wide-angle reflections reveal the crustal structure of the wedge and geometry of the subducting oceanic plate at high resolution. The images shed light on the accretionary processes, in particular the generation of continental crust by basal accretion, and provide vital basic information for hazard assessment and tsunami modeling.

Supplemental Material: Anatomy of a crustal-scale accretionary complex: Insights from deep seismic sounding of the onshore western Makran subduction zone, Iran

Description and illustrations of the seismic data set, methods, and resolution estimates.<br>

Supplemental Material: Anatomy of a crustal-scale accretionary complex: Insights from deep seismic sounding of the onshore western Makran subduction zone, Iran

Description and illustrations of the seismic data set, methods, and resolution estimates.<br>

Post-critical SsPmp and its applications to virtual deep seismic sounding (VDSS)—3: back-projection imaging of the crust–mantle boundary in a heterogeneous lithosphere, theory and application

SUMMARY Virtual deep seismic sounding (VDSS) uses the arrival time of post-critical SsPmp relative to the direct S wave to infer Moho depth at the Pmp reflection point. Due to the large offset between the virtual source and the receiver, SsPmp is more sensitive to lateral variations of structures than near-vertical phases such as Ps, which is used to construct conventional P receiver functions. However, the way post-critical SsPmp is affected by lateral variations in lithospheric structure is not well understood, and previous studies largely assumed a 1-D structure when analysing SsPmp waveforms. Here we present synthetic tests with various 2-D models to show that lateral variations in lithospheric structures, from the lithosphere–asthenosphere boundary (LAB) to sedimentary basins, profoundly affect traveltime, phase and amplitude of post-critical SsPmp, and that a 1-D approximation is usually inappropriate when analysing 2-D data. Despite these strong effects we show, with synthetic examples and the ChinArray data from the Ordos Block in northern China, that a simple ray-theory-based back-projection method can retrieve the geometry of the crust–mantle boundary (CMB) given array observations in cases with moderate lateral variations in the CMB and/or the LAB. The success of our back-projection method indicates that ray-theory approximations are sufficient in modelling SsPmp traveltimes in the presence of moderate lateral heterogeneity. In contrast, we show that the ray theory is generally insufficient in modelling SsPmp phase shifts in a strongly heterogeneous lithosphere due to non-planar downgoing P waves incident at the CMB. Nonetheless, our results demonstrate the feasibility of direct imaging of the CMB with post-critical SsPmp even in the presence of 2-D variations of lithospheric structure.