Numerical Simulation Of Lithospheric Extension With Lateral Change Of Rheological Strength

These lithospheres whose transverse strength has changed may originate from the fusion of continents with different mechanical properties or the evolution of materials within the lithosphere.The lateral variation of the continental lithosphere strength is an important factor controlling the localization of deformation,as well as an important factor controlling the deformation history and geometry of the mountain belt in the plate.This paper uses three lithospheres of different strengths: weak lithosphere,medium-strength lithosphere,and strong lithosphere.Through a series of combinations,the lateral strength of the lithosphere is changed.Three-dimensional and two-dimensional numerical simulation experiments are performed.Deformation under the control of boundary conditions and gravity expansion is studied.The deformation mode of the lithosphere with changes in lateral strength and the evolution of surface topography are studied.The simulation results show that when there is no change in the transverse strength,the crust and lithosphere can withstand uniform thinning for a long time,and the crust ruptures to form normal faults,ridges,and other structures.If there is a fragile upper mantle,the fragile upper mantle Yield occurred,and the weak lithosphere consisting of the brittle upper crust,the tough lower crust,and the ductile mantle uniformly thinned the most.The deformation is always concentrated in the weaker lithosphere,the brittle upper mantle of the stronger lithosphere fails to yield and rupture,and two mantle circulations are formed on both sides of the ductile mantle and asthenosphere where the upwelling occurred.Both sides are subject to stretching,and this mantle circulation will be more symmetrical.The upwelling flow of the ductile mantle and soft current drives the deformation of the crust,and the flow also causes the surface topography to change with time.When the weaker lithosphere is sandwiched in the middle of the stronger lithosphere and the scale is smaller,the crust is constricted to form a narrow rift valley.When the weaker lithosphere is larger,structures such as wide fractures and extended basins are formed.When the intensity of the lithosphere is distributed symmetrically on both sides,the lithosphere interface will tilt,and the weaker lithosphere crust will be broken due toextension,and the crustal displacement on the Moho surface will be partially thinned.From the geomorphology of the three-dimensional model,The surface of the lithosphere interface with varying strength subsided first,and then rose up with the ductile mantle.The mechanical coupling between the brittle and ductile crust layer and the brittle and ductile mantle lithosphere strongly controls the surface structure.Once the brittle mantle of the stronger lithosphere ruptures locally and the brittle mantle necks down,it will be transformed into a narrow rift valley structure in the earth.,Shear and tensile failure occurred on the ground surface.Lateral changes in intensity The lithosphere undergoes folding and bending under the action of extension.The wavelength depends on the magnitude of the intensity change.These series of models help explain the first-order tectonic behavior of the extensional lithosphere with varying lateral strength.For example,the evolutionary behavior of the lithospheric extension basin mountains,detached faults,metamorphic core complexes,and rifts will appear as the strength of the extension lithospheric changes.