[1] A global Earth Magnetic Anomaly Grid (EMAG2) has been compiled from satellite, ship, and airborne magnetic measurements. EMAG2 is a significant update of our previous candidate grid for the World Digital Magnetic Anomaly Map. The resolution has been improved from 3 arc min to 2 arc min, and the altitude has been reduced from 5 km to 4 km above the geoid. Additional grid and track line data have been included, both over land and the oceans. Wherever available, the original shipborne and airborne data were used instead of precompiled oceanic magnetic grids. Interpolation between sparse track lines in the oceans was improved by directional gridding and extrapolation, based on an oceanic crustal age model. The longest wavelengths (>330 km) were replaced with the latest CHAMP satellite magnetic field model MF6. EMAG2 is available at http://geomag.org/models/EMAG2 and for permanent archive at http://earthref.org/ cgi-bin/er.cgi?s=erda.cgi?n=970.

This combination of textbook and reference manual provides a comprehensive account of gravity and magnetic methods for exploring the subsurface using surface, marine, airborne and satellite measurements. It describes key current topics and techniques, physical properties of rocks and other earth materials, and digital data analysis methods used to process and interpret anomalies for subsurface information. Each chapter starts with an overview and concludes by listing key concepts to consolidate new learning. An accompanying website presents problem sets and interactive computer-based exercises, providing hands-on experience of processing, modeling and interpreting data. A comprehensive online suite of full-color case histories illustrates the practical utility of modern gravity and magnetic surveys. This is an ideal text for advanced undergraduate and graduate courses and reference text for research academics and professional geophysicists. It is a valuable resource for all those interested in petroleum, engineering, mineral, environmental, geological and archeological exploration of the lithosphere.

The second generation Antarctic magnetic anomaly compilation for the region south of 60°S includes some 3.5 million line-km of aeromagnetic and marine magnetic data that more than doubles the initial map's near-surface database. For the new compilation, the magnetic data sets were corrected for the International Geomagnetic Reference Field, diurnal effects, and high-frequency errors and leveled, gridded, and stitched together. The new magnetic data further constrain the crustal architecture and geological evolution of the Antarctic Peninsula and the West Antarctic Rift System in West Antarctica, as well as Dronning Maud Land, the Gamburtsev Subglacial Mountains, the Prince Charles Mountains, Princess Elizabeth Land, and Wilkes Land in East Antarctica and the circumjacent oceanic margins. Overall, the magnetic anomaly compilation helps unify disparate regional geologic and geophysical studies by providing new constraints on major tectonic and magmatic processes that affected the Antarctic from Precambrian to Cenozoic times.Plain Language Summary Given the ubiquitous polar cover of snow, ice, and seawater, the magnetic anomaly compilation offers important constraints on the global tectonic processes and crustal properties of the Antarctic. It also links widely separated areas of outcrop to help unify disparate geologic studies and provides insights on the lithospheric transition between Antarctica and adjacent oceans, as well as the geodynamic evolution of the Antarctic lithosphere in the assembly and breakup of the Gondwana, Rodinia, and Columbia supercontinents and key piercing points for reconstructing linkages between the protocontinents. The magnetic data together with ice-probing radar and gravity information greatly facilitate understanding the evolution of fundamental large-scale geological processes such as continental rifting, intraplate mountain building, subduction and terrane accretion processes, and intraplate basin formation.

S U M M A R YSatellite-measured regional gravity and terrain elevation data are becoming increasingly available for improving our understanding of the geological properties and history of the Earth, Moon, Mars, Venus and other planets. In assessing the geological significance of the existing and growing volumes of these regional data sets, there is great need for computing theoretical anomalous gravity fields from geological models in spherical coordinates. In the present study, we explicitly develop the elegant Gauss-Legendre quadrature formulation for numerically modelling the complete gravity effects (i.e. potential, vector and tensor gradient fields) of the spherical prism. As an application, we investigate the gradient components of the isostatic gravity anomalies that the upcoming Gravity Field and Steady State Ocean Circulation Explorer (GOCE) satellite mission is likely to map over a large tectonically active region of the Middle East centred on Iran.

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Abstract. We investigated the use of enhanced spectral correlation theory for modeling the crustal features of the Antarctic from regional observations of gravity and terrain. The analysis considered lø-gridded free-air gravity anomalies and topographic rock, ice, and water components for the region south of 60øS. We modeled terrain gravity effects at 150-kin altitude by Gauss-Legendre quadrature (GLQ) integration assuming densities of 2800 kg/m 3 for rock, 900 kg/m 3 for ice, and 1030 kg/m • for seawater. These effects are substantial relative to the free-air anomalies and must be compensated by the effects of subsurface density variations. Significant terrain-correlated free-Mr anomalies were revealed by the wavenumber correlation spectrum between the free-air anomalies and the modeled terrain gravity effects, which we interpreted mostly to reflect possible isostatic irabalances of the crust. Subtracting the terrain-correlated free-air anomalies from the total freeair anomalies and topographic gravity effects yielded terrain-decorrelated free-air anomalies and the gravity effects of isostatically compensated terrain features, respectively, which are uncorrelated with each other. The compensating effects that annihilate the latter were attributed to undulations of the Moho, which we estimated by inversion using GLQ integration and a mantle-to-crust density contrast

The total electron content (TEC) measurements of the Global Navigation Satellite System (GNSS) revealed traveling ionospheric disturbances (TID) that locate North Korea's underground nuclear explosion (UNE) of 25 May 2009 to within about 3.5 km of its seismically determined epicenter. The random chance for this pattern of TIDs to register across the eleven GNSS stations is roughly 1 in 19 billion. Monte Carlo analysis of nearly 1,300 TIDs from a 7‐station subset of the 11 GNSS stations supports the statistical strength of the array's signature. The UNE was also detected by seismic stations and possibly a local infrasound network of the International Monitoring System (IMS) of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO), but no radionuclide evidence was found. Thus, global GNSS infrastructure enables mapping spatial and temporal variations of TEC that augment and complement other methods of detecting and locating clandestine UNEs.