Surface Topography Anomalies Induced by Geodynamic Processes in the Southeast Carpathians

2020 ◽  
Author(s):  
Ebru Şengül Uluocak ◽  
Russell N. Pysklywec ◽  
Oğuz H. Göğüş ◽  
Emin Ulugergerli
Keyword(s):  
Surface Topography ◽  
Mantle Flow ◽  
Isostatic Compensation ◽  
Subsurface Structures ◽  
Free Air ◽  
Dynamic Forces ◽  
Geodynamic Processes ◽  
Flow Components ◽  
Mountain Chain ◽  
Free Air Gravity

<p>Southeast Carpathians with deep basins (e.g., Transylvania and Focsani) and the mountain chain (SE Carpathians Mountain with ~1.5 km elevation) are characterized by unique morphological features.  The highly-variable subsurface structures (e.g., Vrancea slab) related to post-collisional tectonics are imaged by geophysical studies. Numerical modeling studies are performed to understand the deformation linked with active geodynamic processes developing in the east part of the region. Here, we present our multi-dimensional (2D-3D) thermo-mechanical modeling results with varying temperatures and crustal configurations. We analyze modeling results together with the observations in terms of possible mantle flow components of the surface topography in Southeast Carpathians. In addition to residual topography calculations, non-isostatic compensation of the elevation is interpreted based on admittance functions between free-air gravity and topography. Our results indicate that mantle flow induced dynamic forces beneath the region modify the elevation with positive amplitudes over the Transylvania Basin (0.8-1 km) and the high SE Carpathian Mountains (~ 1 km) and subsidence of the Focsani Basin (0.5-1 km).</p>

GPS Imaging of Mantle Driven Uplift of the Apennines, Italy

2020 ◽  
Author(s):  
Nicola D'Agostino ◽  
William C. Hammond
Keyword(s):  
Entire Length ◽  
Campi Flegrei ◽  
Long Wavelength ◽  
Free Air ◽  
Crustal Thinning ◽  
Geothermal Potential ◽  
Mountain Chain ◽  
Free Air Gravity ◽  
High Topography ◽  
Tyrrhenian Basin

<p>One way for the continental lithosphere to extend is to increase its regional elevation, yet the mechanism for the formation of high-topography in actively extending continental settings (e.g., Tibet, Basin and Range, southwestern Balkans, Apennines) is still uncertain. It has been suggested that active extension in the Apennines Mountain chain in Italy is intimately related with regional topographic elevation. We use a newly updated GPS dataset and the GPS Imaging technique to show that the dynamic relief of the Apennines is currently increasing along its entire length by ~1 mm/yr. We image positive uplift along the entire length of the Apennine crest including the northern Apennines, Calabria and northern Sicily. The maximum rate is geographically aligned with the highest elevations and the topographic drainage divide. Relief is increasing in a ~120 km wide zone with a profile similar to the long wavelength topography, but not similar to the shorter wavelength topography generated by active faulting and erosion. A zone of minor active uplift is aligned with areas having restive volcanic fields and high geothermal potential west of the Apennines: e.g., Campi Flegrei, Alban Hills, and Lago Bolsena. However, the primary uplift axis aligns with the topography and zone of extension accommodating east-northeast translation of the Adriatic microplate relative to the Tyrrhenian Basin. Broad uplift occurs despite that the expected consequence of extension is crustal thinning and subsidence.   Anomalies in free-air gravity and deep seismic wavespeed suggest that elevation gain is driven by forces originating in the mantle. We use these results to address the hypothesis that these forces result from upward flow of asthenospheric mantle beneath the Apennines, possibly related to a sinking and detached slab previously attached to the Adriatic microplate, or from extensional flank flexure across the axis of the Apennine rift.</p>

5. Gravity and the figure of the Earth

2018 ◽  
pp. 69-91
Author(s):  
William Lowrie
Keyword(s):  
Accurate Determination ◽  
Measurement Techniques ◽  
Gravity Anomalies ◽  
Dynamic Processes ◽  
The Core ◽  
The Earth ◽  
Free Air ◽  
Figure Of The Earth ◽  
Free Air Gravity

‘Gravity and the figure of the Earth’ discusses the measurement of gravity and its variation at the Earth’s surface and with depth. Gravity is about 0.5 per cent stronger at the poles than at the equator and it first increases with depth until the core–mantle boundary and then sinks to zero at the Earth’s centre. Using satellites to carry out geodetic and gravimetric observations has revolutionized geodesy, creating a powerful geophysical tool for observing and measuring dynamic processes on the Earth. The various measurement techniques employed fall in two categories: precise location of a position on the Earth (such as GPS) and accurate determination of the geoid and gravitational field. Bouguer and free-air gravity anomalies and isostasy are explained.

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