The Gravity Sandbox v1

Editable geometry with topography and gravity

Elevation is positive upward. Drag vertices without allowing self intersections. Control body density and surrounding rock density. Gravity is computed along the surface using a discretized mass summation, meant for intuition, not inversion or design.

Controls

The body stays below the surface. Crossing edges are rejected.

Ready

Topography type Flat Hill in the center Hill on one side Two hills on both sides Topography roughness Relief amplitude (m)

Body density rho body (kg/m3) Surrounding rock density rho bg (kg/m3) Reference level depth (m)0 Remove body part above reference level

When enabled, only the portion of the polygon deeper than the reference level contributes to gravity. This is a didactic filter, not a field correction.

Gravity plot Anomaly demeaned Absolute g

Mode Forward modelling Target matching

Auto save when RMS misfit < (mGal)

No target

Saved models that fit the target

Body shape preset Dike rising from depth Horizontal lens Circle Gravity resolution Fast Medium Fine

Vertices 0

Area 0

Self intersect No

Quality OK

The blue band is gravity along the surface in mGal. The black curve is topography as elevation upward. The polygon represents a 2D body with a fixed out of plane thickness.

Applied property	Value	Meaning for the model