Assessing intraplate earthquake hazards from satellite geopotential field observations

Satellite magnetic and gravity field observations provide important constraints on the poorly understood lithospheric properties of intraplate earthquakes because they map lateral long-wavelength contrasts in magnetization and density, respectively, related to petrological, structural, and thermal variations that help control the distribution of lithospheric stress. These anomalies are each a product of the vertically integrated physical property times the layer thickness. Thus, they constrain and enhance the geological utility of near-surface geopotential surveys, as well as seismic, GPS, and other geophysical observations that map the geological and dynamic properties of the lithosphere. To illustrate this synergy, we consider the influence of the US Transcontinental Magnetic Anomaly (TMA) on crustal stress and earthquake activity along the 38th parallel. In another example, we compare crustal earthquake stress constraints from gravity and seismic observations of the US mid-continent and North Andes microplate where starkly contrasting plate tectonic forces operate.