Intraplate stresses and seismicity: The role of topography and density heterogeneities

Abstract

Abstract The stress induced by the topography and by density heterogeneities in the lithosphere has been computed for two different tectonic regions of the North American plate. The lithosphere was assumed to consist of a two-dimensional layered elastic slab over an inviscid fluid. The calculations show that these stresses are locally comparable in magnitude to the regional tectonic stress (~ 20–50 MPa). Two areas have been analyzed in greater detail: the southeastern United States and the Rio Grande Rift. The stress in the southeastern United States is computed along a cross-section perpendicular to the strike of the Appalachian Mountains; the computed stress appears largest beneath the Blue Ridge and Valley and Ridge provinces where the Appalachian seismicity is located. The stress in the western United States is computed along a cross-section perpendicular to the Rio Grande Rift. Large stress is shown beneath the rift and the adjacent regions: the stress induced by surface and internal loading is extensional in the Rio Grande Rift and compressional in the Colorado Plateau and in the Great Plains.