Large-Scale Present-Day Plate Boundary Deformations in the Eastern Hemisphere Determined from VLBI Data: Implications for Plate Tectonics and Indian Ocean Growth

Abstract

Dynamics of the planet Earth is the manifestation of the diverse plate tectonic processes, which have been operational since the Archean period of Earth evolution and continue to deform the plate boundaries. Very Long Baseline Interferometry (VLBI) is an efficient space geodetic method that allows the precise measurement of plate motions and associated deformations. We analyze here the VLBI measurements made during a period of about three decades at five locations on the Eastern hemisphere of the globe, which are geographically distributed over five continents (plates) around the Indian Ocean. The computed baseline length rates show the deformation pattern and its rate at the boundaries between the major tectonic plates constituting the Eastern Earth hemisphere. The African 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 2 (Nubian) and Antarctic plates are moving apart at 13.5 mm/yr, which is mostly attributed to South West Indian Ridge spreading. Similarly, a spreading rate of 59.0 mm/yr is observed for the South East Indian Ridge that separates the Antarctic and Australian plates. Shortening at the rate of 3.9 mm/yr is estimated across the subduction boundary between Africa (Nubia) and Eurasia. Similar kind of convergence process is evident between the Australian and Sunda blocks (of the Eurasian plate). The associated deformation of -54.8 mm/yr appears to be chiefly accommodated along the Banda arc system, where the Australian plate is subducting under the Sunda block. VLBI sites within the Eurasian plate, Wettzell in Germany and Seshan on the South China block, are moving apart at a rate of 3.6 mm/yr. This relative motion between locations on the same plate is interpreted to be due to the deformation process along a large strike-slip fault, which is identified as the Western boundary of South China block. Indian Ocean expansion, at the rate of +91.5 m 2 /yr, is also estimated from the deformation rate estimated within the five baselines studied here. From the Hurst exponent values, which is an indicator of the future trend of a time series data, we predict the deceleration of the various tectonic processes that are operational at present.

Changes in atmospheric water content associated with an unusual high snowfall during June 2004 at Maitri station (Schirmacher Oasis, East Antarctica) and the role of South West Indian ridge geodynamics

“…This slow spreading ridge (spreading rate between 13 and 18 mm/year) (e.g. DeMets et al 2010;Akilan et al 2015b) is characterized by significant upper crustal seismicity (Negishi et al 1998;Premkishore et al 2006;Rao et al 2007;Srinivas et al 2008;Akilan et al 2010;Rao et al 2012). Table 2 lists the earthquakes occurred in the SWIR segment between the Bovet hot spot (54°24 0 S, 3°24 0 E) and Marion (46°54 0 S, 37°36 0 E) during the complete polar night period.…”

Ionospheric Total Electron Content (TEC) Anomalies as Earthquake Precursors: Unveiling the Geophysical Connection Leading to the 2023 Moroccan 6.8 Mw Earthquake

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