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166 results on '"Mukhopadhyay, Basab"'

21. High velocity lower crust with anomalous rheological parameters under the Red Sea Passive Margin, SW Saudi Arabia – insight into the evolution of the Hijaz-Asir Escarpment Zone.

Author

Mukhopadhyay, Manoj, Mukhopadhyay, Basab, Mogren, Saad, and Ibrahim, Elkhedr

Subjects
*POISSON'S ratio, *CLIFFS, *BULK modulus, *TOPOGRAPHIC maps, *ACOUSTIC impedance, *DIORITE, *SEISMIC anisotropy
Abstract

The Red Sea Passive Margin (RSPM) in SW Saudi Arabia is characterized by two morphological provinces; the Red Sea Coastal Plains (RSCP) and the Hijaz-Asir Escarpment Zone (HAEZ) at the Arabian Shield Edge (ASE). Of these, the HAEZ is conspicuous by its seaward-facing heights of > 3 km. Based on the available receiver function analysis (REF) results from 25 seismic stations, we first present the Moho relief map underlying the RSPM to demonstrate that: (i) the transitional crust under the coastal region is 20–25 km thick which steadily increases landward to attain a thickness of ∼40 km below ASE, across an intervening region of depressed Moho with depths of 45–52 km. The latter exhibits significant regional extent and displays a close correlation with the topography of the HAEZ, suggesting a tectonic control on its formation. Eight rheological parameters for the upper as well as the lower crust are computed from the REF data, namely; Vp, Vp / Vs , density (ρ), Lame's first constant (λ), Lame's second constant (μ), Poisson's ratio (σ), bulk modulus (K) and acoustic impedance (AI). Their 2-D distribution for the lower crust unravels, for the first time, a high velocity lower crust (HVLC) underneath the HAEZ. The rheological character of the HVLC is further elucidated by investigating the relations between six rheological parameters: Vp – Vp / Vs, Vp / Vs– lower crustal thickness (h LC), Vs /ρ– h LC, λ–ρ, σ–ρ and λ–μ. The results indicate that lithology of the lower crust varies from diorite–felsic gneiss under RSCP to gabbro–diabase and mafic gneiss under HAEZ. We conjecture that the HVLC is an outcome of the exchange of materials from the subcrust at the hinterland of the RSPM directly underlying the HAEZ. Deep seismic control can only resolve the finer details of such crustal transformation. [ABSTRACT FROM AUTHOR]

Published
2024
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48. Slab tear and tensional fault systems in the Sunda–Andaman Benioff zone: implications on tectonics and potential seismic hazard.

Author

Mukhopadhyay, Basab, Dasgupta, Sujit, and Mukherjee, Pralay

Subjects
*GEOLOGIC faults, *BENIOFF zones, *PLATE tectonics, *EARTHQUAKE hazard analysis, *TRENCHES
Abstract

Transverse slab tear faults and longitudinal trench parallel extensional faults present on the top part of Benioff zone in Sunda–Andaman arc between latitude 6°–15°N and longitude 90°–98°E are marked by seismotectonic analysis using contemporary data related to regional tectonics, seismicity, centroid moment tensor (CMT) fault plane solutions, etc. Characteristics of ten numbers of transverse slab tear faults is taken from our previous studies, whereas four numbers of longitudinal trench parallel extensional faults are marked by the present study. These two sets of fault systems make high angle between them and tectonically complement each other. The disposition, origin, tectonic framework, depth of penetration and seismotectonic evaluations of the fault systems are analyzed. An effort is made to identify the potential seismic hazard in the zone between trench and forearc containing Andaman Group of Island. [ABSTRACT FROM PUBLISHER]

Published
2016
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