Scientific support of the Apollo infrared scanning radiometer experiment

NASA Technical Reports Server (NTRS)

Mendell, W. W.

1976-01-01

The Infrared Scanning Radiometer (ISR) was designed to map the thermal emission of the lunar surface from the service module of the orbiting Apollo 17 spacecraft. Lunar surface nighttime temperatures, which are extremely difficult to map from earth based telescopes were measured. The ISR transmitted approximately 90 hours of lunar data spread over 5 days in lunar orbit. Approximately 10 to the 8th power independent lunar temperature measurements were made with an absolute accuracy of 2K. Spatial resolution at nadir was approximately 2.2 km (depending on orbital altitude), exceeding that of earth based measurements by at least an order of magnitude. Preliminary studies of the data reveal the highest population of thermal anomalies (or hot spots) in Oceanus Procellarum. Very few anomalies exist on the far side of the moon as was predicted from the association of anomalies with mare on the near side. A number of negative anomalies (or cold spots) have also been found.

Sensitivity of Asian Summer Monsoon precipitation to tropical sea surface temperature anomalies

NASA Astrophysics Data System (ADS)

Fan, Lei; Shin, Sang-Ik; Liu, Zhengyu; Liu, Qinyu

2016-10-01

Sensitivity of Asian Summer Monsoon (ASM) precipitation to tropical sea surface temperature (SST) anomalies was estimated from ensemble simulations of two atmospheric general circulation models (GCMs) with an array of idealized SST anomaly patch prescriptions. Consistent sensitivity patterns were obtained in both models. Sensitivity of Indian Summer Monsoon (ISM) precipitation to cooling in the East Pacific was much weaker than to that of the same magnitude in the local Indian-western Pacific, over which a meridional pattern of warm north and cold south was most instrumental in increasing ISM precipitation. This indicates that the strength of the ENSO-ISM relationship is due to the large-amplitude East Pacific SST anomaly rather than its sensitivity value. Sensitivity of the East Asian Summer Monsoon (EASM), represented by the Yangtze-Huai River Valley (YHRV, also known as the meiyu-baiu front) precipitation, is non-uniform across the Indian Ocean basin. YHRV precipitation was most sensitive to warm SST anomalies over the northern Indian Ocean and the South China Sea, whereas the southern Indian Ocean had the opposite effect. This implies that the strengthened EASM in the post-Niño year is attributable mainly to warming of the northern Indian Ocean. The corresponding physical links between these SST anomaly patterns and ASM precipitation were also discussed. The relevance of sensitivity maps was justified by the high correlation between sensitivity-map-based reconstructed time series using observed SST anomaly patterns and actual precipitation series derived from ensemble-mean atmospheric GCM runs with time-varying global SST prescriptions during the same period. The correlation results indicated that sensitivity maps derived from patch experiments were far superior to those based on regression methods.

New gravity anomaly map of Taiwan and its surrounding regions with some tectonic interpretations

NASA Astrophysics Data System (ADS)

Doo, Wen-Bin; Lo, Chung-Liang; Hsu, Shu-Kun; Tsai, Ching-Hui; Huang, Yin-Sheng; Wang, Hsueh-Fen; Chiu, Shye-Donq; Ma, Yu-Fang; Liang, Chin-Wei

2018-04-01

In this study, we compiled recently collected (from 2005 to 2015) and previously reported (published and open access) gravity data, including land, shipborne and satellite-derived data, for Taiwan and its surrounding regions. Based on the cross-over error analysis, all data were adjusted; and, new Free-air gravity anomalies were obtained, shedding light on the tectonics of the region. To obtain the Bouguer gravity anomalies, the densities of land terrain and marine sediments were assumed to be 2.53 and 1.80 g/cm3, respectively. The updated gravity dataset was gridded with a spacing of one arc-minute. Several previously unnoticed gravity features are revealed by the new maps and can be used in a broad range of applications: (1) An isolated gravity high is located between the Shoushan and the Kaoping Canyon off southwest Taiwan. (2) Along the Luzon Arc, both Free-air and Bouguer gravity anomaly maps reveal a significant gravity discontinuity feature at the latitude of 21°20‧N. (3) In the southwestern Okinawa Trough, the NE-SW trending cross-back-arc volcanic trail (CBVT) marks the low-high gravity anomaly (both Free-air and Bouguer) boundary.

Density Of The Continental Roots: Compositional And Thermal Effects

NASA Astrophysics Data System (ADS)

Kaban, M. K.; Schwintzer, P.; Artemieva, I.; Mooney, W. D.

We use gravity, thermal, and seismic data to examine how the density and composi- tion of lithospheric roots vary beneath the cratons. Our interpretation is based on the gravity anomalies calculated by subtracting the gravitational effects of bathymetry, to- pography, and the crust from the observed gravity field, and the residual topography that characterizes the isostatic state of the lithosphere. We distinguish the effects of temperature and compositional variations in producing lithospheric density anomalies using two independent temperature constrains: based on interpretation of the surface heat flow data and estimated from global seismic tomography data. We find that in situ lithospheric density differs significantly between individual cratons, with the most dense values found beneath Eurasia and the least dense values beneath South Africa. This demonstrates that there is not a simple compensation of thermal and composition effects. We present a new gravity anomaly map that was corrected for crustal density structure and lithospheric temperatures. This map reveals differences in lithospheric composition, that are the result of the petrologic processes that have formed and mod- ified the lithosphere. All significant negative gravity anomalies are found in cratonic regions. In contrast, positive gravity anomalies are found in two distinct regions: near ocean-continent and continent-continent subduction zones, and within some continen- tal interiors. The origin of the latter positive anomalies is uncertain.

Nure aerial gamma-ray and magnetic reconnaissance survey: Chugach/Yakutat area, Alaska, Mt. Saint Elias Quadrangle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1978-10-01

Volume II contains the following data on Mt. Saint Elias, Alaska: geologic base map, flight path map, anomaly maps (U, Th, K, UlTh, UlK, ThlK), radiometric multiple-parameter stacked profiles, magnetic and ancillary profile data, and statistical data. (LK)

Aeromagnetic Map with Geology of the Los Angeles 30 x 60 Minute Quadrangle, Southern California

USGS Publications Warehouse

Langenheim, V.E.; Hildenbrand, T.G.; Jachens, R.C.; Campbell, R.H.; Yerkes, R.F.

2006-01-01

Introduction: An important objective of geologic mapping is to project surficial structures and stratigraphy into the subsurface. Geophysical data and analysis are useful tools for achieving this objective. This aeromagnetic anomaly map provides a three-dimensional perspective to the geologic mapping of the Los Angeles 30 by 60 minute quadrangle. Aeromagnetic maps show the distribution of magnetic rocks, primarily those containing magnetite (Blakely, 1995). In the Los Angeles quadrangle, the magnetic sources are Tertiary and Mesozoic igneous rocks and Precambrian crystalline rocks. Aeromagnetic anomalies mark abrupt spatial contrasts in magnetization that can be attributed to lithologic boundaries, perhaps caused by faulting of these rocks or by intrusive contacts. This aeromagnetic map overlain on geology, with information from wells and other geophysical data, provides constraints on the subsurface geology by allowing us to trace faults beneath surficial cover and estimate fault dip and offset. This map supersedes Langenheim and Jachens (1997) because of its digital form and the added value of overlaying the magnetic data on a geologic base. The geologic base for this map is from Yerkes and Campbell (2005); some of their subunits have been merged into one on this map.

Lithospheric magnetic field modelling of the African continent

NASA Astrophysics Data System (ADS)

Hemant, K.; Maus, S.

2003-04-01

New magnetic satellite missions in low-earth orbit are providing increasingly accurate maps of the lithospheric magnetic field. These maps can be used to infer the geological structure of regions hidden by Phanerozoic cover, taking into account our knowledge of crustal structure from surface geology and seismic methods. A GIS based modelling technique has been developed to model the various geological units of the continents using the UNESCO geological map of the world, supported by background geological information from various sources. Geological units of each region are assigned a susceptibility value based on laboratory values of the constituent rock types. Then, using the 3SMAC seismic crustal structure, a vertically integrated susceptibility (VIS) model is computed at each point of the region. Starting with this VIS model, the total field anomaly is computed at an altitude of 400 km and compared with the MF2 lithospheric magnetic field model derived from CHAMP data. The modelling results of the Precambrian units of the West African cratons agree well with MF2. The anomaly in the Central African cratonic region also correlates well, although part of it is unaccounted for as yet. Furthermore, the anomalies over the Tanzanian craton and surrounding region agree very well. Most of the regions around the South African cratons are hidden by Phanerozoic cover, yet the results above the Kaapvaal craton and the southern Zimbabwe craton around the Limpopo belt show good correspondence with the observed anomaly map. The results also suggest a probable extension of the Precambrian units below the sediments of younger age. In general, the lower crust is likely to be more mafic than presumed in our current understanding of Central Africa. Deviations in the magnitude of the anomalies in some regions are likely to be due to incomplete seismic information in those regions. Thus, the thickness of crustal layers derived from magnetic anomalies for these locations may help to constrain future geophysical models in the less explored regions of Africa.

Geologic and geophysical maps of the eastern three-fourths of the Cambria 30' x 60' quadrangle, central California Coast Ranges

USGS Publications Warehouse

Graymer, R.W.; Langenheim, V.E.; Roberts, M.A.; McDougall, Kristin

2014-01-01

The Cambria 30´ x 60´ quadrangle comprises southwestern Monterey County and northwestern San Luis Obispo County. The land area includes rugged mountains of the Santa Lucia Range extending from the northwest to the southeast part of the map; the southern part of the Big Sur coast in the northwest; broad marine terraces along the southwest coast; and broadvalleys, rolling hills, and modest mountains in the northeast. This report contains geologic, gravity anomaly, and aeromagnetic anomaly maps of the eastern three-fourths of the 1:100,000-scale Cambria quadrangle and the associated geologic and geophysical databases (ArcMap databases), as well as complete descriptions of the geologic map units and the structural relations in the mapped area. A cross section is based on both the geologic map and potential-field geophysical data. The maps are presented as an interactive, multilayer PDF, rather than more traditional pre-formatted map-sheet PDFs. Various geologic, geophysical, paleontological, and base map elements are placed on separate layers, which allows the user to combine elements interactively to create map views beyond the traditional map sheets. Four traditional map sheets (geologic map, gravity map, aeromagnetic map, paleontological locality map) are easily compiled by choosing the associated data layers or by choosing the desired map under Bookmarks.

A global magnetic anomaly map. [obtained from POGO satellite data

NASA Technical Reports Server (NTRS)

Regan, R. D.; Davis, W. M.; Cain, J. C.

1974-01-01

A subset of POGO satellite magnetometer data has been formed that is suitable for analysis of crustal magnetic anomalies. Using a thirteenth order field model, fit to these data, magnetic residuals have been calculated over the world to latitude limits of plus 50 deg. These residuals averaged over one degree latitude-longitude blocks represent a detailed global magnetic anomaly map derived solely from satellite data. Preliminary analysis of the map indicates that the anomalies are real and of geological origin.

MAGSAT anomaly field data of the crustal properties of Australia

NASA Technical Reports Server (NTRS)

1983-01-01

Progress is reported in producing maps of Australia showing; crustal magnetic anomalies at constant elevation; bulk surface magnetization; and the geomagnetic field intensity, inclination and declination for the Australian region from global models of the geomagnetic field derived from MAGSAT data. The development of a data base management system is also considered.

Mapping Shear-wave Velocity Structures of the "African Anomaly" Along a Northwest to Southeast Arc From New Zealand to the Mid-Atlantic Ridge

NASA Astrophysics Data System (ADS)

Frodsham, A. E.; Wen, L.

2006-12-01

A previous study [Wang and Wen, 2006] investigated the geometry and shear velocity structure of the "African Anomaly" along a great circle arc from the East Pacific Rise to the Japan Sea, and concluded the anomaly extends 1300 km above the core-mantle boundary, that the sides of the anomaly slope towards the apex and has velocity deviations of -5% in the base and -2% to -3% in the mid-lower mantle. Wang and Wen [2004] also reported on the very low velocity province that forms the base of the "African Anomaly" and its lateral extent, but the northern edge of the anomaly was poorly constrained because of the nature of the seismic data. In this presentation we focus on the nature of the anomaly in a cross-section of the mantle along a great arc, from New Zealand, to the Mid-Atlantic Ridge off the coast of Newfoundland, centered over the anomaly. In particular, we focus on the northern edge of the "African Anomaly" where a paucity of large, deep focus earthquakes makes seismic arrivals from the northwest difficult to analyze. We map the lateral extent, thickness, and shear velocity structures of the "African Anomaly" on the basis of forward travel time and waveform modeling of direct S, ScS, and SKS waves. Seismic data used in this study were collected from PASSCAL arrays: KAAPVAAL seismic array (operating years 1997-1999), Tanzania seismic array (1994- 1995), Ethiopia/Kenya seismic array (2000-2002), and the Global Seismographic Network (1994-2002). We minimize uncertainty from earthquake mislocation by relocation of the earthquakes using a global tomographic shear wave velocity model and also correct for heterogeneities outside the anomaly. We explore various methods of data processing, such as frequency filtration, low fold stacking, and cross correlation, to best interpret the arrival times of the various seismic phases and constrain the nature of the "African Anomaly" along a northwest to southeast cross-section.

Lateral Variations in Geologic Structure and Tectonic Setting from Remote Sensing Data

DTIC Science & Technology

1983-05-01

bodies. Analogous magnetic anomaly patterns perhaps can be inferred, since regional lithologies are comparable with some volcanic bodies around the...32 14 Geologic map of the Katahdin Batholith . . . . . . . . . . . 34 15 Bouguer gravity map of Mai ne ... ............ . 36 16 Magnetic anomaly map... magnetic anomaly patterns perhaps can be inferred, since regional lithologies are comparable with some volcanic bodies around the plutons. Linear

Aeromagnetic survey map of Sacramento Valley, California

USGS Publications Warehouse

Langenheim, Victoria E.

2015-01-01

Three aeromagnetic surveys were flown to improve understanding of the geology and structure in the Sacramento Valley. The resulting data serve as a basis for geophysical interpretations, and support geological mapping, water and mineral resource investigations, and other topical studies. Local spatial variations in the Earth's magnetic field (evident as anomalies on aeromagnetic maps) reflect the distribution of magnetic minerals, primarily magnetite, in the underlying rocks. In many cases the volume content of magnetic minerals can be related to rock type, and abrupt spatial changes in the amount of magnetic minerals commonly mark lithologic or structural boundaries. Bodies of serpentinite and other mafic and ultramafic rocks tend to produce the most intense positive magnetic anomalies (for example, in the northwest part of the map). These rock types are the inferred sources, concealed beneath weakly magnetic, valley-fill deposits, of the most prominent magnetic features in the map area, the magnetic highs that extend along the valley axis. Cenozoic volcanic rocks are also an important source of magnetic anomalies and coincide with short-wavelength anomalies that can be either positive (strong central positive anomaly flanked by lower-amplitude negative anomalies) or negative (strong central negative anomaly flanked by lower-amplitude positive anomalies), reflecting the contribution of remanent magnetization. Rocks with more felsic compositions or even some sedimentary units also can cause measurable magnetic anomalies. For example, the long, linear, narrow north-trending anomalies (with amplitudes of <50 nanoteslas [nT]) along the western margin of the valley coincide with exposures of the Mesozoic Great Valley sequence. Note that isolated, short-wavelength anomalies, such as those in the city of Sacramento and along some of the major roads, are caused by manmade features.

The frequency-domain approach for apparent density mapping

NASA Astrophysics Data System (ADS)

Tong, T.; Guo, L.

2017-12-01

Apparent density mapping is a technique to estimate density distribution in the subsurface layer from the observed gravity data. It has been widely applied for geologic mapping, tectonic study and mineral exploration for decades. Apparent density mapping usually models the density layer as a collection of vertical, juxtaposed prisms in both horizontal directions, whose top and bottom surfaces are assumed to be horizontal or variable-depth, and then inverts or deconvolves the gravity anomalies to determine the density of each prism. Conventionally, the frequency-domain approach, which assumes that both top and bottom surfaces of the layer are horizontal, is usually utilized for fast density mapping. However, such assumption is not always valid in the real world, since either the top surface or the bottom surface may be variable-depth. Here, we presented a frequency-domain approach for apparent density mapping, which permits both the top and bottom surfaces of the layer to be variable-depth. We first derived the formula for forward calculation of gravity anomalies caused by the density layer, whose top and bottom surfaces are variable-depth, and the formula for inversion of gravity anomalies for the density distribution. Then we proposed the procedure for density mapping based on both the formulas of inversion and forward calculation. We tested the approach on the synthetic data, which verified its effectiveness. We also tested the approach on the real Bouguer gravity anomalies data from the central South China. The top surface was assumed to be flat and was on the sea level, and the bottom surface was considered as the Moho surface. The result presented the crustal density distribution, which was coinciding well with the basic tectonic features in the study area.

Bouguer gravity anomaly and isostatic residual gravity maps of the Tonopah 1 degree by 2 degrees Quadrangle, central Nevada

USGS Publications Warehouse

Plouff, Donald

1992-01-01

A residual isostatic gravity map (sheet 2) was prepared so that the regional effect of isostatic compensation present on the Bouguer gravity anomaly map (sheet 1) would be minimized. Isostatic corrections based on the Airy-Heiskanen system (Heiskanen and Vening Meinesz, 1958, p. 135-137) were estimated by using 3-minute topographic digitization and applying the method of Jachens and Roberts (1981). Parameters selected for the isostatic model were 25 km for the normal crustal thickness at sea level, 2.67 g/cm3 for the density of the crust, and 0.4 g/cm3 for the contrast in density between the crust and the upper mantle. These parameters were selected so that the isostatic residual gravity map would be consistent with isostatic residual gravity maps of the adjacent Walker Lake quadrangle (Plouff, 1987) and the state of Nevada (Saltus, 1988c).

Gravity and magnetic anomaly modeling and correlation using the SPHERE program and Magsat data

NASA Technical Reports Server (NTRS)

Braile, L. W.; Hinze, W. J. (Principal Investigator); Vonfrese, R. R. B.

1980-01-01

The spherical Earth inversion, modeling, and contouring software were tested and modified for processing data in the Southern Hemisphere. Preliminary geologic/tectonic maps and selected cross sections for South and Central America and the Caribbean region are being compiled and as well as gravity and magnetic models for the major geological features of the area. A preliminary gravity model of the Andeas Beniff Zone was constructed so that the density columns east and west of the subducted plates are in approximate isostatic equilibrium. The magnetic anomaly for the corresponding magnetic model of the zone is being computed with the SPHERE program. A test tape containing global magnetic measurements was converted to a tape compatible with Purdue's CDC system. NOO data were screened for periods of high diurnal activity and reduced to anomaly form using the IGS-75 model. Magnetic intensity anomaly profiles were plotted on the conterminous U.S. map using the track lines as the anomaly base level. The transcontinental magnetic high seen in POGO and MAGSAT data is also represented in the NOO data.

Gravimetric maps of the Central African Republic

NASA Technical Reports Server (NTRS)

Albouy, J.; Godivier, R. (Principal Investigator)

1982-01-01

Gravimetric maps of the Central African Republic are described including a map of Bouguer anomalies at 1/1,000,000 in two sections (eastern sheet, western sheet) and a map, in color, of Bouguer anomalies at 1/2,000,000. Instrumentation, data acquisition, calibration, and data correction procedures are discussed.

Preliminary aeromagnetic anomaly map of California

USGS Publications Warehouse

Roberts, Carter W.; Jachens, Rober C.

1999-01-01

The magnetization in crustal rocks is the vector sum of induced in minerals by the Earth’s present main field and the remanent magnetization of minerals susceptible to magnetization (chiefly magnetite) (Blakely, 1995). The direction of remanent magnetization acquired during the rock’s history can be highly variable. Crystalline rocks generally contain sufficient magnetic minerals to cause variations in the Earth’s magnetic field that can be mapped by aeromagnetic surveys. Sedimentary rocks are generally weakly magnetized and consequently have a small effect on the magnetic field: thus a magnetic anomaly map can be used to “see through” the sedimentary rock cover and can convey information on lithologic contrasts and structural trends related to the underlying crystalline basement (see Nettleton,1971; Blakely, 1995). The magnetic anomaly map (fig. 2) provides a synoptic view of major anomalies and contributes to our understanding of the tectonic development of California. Reference fields, that approximate the Earth’s main (core) field, have been subtracted from the recorded magnetic data. The resulting map of the total magnetic anomalies exhibits anomaly patterns related to the distribution of magnetized crustal rocks at depths shallower than the Curie point isotherm (the surface within the Earth beneath which temperatures are so high that rocks lose their magnetic properties). The magnetic anomaly map has been compiled from existing digital data. Data obtained from aeromagnetic surveys that were made at different times, spacings and elevations, were merged by analytical continuation of each set onto a common surface 305 m (1000 ft) above terrain. Digital data in this compatible form allows application of analytical techniques (Blakley, 1995) that can be used to enhance anomaly characteristics (e.g., wavelength and trends) and provide new interpretive information.

Exploring the combined effects of the Arctic Oscillation and ENSO on the wintertime climate over East Asia using self-organizing maps

NASA Astrophysics Data System (ADS)

Huang, Wenyu; Chen, Ruyan; Yang, Zifan; Wang, Bin; Ma, Wenqian

2017-09-01

To examine the combined effects of the different spatial patterns of the Arctic Oscillation (AO)-related sea level pressure (SLP) anomalies and the El Niño-Southern Oscillation (ENSO)-related sea surface temperature (SST) anomalies on the wintertime surface temperature anomalies over East Asia, a nonlinear method based on self-organizing maps is employed. Investigation of identified regimes reveals that the AO can affect East Asian temperature anomalies when there are significant SLP anomalies over the Arctic Ocean and northern parts of Eurasian continent. Analogously, ENSO is found to affect East Asian temperature anomalies when significant SST anomalies are present over the tropical central Pacific. The regimes with the warmest and coldest temperature anomalies over East Asia are both associated with the negative phase of the AO. The ENSO-activated, Pacific-East Asian teleconnection pattern could affect the higher latitude continental regions when the impact of the AO is switched off. When the spatial patterns of the AO and ENSO have significant, but opposite, impacts on the coastal winds, no obvious temperature anomalies can be observed over south China. Further, the circulation state with nearly the same AO and Niño3 indices may drive rather different responses in surface temperature over East Asia. The well-known continuous weakening (recovery) of the East Asian winter monsoon that occurred around 1988 (2009) can be attributed to the transitions of the spatial patterns of the SLP anomalies over the Arctic Ocean and Eurasian continent, through their modulation on the occurrences of the Ural and central Siberian blocking events.

Gravity Anomalies in the Northern Hawaiian Islands: Evidence for an Alternative Magma Chamber on Kauai and a Conjoined Niihau-Kauai Island

NASA Astrophysics Data System (ADS)

Flinders, A. F.; Ito, G.; Garcia, M.; Kim, S.; Appelgate, B.

2008-12-01

The shield stage evolution of the islands of Kauai and Niihau are poorly understood. Previous land-based gravity surveys provide only a coarse constraint on the observed gravitational field. Questions as to whether the island of Kauai was formed by a single or multiple shields and the developmental relationship between these neighboring islands are still debated. Our new land-based gravity survey of Kauai and ship-board gravity surveys around both islands identified large complete Bouguer gravitational anomalies under Kauai's Lihue Basin and offshore in the Kaulakahi Channel, a 30-km-long bathymetric ridge connecting the two islands. These gravitational highs are consistent in size and magnitude with those of other Hawaiian islands and imply local zones of high density crust, most likely attributed to magmatic intrusions; e.g. former magma chambers, or rift zones. The Lihue Basin anomaly observed is offset 20 km east from the geologically mapped caldera region. This offset implies either the unlikely case that the shield stage plumbing system connecting the magma chamber and caldera could have been inclined by up to 75 degrees from the vertical, or that the currently mapped caldera is a late feature, unrelated to shield volcanism. The location of the gravitational anomaly, in the Kaulakahi Channel, 20 km east of Niihau is consistent with geologic mapping, which indicates that Niihau is a remnant of an ancient shield volcano centered east of the island. The proximity of the Niihau gravitational anomaly 10 km from the western edge of Kauai supports the hypothesis that the two volcanoes were part of the same island.

Gravity and isostatic anomaly maps of Greece produced

NASA Astrophysics Data System (ADS)

Lagios, E.; Chailas, S.; Hipkin, R. G.

A gravity anomaly map of Greece was first compiled in the early 1970s [Makris and Stavrou, 1984] from all available gravity data collected by different Hellenic institutions. However, to compose this map the data had to be smoothed to the point that many of the smaller-wavelength gravity anomalies were lost. New work begun in 1987 has resulted in the publication of an updated map [Lagios et al., 1994] and an isostatic anomaly map derived from it.The gravity data cover the area between east longitudes 19° and 27° and north latitudes 32° and 42°, organized in files of 100-km squares and grouped in 10-km squares using UTM zone 34 coordinates. Most of the data on land come from the gravity observations of Makris and Stavrou [1984] with additional data from the Institute of Geology and Mining Exploration, the Public Oil Corporation of Greece, and Athens University. These data were checked using techniques similar to those used in compiling the gravity anomaly map of the United States, but the horizontal gradient was used as a check rather than the gravity difference. Marine data were digitized from the maps of Morelli et al. [1975a, 1975b]. All gravity anomaly values are referred to the IGSN-71 system, reduced with the standard Bouger density of 2.67 Mg/m3. We estimate the errors of the anomalies in the continental part of Greece to be ±0.9 mGal; this is expected to be smaller over fairly flat regions. For stations whose height has been determined by leveling, the error is only ±0.3 mGal. For the marine areas, the errors are about ±5 mGal [Morelli, 1990].

Planck CMB anomalies: astrophysical and cosmological secondary effects and the curse of masking

NASA Astrophysics Data System (ADS)

Rassat, A.; Starck, J.-L.; Paykari, P.; Sureau, F.; Bobin, J.

2014-08-01

Large-scale anomalies have been reported in CMB data with both WMAP and Planck data. These could be due to foreground residuals and or systematic effects, though their confirmation with Planck data suggests they are not due to a problem in the WMAP or Planck pipelines. If these anomalies are in fact primordial, then understanding their origin is fundamental to either validate the standard model of cosmology or to explore new physics. We investigate three other possible issues: 1) the trade-off between minimising systematics due to foreground contamination (with a conservative mask) and minimising systematics due to masking, 2) astrophysical secondary effects (the kinetic Doppler quadrupole and kinetic Sunyaev-Zel'dovich effect), and 3) secondary cosmological signals (the integrated Sachs-Wolfe effect). We address the masking issue by considering new procedures that use both WMAP and Planck to produce higher quality full-sky maps using the sparsity methodology (LGMCA maps). We show the impact of masking is dominant over that of residual foregrounds, and the LGMCA full-sky maps can be used without further processing to study anomalies. We consider four official Planck PR1 and two LGMCA CMB maps. Analysis of the observed CMB maps shows that only the low quadrupole and quadrupole-octopole alignment seem significant, but that the planar octopole, Axis of Evil, mirror parity and cold spot are not significant in nearly all maps considered. After subtraction of astrophysical and cosmological secondary effects, only the low quadrupole may still be considered anomalous, meaning the significance of only one anomaly is affected by secondary effect subtraction out of six anomalies considered. In the spirit of reproducible research all reconstructed maps and codes will be made available for download here http://www.cosmostat.org/anomaliesCMB.html.

A Hybrid Semi-Supervised Anomaly Detection Model for High-Dimensional Data.

PubMed

Song, Hongchao; Jiang, Zhuqing; Men, Aidong; Yang, Bo

2017-01-01

Anomaly detection, which aims to identify observations that deviate from a nominal sample, is a challenging task for high-dimensional data. Traditional distance-based anomaly detection methods compute the neighborhood distance between each observation and suffer from the curse of dimensionality in high-dimensional space; for example, the distances between any pair of samples are similar and each sample may perform like an outlier. In this paper, we propose a hybrid semi-supervised anomaly detection model for high-dimensional data that consists of two parts: a deep autoencoder (DAE) and an ensemble k -nearest neighbor graphs- ( K -NNG-) based anomaly detector. Benefiting from the ability of nonlinear mapping, the DAE is first trained to learn the intrinsic features of a high-dimensional dataset to represent the high-dimensional data in a more compact subspace. Several nonparametric KNN-based anomaly detectors are then built from different subsets that are randomly sampled from the whole dataset. The final prediction is made by all the anomaly detectors. The performance of the proposed method is evaluated on several real-life datasets, and the results confirm that the proposed hybrid model improves the detection accuracy and reduces the computational complexity.

A Hybrid Semi-Supervised Anomaly Detection Model for High-Dimensional Data

PubMed Central

Jiang, Zhuqing; Men, Aidong; Yang, Bo

2017-01-01

Anomaly detection, which aims to identify observations that deviate from a nominal sample, is a challenging task for high-dimensional data. Traditional distance-based anomaly detection methods compute the neighborhood distance between each observation and suffer from the curse of dimensionality in high-dimensional space; for example, the distances between any pair of samples are similar and each sample may perform like an outlier. In this paper, we propose a hybrid semi-supervised anomaly detection model for high-dimensional data that consists of two parts: a deep autoencoder (DAE) and an ensemble k-nearest neighbor graphs- (K-NNG-) based anomaly detector. Benefiting from the ability of nonlinear mapping, the DAE is first trained to learn the intrinsic features of a high-dimensional dataset to represent the high-dimensional data in a more compact subspace. Several nonparametric KNN-based anomaly detectors are then built from different subsets that are randomly sampled from the whole dataset. The final prediction is made by all the anomaly detectors. The performance of the proposed method is evaluated on several real-life datasets, and the results confirm that the proposed hybrid model improves the detection accuracy and reduces the computational complexity. PMID:29270197

Contour maps of lunar remanent magnetic fields

NASA Technical Reports Server (NTRS)

Hood, L. L.; Russell, C. T.; Coleman, P. J., Jr.

1981-01-01

The 2605 usable orbits of Apollo 15 and 16 subsatellite magnetometer data have been reexamined for intervals suitable for analysis of crustal magnetic anomalies. To minimize plasma-related disturbances, segments from 274 of these orbits were selected from times when the moon was either in a lobe of the geomagnetic tail or in the solar wind with the subsatellites in the lunar wake. External field contributions which remained in the selected intervals were minimized by (1) quadratic detrending of individual orbit segments with lengths much greater than anomaly wavelengths and (2) two-dimensional filtering with minimum passed wavelengths less than or equal to anomaly wavelengths. Improvements in coverage, accuracy, and resolution of previously published anomaly maps produced from these data are obtained. In addition to improved maps of the Reiner Gamma and Van de Graaff-Aitken anomalies studied previously, a third region of relatively high-amplitude anomalies centered near the crater Gerasimovich on the southeastern far side has been mapped. Both the Van de Graaff-Aitken region and the Gerasimovich region are marked by the general occurrence of extensive groups of Reiner Gamma-type swirls.

Global equivalent magnetization of the oceanic lithosphere

NASA Astrophysics Data System (ADS)

Dyment, J.; Choi, Y.; Hamoudi, M.; Lesur, V.; Thebault, E.

2015-11-01

As a by-product of the construction of a new World Digital Magnetic Anomaly Map over oceanic areas, we use an original approach based on the global forward modeling of seafloor spreading magnetic anomalies and their comparison to the available marine magnetic data to derive the first map of the equivalent magnetization over the World's ocean. This map reveals consistent patterns related to the age of the oceanic lithosphere, the spreading rate at which it was formed, and the presence of mantle thermal anomalies which affects seafloor spreading and the resulting lithosphere. As for the age, the equivalent magnetization decreases significantly during the first 10-15 Myr after its formation, probably due to the alteration of crustal magnetic minerals under pervasive hydrothermal alteration, then increases regularly between 20 and 70 Ma, reflecting variations in the field strength or source effects such as the acquisition of a secondary magnetization. As for the spreading rate, the equivalent magnetization is twice as strong in areas formed at fast rate than in those formed at slow rate, with a threshold at ∼40 km/Myr, in agreement with an independent global analysis of the amplitude of Anomaly 25. This result, combined with those from the study of the anomalous skewness of marine magnetic anomalies, allows building a unified model for the magnetic structure of normal oceanic lithosphere as a function of spreading rate. Finally, specific areas affected by thermal mantle anomalies at the time of their formation exhibit peculiar equivalent magnetization signatures, such as the cold Australian-Antarctic Discordance, marked by a lower magnetization, and several hotspots, marked by a high magnetization.

Aeromagnetic and aeromagnetic-based geologic maps of the Coastal Belt, Franciscan Complex, northern California

USGS Publications Warehouse

Langenheim, V.E.; Jachens, R.C.; McLaughlin, R.J.

2011-01-01

The Coastal belt of the Franciscan Complex represents a Late Cretaceous to Miocene accretionary prism and overlying slope deposits. Its equivalents may extend from the offshore outer borderland of southern California to north of the Mendocino Triple Junction under the Eel River Basin and in the offshore of Cascadia. The Coastal belt is exposed on land in northern California, yet its structure and stratigraphy are incompletely known because of discontinuous exposure, structural disruption, and lithologically non-distinctive clastic rocks. The intent of this report is to make available, in map form, aeromagnetic data covering the Coastal belt that provide a new dataset to aid in mapping, understanding, and interpreting the incompletely understood geology and structure in northern California.The newly merged aeromagnetic data over the Coastal belt of the Franciscan Complex reveal long, linear anomalies that indicate remarkably coherent structure within a terrane where mapping at the surface indicates complex deformation and that has been described as "broken formation" and, even locally as "mélange". The anomalies in the Coastal belt are primarily sourced by volcanic-rich graywackes and exotic blocks of basalt. Some anomalies along the contact of the Coastal belt with the Central belt are likely caused by local interleaving of components of the Coast Ranges ophiolite. These data can be used to map additional exotic blocks within the Coastal belt and to distinguish lithologically indistinct graywackes within the Coastal terrane. Using anomaly asymmetry allows projection of these "layers" into the subsurface. This analysis indicates predominant northeast dips consistent with tectonic interleaving of blocks within a subduction zone.

Subduction-zone magnetic anomalies and implications for hydrated forearc mantle

USGS Publications Warehouse

Blakely, R.J.; Brocher, T.M.; Wells, R.E.

2005-01-01

Continental mantle in subduction zones is hydrated by release of water from the underlying oceanic plate. Magnetite is a significant byproduct of mantle hydration, and forearc mantle, cooled by subduction, should contribute to long-wavelength magnetic anomalies above subduction zones. We test this hypothesis with a quantitative model of the Cascadia convergent margin, based on gravity and aeromagnetic anomalies and constrained by seismic velocities, and find that hydrated mantle explains an important disparity in potential-field anomalies of Cascadia. A comparison with aeromagnetic data, thermal models, and earthquakes of Cascadia, Japan, and southern Alaska suggests that magnetic mantle may be common in forearc settings and thus magnetic anomalies may be useful in mapping hydrated mantle in convergent margins worldwide. ?? 2005 Geological Society of America.

Airborne gamma-ray spectrometer and magnetometer survey: Concrete quadrangle (Washington). Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1981-01-01

Twenty-five uranium anomalies meet the minimum statistical requirements as defined. These anomalies are tabulated and are shown on the Uranium Anomaly Interpretation Map. Potassium (%K), equivalent Uranium (ppM eU), equivalent Thorium (ppM eT), eU/eT, eU/K, eT/K, and magnetic pseudo-contour maps are presented. Stacked Profiles showing geologic strips maps along each flight-line, together with sensor data, and ancillary data are presented. All maps and profiles were prepared on a scale of 1:250,000, but have been reduced to 1:500,000 for presentation.

World Digital Magnetic Anomaly Map, development towards the Second Edition. (Invited)

NASA Astrophysics Data System (ADS)

Korhonen, J. V.

2009-12-01

Magnetic anomalies are small deviations in the Earth’s main magnetic field, caused by variation of magnetization in the uppermost lithosphere. Magnetic anomalies provide spatial key information for understanding the structure and evolution of the Earths crust. In practice these anomalies are used e.g. for assessment and prospecting of geological natural resources and planning of land use. A common way to calculate a magnetic anomaly value has been to subtract International Geomagnetic Reference Field (IGRF) from a total field measurement that is cleaned from short term variation of the Earth's magnetic field. World Digital Magnetic Anomaly Map (WDMAM) is a collaborative project between member organizations of International Association of Geomagnetism and Aeronomy (IAGA) and the Commission for Geological Map of the World (CGMW). The First Edition of the map was published in 2007. It consisted of a paper map 1:50 Million and a 3 minutes global grid of total field anomalies at an altitude of 5 km above the geoid. The First Edition was aimed to compile as much as possible available land and sea magnetic data, and homogenize it by comparing anomalies with a satellite magnetic lithospheric field model. This first version was prepared in a tight schedule, to show the usefulness of the map to the community and to form a basis for later development and future editions of the map. Hence, much was left to be improved for the second edition, including sparse coverage in two continents and all southern seas. The satellite models were understood to gain more detail in near future when the CHAMP-satellite would reach lower orbits, and hence higher resolution. The SWARM-satellite constellation was seen to produce even more suitable data in a few years thereafter. Ocean magnetic data sets required careful processing and leveling. The method of homogenization of anomalies included replacing long wavelength information by satellite model spectral data, and hence rejecting corresponding measurements. A challenge was left to include high quality anomaly levels of near ground measurements in global magnetic anomaly grid, where available. For these purposes WDMAM task force calls for both new and improved old data sets, advanced methods for data processing and compilation, and improved anomaly definition schemes. All these would be put together and submitted as candidate grids in 2010, and finally released as WDMAM 2011 (Second Edition) at IUGG 2011, in Australia. All contributions towards this purpose are solicited.

Effect of Varying Crustal Thickness on CHAMP Geopotential Data

NASA Technical Reports Server (NTRS)

Taylor, P. T.; Kis, K. I.; vonFrese, R. R. B.; Korhonen, J. V.; Wittmann, G.; Kim, H. R.; Potts, L. V.

2003-01-01

To determine the effect of crustal thickness variation on satellite-altitude geopotential anomalies we compared two regions of Europe with vastly different values, Central/Southern Finland and the Pannonian Basin. Crustal thickness exceeds 62 km in Finland and is less than 26 km in the Pannonian Basin. Heat-flow maps indicate that the thinner and more active crust of the Pannonian Basin has a value nearly three times that of the Finnish Svecofennian Province. Ground based gravity mapping in Hungary shows that the free-air gravity anomalies across the Pannonian Basin are near 0 to +20 mGal with shorter wavelength anomalies from +40 to less than +60 mGal and some 0 to greater than -20 mGal. Larger anomalies are detected in the mountainous areas. The minor value anomalies can indicate the isostatic equilibrium for Hungary (the central part of the Pannonian Basin). Gravity data over Finland are complicated by de-glaciation. CHAMP gravity data (400 km) indicates a west-east positive gradient of greater than 4 mGal across Central/Southern Finland and an ovoid positive anomaly (approximately 4 mGal) quasi-coincidental with the magnetic anomaly traversing the Pannonian Basin. CHAMP magnetic data (425 km) reveal elongated semicircular negative anomalies for both regions with South-Central Finland having larger amplitude (less than -6 nT) than that over the Pannonian Basin, Hungary (less than -5 nT). In both regions subducted oceanic lithosphere has been proposed as the anomalous body.

Application of filtering techniques in preprocessing magnetic data

NASA Astrophysics Data System (ADS)

Liu, Haijun; Yi, Yongping; Yang, Hongxia; Hu, Guochuang; Liu, Guoming

2010-08-01

High precision magnetic exploration is a popular geophysical technique for its simplicity and its effectiveness. The explanation in high precision magnetic exploration is always a difficulty because of the existence of noise and disturbance factors, so it is necessary to find an effective preprocessing method to get rid of the affection of interference factors before further processing. The common way to do this work is by filtering. There are many kinds of filtering methods. In this paper we introduced in detail three popular kinds of filtering techniques including regularized filtering technique, sliding averages filtering technique, compensation smoothing filtering technique. Then we designed the work flow of filtering program based on these techniques and realized it with the help of DELPHI. To check it we applied it to preprocess magnetic data of a certain place in China. Comparing the initial contour map with the filtered contour map, we can see clearly the perfect effect our program. The contour map processed by our program is very smooth and the high frequency parts of data are disappeared. After filtering, we separated useful signals and noisy signals, minor anomaly and major anomaly, local anomaly and regional anomaly. It made us easily to focus on the useful information. Our program can be used to preprocess magnetic data. The results showed the effectiveness of our program.

Upper Lithospheric Sources of Magnetic and Gravity Anomalies of The Fennoscandian Shield

NASA Astrophysics Data System (ADS)

Korhonen, J. V.; Koistinen, T.; Working GroupFennoscandian Geophysical Maps

Magnetic total intensity anomalies (DGRF-65), Bouguer anomalies (d=2670 kg/m3) and geological units from 3400 Ma to present of the Fennoscandian Shield have been digitally compiled and printed as maps 1:2 000 000. Insert maps 1:15,000,000 com- pare anomaly components in different source scales: pseudogravimetric anomaly ver- sus Bouguer anomaly, DGRF-65 anomaly versus pseudomagnetic anomaly, magnetic vertical derivative versus second derivative of Bouguer anomaly. Data on bulk density, total magnetisation and lithology of samples have been presented as scatter diagrams and distribution maps of the average petrophysical properties in space and time. In sample level, the bulk density correlates with the lithology and, together with mag- netisation, establishes four principal populations of petrophysical properties. The av- erage properties, calculated for 5 km x 5 km cells, correlate only weakly with av- erage Bouguer-anomaly and magnetic anomaly, revealing major deep seated sources of anomalies. Pseudogravimetric and Bouguer anomalies correlate only locally with each other. The correlation is negative in the area of felsic Palaeoproterozoic rocks in W- and NW-parts of the Shield. In 2D models the sources of gravity anomalies are explained by lateral variation of density in upper and lower crust. Smoothly varying regional components are explained by boundaries of the lower crust, the upper mantle and the astenosphere. Magnetic anomalies are explained by lateral variation of magnetisation in the upper crust. Re- gional components are due to the lateral variation of magnetisation in the lower crust and the boundaries of lower crust and mantle and the Curie isotherm of magnetite.

Imprint of Southern Red Sea Major Tectonic Zone In A New Bouguer Anomaly Map of Southern Yemen Margin

NASA Astrophysics Data System (ADS)

Blecha, V.

A new Bouguer anomaly map of western part of southern Yemen margin has been compiled. Densities of rock samples from main geological units (Precambrian base- ment, Mesozoic sediments, Tertiary volcanites) have been measured and used for grav- ity modeling. Regional gravity map indicates decrease of thickness of continental crust from volcanites of the Yemen Trap Series towards the coast of the Gulf of Aden. Most remarkable feature in the map of residual anomalies is a positive anomaly over the Dhala graben. The Dhala graben is a prominent geological structure in the area of study trending parallel to the Red Sea axis. Gravity modeling on a profile across the Dhala graben presumes intrusive plutonic rocks beneath the graben. There are two other areas in the southwestern tip of Arabia, which have essentially the same struc- tural position as the Dhala graben: the Jabal Tirf volcanic rift zone in the southern Saudi Arabia and Jabal Hufash extensional zone in northern Yemen. All three areas extend along the line trending parallel to the Red Sea axis with length of about 500 km. The line coincides with the axis of Afar (Danakil) depression after Arabia is shifted and rotated back to Africa. These facts imply conclusion that the Oligocene - Early Miocene magmatic activity on the Jabal Tirf - Dhala lineament is related to the same original deep tectonic zone, forming present-day Afar depression and still active.

Regional geochemistry Bandung Quadrangle West Java: for environmental and resources studies

NASA Astrophysics Data System (ADS)

Sendjaja, Purnama; Baharuddin

2017-06-01

Geochemical mapping based on the stream sediment method has been carried out in the whole of Java Region by the Centre for Geological Survey. The Regional Geochemistry Bandung Quadrangle as part of West Java Region has been mapped in 1:100.000 scale map, base on the Geological Map of Bandung Quadrangle. About 82 stream sediment samples collected and sieved in the 80 mesh sieve fraction during the field work session at 2011. This fraction was prepared and analysed for 30 elements by X-ray fluorescence spectrometry at the Centre for Geological Survey Laboratory. There are some elements indicating significant anomaly in this region, and it is important to determine the present abundance and spatial distribution of the elements for presuming result from natural product or derived from human activities. The volcanic products (Tangkuban Perahu Volcano, Volcanic Rock Complex and Quarternary Volcanic-Alluvial Deposit) are clearly identified on the distribution of As, Ba, Cl, Cu, Zr and La elements. However Mn, Zn, V and Sr are related to precipitation in the Tertiary Sediments, while the influence of human activities are showing from a geochemical map of Cl, Cr, Cu, Pb and Zn that show scattered anomalies localized close to the cities, farming and industries.

High resolution Slovak Bouguer gravity anomaly map and its enhanced derivative transformations: new possibilities for interpretation of anomalous gravity fields

NASA Astrophysics Data System (ADS)

Pašteka, Roman; Zahorec, Pavol; Kušnirák, David; Bošanský, Marián; Papčo, Juraj; Szalaiová, Viktória; Krajňák, Martin; Ivan, Marušiak; Mikuška, Ján; Bielik, Miroslav

2017-06-01

The paper deals with the revision and enrichment of the present gravimetric database of the Slovak Republic. The output of this process is a new version of the complete Bouguer anomaly (CBA) field on our territory. Thanks to the taking into account of more accurate terrain corrections, this field has significantly higher quality and higher resolution capabilities. The excellent features of this map will allow us to re-evaluate and improve the qualitative interpretation of the gravity field when researching the structural and tectonic geology of the Western Carpathian lithosphere. In the contribution we also analyse the field of the new CBA based on the properties of various transformed fields - in particular the horizontal gradient, which by its local maximums defines important density boundaries in the lateral direction. All original and new transformed maps make a significant contribution to improving the geological interpretation of the CBA field. Except for the horizontal gradient field, we are also interested in a new special transformation of TDXAS, which excellently separates various detected anomalies of gravity field and improves their lateral delimitation.

Remanent magnetization and three-dimensional density model of the Kentucky anomaly region

NASA Technical Reports Server (NTRS)

1982-01-01

Existing software was modified to handle 3-D density and magnetization models of the Kentucky body and is being tested. Gravity and magnetic anomaly data sets are ready for use. A preliminary block model is under construction using the 1:1,000,000 maps. An x-y grid to overlay the 1:2,500,000 Albers maps and keyed to the 1:1,000,000 scale block models was created. Software was developed to generate a smoothed MAGSAT data set over this grid; this is to be input to an inversion program for generating the regional magnetization map. The regional scale 1:2,500,000 map mosaic is being digitized using previous magnetization models, the U.S. magnetic anomaly map, and regional tectonic maps as a guide.

An interpretation of the 1996 aeromagnetic data for the Santa Cruz basin, Tumacacori Mountains, Santa Rita Mountains, and Patagonia Mountains, south-central Arizona

USGS Publications Warehouse

Gettings, Mark E.

2002-01-01

High resolution aeromagnetic survey data flown at 250 m above the terrain and 250 m line spacing over the Santa Cruz Valley and the surrounding Tumacacori, Patagonia, and Santa Rita Mountains has been interpreted by correlation of the magnetic anomaly field and various derivative maps with geologic maps. Measurements of in-situ magnetic properties of several of the map units determined whether or not mapped lithologies were responsible for observed anomalies. Correlation of the magnetic anomaly field with mapped geology shows that numerous map units of volcanic and intrusive rocks from Jurassic Middle Tertiary in age are reversely polarized, some of which have not been previously reported. Trends derived from the magnetic anomaly data correlate closely with structures from major tectonic events in the geologic history of the area including Triassic-Jurassic crustal accretion and magmatism, Laramide magmatism and tectonism, northeast-southwest Mid-Tertiary extension, and east-west Basin and Range extension. Application of two textural measures to the magnetic anomaly data, number of peaks and troughs per km (a measure of roughness) and Euclidean length per km (a measure of amplitude), delineated areas of consistent magnetic anomaly texture. These measures were successful at the delineation of areas of consistent magnetic lithology both on the surface and in the subsurface beneath basin fill. Several areas of basement prospective for mineral resources beneath basin fill were identified.

Towards developing an analytical procedure of defining the equatorial electrojet for correcting satellite magnetic anomaly data

NASA Technical Reports Server (NTRS)

Ravat, Dhananjay; Hinze, William J.

1991-01-01

Analysis of the total magnetic intensity MAGSAT data has identified and characterized the variability of ionospheric current effects as reflected in the geomagnetic field as a function of longitude, elevation, and time (daily as well as monthly variations). This analysis verifies previous observations in POGO data and provides important boundary conditions for theoretical studies of ionospheric currents. Furthermore, the observations have led to a procedure to remove these temporal perturbations from lithospheric MAGSAT magnetic anomaly data based on 'along-the-dip-latitude' averages from dawn and dusk data sets grouped according to longitudes, time (months), and elevation. Using this method, high-resolution lithospheric magnetic anomaly maps have been prepared of the earth over a plus or minus 50 deg latitude band. These maps have proven useful in the study of the structures, nature, and processes of the lithosphere.

Lithologic boundaries from gravity and magnetic anomalies over Proterozoic Dalma volcanics

NASA Astrophysics Data System (ADS)

Yadav, Pramod Kumar; Adhikari, P. K.; Srivastava, Shalivahan; Maurya, Ved P.; Tripathi, Anurag; Singh, Shailendra; Singh, Roshan K.; Bage, Ashish K.

2018-03-01

Dalma volcanics (DVs) has intruded the older Singhbhum Group of Metapelites. Despite DVs being rich in mineralisation, its boundaries are not clearly demarcated. Gravity and magnetic surveys have been attempted for mapping the boundaries in DVs. These surveys were made in the northern fringe of the DVs over an area of ˜ 0.70 km2 along 13 parallel lines at 50 m spacing. The data was acquired at ˜ 25 m spacing. The surveys were taken for determination of lithological boundaries, depths and nature of causative source using Euler depth solutions and radially averaged power spectrum (RAPS). Residual anomaly maps of gravity and magnetic intensity show the same trend as that of Bouguer gravity anomaly and total magnetic intensity anomaly map indicating towards shallow sources. The magnetic map in general follows the same pattern as that of gravity anomaly maps. The map shows coincident high gravity and magnetic anomalies. These anomalies together with resistivity signatures confirm that the northern fringe of DVs hosts volcanogenic massive sulphide settings. The Euler depth solution delineated the lateral boundaries and nature of the source. It seems that the source is of spherical nature lying within a depth range of 25-40 m. The obtained lithological (vertical) units from RAPS are between Lower DVs, Upper DVs and Singhbhum Group Metapelites at depths of ˜ 15, ˜ 25 and ˜ 40 m, respectively. The metallogeny is associated with the Upper DVs and the corresponding delineated lithological (vertical) unit is indicative of the top of the ore body. Good agreement is observed with the geological succession from the drilling data and resistivity data. The findings suggest that the northern fringe of DVs could be a preferred target for drilling.

Use of MAGSAT anomaly data for crustal structure and mineral resources in the US midcontinent

NASA Technical Reports Server (NTRS)

Carmichael, R. S. (Principal Investigator)

1982-01-01

Progress in the correlation of MAGSAT anomaly maps with geological and geophysical data sets is reported. An excerpt from Bouguer gravity map of the U.S. was filtered to retain wavelengths of 250 km, thus being physically somewhat analogous to MAGSAT data at 400 km height. Residual anomalies were extracted to compare with the satellite magnetics.

Improved determination of vector lithospheric magnetic anomalies from MAGSAT data

NASA Technical Reports Server (NTRS)

Ravat, Dhananjay

1993-01-01

Scientific contributions made in developing new methods to isolate and map vector magnetic anomalies from measurements made by Magsat are described. In addition to the objective of the proposal, the isolation and mapping of equatorial vector lithospheric Magsat anomalies, isolation of polar ionospheric fields during the period were also studied. Significant progress was also made in isolation of polar delta(Z) component and scalar anomalies as well as integration and synthesis of various techniques of removing equatorial and polar ionospheric effects. The significant contributions of this research are: (1) development of empirical/analytical techniques in modeling ionospheric fields in Magsat data and their removal from uncorrected anomalies to obtain better estimates of lithospheric anomalies (this task was accomplished for equatorial delta(X), delta(Z), and delta(B) component and polar delta(Z) and delta(B) component measurements; (2) integration of important processing techniques developed during the last decade with the newly developed technologies of ionospheric field modeling into an optimum processing scheme; and (3) implementation of the above processing scheme to map the most robust magnetic anomalies of the lithosphere (components as well as scalar).

National Magnetic Anomaly Map

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1976-01-01

A record of the conclusions of a three-day meeting and workshop of the Committee for a National Magnetic Anomaly Map held in February 1976 is presented. The purpose of he workshop was to prepare a statement of the benefits, objectives, specifications, and requirements of a NMAM and establish a working plan for producing the map. (ACR)

Interpretation of the 'Trans European Suture Zone' by a multiscale aeromagnetic dataset

NASA Astrophysics Data System (ADS)

Milano, Maurizio; Fedi, Maurizio

2015-04-01

One of the main goals in crustal geomagnetic prospecting is to obtain information about the sources of magnetic anomalies in order to model the geological structure of the Earth's crust. A "multiscale approach" is very useful to analyze, concurrently, the effects of sources placed at different depths, observing the potential field at various altitudes from the Earth's surface. The aim of this work is the study of the main geological structure of Central Europe, the "Trans European Suture Zone", using high-resolution aeromagnetic data. The 'TESZ' is the most prominent geological boundary in Europe, oriented NW-SE from the North Sea to the Black Sea and separating The Paleozoic platform in the south and west from the Precambrian East European craton. At high altitudes the European magnetic field is characterized by a large and extended magnetic low, which is related to the deep TESZ structure. The study of this anomaly field began by detecting the position of the anomaly sources using the properties of the Analytical Signal modulus (AS). The AS map presents anomalies in which the dipolar behavior of the magnetic anomaly field is substantially removed and the maxima are placed directly above the anomaly sources. The multiridge method has been applied to the Analytical Signal modulus in order to have information about the sources' depths in the TESZ region. Many profiles were tracked transversely to the fault line in order to map at depth the main magnetic discontinuities. Cause of the low heat flow of the Central Europe, we were able to get information also in the lower crust and to map the deep Moho discontinuity. Available geological sections based on seismic data show consistent results with our interpretation.

World Digital Magnetic Anomaly Map version 2 (WDMAM v.2) - released for research and education

NASA Astrophysics Data System (ADS)

CHOI-Dyment, Y.; Lesur, V.; Dyment, J.; Hamoudi, M.; Thebault, E.; Catalan, M.

2015-12-01

The World Digital Magnetic Anomaly Map is an international initiative carried out under the auspices of the International Association of Geomagnetism and Aeronomy (IAGA) and the Commission for the Geological Map of the World (CGMW). A first version of the map has been published and distributed eight years ago (WDMAM v1; Korhonen et al., 2007). We have produced a candidate which has been accepted as the second version of this map (WDMAM v2) at the International Union of Geophysics and Geodesy in Prag, in June 2015. On land, we adopted an alternative approach avoiding any unnecessary processing on existing aeromagnetic compilations. When available, we used the original aeromagnetic data. As a result the final compilation remains an acceptable representation of the national and international data grids. Over oceanic areas the marine data have been extended. In areas of insufficient data coverage, a model has been computed based on a modified digital grid of the oceanic lithosphere age, considering plate motions in the determination of magnetization vector directions. This model has been further adjusted to the available data, resulting in a better representation of the anomalies. The final grid will be periodically upgraded. Version 2.0 has been released and is available at wdmam.org to support both research and education projects. Colleagues willing to contribute data for future releases (and become a co-author of the map) should contact any of the authors or Jerome Dyment (chair of the WDMAM Task Force) at jdy@ipgp.fr .

Imaging Small-scale Seafloor and Sub-seafloor Tectonic Fabric Using Satellite Altimetry

NASA Astrophysics Data System (ADS)

Sandwell, D. T.; Müller, D.; Matthews, K. J.; Smith, W. H. F.

2017-12-01

Marine gravity anomalies derived from satellite radar altimetry now provide an unprecedented resolution of about 7 km for mapping small-scale seafloor and sub-seafloor tectonic fabric. These gravity maps are improving rapidly because three satellite altimeters are currently collecting data with dense track coverage: (1) CryoSat-2 has routinely collected altimetry data over ice, land, and ocean since July 2010. The satellite has a long 369-day repeat cycle resulting in an average ground track spacing of 3.5 km at the equator. To date it has completed more than 7 geodetic mappings of the ocean surface. (2) The SARAL AltiKa altimeter began a non-repeat orbit phase in July 2016. AltiKa has a new Ka-band instrument with a factor of 2 better range precision than all previous altimeters. (3) Jason-2 was placed in a geodetic orbit starting July 2017. It has lower inclination coverage to provide improved gravity recovery for N-S trending anomalies. These data combined with sparse soundings will provide a dramatic improvement in predicted bathymetry and thus help guide future deep ocean surveys. The most recent global marine gravity anomaly map based on these geodetic mission data with 2-pass retracking for optimal range precision has an accuracy that is 2-4 times better than the maps derived from Geosat and ERS-1. The new data reveal the detailed fabric of fracture zones, previously unmapped, now extinct oceanic microplates in the central Pacific, and fault networks buried beneath thick sediments along continental margins. By combining satellite altimetry with marine magnetic anomalies and seafloor age dates from rock samples we are able to pinpoint the geometry and age of major plate reorganizations, particularly the enigmatic 100 Ma event, which occurred during the Cretaceous Magnetic Superchron.

Planck CMB Anomalies: Astrophysical and Cosmological Secondary Effects and the Curse of Masking

NASA Astrophysics Data System (ADS)

Rassat, Anais

2016-07-01

Large-scale anomalies have been reported in CMB data with both WMAP and Planck data. These could be due to foreground residuals and or systematic effects, though their confirmation with Planck data suggests they are not due to a problem in the WMAP or Planck pipelines. If these anomalies are in fact primordial, then understanding their origin is fundamental to either validate the standard model of cosmology or to explore new physics. We investigate three other possible issues: 1) the trade-off between minimising systematics due to foreground contamination (with a conservative mask) and minimising systematics due to masking, 2) astrophysical secondary effects (the kinetic Doppler quadrupole and kinetic Sunyaev-Zel'dovich effect), and 3) secondary cosmological signals (the integrated Sachs-Wolfe effect). We address the masking issue by considering new procedures that use both WMAP and Planck to produce higher quality full-sky maps using the sparsity methodology (LGMCA maps). We show the impact of masking is dominant over that of residual foregrounds, and the LGMCA full-sky maps can be used without further processing to study anomalies. We consider four official Planck PR1 and two LGMCA CMB maps. Analysis of the observed CMB maps shows that only the low quadrupole and quadrupole-octopole alignment seem significant, but that the planar octopole, Axis of Evil, mirror parity and cold spot are not significant in nearly all maps considered. After subtraction of astrophysical and cosmological secondary effects, only the low quadrupole may still be considered anomalous, meaning the significance of only one anomaly is affected by secondary effect subtraction out of six anomalies considered. In the spirit of reproducible research all reconstructed maps and codes are available online.

3D gravimetric investigation of the Cerro do Jarau structure, Rio Grande do Sul, Brazil

NASA Astrophysics Data System (ADS)

Giacomini, Bruno B.; Leite, Emilson P.; Crósta, Alvaro P.

2017-04-01

The Cerro do Jarau structure is possibly the third Brazilian basaltic crater formed in continental flood basalt of the Serra Geral Formation, Paraná Basin, a large igneous province (LIP) in southern Brazil. It is a nearly circular landform with a diameter of approximately 13 km that rises 200 m above the plains of the "pampas" in southern Brazil. In this work, Bouguer anomalies were calculated from gravity accelerations measured on the area of this structure. The residual Bouguer map shows a strong positive anomaly trending NE-SW, located in the northeastern part of the structure, a feature not commonly associated with impact structures. However, the negative anomaly present in its center and the circular positive anomaly surrounding the central portion are typical of impact structures. The residual Bouguer anomaly varies from -2 mGal to 8 mGal. The positive circular anomaly is not spatially coincident with the rim of the structure. Based on the interpretation of our gravimetric data, the estimated diameter of the structure is 12 km and the central portion has a diameter of approximately 5 km, both slightly smaller than previously suggested. The Bouguer anomaly map was inverted into a 3D density model using a constrained inversion method with a maximum density contrast of 0.5 g cm-3. This model was interpreted to associate densities with rock types, resulting in a geological model. This geological model is in accordance with the meteorite impact nature of Cerro do Jarau.

Paleo-Pole Positions from Martian Magnetic Anomaly Data

NASA Technical Reports Server (NTRS)

Taylor, Patrick T.; Frawley, James J.

2003-01-01

Magnetic component anomaly maps were made from five mapping cycles of the Mars Global Surveyor s magnetometer data. Our goal was to find and isolate positive and negative anomaly pairs which would indicate magnetization of a single source body. From these anomalies we could compute the direction of the magnetizing vector and subsequently the location of the magnetic pole existing at the time of magnetization. We found nine suitable anomaly pairs and from these we computed four North and 3 South poles with two at approximately 60 degrees north latitude. These results suggest that during the existence of the Martian main magnetic field it experienced several reversals.

Paleo-Pole Positions from Martian Magnetic Anomaly Data

NASA Technical Reports Server (NTRS)

Frawley, James J.; Taylor, Patrick T.

2004-01-01

Magnetic component anomaly maps were made from five mapping cycles of the Mars Global Surveyor's magnetometer data. Our goal was to find and isolate positive and negative anomaly pairs which would indicate magnetization of a single source body. From these anomalies we could compute the direction of the magnetizing vector and subsequently the location of the magnetic pole existing at the time of magnetization. We found nine suitable anomaly pairs and from these we computed paleo-poles that were nearly equally divided between north, south and mid-latitudes. These results suggest that during the existence of the martian main magnetic field it experienced several reversals and excursions.

The thickness of cover sequences in the Western Desert of Iraq from a power spectrum analysis of gravity and magnetic data

NASA Astrophysics Data System (ADS)

Mousa, Ahmed; Mickus, Kevin; Al-Rahim, Ali

2017-05-01

The Western Desert of Iraq is part of the stable shelf region on the Arabian Plate where the subsurface structural makeup is relatively unknown due to the lack of cropping out rocks, deep drill holes and deep seismic refraction and reflection profiles. To remedy this situation, magnetic and gravity data were analyzed to determine the thickness of the Phanerozoic cover sequences. The 2-D power spectrum method was used to estimate the depth to density and magnetic susceptibility interfaces by using 0.5° square windows. Additionally, the gravity data were analyzed using isostatic residual and decompensative methods to isolate gravity anomalies due to upper crustal density sources. The decompensative gravity anomaly and the differentially reduced to the pole magnetic map indicate a series of mainly north-south and northwest-southeast trending maxima and minima anomalies related to Proterozoic basement lithologies and the varying thickness of cover sequences. The magnetic and gravity derived thickness of cover sequences maps indicate that these thicknesses range from 4.5 to 11.5 km. Both maps in general are in agreement but more detail in the cover thicknesses was determined by the gravity analysis. The gravity-based cover thickness maps indicates regions with shallower depths than the magnetic-based cover thickness t map which may be due to density differences between limestone and shale units within the Paleozoic sediments. The final thickness maps indicate that the Western Desert is a complicated region of basins and uplifts that are more complex than have been shown on previous structural maps of the Western Desert. These basins and uplifts may be related to Paleozoic compressional tectonic events and possibly to the opening of the Tethys Ocean. In addition, petroleum exploration could be extended to three basins outlined by our analysis within the relatively unexplored western portions of the Western Desert.

Multilayer apparent magnetization mapping approach and its application in mineral exploration

NASA Astrophysics Data System (ADS)

Guo, L.; Meng, X.; Chen, Z.

2016-12-01

Apparent magnetization mapping is a technique to estimate magnetization distribution in the subsurface from the observed magnetic data. It has been applied for geologic mapping and mineral exploration for decades. Apparent magnetization mapping usually models the magnetic layer as a collection of vertical, juxtaposed prisms in both horizontal directions, whose top and bottom surfaces are assumed to be horizontal or variable-depth, and then inverts or deconvolves the magnetic anomalies in the space or frequency domain to determine the magnetization of each prism. The conventional mapping approaches usually assume that magnetic sources contain no remanent magnetization. However, such assumptions are not always valid in mineral exploration of metallic ores. In this case, the negligence of the remanence will result in large geologic deviation or the occurrence of negative magnetization. One alternate strategy is to transform the observed magnetic anomalies into some quantities that are insensitive or weakly sensitive to the remanence and then subsequently to perform inversion on these quantities, without needing any a priori information about remanent magnetization. Such kinds of quantities include the amplitude of the magnetic total field anomaly (AMA), and the normalized magnetic source strength (NSS). Here, we present a space-domain inversion approach for multilayer magnetization mapping based on the AMA for reducing effects of remanence. In the real world, magnetization usually varies vertically in the subsurface. If we use only one-layer model for mapping, the result is simply vertical superposition of different magnetization distributions. Hence, a multi-layer model for mapping would be a more realistic approach. We test the approach on the real data from a metallic deposit area in North China. The results demonstrated that our approach is feasible and produces considerable magnetization distribution from top layer to bottom layer in the subsurface.

Development of a Global Agricultural Hotspot Detection and Early Warning System

NASA Astrophysics Data System (ADS)

Lemoine, G.; Rembold, F.; Urbano, F.; Csak, G.

2015-12-01

The number of web based platforms for crop monitoring has grown rapidly over the last years and anomaly maps and time profiles of remote sensing derived indicators can be accessed online thanks to a number of web based portals. However, while these systems make available a large amount of crop monitoring data to the agriculture and food security analysts, there is no global platform which provides agricultural production hotspot warning in a highly automatic and timely manner. Therefore a web based system providing timely warning evidence as maps and short narratives is currently under development by the Joint Research Centre. The system (called "HotSpot Detection System of Agriculture Production Anomalies", HSDS) will focus on water limited agricultural systems worldwide. The automatic analysis of relevant meteorological and vegetation indicators at selected administrative units (Gaul 1 level) will trigger warning messages for the areas where anomalous conditions are observed. The level of warning (ranging from "watch" to "alert") will depend on the nature and number of indicators for which an anomaly is detected. Information regarding the extent of the agricultural areas concerned by the anomaly and the progress of the agricultural season will complement the warning label. In addition, we are testing supplementary detailed information from other sources for the areas triggering a warning. These regard the automatic web-based and food security-tailored analysis of media (using the JRC Media Monitor semantic search engine) and the automatic detection of active crop area using Sentinel 1, upcoming Sentinel-2 and Landsat 8 imagery processed in Google Earth Engine. The basic processing will be fully automated and updated every 10 days exploiting low resolution rainfall estimates and satellite vegetation indices. Maps, trend graphs and statistics accompanied by short narratives edited by a team of crop monitoring experts, will be made available on the website on a monthly basis.

Identification of mineral resources in Afghanistan-Detecting and mapping resource anomalies in prioritized areas using geophysical and remote sensing (ASTER and HyMap) data

USGS Publications Warehouse

King, Trude V.V.; Johnson, Michaela R.; Hubbard, Bernard E.; Drenth, Benjamin J.

2011-01-01

During the independent analysis of the geophysical, ASTER, and imaging spectrometer (HyMap) data by USGS scientists, previously unrecognized targets of potential mineralization were identified using evaluation criteria most suitable to the individual dataset. These anomalous zones offer targets of opportunity that warrant additional field verification. This report describes the standards used to define the anomalies, summarizes the results of the evaluations for each type of data, and discusses the importance and implications of regions of anomaly overlap between two or three of the datasets.

Use of MAGSAT anomaly data for crustal structure and mineral resources in the US midcontinent

NASA Technical Reports Server (NTRS)

Carmichael, R. S. (Principal Investigator)

1981-01-01

While the preliminary magnetic anomaly map for the centra midcontinent is only in the hand-drawn stage, it agrees in broad aspects with the preliminary global MAGSAT map provided by NASA. Because of data evaluation and finer scale averaging, there are more detailed features which hold promise for eventual geological/crustal interpretation. Some current analysis is directed at examining whether a map data feature such as an elongated anomaly or trend, which seems parallel to satellite data tracks, is likely of crustal origin or is an artifact of the data set.

Aeromagnetic interpretation and mineral investigations in the Bolu, Canakkale-Karabiga, Demirkoy, Ezine, and Orhaneli areas of northwestern Turkey in 1968

USGS Publications Warehouse

Jacobson, Herbert Samuel; Tumer, Ural; Karahacioglu, Hamit

1972-01-01

This report reviews progress made during 1968 in the continuing Joint Haden Tetkik ve Arama Enstitusu (MSA)-U. S. Geological Survey (USGS) Mineral Exploration and Training Project, Subproject 2. Subproject 2 is concerned with aeromagnetic interpretation of MTA's aeromagnetic surveys, and ground investigations of selected aeromagnetic anomalies. This report includes new aeromagnetic maps for the Bolu, Canakkale-Karabiga, Demirkoy, and Orhaneli areas and reviews ground investigations in five areas. Activities for each area are sunmarized below: 1. Bolu area: The aeromagnetic map shows two belts of anomalies related to regional magnetite-bearing formations and a group of discrete anomalies, some of which may reflect significant concentrations of magnetite. To date three of these anomalies have been checked on the ground and at one a metamorphic rock containing 14 percent magnetite was observed. 2. Canakkale-Karabiga area: Ground checks were made of six aeromagnetic anomalies. At one locality (Cakirly-Koyu) 6 km south of Nazmara Sea a small magnetite deposit was found. The magnetic anomaly over the area is 150 meters long, and about 3 meters deep in the center of the anomaly exposed massive magnetite boulders. 3. Demirkoy area: The aeromagnetic map shows only one significant anomaly which was checked on the ground and found to be caused by minor magnetite at an intrusive contact. 4. Ezine area: A ground survey of 4.5 sq km area was made where magnetite boulders are locally present on the surface. No significant magnetic anomaly or iron mineralization were found. 5. Orhaneli area: The aeromagnetic map o# the area showed regional magnetic anomaly patterns related to magnetite in mafic intrusives, ultramafic rocks, and mafic flow rocks. In addition 16 localized anomalies were identified. Most of these anomalies were checked on the ground but no significant iron deposits were found. The largest deposit found was a one-meter wide magnetite vein. During the 1969 field season further investigation of anomalies in the Bolu and Orhaneli areas is planned.

Magnetic mapping of Spanish Canary archipelago [ZEEE project

NASA Astrophysics Data System (ADS)

Catalan, M.; Martin, J.; Marin, J. A.; Agudo, L. M.

2003-04-01

The Spanish Exclusive Economic Zone [ZEEE] Project constitutes the most intensive mapping to date of the sea floor off Spain's coast. This extensive geophysical survey is being undertaken by a Spanish government team. The first phase [1995-1997] concentrated its efforts in the Balearic sea. The geomagnetic data acquired for this area, has already being reduced and stored as a data base, and six scalar magnetic anomaly maps have been produced at a scale of 1:200.000, and another that cover the whole zone at a scale of 1:500.000. Since 1998, the Project has systematically surveyed the Canary archipelago, ending on October 2002. This group of islands, located off the West African Continental Margin, conform an intraplate volcanic archipelago which reflects a magmatic story that started probably at Tertiary. This Communication describes its main technical details, discusses the scalar magnetic map and presents a regional analysis of the Canary islands magnetic picture, trying to identify the different intra-crustal structures which generate the anomalies.

Mapping of the total magnetic field in the area of Lake Balaton

NASA Astrophysics Data System (ADS)

Visnovitz, Ferenc; Hegyi, Betti; Raveloson, Andrea; Rozman, Gábor; Lenkey, László; Kovács, Péter; Csontos, András; Heilig, Balázs; Horváth, Ferenc

2017-04-01

The Lake Balaton with 600 km2 area represents the largest lake in Central Europe and a blank spot on the magnetic anomaly map of Hungary. It is because the construction of the Hungarian magnetic anomaly map dates back to the 1960s and relied mainly on classical vertical-field balance surveys. To fill the gap, we initiated a systematic mapping using modern magnetometers and positioning system in the framework of a complex geophysical study of Lake Balaton (National Research Project 109255 K). The main goal of this study has been to identify subvolcanic bodies and tectonic structures below the lake and correlate them with well-known features mapped onshore in the vicinity of Balaton. During the magnetic survey an Overhauser field magnetometer (GEM System, GSM-19) was mounted on a plastic boat and towed behind a motorboat in a distance of 20 m with a speed of 6 to 16 km/h depending on weather conditions. Tests measurements showed that at this distance the magnetic noise generated by the motorboat was negligible. We measured total field values with a sampling interval of 1 to 2 s. As a result, the whole lake has been covered by magnetic profiles in an orthogonal grid with spacing of 1 km. During data interpretation we applied for correction of temporal variation of magnetic field registered in the Tihany Geophysical Observatory and normal field correction from a regional model. The final anomaly map in the western part of the lake shows anomalies with amplitudes of 20 to 60 nT and a half wavelength of 0.5 to 1 km. A larger feature was recognized related to the Badacsony Hill a major basaltic bute at the northern shore of the lake. In the middle part of the lake the total field is rather smooth, no significant anomaly has been revealed. However, slight disturbances can be noticed in the proximity of a neotectonic fault zone mapped by high resolution seismic data. In the eastern part of the lake few low amplitude (5-20 nT) anomalies have been observed that are associated also with seismically mapped strike-slip faults. As an interesting by-product a map was created showing short wavelength anomalies that are most probably caused by artificial metal objects sank and stuck in the lake mud. Some of these anomalies can be caused by parts of fallen warplanes and sunken tanks from military activities during the II. World War.

Thermal surveillance of active volcanoes

NASA Technical Reports Server (NTRS)

Friedman, J. D. (Principal Investigator)

1973-01-01

The author has identified the following significant results. There are three significant scientific results of the discovery of 48 pinpoint anomalies on the upper flanks of Mt. Rainier: (1) Many of these points may actually be the location of fumarolic vapor emission or warm ground considerably below the summit crater. (2) Discovery of these small anomalies required specific V/H scanner settings for precise elevation on Mt. Rainier's flank, to avoid smearing the anomalies to the point of nonrecognition. Several past missions flown to map the thermal anomalies of the summit area did not/detect the flank anomalies. (3) This illustrates the value of the aerial IR scanner as a geophysical tool suited to specific problem-oriented missions, in contrast to its more general value in a regional or reconnaissance anomaly-mapping role.

Application of diffusion maps to identify human factors of self-reported anomalies in aviation.

PubMed

Andrzejczak, Chris; Karwowski, Waldemar; Mikusinski, Piotr

2012-01-01

A study investigating what factors are present leading to pilots submitting voluntary anomaly reports regarding their flight performance was conducted. Diffusion Maps (DM) were selected as the method of choice for performing dimensionality reduction on text records for this study. Diffusion Maps have seen successful use in other domains such as image classification and pattern recognition. High-dimensionality data in the form of narrative text reports from the NASA Aviation Safety Reporting System (ASRS) were clustered and categorized by way of dimensionality reduction. Supervised analyses were performed to create a baseline document clustering system. Dimensionality reduction techniques identified concepts or keywords within records, and allowed the creation of a framework for an unsupervised document classification system. Results from the unsupervised clustering algorithm performed similarly to the supervised methods outlined in the study. The dimensionality reduction was performed on 100 of the most commonly occurring words within 126,000 text records describing commercial aviation incidents. This study demonstrates that unsupervised machine clustering and organization of incident reports is possible based on unbiased inputs. Findings from this study reinforced traditional views on what factors contribute to civil aviation anomalies, however, new associations between previously unrelated factors and conditions were also found.

Contribution de la gravimétrie à l'étude de la structure du bassin de Tadla (Maroc) : Implications hydrogéologiques

NASA Astrophysics Data System (ADS)

Najine, Abdessamad; Jaffal, Mohammed; Khammari, Kamal El; Aïfa, Tahar; Khattach, Driss; Himi, Mahjoub; Casas, Albert; Badrane, Said; Aqil, Hicham

2006-08-01

This study is based on the analysis and the interpretation of the gravity data of the Tadla basin. Its purpose is to increase the knowledge of this basin structure. A residual anomaly map was first calculated from the Bouguer anomaly data witch are strongly affected by a regional gradient. The computed map provides information on the ground density variation but it does not bring enough of new elements. Data filtering allows us to emphasize the structures affecting the basin. We chose the horizontal gradient coupled to the upward continuation techniques that permit to highlight news structures and to give information on their dip. The elaborated structural map of the study area constitutes a useful document for rationalizing the future groundwater exploration in the Tadla basin. To cite this article: A. Najine et al., C. R. Geoscience 338 (2006).

MAGSAT investigation of crustal magnetic anomalies in the eastern Indian Ocean

NASA Technical Reports Server (NTRS)

Sailor, R. V.; Lazarewicz, A. R.

1983-01-01

Crustal magnetic anomalies in a region of the eastern Indian Ocean were studied using data from NASA's MAGSAT mission. The investigation region (0 deg to 50 deg South, 75 to 125 deg East) contains several important tectonic features, including the Broken Ridge, Java Trench, Ninetyeast Ridge, and Southeast Indian Ridge. A large positive magnetic anomaly is associated with the Broken Ridge and smaller positive anomalies correlate with the Ninetyeast Ridge and western Australia. Individual profiles of scalar data (computed from vector components) were considered to determine the overall data quality and resolution capability. A set of MAGSAT ""Quiet-Time'' data was used to compute an equivalent source crustal magnetic anomaly map of the study region. Maps of crustal magnetization and magnetic susceptibility were computed from the equivalent source dipoles. Gravity data were used to help interpretation, and a map of the ratio of magnetization to density contrasts was computed using Poisson's relation. The results are consistent with the hypothesis of induced magnetization of a crustal layer having varying thickness and composition.

A simple Bouguer gravity anomaly map of southwestern Saudi Arabia and an initial interpretation

USGS Publications Warehouse

Gettings, M.E.

1983-01-01

Approximately 2,200 gravity stations on a 10-km2 grid were used to construct a simple Bouguer gravity anomaly map at 1:2,000,000 scale along a 150-km-wide by 850-km-long strip of the Arabian Peninsula from Sanam, southwest of Ar Riyad, through the Farasan Islands and including offshore islands, the coastal plain, and the Hijaz-Asir escarpment from Jiddah to the Yemen border. On the Precambrian Arabian Shield, local positive gravity anomalies are associated with greenstone belts, gneiss domes, and the Najd fault zones. Local negative gravity anomalies correlate with granitic plutonic rocks. A steep gravity gradient of as much as 4 mgal-km-1 marks the continental margin on the coastal plain near the southwestern end of the strip. Bouguer gravity anomaly values range from -10 to +40 mgal southwest of this gradient and from -170 to -100 mgal in a 300-km-wide gravity minimum northeast of the gradient. Farther northeast, the minimum is terminated by a regional gradient of about 0.1 mgal-km-1 that increases toward the Arabian Gulf. The regional gravity anomaly pattern has been modeled by using seismic refraction and Raleigh wave studies, heat-flow measurements, and isostatic considerations as constraints. The model is consistent with the hypothesis of upwelling of hot mantle material beneath the Red Sea and lateral mantle flow beneath the Arabian plate. The model yields best-fitting average crustal densities of 2.80 g-cm-3 (0-20 km depth) and 3.00 g-cm-3 (20-40 km depth) southwest of the Nabitah suture zone and 2.74 g-cm-3 (0-20 km depth) and 2.94 g-cm-3 (20-40 km depth) northeast of the suture zone. The gravity model requires that the crust be about 20 km thick at the continental margin and that the lower crust between the margin and Bishah (lat 20? N., long 42.5? E.) be somewhat denser than the lower crust to the northeast. Detailed correlations between 1:250,000- and 1:500,000-scale geologic maps and the gravity anomaly map suggest that the greenstone belts associated with gravity highs contain a large proportion of gabbroic and dioritic intrusive rocks and that the bulk density of the upper crust associated with some of the batholithic complexes has been lowered by the large-scale intrusion of granitic material at depth, as well as by that exposed at the surface. A comparison of known base and precious metals occurrences with the Bouguer gravity anomaly field shows, in some cases, a correlation between such occurrences and the features of the gravity anomaly map. Several areas were identified between known mineral occurrences along gravity-defined structures that may contain mineral deposits if the lithologic environment is favorable.

Spatial-temporal event detection in climate parameter imagery.

DOE Office of Scientific and Technical Information (OSTI.GOV)

McKenna, Sean Andrew; Gutierrez, Karen A.

Previously developed techniques that comprise statistical parametric mapping, with applications focused on human brain imaging, are examined and tested here for new applications in anomaly detection within remotely-sensed imagery. Two approaches to analysis are developed: online, regression-based anomaly detection and conditional differences. These approaches are applied to two example spatial-temporal data sets: data simulated with a Gaussian field deformation approach and weekly NDVI images derived from global satellite coverage. Results indicate that anomalies can be identified in spatial temporal data with the regression-based approach. Additionally, la Nina and el Nino climatic conditions are used as different stimuli applied to themore » earth and this comparison shows that el Nino conditions lead to significant decreases in NDVI in both the Amazon Basin and in Southern India.« less

Segmentation of singularity maps in the context of soil porosity

NASA Astrophysics Data System (ADS)

Martin-Sotoca, Juan J.; Saa-Requejo, Antonio; Grau, Juan; Tarquis, Ana M.

2016-04-01

Geochemical exploration have found with increasingly interests and benefits of using fractal (power-law) models to characterize geochemical distribution, including concentration-area (C-A) model (Cheng et al., 1994; Cheng, 2012) and concentration-volume (C-V) model (Afzal et al., 2011) just to name a few examples. These methods are based on the singularity maps of a measure that at each point define areas with self-similar properties that are shown in power-law relationships in Concentration-Area plots (C-A method). The C-A method together with the singularity map ("Singularity-CA" method) define thresholds that can be applied to segment the map. Recently, the "Singularity-CA" method has been applied to binarize 2D grayscale Computed Tomography (CT) soil images (Martin-Sotoca et al, 2015). Unlike image segmentation based on global thresholding methods, the "Singularity-CA" method allows to quantify the local scaling property of the grayscale value map in the space domain and determinate the intensity of local singularities. It can be used as a high-pass-filter technique to enhance high frequency patterns usually regarded as anomalies when applied to maps. In this work we will put special attention on how to select the singularity thresholds in the C-A plot to segment the image. We will compare two methods: 1) cross point of linear regressions and 2) Wavelets Transform Modulus Maxima (WTMM) singularity function detection. REFERENCES Cheng, Q., Agterberg, F. P. and Ballantyne, S. B. (1994). The separation of geochemical anomalies from background by fractal methods. Journal of Geochemical Exploration, 51, 109-130. Cheng, Q. (2012). Singularity theory and methods for mapping geochemical anomalies caused by buried sources and for predicting undiscovered mineral deposits in covered areas. Journal of Geochemical Exploration, 122, 55-70. Afzal, P., Fadakar Alghalandis, Y., Khakzad, A., Moarefvand, P. and Rashidnejad Omran, N. (2011) Delineation of mineralization zones in porphyry Cu deposits by fractal concentration-volume modeling. Journal of Geochemical Exploration, 108, 220-232. Martín-Sotoca, J. J., Tarquis, A. M., Saa-Requejo, A. and Grau, J. B. (2015). Pore detection in Computed Tomography (CT) soil images through singularity map analysis. Oral Presentation in PedoFract VIII Congress (June, La Coruña - Spain).

The mineralogy of global magnetic anomalies

NASA Technical Reports Server (NTRS)

Haggerty, S. E. (Principal Investigator)

1984-01-01

Experimental and analytical data on magnetic mineralogy was provided as an aid to the interpretation of magnetic anomaly maps. An integrated program, ranging from the chemistry of materials from 100 or more km depth within the Earth, to an examination of the MAGSAT anomaly maps at about 400 km above the Earth's surface, was undertaken. Within this framework, a detailed picture of the pertinent mineralogical and magnetic relationships for the region of West Africa was provided. Efforts were directed toward: (1) examining the geochemistry, mineralogy, magnetic properties, and phases relations of magnetic oxides and metal alloys in rocks demonstrated to have originated in the lower crust of upper mantle, (2) examining the assumption that these rocks portray the nature of their source regions; and (3) examining the regional geology, tectonics, gravity field and the MAGSAT anomaly maps for West Africa.

Release of the World Digital Magnetic Anomaly Map version 2 (WDMAM v2) scheduled

NASA Astrophysics Data System (ADS)

Dyment, Jérôme; Lesur, Vincent; Choi, Yujin; Hamoudi, Mohamed; Thébault, Erwan; Catalan, Manuel

2015-04-01

The World Digital Magnetic Anomaly Map is an international initiative carried out under the auspices of the International Association of Geomagnetism and Aeronomy (IAGA) and the Commission for the Geological Map of the World (CGMW). A first version of the map has been published and distributed eight years ago (WDMAM v1; Korhonen et al., 2007). After a call for an improved second version of the map in 2011, the slow process of data compilation, map preparation, evaluation and finalization is near completion, and the WDMAM v2 will be released at the International Union of Geophysics and Geodesy (IUGG) meeting to be held in Prag in June-July 2015. In this presentation we display several shortcomings of the WDMAM v1, both on continental and oceanic areas, that are hopefully alleviated in the WDMAM v2, and discuss the process leading to the new map. We reiterate a long-standing call for aeromagnetic and marine magnetic data contribution, and explore future directions to pursue the effort toward a more complete, higher resolution magnetic anomaly map of the World.

A remanent and induced magnetization model of Magsat vector anomalies over the west African craton

NASA Technical Reports Server (NTRS)

Toft, P. B.; Haggerty, S. E.

1986-01-01

Scalar and vector Magsat anomalies over the west African craton are analyzed by forward and inverse models. A forward model of the Man shield is based on Liberia. Induced magnetization contrasts due to sporadic iron-formations and to regional metamorphic rocks, and a contrast in remanent magnetization within the lower crust are included. This combination reproduces the location, magnitude and adopted local zero level of anomalies in the initial Magsat maps. An inverse model of the Reguibat shield estimates the magnetization contrast of its lithosphere, and when magnetism is restricted to shallower than 75 km both shields can be represented by a susceptibility contrast of +0.02. A residual anomaly between the shields involves a relative deficiency of induced magnetization along with other causes.

A remanent and induced magnetization model of Magsat vector anomalies over the west African craton

NASA Astrophysics Data System (ADS)

Toft, P. B.; Haggerty, S. E.

1986-04-01

Scalar and vector Magsat anomalies over the west African craton are analyzed by forward and inverse models. A forward model of the Man shield is based on Liberia. Induced magnetization contrasts due to sporadic iron-formations and to regional metamorphic rocks, and a contrast in remanent magnetization within the lower crust are included. This combination reproduces the location, magnitude and adopted local zero level of anomalies in the initial Magsat maps. An inverse model of the Reguibat shield estimates the magnetization contrast of its lithosphere, and when magnetism is restricted to shallower than 75 km both shields can be represented by a susceptibility contrast of +0.02. A residual anomaly between the shields involves a relative deficiency of induced magnetization along with other causes.

Distribution of the Crustal Magnetic Field in Sichuan-Yunnan Region, Southwest China

PubMed Central

Bai, Chunhua; Kang, Guofa; Gao, Guoming

2014-01-01

Based on the new and higher degree geomagnetic model NGDC-720-V3, we have investigated the spatial distribution, the altitude decay characteristics of the crustal magnetic anomaly, the contributions from different wavelength bands to the anomaly, and the relationship among the anomaly, the geological structure, and the geophysical field in Sichuan-Yunnan region of China. It is noted that the most outstanding feature in this area is the strong positive magnetic anomaly in Sichuan Basin, a geologically stable block. Contrasting with this feature, a strong negative anomaly can be seen nearby in Longmen Mountain block, an active block. This contradiction implies a possible relationship between the magnetic field and the geological activity. Completely different feature in magnetic field distribution is seen in the central Yunnan block, another active region, where positive and negative anomalies distribute alternatively, showing a complex magnetic anomaly map. Some fault belts, such as the Longmen Mountain fault, Lijiang-Xiaojinhe fault, and the Red River fault, are the transitional zones of strong and weak or negative and positive anomalies. The corresponding relationship between the magnetic anomaly and the geophysical fields was confirmed. PMID:25243232

Delineation of The Sumatra Fault in The Central Part of West Sumatra based on Gravity Method

NASA Astrophysics Data System (ADS)

Saragih, R. D.; Brotopuspito, K. S.

2018-04-01

The Sumatra Fault System is elongated across the Sumatra Island, Indonesia, Southeast Asia including the central part of West Sumatra, Indonesia, Southeast Asia. The Sumatra Fault and subsurface structure on the Central Part of West Sumatra had been analyzed using gravity method. Bouguer anomaly data were obtained from GRDC (Geological Research and Development Centre) maps, Bandung, Indonesia (i.e. without terrain correction). In this study, terrain correction had been applied to these Bouguer data. Bouguer anomaly in a horizontal plane at 3000 meters high and equivalent depth of mass point 7000 meters were obtained using Dampney Method. Residual and regional anomalies were separated using upward continuation method at 8000 meters high. The result of the SVD on residual anomaly shows two negative anomalies on northwest – southeast. The zero miligal per meter square quantity coincides remarkably well with trace faults which is a part of the Sumatra Fault System. Two negative anomalies are located around the Sianok Segment and Sumani Segment.

The next generation Antarctic digital magnetic anomaly map

USGS Publications Warehouse

von Frese, R.R.B; Golynsky, A.V.; Kim, H.R.; Gaya-Piqué, L.; Thébault, E.; Chiappinii, M.; Ghidella, M.; Grunow, A.; ,

2007-01-01

S (Golynsky et al., 2001). This map synthesized over 7.1 million line-kms of survey data available up through 1999 from marine, airborne and Magsat satellite observations. Since the production of the initial map, a large number of new marine and airborne surveys and improved magnetic observations from the Ørsted and CHAMP satellite missions have become available. In addition, an improved core field model for the Antarctic has been developed to better isolate crustal anomalies in these data. The next generation compilation also will likely represent the magnetic survey observations of the region in terms of a high-resolution spherical cap harmonic model. In this paper, we review the progress and problems of developing an improved magnetic anomaly map to facilitate studies of the Antarctic crustal magnetic field

Middle Atmosphere Program. Handbook for MAP, Volume 10

NASA Technical Reports Server (NTRS)

Taubenheim, J. (Editor)

1984-01-01

The contributions of ground based investigations to the study of middle atmospheric phenomena are addressed. General topics include diagnostics of the middle atmosphere from D region properties, winter anomaly, seasonal variations and disturbances, dynamics and theoretical models, ground based tracking of winds and waves, lower thermosphere phenomena, and solar-terrestrial influences.

Tectonic Interpretation of CHAMP Geopotential Data over the Northern Adriatic Sea.

NASA Astrophysics Data System (ADS)

Taylor, P. T.; Kim, H. R.; Mayer-Gürr, T.

2006-05-01

Recent aeromagnetic anomaly compilations (Chiappini et al., 2000 and Tontini et al., 2004) show a large positive (>700 nT) northwest-southeast trending magnetic anomaly off the Dalmatian coast. Unfortunately these aeromagnetic data cover only a part of this anomaly. We wanted to investigate if this large magnetic anomaly could be detected at satellite altitude and what is the extent and source of this feature. Therefore, magnetic and gravity anomaly maps were made from the CHAMP geopotential data, measured at the current low altitude of 345-350 km over the northern Adriatic Sea. We made the magnetic anomaly map over this relatively small region using 36 descending and 85 ascending orbits screened to be at the lowest altitude and the most magnetically quietest data. We removed the main field component (i.e., IGRF-10 up to degree and order 13) and then demeaned individual tracks and subtracted a second order polynomial to remove regional and/or un-modeled external field features. The resulting map from these well-correlated anomalies revealed a positive magnetic anomaly (>2 nT). Reduction-to-the pole brought these CHAMP anomaly features into coincidence with the aeromagnetic data. Previously Cantini et al. (1999) compared the surface magnetic data with MAGSAT by continuing upward the former and downwards the latter to 100 km and found a good correlation for wavelengths of 300-500 km. We also investigated the CHAMP gravity data. They were reduced using the kinematic short-arc integration method (Ilk et al., 2005 and Mayer Gürr et al., 2005). However, no corresponding short-wavelength gravity anomaly was observed in our study area. This tectonically complex region is under horizontal stress and the source of the large magnetic anomaly can be modelled by an associated ophiolite melange.

Analysis of pre-earthquake ionospheric anomalies before the global M = 7.0+ earthquakes in 2010

NASA Astrophysics Data System (ADS)

Yao, Y. B.; Chen, P.; Zhang, S.; Chen, J. J.; Yan, F.; Peng, W. F.

2012-03-01

The pre-earthquake ionospheric anomalies that occurred before the global M = 7.0+ earthquakes in 2010 are investigated using the total electron content (TEC) from the global ionosphere map (GIM). We analyze the possible causes of the ionospheric anomalies based on the space environment and magnetic field status. Results show that some anomalies are related to the earthquakes. By analyzing the time of occurrence, duration, and spatial distribution of these ionospheric anomalies, a number of new conclusions are drawn, as follows: earthquake-related ionospheric anomalies are not bound to appear; both positive and negative anomalies are likely to occur; and the earthquake-related ionospheric anomalies discussed in the current study occurred 0-2 days before the associated earthquakes and in the afternoon to sunset (i.e. between 12:00 and 20:00 local time). Pre-earthquake ionospheric anomalies occur mainly in areas near the epicenter. However, the maximum affected area in the ionosphere does not coincide with the vertical projection of the epicenter of the subsequent earthquake. The directions deviating from the epicenters do not follow a fixed rule. The corresponding ionospheric effects can also be observed in the magnetically conjugated region. However, the probability of the anomalies appearance and extent of the anomalies in the magnetically conjugated region are smaller than the anomalies near the epicenter. Deep-focus earthquakes may also exhibit very significant pre-earthquake ionospheric anomalies.

In-Situ Hydraulic Conductivities of Soils and Anomalies at a Future Biofuel Production Site

NASA Astrophysics Data System (ADS)

Williamson, M. F.; Jackson, C. R.; Hale, J. C.; Sletten, H. R.

2010-12-01

Forested hillslopes of the Upper Coastal Plain at the Savannah River Site, SC, feature a shallow clay loam argillic layer with low median saturated hydraulic conductivity. Observations from a grid of shallow, maximum-rise piezometers indicate that perching on this clay layer is common. However, flow measurements from an interflow-interception trench indicate that lateral flow is rare and most soil water percolates through the clay layer. We hypothesize that the lack of frequent lateral flow is due to penetration of the clay layer by roots of pine trees. We used ground penetrating radar (GPR) to map the soil structure and potential anomalies, such as root holes, down to two meters depth at three 10×10-m plots. At each plot, a 1×10-m trench was later back-hoe excavated along a transect that showed the most anomalies on the GPR maps. Each trench was excavated at 0.5-m intervals until the clay layer was reached (two plots were excavated to a final depth of 0.875 m and the third plot was excavated to a final depth of 1.0 m). At each interval, compact constant-head permeameters (CCHPs) were used to measure in-situ hydraulic conductivities in the clay-loam matrix and in any visually apparent anomalies. Conductivity was also estimated using a second 1×10-m transect of CCHP measurements taken within randomly placed augur holes. Additional holes targeted GPR anomalies. The second transect was created in case the back-hoe impacted conductivity readings. High-conductivity anomalies were also visually investigated by excavating with a shovel. Photographs of soil wetness were taken at visually apparent anomalies with a multispectral camera. We discovered that all visually apparent anomalies found are represented on the GPR maps, but that not all of the predicted anomalies on the GPR maps are visually apparent. We discovered that tree root holes create anomalies, but that there were also many conductivity anomalies that could not be visually distinguished from low-conductivity soil.

Structural-geophysical model of the basement complex of the Aden-Red Sea region

NASA Astrophysics Data System (ADS)

Isaev, E. N.

1987-11-01

A relief map of the basement complex underlying the volcanogenic sedimentary cover has been constructed on the basis of composite Bouguer anomaly maps and maps of magnetic anomalies ΔT. Seismic and geological data on the Gulf of Aden and the Red Sea as well as on adjacent areas of Africa and Arabia have also been used. The mid-Red Sea and mid-Aden uplifts (similar to the mid-oceanic ones) as well as the foredeep have been identified. The thickness of cover in the foredeeps is 6-8 km. A regional negative Bouguer anomaly crosses the Aden-Red Sea rift system and includes the area of young volcanism. Intensive linear magnetic anomalies are traceable only within the area of overlap of the rift system and the zone of young volcanism. Rift system apophyses have advanced into the continent and their nature is similar to that of the Afar triangle.

Application of total-count aeroradiometric maps to the exploration for heavy-mineral deposits in the coastal plain of Virginia, with a section on field-spectrometer-data reduction

USGS Publications Warehouse

Grosz, A.E.; Kosanke, Kenneth L.

1983-01-01

Total-count contoured aeroradiometric maps for the Coastal Plain of Virginia were used in an effort to locate economic heavy-mineral placer deposits. The principle behind this approach is that heavy- mineral suites commonly contain radioactive minerals that, if the concentration of heavy minerals is exposed at or within inches of the surface, enable the deposit to be located by use of airborne instruments because of its radiometric contrast with the host sediment. Detailed and regional geologic maps, soil maps, land-use and land- cover maps, information on fertilizer use, and ground-spectrometer data were used to study aeroradiometric anomalies for efficient exploration. Aeroradiometric anomalies in the Coastal Plain of Virginia have three general causes. First, the most intense anomalies are associated with cultural features, such as roads made of granitic material. Second, most anomalies of high to intermediate intensity are associated with land used for agricultural purposes and evidently are caused by applications of radioactive fertilizer. Third, anomalies of intermediate to low intensity are associated with heavy-mineral deposits. Results of this study show that aeroradiometric anomalies associated with heavy-mineral accumulations in the Coastal Plain of Virginia have ground radiometric spectra in which thorium is the strongest component and uranium and potassium are lesser components. Heavy-mineral accumulations found in this study by use of the aeroradiometric data are not considered to be of economic importance, mostly because of the low percentage of economic minerals in the heavy-mineral suites and also because of other factors such as the very fine grained nature of the host sediments and competing land use.

Feasibility of anomaly detection and characterization using trans-admittance mammography with 60 × 60 electrode array

NASA Astrophysics Data System (ADS)

Zhao, Mingkang; Wi, Hun; Lee, Eun Jung; Woo, Eung Je; In Oh, Tong

2014-10-01

Electrical impedance imaging has the potential to detect an early stage of breast cancer due to higher admittivity values compared with those of normal breast tissues. The tumor size and extent of axillary lymph node involvement are important parameters to evaluate the breast cancer survival rate. Additionally, the anomaly characterization is required to distinguish a malignant tumor from a benign tumor. In order to overcome the limitation of breast cancer detection using impedance measurement probes, we developed the high density trans-admittance mammography (TAM) system with 60 × 60 electrode array and produced trans-admittance maps obtained at several frequency pairs. We applied the anomaly detection algorithm to the high density TAM system for estimating the volume and position of breast tumor. We tested four different sizes of anomaly with three different conductivity contrasts at four different depths. From multifrequency trans-admittance maps, we can readily observe the transversal position and estimate its volume and depth. Specially, the depth estimated values were obtained accurately, which were independent to the size and conductivity contrast when applying the new formula using Laplacian of trans-admittance map. The volume estimation was dependent on the conductivity contrast between anomaly and background in the breast phantom. We characterized two testing anomalies using frequency difference trans-admittance data to eliminate the dependency of anomaly position and size. We confirmed the anomaly detection and characterization algorithm with the high density TAM system on bovine breast tissue. Both results showed the feasibility of detecting the size and position of anomaly and tissue characterization for screening the breast cancer.

Worldwide complete spherical Bouguer and isostatic anomaly maps

NASA Astrophysics Data System (ADS)

Bonvalot, S.; Balmino, G.; Briais, A.; Peyrefitte, A.; Vales, N.; Biancale, R.; Gabalda, G.; Reinquin, F.

2011-12-01

We present here a set of digital maps of the Earth's gravity anomalies (surface "free air", Bouguer and isostatic), computed at Bureau Gravimetric International (BGI) as a contribution to the Global Geodetic Observing Systems (GGOS) and to the global geophysical maps published by the Commission for the Geological Map of the World (CGMW). The free air and Bouguer anomaly concept is extensively used in geophysical interpretation to investigate the density distributions in the Earth's interior. Complete Bouguer anomalies (including terrain effects) are usually computed at regional scales by integrating the gravity attraction of topography elements over and beyond a given area (under planar or spherical approximations). Here, we developed and applied a worldwide spherical approach aimed to provide a set of homogeneous and high resolution gravity anomaly maps and grids computed at the Earth's surface, taking into account a realistic Earth model and reconciling geophysical and geodetic definitions of gravity anomalies. This first version (1.0) has been computed by spherical harmonics analysis / synthesis of the Earth's topography-bathymetry up to degree 10800. The detailed theory of the spherical harmonics approach is given in Balmino et al., (Journal of Geodesy, submitted). The Bouguer and terrain corrections have thus been computed in spherical geometry at 1'x1' resolution using the ETOPO1 topography/bathymetry, ice surface and bedrock models from the NOAA (National Oceanic and Atmospheric Administration) and taking into account precise characteristics (boundaries and densities) of major lakes, inner seas, polar caps and of land areas below sea level. Isostatic corrections have been computed according to the Airy Heiskanen model in spherical geometry for a constant depth of compensation of 30km. The gravity information given here is provided by the Earth Geopotential Model (EGM2008), developed at degree 2160 by the National Geospatial Intelligence Agency (NGA) (Pavlis et al., 2008), which represents the best up-to-date global gravity model (including surface gravity measurements from land, marine and airborne surveys as well as gravity and altimetry satellite measurements). The surface gravity anomaly (free air) is computed at the Earth's surface in the context of Molodensky theory and includes corrections from the mass of the atmosphere. The way gravity anomalies are computed on a worldwide basis slightly differs from the classical usage, but meets modern concerns which tend to take the real Earth into account. The resulting anomaly maps and grids will be distributed for scientific and education purposes by the Commission for the Geological Map of the World (CGMW) with support of UNESCO and other institutions. Upgraded versions might be done as soon as new global gravity model is available (including satellite GOCE and new surface measurements: ground, airborne). Visit / contact BGI (http://bgi.omp.obs-mip.fr) and CCMW (http://ccgm.free.fr) for more information.

Location, structure, and seismicity of the Seattle fault zone, Washington: Evidence from aeromagnetic anomalies, geologic mapping, and seismic-reflection data

USGS Publications Warehouse

Blakely, R.J.; Wells, R.E.; Weaver, C.S.; Johnson, S.Y.

2002-01-01

A high-resolution aeromagnetic survey of the Puget Lowland shows details of the Seattle fault zone, an active but largely concealed east-trending zone of reverse faulting at the southern margin of the Seattle basin. Three elongate, east-trending magnetic anomalies are associated with north-dipping Tertiary strata exposed in the hanging wall; the magnetic anomalies indicate where these strata continue beneath glacial deposits. The northernmost anomaly, a narrow, elongate magnetic high, precisely correlates with magnetic Miocene volcanic conglomerate. The middle anomaly, a broad magnetic low, correlates with thick, nonmagnetic Eocene and Oligocene marine and fluvial strata. The southern anomaly, a broad, complex magnetic high, correlates with Eocene volcanic and sedimentary rocks. This tripartite package of anomalies is especially clear over Bainbridge Island west of Seattle and over the region east of Lake Washington. Although attenuated in the intervening region, the pattern can be correlated with the mapped strike of beds following a northwest-striking anticline beneath Seattle. The aeromagnetic and geologic data define three main strands of the Seattle fault zone identified in marine seismic-reflection profiles to be subparallel to mapped bedrock trends over a distance of >50 km. The locus of faulting coincides with a diffuse zone of shallow crustal seismicity and the region of uplift produced by the M 7 Seattle earthquake of A.D. 900-930.

Paleomagnetic determinations on Lanzarote from magnetic and gravity anomalies: Implications for the early history of the Canary Islands

NASA Astrophysics Data System (ADS)

Blanco-Montenegro, I.; Montesinos, F. G.; GarcíA, A.; Vieira, R.; VillalaíN, J. J.

2005-12-01

The Bouguer and aeromagnetic anomaly maps of Lanzarote show a gravity high and a dipolar magnetic anomaly over the central part of the island, indicating one isolated source. Assuming that the structure responsible for both anomalies is the same, a methodology has been designed to estimate the total magnetization vector of the source, which is interpreted as a large intrusive body (mafic core) positioned as a result of magma rising to the surface during the early stages of growth of Lanzarote. Considering its geometry to be known from a previous three-dimensional (3-D) gravity model, the approach proposed in this paper is based on the delineation of magnetic contacts through analysis of the horizontal gradient of the reduced-to-the-pole anomaly map, comparison between the gravity and the pseudogravity anomalies, and 3-D forward magnetic modeling. The total magnetization vector obtained by this method is defined by a module of 4.5 A m-1 and a direction D = -20° and I = 30°. Comparing the paleomagnetic pole, obtained from this direction, with the apparent polar wander path of Africa for the last 160 Myr, it is concluded that the main component of the total magnetization vector is probably a primary natural remanent magnetization (NRM) which could have been acquired between 60 and 100 Ma. This result suggests that the emplacement of magmas at shallow depths linked to the beginning of volcanism in Lanzarote took place during the Upper Cretaceous, thus providing the first evidence of a timeline for the early formative stages of this volcanic island.

Spatially-Aware Temporal Anomaly Mapping of Gamma Spectra

NASA Astrophysics Data System (ADS)

Reinhart, Alex; Athey, Alex; Biegalski, Steven

2014-06-01

For security, environmental, and regulatory purposes it is useful to continuously monitor wide areas for unexpected changes in radioactivity. We report on a temporal anomaly detection algorithm which uses mobile detectors to build a spatial map of background spectra, allowing sensitive detection of any anomalies through many days or months of monitoring. We adapt previously-developed anomaly detection methods, which compare spectral shape rather than count rate, to function with limited background data, allowing sensitive detection of small changes in spectral shape from day to day. To demonstrate this technique we collected daily observations over the period of six weeks on a 0.33 square mile research campus and performed source injection simulations.

Investigation from Japanese MAGSAT team

NASA Technical Reports Server (NTRS)

Fukushima, N. (Principal Investigator)

1981-01-01

The acquisition of tapes which contain vector and scalar data decimated at an interval of 0.5 sec, together with time and position data, is reported. Progress in the study of magnetic anomalies in the vicinity of Japan and in electric currents in the ionosphere and magnetosphere is also reported. MAGSAT data was used in obtaining a map of total force anomaly for the area of latitude 10-70 deg N and longitude 110-170 deg E. One of the outstanding features in the map of the magnetic anomaly is a negative magnetic anomaly in the Okhotsk Sea, which is of geophysical interest because of its possible connection with high heat flow values in that area.

Magsat to CHAMP: Magnetic Satellite Explorations of Lithospheric Anomalies over Kursk, Bangui and the Antarctic

NASA Technical Reports Server (NTRS)

Kim, H.; Taylor, Patrick T.; vonFrese, R. R.; Kim, J. W.

2004-01-01

We compare crustal magnetic anomaly maps over the Kursk (Russia) and Bangui (Central African Republic) isolated anomalies and the Antarctic derived from the Magsat, \\Orsted and CHAMP satellite fields. We wish to demonstrate how progress in satellite magnetic missions has improved the recovery of the crustal magnetic field. The 6-month long Magsat mission of 25 years ago generated two major methods of processing satellite magnetic anomaly data for lithospheric studies. The first was a global perspective using spherical harmonics that emphasize the more regional and global lithospheric fields. However, these fields commonly do not resolve local anomaly features in any detail. Therefore a second procedure involved the use of the individual satellite orbit or track data to recover small-scale anomalies on a regional scale. We present results over prominent magnetic anomalies such as Kursk, Bangui and the large Antarctic continent that demonstrate how the various analysis methods affect the recovery of crustal anomalies. The more recent \\Orsted and CHAMP missions are successfully recording data with an improved accuracy and with full spatial and temporal coverage. We show and interpret the total magnetic intensity anomaly maps over these areas from all three satellite magnetometer data sets.

Statistical analysis of ionospheric TEC anomalies before global M w ≥ 7.0 earthquakes using data of CODE GIM

NASA Astrophysics Data System (ADS)

Liu, Wenjing; Xu, Liang

2017-07-01

Based on Center of Orbit Determination in Europe (CODE) global ionospheric map (GIM) data, a statistical analysis of local total electron content (TEC) anomalies before 121 low-depth ( D ≤ 100 km) strong ( M w ≥ 7.0) earthquakes has been made using the sliding median differential calculation method combining with a new approach of image processing technique. The results show that significant local TEC anomalies could be observed 0-6 days before 80 earthquakes, about 66.1% out of the total. The positive anomalies occur more often than negative ones. For 26 cases, both positive and negative anomalies are observed before the shock. The pre-earthquake TEC anomalies show local time recurrence for 38 earthquakes, which occur around the same local time on different days. The local time distribution of the pre-earthquake TEC anomalies mainly concentrates between 19 and 06 LT, roughly from the sunset to sunrise. Most of the pre-earthquake TEC anomalies do not locate above the epicenter but shift to the south. The pre-earthquake TEC anomalies could be extracted near the magnetic conjugate point of the epicenter for 40 events, which is 50% out of the total 80 cases with significant local TEC anomalies. In general, the signs of the anomalies around epicenter and its conjugate point are the same, but the abnormal magnitude and lasting time are not.

Mapping Curie temperature depth in the western United States with a fractal model for crustal magnetization

USGS Publications Warehouse

Bouligand, C.; Glen, J.M.G.; Blakely, R.J.

2009-01-01

We have revisited the problem of mapping depth to the Curie temperature isotherm from magnetic anomalies in an attempt to provide a measure of crustal temperatures in the western United States. Such methods are based on the estimation of the depth to the bottom of magnetic sources, which is assumed to correspond to the temperature at which rocks lose their spontaneous magnetization. In this study, we test and apply a method based on the spectral analysis of magnetic anomalies. Early spectral analysis methods assumed that crustal magnetization is a completely uncorrelated function of position. Our method incorporates a more realistic representation where magnetization has a fractal distribution defined by three independent parameters: the depths to the top and bottom of magnetic sources and a fractal parameter related to the geology. The predictions of this model are compatible with radial power spectra obtained from aeromagnetic data in the western United States. Model parameters are mapped by estimating their value within a sliding window swept over the study area. The method works well on synthetic data sets when one of the three parameters is specified in advance. The application of this method to western United States magnetic compilations, assuming a constant fractal parameter, allowed us to detect robust long-wavelength variations in the depth to the bottom of magnetic sources. Depending on the geologic and geophysical context, these features may result from variations in depth to the Curie temperature isotherm, depth to the mantle, depth to the base of volcanic rocks, or geologic settings that affect the value of the fractal parameter. Depth to the bottom of magnetic sources shows several features correlated with prominent heat flow anomalies. It also shows some features absent in the map of heat flow. Independent geophysical and geologic data sets are examined to determine their origin, thereby providing new insights on the thermal and geologic crustal structure of the western United States.

Statistical seismo-ionospheric precursors of M7.0+ earthquakes in Circum-Pacific seismic belt by GPS TEC measurements

NASA Astrophysics Data System (ADS)

Li, Wang; Yue, Jianping; Guo, Jinyun; Yang, Yang; Zou, Bin; Shen, Yi; Zhang, Kefei

2018-03-01

The Circum-Pacific seismic belt is the region heavily affected by earthquakes in the world. The relationship between earthquake (e.g., the geographic location, occurrence time, magnitude, and focal depth) and ionospheric anomalies in the belt was investigated using 100 M7.0+ earthquakes during 2006-2015. The ground-based GPS measurements and global ionosphere map (GIM) data were used for the analyses of the ionospheric variations preceding the earthquakes. The results indicated that the occurrence rate of total electron content (TEC) anomalies was proportional to the magnitude and inversely proportional to the focal depth to a certain degree, and the occurrence frequency of anomalies had a rising trend with the days getting close to the main shock. The occurrence rate of TEC anomalies in the Southern hemisphere was larger than that in the Northern hemisphere. Besides, the spatial characteristics of TEC anomalies showed that the anomalies in low-middle latitudes did not coincide with the epicenter, sometimes the anomalies were also observed in the corresponding conjugated region. However, the TEC anomalies in the high latitude usually appeared around the epicenter and within the seismogenic zone while no TEC anomalies appeared in the conjugated area. These results may have potential applications to the earthquake prediction in the Circum-Pacific seismic belt.

Interpretation of detailed aerial gamma-ray survey, Jabal Ashirah area, southeastern Arabian Shield, Kingdom of Saudi Arabia

USGS Publications Warehouse

Duval, J.S.

1987-01-01

A detailed aerial gamma-ray spectrometric survey of the Jabal Ashirah area in the southeastern Arabian Shield has been analyzed using computer-classification algorithms. The analysis resulted in maps that show radiometric map units and gamma-ray anomalies indicating the presence of possible concentrations of potassium and uranium. The radiometric-unit map was interpreted to 'produce a simplified radiolithic map that was correlated with the mapped geology. The gamma-ray data show uranium anomalies that coincide with a tin-bearing granite, but known gold and nickel mineralization do not have any associated gamma-ray signatures.

Missouri aeromagnetic and gravity maps and data: a web site for distribution of data

USGS Publications Warehouse

Kucks, Robert P.; Hill, Patricia L.

2005-01-01

Magnetic anomalies are due to variations in the Earth's magnetic field caused by the uneven distribution of magnetic minerals (primarily magnetite) in the rocks that make up the upper part of the Earth's crust. The features and patterns of the magnetic anomalies can be used to delineate details of subsurface geology, including the locations of buried faults and magnetite-bearing rocks and the depth to the base of sedimentary basins. This information is valuable for mineral exploration, geologic mapping, and environmental studies. The Missouri magnetic map is constructed from grids that combine information collected in 25 separate magnetic surveys conducted between 1943 and 1987. The data from these surveys are of varying quality. The design and specifications (terrain clearance, sampling rates, line spacing, and reduction procedures) varied from survey to survey depending on the purpose of the project and the technology of that time. Every attempt was made to acquire the data in digital form.

Anisotropic Solar Wind Sputtering of the Lunar Surface Induced by Crustal Magnetic Anomalies

NASA Technical Reports Server (NTRS)

Poppe, A. R.; Sarantos, M.; Halekas, J. S.; Delory, G. T.; Saito, Y.; Nishino, M.

2014-01-01

The lunar exosphere is generated by several processes each of which generates neutral distributions with different spatial and temporal variability. Solar wind sputtering of the lunar surface is a major process for many regolith-derived species and typically generates neutral distributions with a cosine dependence on solar zenith angle. Complicating this picture are remanent crustal magnetic anomalies on the lunar surface, which decelerate and partially reflect the solar wind before it strikes the surface. We use Kaguya maps of solar wind reflection efficiencies, Lunar Prospector maps of crustal field strengths, and published neutral sputtering yields to calculate anisotropic solar wind sputtering maps. We feed these maps to a Monte Carlo neutral exospheric model to explore three-dimensional exospheric anisotropies and find that significant anisotropies should be present in the neutral exosphere depending on selenographic location and solar wind conditions. Better understanding of solar wind/crustal anomaly interactions could potentially improve our results.

Comparison of satellite-derived LAI and precipitation anomalies over Brazil with a thermal infrared-based Evaporative Stress Index for 2003-2013

NASA Astrophysics Data System (ADS)

Anderson, Martha C.; Zolin, Cornelio A.; Hain, Christopher R.; Semmens, Kathryn; Tugrul Yilmaz, M.; Gao, Feng

2015-07-01

Shortwave vegetation index (VI) and leaf area index (LAI) remote sensing products yield inconsistent depictions of biophysical response to drought and pluvial events that have occurred in Brazil over the past decade. Conflicting reports of severity of drought impacts on vegetation health and functioning have been attributed to cloud and aerosol contamination of shortwave reflectance composites, particularly over the rainforested regions of the Amazon basin which are subject to prolonged periods of cloud cover and episodes of intense biomass burning. This study compares timeseries of satellite-derived maps of LAI from the Moderate Resolution Imaging Spectroradiometer (MODIS) and precipitation from the Tropical Rainfall Mapping Mission (TRMM) with a diagnostic Evaporative Stress Index (ESI) retrieved using thermal infrared remote sensing over South America for the period 2003-2013. This period includes several severe droughts and floods that occurred both over the Amazon and over unforested savanna and agricultural areas in Brazil. Cross-correlations between absolute values and standardized anomalies in monthly LAI and precipitation composites as well as the actual-to-reference evapotranspiration (ET) ratio used in the ESI were computed for representative forested and agricultural regions. The correlation analyses reveal strong apparent anticorrelation between MODIS LAI and TRMM precipitation anomalies over the Amazon, but better coupling over regions vegetated with shorter grass and crop canopies. The ESI was more consistently correlated with precipitation patterns over both landcover types. Temporal comparisons between ESI and TRMM anomalies suggest longer moisture buffering timescales in the deeper rooted rainforest systems. Diagnostic thermal-based retrievals of ET and ET anomalies, such as used in the ESI, provide independent information on the impacts of extreme hydrologic events on vegetation health in comparison with VI and precipitation-based drought indicators, and used in concert may provide a more reliable evaluation of natural and managed ecosystem response to variable climate regimes.

Application of remote sensing to reconnaissance geologic mapping and mineral exploration

NASA Technical Reports Server (NTRS)

Birnie, R. W.; Dykstra, J. D.

1978-01-01

A method of mapping geology at a reconnaissance scale and locating zones of possible hydrothermal alteration has been developed. This method is based on principal component analysis of Landsat digital data and is applied to the desert area of the Chagai Hills, Baluchistan, Pakistan. A method for airborne spectrometric detection of geobotanical anomalies associated with prophyry Cu-Mo mineralization at Heddleston, Montana has also been developed. This method is based on discriminants in the 0.67 micron and 0.79 micron region of the spectrum.

Mapping temperature and radiant geothermal heat flux anomalies in the Yellowstone geothermal system using ASTER thermal infrared data

USGS Publications Warehouse

Vaughan, R. Greg; Lowenstern, Jacob B.; Keszthelyi, Laszlo P.; Jaworowski, Cheryl; Heasler, Henry

2012-01-01

The purpose of this work was to use satellite-based thermal infrared (TIR) remote sensing data to measure, map, and monitor geothermal activity within the Yellowstone geothermal area to help meet the missions of both the U.S. Geological Survey Yellowstone Volcano Observatory and the Yellowstone National Park Geology Program. Specifically, the goals were to: 1) address the challenges of remotely characterizing the spatially and temporally dynamic thermal features in Yellowstone by using nighttime TIR data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and 2) estimate the temperature, geothermal radiant emittance, and radiant geothermal heat flux (GHF) for Yellowstone’s thermal areas (both Park wide and for individual thermal areas). ASTER TIR data (90-m pixels) acquired at night during January and February, 2010, were used to estimate surface temperature, radiant emittance, and radiant GHF from all of Yellowstone’s thermal features, produce thermal anomaly maps, and update field-based maps of thermal areas. A background subtraction technique was used to isolate the geothermal component of TIR radiance from thermal radiance due to insolation. A lower limit for the Yellowstone’s total radiant GHF was established at ~2.0 GW, which is ~30-45% of the heat flux estimated through geochemical (Cl-flux) methods. Additionally, about 5 km2 was added to the geodatabase of mapped thermal areas. This work provides a framework for future satellite-based thermal monitoring at Yellowstone as well as exploration of other volcanic / geothermal systems on a global scale.

Investigation of the Crust of the Pannonian Basin, Hungary Using Low-Altitude CHAMP Horizontal Gradient Magnetic Anomalies

NASA Technical Reports Server (NTRS)

Taylor, Patrick T.; Kis, Karoly I.; Puszta, Sandor; Wittmann, Geza; Kim, Hyung Rae; Toronyi, B.

2011-01-01

The Pannonian Basin is a deep intra-continental basin that formed as part of the Alpine orogeny. It is some 600 by 500 km in area and centered on Hungary. This area was chosen since it has one of the thinnest continental crusts in Europe and is the region of complex tectonic structures. In order to study the nature of the crustal basement we used the long-wavelength magnetic anomalies acquired by the CHAMP satellite. The SWARM constellation, scheduled to be launched next year, will have two lower altitude satellites flying abreast, with a separation of between ca. 150 to 200 km. to record the horizontal magnetic gradient. Since the CHAMP satellite has been in orbit for eight years and has obtained an extensive range of data, both vertically and horizontally there is a large enough data base to compute the horizontal magnetic gradients over the Pannonian Basin region using these many CHAMP orbits. We recomputed a satellite magnetic anomaly map, using the spherical-cap method of Haines (1985), the technique of Alsdorf et al. (1994) and from spherical harmonic coefficients of MF6 (Maus et aI., 2008) employing the latest and lowest altitude CHAMP data. We then computed the horizontal magnetic anomaly gradients (Kis and Puszta, 2006) in order to determine how these component data will improve our interpretation and to preview what the SW ARM mission will reveal with reference to the horizontal gradient anomalies. The gradient amplitude of an 1000 km northeast-southwest profile through our horizontal component anomaly map varied from 0 to 0.025 nT/km with twin positive anomalies (0.025 and 0.023 nT/km) separated by a sharp anomaly negative at o nT/km. Horizontal gradient indicate major magnetization boundaries in the crust (Dole and Jordan, 1978 and Cordell and Grauch, 1985). Our gradient anomaly was modeled with a twodimensional body and the anomaly, of some 200 km, correlates with a 200 km area of crustal thinning in the southwestern Pannonian Basin.

Residual depth anomalies and the origin of the Australian-Antarctic discordance zone

NASA Astrophysics Data System (ADS)

Marks, Karen M.; Vogt, Peter R.; Hall, Stuart A.

1990-10-01

A new, high resolution depth anomaly map covering the anomalously deep and rough Australian-Antarctic Discordance (AAD) has been constructed using crustal ages derived from a detailed aeromagnetic survey. The map shows a large, arcuate-shaped, negative depth anomaly that is centered on the Southeast Indian Ridge and trends NNE across the Australian plate (SSE across the Antarctic plate). Within this broad scale feature, two prominent depth anomaly lows are observed at 45°S, 128°E (the northern flank) and 54°S, 125°E (the southern flank). Both lows are associated with 15 Ma oceanic crust. The observed depth anomaly patterns are compared with the distinctive patterns predicted by coldspot, downwelling limbs of convection cells, and thin crust models of the discordance source. The observed depth anomaly does not result from absolute plate motions over a fixed coldspot source because the predicted ENE trend on the Antarctic plate is not in agreement with the SSE trend observed. The symmetric arrangement of the large-scale depth anomaly and prominent lows about the ridge axis suggests instead a source that has varied in strength but remained located at the ridge axis as the ridge migrated northeastward in the absolute reference frame. The organized pattern of elongated depth anomaly highs and lows predicted for upper mantle convection (cells) is not evident in the observed depth anomaly map. Thus a convergence of downwelling limbs of convection cells beneath the discordance is not indicated. If the source of cooler upwelling that produces less magma and hence thin crust has not varied over time, nor migrated along the ridge, then the predicted depth anomaly would persist unchanged with distance from the ridge axis, and trend in the direction of relative plate motion (parallel to fracture zones). The observed depth anomaly trends obliquely across fracture zones and changes in both amplitude and location relative to the ridge axis, and is therefore not consistent with cool upwelling producing thin crust. To explain the features of the depth anomaly map, we propose that asthenospheric material flowing from the Amsterdam hotspot in the west, and the Balleny and Tasmantid hotspots in the east, collides within the discordance. Propagating rifts converging on the AAD provide evidence for such asthenospheric flow. Attenuated shear velocities beneath the George V fracture zone complex, and lavas geochemically identical to those from propagating rifts associated with hotspots, suggest a thermal anomaly producing additional asthenospheric flow east of the AAD. The increased flow and greater proximity of the discordance to the thermal anomaly and hotspots to the east produce a higher pressure gradient, and hence greater driving force, which results in a westward migration of the collision zone with time. Seafloor spreading over the westward moving collision zone has produced the observed arcuate-shaped anomaly with the accompanying oblique depth anomaly trends. We cannot decipher from depth anomalies alone whether the converging flows downwell within the AAD or simply mix with upwelling materials.

A comparison of infrared, radar, and geologic mapping of lunar craters

USGS Publications Warehouse

Thompson, T.W.; Masursky, H.; Shorthill, R.W.; Tyler, G.L.; Zisk, S.H.

1974-01-01

Between 1000 and 2000 infrared (eclipse) and radar anomalies have been mapped on the nearside hemisphere of the Moon. A study of 52 of these anomalies indicates that most are related to impact craters and that the nature of the infrared and radar responses is compatible with a previously developed geologic model of crater aging processes. The youngest craters are pronounced thermal and radar anomalies; that is, they have enhanced eclipse temperatures and are strong radar scatterers. With increasing crater age, the associated thermal and radar responses become progressively less noticeable until they assume values for the average lunar surface. The last type of anomaly to disappear is radar enhancement at longer wavelengths. A few craters, however, have infrared and radar behaviors not predicted by the aging model. One previously unknown feature - a field strewn with centimeter-sized rock fragments - has been identified by this technique of comparing maps at the infrared, radar, and visual wavelengths. ?? 1974 D. Reidel Publishing Company, Dordrecht-Holland.

Shaded relief aeromagnetic map of the Santa Clara Valley and vicinity, California

USGS Publications Warehouse

Roberts, Carter W.; Jachens, Robert C.

2003-01-01

This aeromagnetic map covers the southern portion of San Francisco Bay, the Santa Clara Valley and surrounding mountains, part of which has been modelled in threedimensions (Jachens and other, 2001). The magnetic anomaly map has been compiled from existing digital data. Data was obtained from six aeromagnetic surveys that were flown at different times, spacings and elevations. The International Geomagnetic Reference Field (IGRF) for the date of each survey had been removed in the initial processing. The resulting residual magnetic anomalies were analytically continued onto a common surface 305 m (1000 ft) above terrain. Portions of each survey were substantially above the specified flight height listed in the table. The surveys were then merged together using a commercial software package called Oasis Montage. The gray lines on the map indicate the extent of each survey. The program used these regions of overlap to determine the best fit between surveys. Black dots show probable edges of magnetic bodies defined by the maximum horizontal gradient determined using a computer program by Blakely (1995). Crystalline rocks generally contain sufficient magnetic minerals to cause variations in the Earth’s magnetic field that can be mapped by aeromagnetic surveys. Sedimentary rocks are generally weakly magnetized and consequently have a small effect on the magnetic field: thus a magnetic anomaly map can be used to “see through” the sedimentary rock cover and can convey information on lithologic contrasts and structural trends related to the underlying crystalline basement (see Nettleton,1971; Blakely, 1995). Faults often cut magnetic bodies and offset magnetic anomalies can thus be used to help determine fault motion. Serpentinite, which is highly magnetic, is often found along faults. On this map areas of low magnetic anomalies are shown in blues and green while highs are shown in reds and magentas. Faults are from Brabb and others, 1998a,1998b, Graymer and others 1996, Lienkaemper, 1992 and Wentworth and others 1998.

World Gravity Map: a set of global complete spherical Bouguer and isostatic anomaly maps and grids

NASA Astrophysics Data System (ADS)

Bonvalot, S.; Balmino, G.; Briais, A.; Kuhn, M.; Peyrefitte, A.; Vales, N.; Biancale, R.; Gabalda, G.; Reinquin, F.

2012-04-01

We present here a set of digital maps of the Earth's gravity anomalies (surface free air, Bouguer and isostatic), computed at Bureau Gravimetric International (BGI) as a contribution to the Global Geodetic Observing Systems (GGOS) and to the global geophysical maps published by the Commission for the Geological Map of the World (CGMW) with support of UNESCO and other institutions. The Bouguer anomaly concept is extensively used in geophysical interpretation to investigate the density distributions in the Earth's interior. Complete Bouguer anomalies (including terrain effects) are usually computed at regional scales by integrating the gravity attraction of topography elements over and beyond a given area (under planar or spherical approximations). Here, we developed and applied a worldwide spherical approach aimed to provide a set of homogeneous and high resolution gravity anomaly maps and grids computed at the Earth's surface, taking into account a realistic Earth model and reconciling geophysical and geodetic definitions of gravity anomalies. This first version (1.0) has been computed by spherical harmonics analysis / synthesis of the Earth's topography-bathymetry up to degree 10800. The detailed theory of the spherical harmonics approach is given in Balmino et al., (Journal of Geodesy, 2011). The Bouguer and terrain corrections have thus been computed in spherical geometry at 1'x1' resolution using the ETOPO1 topography/bathymetry, ice surface and bedrock models from the NOAA (National Oceanic and Atmospheric Administration) and taking into account precise characteristics (boundaries and densities) of major lakes, inner seas, polar caps and of land areas below sea level. Isostatic corrections have been computed according to the Airy-Heiskanen model in spherical geometry for a constant depth of compensation of 30km. The gravity information given here is provided by the Earth Geopotential Model (EGM2008), developed at degree 2160 by the National Geospatial Intelligence Agency (NGA) (Pavlis et al., 2008) and the DTU10 (Andersen, 2010) who represents the best up-to-date global gravity models (including surface gravity measurements from land, marine and airborne surveys as well as gravity and altimetry satellite measurements). The surface free-air anomaly is computed at the Earth's surface in the context of Molodensky theory and includes corrections from the mass of the atmosphere. The way gravity anomalies are computed on a worldwide basis slightly differs from the classical usage, but meets modern concerns which tend to take into account of the real Earth. The resulting anomaly maps and grids will be distributed for scientific and education purposes by the Commission for the Geological Map of the World (CGMW) (http://ccgm.free.fr) and by the Bureau Gravimetrique International (BGI) (http://bgi.omp.obs-mip.fr). Upgraded versions might be done as soon as new global gravity model will be available (including satellite GOCE data for instance). Institutions who are interested to contribute with new datasets of surface gravity measurements (i.e. ground, marine or airborne gravity data) are also invited to contact BGI bgi@cnes.fr.

Method of Mapping Anomalies in Homogenous Material

NASA Technical Reports Server (NTRS)

Taylor, Bryant D. (Inventor); Woodard, Stanley E. (Inventor)

2016-01-01

An electrical conductor and antenna are positioned in a fixed relationship to one another. Relative lateral movement is generated between the electrical conductor and a homogenous material while maintaining the electrical conductor at a fixed distance from the homogenous material. The antenna supplies a time-varying magnetic field that causes the electrical conductor to resonate and generate harmonic electric and magnetic field responses. Disruptions in at least one of the electric and magnetic field responses during this lateral movement are indicative of a lateral location of a subsurface anomaly. Next, relative out-of-plane movement is generated between the electrical conductor and the homogenous material in the vicinity of the anomaly's lateral location. Disruptions in at least one of the electric and magnetic field responses during this out-of-plane movement are indicative of a depth location of the subsurface anomaly. A recording of the disruptions provides a mapping of the anomaly.

Study of gravity and magnetic anomalies using MAGSAT data

NASA Technical Reports Server (NTRS)

Braile, L. W.; Hinze, W. J.; Vonfrese, R. R. B. (Principal Investigator)

1981-01-01

The results of modeling satellite-elevation magnetic and gravity data using the constraints imposed by near surface data and seismic evidence shows that the magnetic minimum can be accounted for by either an intracrustal lithologic variation or by an upwarp of the Curie point isotherm. The long wavelength anomalies of the NOO's-vector magnetic survey of the conterminous U.S. were contoured and processed by various frequency filters to enhance particular characteristics. A preliminary inversion of the data was completed and the anomaly field calculated at 450 km from the equivalent magnet sources to compare with the POGO satellite data. Considerable progress was made in studing the satellite magnetic data of South America and adjacent marine areas. Preliminary versions of the 1 deg free-air gravity anomaly map (20 m gal contour interval) and the high cut (lambda approximately 8 deg) filtered anomaly maps are included.

Comparison of liquid-state anomalies in Stillinger-Weber models of water, silicon, and germanium

NASA Astrophysics Data System (ADS)

Dhabal, Debdas; Chakravarty, Charusita; Molinero, Valeria; Kashyap, Hemant K.

2016-12-01

We use molecular dynamics simulations to compare and contrast the liquid-state anomalies in the Stillinger-Weber models of monatomic water (mW), silicon (Si), and germanium (Ge) over a fairly wide range of temperatures and densities. The relationships between structure, entropy, and mobility, as well as the extent of the regions of anomalous behavior, are discussed as a function of the degree of tetrahedrality. We map out the cascade of density, structural, pair entropy, excess entropy, viscosity, and diffusivity anomalies for these three liquids. Among the three liquids studied here, only mW displays anomalies in the thermal conductivity, and this anomaly is evident only at very low temperatures. Diffusivity and viscosity, on the other hand, show pronounced anomalous regions for the three liquids. The temperature of maximum density of the three liquids shows re-entrant behavior consistent with either singularity-free or liquid-liquid critical point scenarios proposed to explain thermodynamic anomalies. The order-map, which shows the evolution of translational versus tetrahedral order in liquids, is different for Ge than for Si and mW. We find that although the monatomic water reproduces several thermodynamic and dynamic properties of rigid-body water models (e.g., SPC/E, TIP4P/2005), its sequence of anomalies follows, the same as Si and Ge, the silica-like hierarchy: the region of dynamic (diffusivity and viscosity) anomalies encloses the region of structural anomalies, which in turn encloses the region of density anomaly. The hierarchy of the anomalies based on excess entropy and Rosenfeld scaling, on the other hand, reverses the order of the structural and dynamic anomalies, i.e., predicts that the three Stillinger-Weber liquids follow a water-like hierarchy of anomalies. We investigate the scaling of diffusivity, viscosity, and thermal conductivity with the excess entropy of the liquid and find that for dynamical properties that present anomalies there is no universal scaling of the reduced property with excess entropy for the whole range of temperatures and densities. Instead, Rosenfeld's scaling holds for all the three liquids at high densities and high temperatures, although deviations from simple exponential dependence are observed for diffusivity and viscosity at lower temperatures and intermediate densities. The slope of the scaling of transport properties obtained for Ge is comparable to that obtained for simple liquids, suggesting that this low tetrahedrality liquid, although it stabilizes a diamond crystal, is already close to simple liquid behavior for certain properties.

Comparison of liquid-state anomalies in Stillinger-Weber models of water, silicon, and germanium.

PubMed

Dhabal, Debdas; Chakravarty, Charusita; Molinero, Valeria; Kashyap, Hemant K

2016-12-07

We use molecular dynamics simulations to compare and contrast the liquid-state anomalies in the Stillinger-Weber models of monatomic water (mW), silicon (Si), and germanium (Ge) over a fairly wide range of temperatures and densities. The relationships between structure, entropy, and mobility, as well as the extent of the regions of anomalous behavior, are discussed as a function of the degree of tetrahedrality. We map out the cascade of density, structural, pair entropy, excess entropy, viscosity, and diffusivity anomalies for these three liquids. Among the three liquids studied here, only mW displays anomalies in the thermal conductivity, and this anomaly is evident only at very low temperatures. Diffusivity and viscosity, on the other hand, show pronounced anomalous regions for the three liquids. The temperature of maximum density of the three liquids shows re-entrant behavior consistent with either singularity-free or liquid-liquid critical point scenarios proposed to explain thermodynamic anomalies. The order-map, which shows the evolution of translational versus tetrahedral order in liquids, is different for Ge than for Si and mW. We find that although the monatomic water reproduces several thermodynamic and dynamic properties of rigid-body water models (e.g., SPC/E, TIP4P/2005), its sequence of anomalies follows, the same as Si and Ge, the silica-like hierarchy: the region of dynamic (diffusivity and viscosity) anomalies encloses the region of structural anomalies, which in turn encloses the region of density anomaly. The hierarchy of the anomalies based on excess entropy and Rosenfeld scaling, on the other hand, reverses the order of the structural and dynamic anomalies, i.e., predicts that the three Stillinger-Weber liquids follow a water-like hierarchy of anomalies. We investigate the scaling of diffusivity, viscosity, and thermal conductivity with the excess entropy of the liquid and find that for dynamical properties that present anomalies there is no universal scaling of the reduced property with excess entropy for the whole range of temperatures and densities. Instead, Rosenfeld's scaling holds for all the three liquids at high densities and high temperatures, although deviations from simple exponential dependence are observed for diffusivity and viscosity at lower temperatures and intermediate densities. The slope of the scaling of transport properties obtained for Ge is comparable to that obtained for simple liquids, suggesting that this low tetrahedrality liquid, although it stabilizes a diamond crystal, is already close to simple liquid behavior for certain properties.

Joint Interpretation of Bathymetric and Gravity Anomaly Maps Using Cross and Dot-Products.

NASA Astrophysics Data System (ADS)

Jilinski, Pavel; Fontes, Sergio Luiz

2010-05-01

0.1 Summary We present the results of joint map interpretation technique based on cross and dot-products applied to bathymetric and gravity anomaly gradients maps. According to the theory (Gallardo, Meju, 2004) joint interpretation of different gradient characteristics help to localize and empathize patterns unseen on one image interpretation and gives information about the correlation of different spatial data. Values of angles between gradients and their cross and dot-product were used. This technique helps to map unseen relations between bathymetric and gravity anomaly maps if they are analyzed separately. According to the method applied for the southern segment of Eastern-Brazilian coast bathymetrical and gravity anomaly gradients indicates a strong source-effect relation between them. The details of the method and the obtained results are discussed. 0.2 Introduction We applied this method to investigate the correlation between bathymetric and gravity anomalies at the southern segment of the Eastern-Brazilian coast. Gridded satellite global marine gravity data and bathymetrical data were used. The studied area is located at the Eastern- Brazilian coast between the 20° W and 30° W meridians and 15° S and 25° S parallels. The volcanic events responsible for the uncommon width of the continental shelf at the Abrolhos bank also were responsible for the formation of the Abrolhos islands and seamounts including the major Vitoria-Trindade chain. According to the literature this volcanic structures are expected to have a corresponding gravity anomaly (McKenzie, 1976, Zembruscki, S.G. 1979). The main objective of this study is to develop and test joint image interpretation method to compare spatial data and analyze its relations. 0.3 Theory and Method 0.3.1 Data sources The bathymetrical satellite data were derived bathymetry 2-minute grid of the ETOPO2v2 obtained from NOAA's National Geophysical Data Center (http://www.ngdc.noaa.gov). The satellite marine gravity 1-minute gridded data were obtained from the Satellite Geodesy at the Scripps Institution of Oceanography, Smith & Sandwell (1997; http://topex.ucsd.edu. Gravity anomaly data were re-gridded using the ETOPO2v2 grid. All calculations and maps were made using MatLab 2007 software. 0.3.2 Cross-Product Cross-product is the result of multiplication of bathymetric and gravity anomaly gradient magnitudes by the sine of the angle between them. According to the definition of gradient cross-product minimal values are expected to be found in points where the angle between gradients is close to zero or where one or both of the gradient magnitudes have values close to zero. It creates an ambiguity and a problem for data interpretation since there is no exact correspondence between bathymetric structures and gravity anomalies. 0.3.3 Dot-Product Dot-product is the result of multiplication of bathymetric and gravity anomaly magnitudes by the cosine on the angle between them. According to the definition of dot-product, values close to zero can be generated by near perpendicular orientation of the gradients or small magnitudes of one or both gradients. So, the results are mutually increased in areas with larger magnitudes or smaller angles between gradients. Due to this mutual amplification dot-products are less affected by the ambiguity of cross-product explained above. The same statistical separation of cross-product was used to support the conclusions. 0.3.4 Statistics and Significance Criteria Statistical analysis was made in order to sort the data into two groups to reduce ambiguity effect: first group - data with magnitudes that could be considered anomalous (where the main minimizing source is the angle between the gradients and the second group - data with magnitudes variations that could be considered as (non significant or background (where cross-product value is determined by the small magnitude). It was chosen to use the mean value and standard deviation (std) to sort the data in such two groups. These values were determined for bathymetric and gravity anomaly gradient magnitudes creating two data sets - one where one or both gradient magnitudes are one standard deviation larger than the mean value with a total of 7831 (anomalous) and a second one where both magnitudes differ smaller than one standard deviation from the mean value with 85584 (background ). Statistical analysis of distribution patterns for both groups was made. 0.4 Examples of Method Application 0.4.1 Map of Angles Between Gradients Figure 1 shows the map of angle values. The angle values were divided into 4 equal intervals. The statistical distribution of angles between gradient in the given intervals is the following (percents of the total): 0 to 60° - 51.39% of the values; 60° to 90° -12.08%; 90° to 120° -14.92%; 120° to 180° -21.18%. It can be seen that 51% of the gradients have a small angle between them, 72% of gradients can be considered as parallel (72%) with angles smaller than 60° or bigger than 120° between them. After statistical separation in the anomalous group almost 91% of the gradients have an angle smaller than 60° while in the background group just 48.6%. From these results we can make a conclusion that the majority of the bathymetric and gravity anomaly gradients are related. Regions with higher gradient magnitudes are characterized by cosine values close to 1 (indicating a small angle between them). The size of the areas characterized by small angles between gradients exceed the size of bathymetric and gravity anomaly isolines characterizing the area of influence of the structures and their effects. Regions with no significant anomalies show uncorrelated value spots. 0.4.2 Map of Cross-Product The resulting map shows small spots of higher cross-product magnitudes following magnitude isolines. About 90% of the values are close to minimum. As was mentioned before, we can presume that areas where bathymetry and gravity anomaly gradient cross-products have smallest magnitudes there is a good correspondence between them indicating a good correspondence between shapes. According to these results for the studied area the shapes and positions of bathymetric structures and gravity anomalies are well correlated suggesting strong correlation between source and its effect. 0.4.3 Map of Dot-Product The resulting map resembles bathymetric and gravity anomaly isolines. All the sea mounts, banks, continental slope and other notable geomorphologic structures and gravity anomalies are well delimitated in the dot-product map eliminating uncorrelated areas where gradient orientations can be considered as near perpendicular. The dot-product map of the studied area suggests a strong source-effect between bathymetry and gravity anomaly. 0.5 Conclusions The joint image interpretation technique uses three different criteria that are sensitive to different gradient properties. Angles between gradients are a good indicator of areas where data are related and it is not sensitive to the magnitudes of the gradients. Angles maps can be used to find areas with direct and inverse relation between mapped properties and contour areas of influence of anomalies unseen on gradient magnitude maps alone. Statistical measures of distribution of angles can be an indicator of relation between data sets as show using significance criteria. Cross-product map has a spotted character of contours. To reduce the effects of the ambiguity the separation into two groups proved to be useful. It helps to separate the cross-product values that are minimized due to gradient magnitudes from those that minimize due to sine values which is a measure of correlation between them. Dot-product values contour areas where gradients are correlated. According to joint image interpretation technique applied bathymetric structures especially the volcanic seamounts and banks in the southern part of East-Brazilian Coast are closely related to the observed gravity anomalies and can be interpreted as sources and effect. This technique also helps to evaluate the shape and dispersion of the gravitational effect from a bathymetrical source. 0.6 References Dehlinger P., Marine Gravity, Elsevier, 1978. Gallardo, L. A., and M. A. Meju., Joint 2D cross-gradient imaging of magnetotelluric and seismic travel-time data for structural and lithological classification, Geophys. J. Int., 169, 1261-1272. (2007) Gallardo, L.A., M. A. Meju (2004), Joint two-dimensional dc resistivity and seismic traveltime inversion with cross-gradients constraints, J. Geophys. Res., 109, B03311, doi:10.1029/2003JB002716 Jacoby, W., and Smilde P. L., Gravity Interpretation, Springer, 2009. McKenzie D. & Bowin C. 1976. The relationship between bathymetry and gravity in Atlantic Ocean. Journal of Geophysical Research, 81: 1903-1915. Roy. K. K., Potential Theory in Applied Geophysics, Springer, 2008. Smith, W. H. F., and D. T. Sandwell, Global seafloor topography from satellite altimetry and ship depth soundings, Science, v. 277, p. 1957-1962, 26 Sept., 1997. Sandwell, D. T., and W. H. F. Smith, Global marine gravity from retracked Geosat and ERS-1 altimetry: Ridge Segmentation versus spreading rate, J. Geophys. Res., 114, B01411, doi:10.1029/2008JB006008, 2009. Zembruscki, S.G. 1979. Geomorfologia da Margem Continental Sul Brasileira e das Bacias Oceânicas Adjacentes. In: Geomorfologia da margem continental brasileira e das áreas oceânicas adjacentes. Série Projeto REMAC, N° 7.

Ionospheric TEC Weather Map Over South America

NASA Astrophysics Data System (ADS)

Takahashi, H.; Wrasse, C. M.; Denardini, C. M.; Pádua, M. B.; de Paula, E. R.; Costa, S. M. A.; Otsuka, Y.; Shiokawa, K.; Monico, J. F. Galera; Ivo, A.; Sant'Anna, N.

2016-11-01

Ionospheric weather maps using the total electron content (TEC) monitored by ground-based Global Navigation Satellite Systems (GNSS) receivers over South American continent, TECMAP, have been operationally produced by Instituto Nacional de Pesquisas Espaciais's Space Weather Study and Monitoring Program (Estudo e Monitoramento Brasileiro de Clima Especial) since 2013. In order to cover the whole continent, four GNSS receiver networks, (Rede Brasileiro de Monitoramento Contínuo) RBMC/Brazilian Institute for Geography and Statistics, Low-latitude Ionospheric Sensor Network, International GNSS Service, and Red Argentina de Monitoreo Satelital Continuo, in total 140 sites, have been used. TECMAPs with a time resolution of 10 min are produced in 12 h time delay. Spatial resolution of the map is rather low, varying between 50 and 500 km depending on the density of the observation points. Large day-to-day variabilities of the equatorial ionization anomaly have been observed. Spatial gradient of TEC from the anomaly trough (total electron content unit, 1 TECU = 1016 el m-2 (TECU) <10) to the crest region (TECU > 80) causes a large ionospheric range delay in the GNSS positioning system. Ionospheric plasma bubbles, their seeding and development, could be monitored. This plasma density (spatial and temporal) variability causes not only the GNSS-based positioning error but also radio wave scintillations. Monitoring of these phenomena by TEC mapping becomes an important issue for space weather concern for high-technology positioning system and telecommunication.

Introducing an operational method to forecast long-term regional drought based on the application of artificial intelligence capabilities

NASA Astrophysics Data System (ADS)

Kousari, Mohammad Reza; Hosseini, Mitra Esmaeilzadeh; Ahani, Hossein; Hakimelahi, Hemila

2017-01-01

An effective forecast of the drought definitely gives lots of advantages in regard to the management of water resources being used in agriculture, industry, and households consumption. To introduce such a model applying simple data inputs, in this study a regional drought forecast method on the basis of artificial intelligence capabilities (artificial neural networks) and Standardized Precipitation Index (SPI in 3, 6, 9, 12, 18, and 24 monthly series) has been presented in Fars Province of Iran. The precipitation data of 41 rain gauge stations were applied for computing SPI values. Besides, weather signals including Multivariate ENSO Index (MEI), North Atlantic Oscillation (NAO), Southern Oscillation Index (SOI), NINO1+2, anomaly NINO1+2, NINO3, anomaly NINO3, NINO4, anomaly NINO4, NINO3.4, and anomaly NINO3.4 were also used as the predictor variables for SPI time series forecast the next 12 months. Frequent testing and validating steps were considered to obtain the best artificial neural networks (ANNs) models. The forecasted values were mapped in verification sector then they were compared with the observed maps at the same dates. Results showed considerable spatial and temporal relationships even among the maps of different SPI time series. Also, the first 6 months forecasted maps showed an average of 73 % agreements with the observed ones. The most important finding and the strong point of this study was the fact that although drought forecast in each station and time series was completely independent, the relationships between spatial and temporal predictions remained. This strong point mainly referred to frequent testing and validating steps in order to explore the best drought forecast models from plenty of produced ANNs models. Finally, wherever the precipitation data are available, the practical application of the presented method is possible.

Surface magnetic field mapping on high albedo marking areas of the moon

NASA Astrophysics Data System (ADS)

Shibuya, H.; Aikawa, K.; Tsunakawa, H.; Takahashi, F.; Shimizu, H.; Matsushima, M.

2009-12-01

The correlation between high albedo markings (HAM) on the surface of the moon and strong magnetic anomalies has been claimed since the early time of the lunar magnetic field study (Hood and Schubert, 1980). Hood et al. (1989) mapped the smoothed magnetic field over the Reiner Gamma region using Lunar Prospector magnetometer (LP-MAG) data, and showed that the position of them matches well. We have developed a method to recover the 3-d magnetic field from satellite field observations (EPR method which stands for Equivalent Pole Reduction; Toyoshima et al. 2008). Applying EPR to the several areas of strong magnetic anomalies, we calculated the magnetic anomaly maps of near surface regions, to see how the anomaly and the HAM correlate each other. The data used is of the Lunar Prospector magnetometer (LP-MAG). They are selected from low altitude observations performed in 1998 to 1999. The areas studied are Reiner Gamma, Airy, Descartes, Abel, and Crisium Antipode regions. The EPR determines a set of magnetic monopoles at the moon surface which produce the magnetic field of the observation. In each studied area, we put poles in 0.1° intervals of both latitude and longitude, then the magnetic field at 5km in altitude is calculated. The field distribution is superimposed with the albedo map made from Clementine data. The total force (Bf) maps indicate that the HMA occurs at the strong anomaly regions, but their shape does not quite overlie. However, taking horizontal component (Bh), not only position but the shape and size of the anomalies coincide with HMA regions. It is particularly true for the Reiner Gamma, and Descartes regions. The shape of HMA fits in a Bh contour. The HMA is argued to be formed by the reduction of solar wind particles which are shielded by the magnetic field. Since the deflection of the charged particle becomes large at large horizontal component, the Bh distribution showed here support the argument.

Crust structure beneath Jilin Province and Liaoning Province in China based on seismic ambient noise tomography

NASA Astrophysics Data System (ADS)

Pang, Guanghua; Feng, Jikun; Lin, Jun

2016-11-01

We imaged the crust structure beneath Jilin Province and Liaoning Province in China with fundamental mode Rayleigh waves recorded by 60 broadband stations deployed in the region. Surface-wave empirical Green's functions were retrieved from cross-correlations of inter-station data and phase velocity dispersions were measured using a frequency-time analysis method. Dispersion measurements were then utilized to construct 2D phase velocity maps for periods between 5 and 35 s. Subsequently, the phase-dispersion curves extracted from each cell of the 2D phase velocity maps were inverted to determine the 3D shear wave velocity structures of the crust. The phase velocity maps at different periods reflected the average velocity structures corresponding to different depth ranges. The maps in short periods, in particular, were in excellent agreement with known geological features of the surface. In addition to imaging shear wave velocity structures of the volcanoes, we show that obvious low-velocity anomalies imaged in the Changbaishan-Tianchi Volcano, the Longgang-Jinlongdingzi Volcano, and the system of the Dunmi Fault crossing the Jingbohu Volcano, all of which may be due to geothermal anomalies.

Remote sensing as a mineral prospecting technique

NASA Technical Reports Server (NTRS)

Meneses, P. R. (Principal Investigator)

1984-01-01

Remote sensing and its application as an alternative technique to mineral resource exploration are reviewed. Emphasis is given here to the analysis of the three basic attributes of remote sensing, i.e., spatial attributes related to regional structural mapping, spectral attributes related to rock discrimination and seasonal attributes related to geobotanic anomalies mapping, all of which are employed in mineral exploration. Special emphasis is given to new developments of the Thematic Mapper of the LANDSAT-5, principally with reference to the application of the bands 1.6 and 2.2 microns to map hydrothermally altered rocks and the band of red and blue shift to geobotanical anomalies mapping.

Airborne gamma-ray spectrometer and magnetometer survey, Cape Flattery quadrange (Washington). Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1981-01-01

No uranium anomalies meet the minimum statistical requirements as defined. There is no Uranium Anomaly Interpretation Map for the Cape Flattery quadrangle. Potassium (%K), equivalent Uranium (ppM eU), equivalent Thorium (ppM eT), eU/eT, eU/K, eT/K, and magnetic pseudo-contour maps are presented in Appendix E. Stacked Profiles showing geologic strip maps along each flight-line, together with sensor data, and ancillary data are presented in Appendix F. All maps and profiles were prepared on a scale of 1:250,000, but have been reduced to 1:500,000 for presentation.

Airborne gamma-ray spectrometer and magnetometer survey, Copalis Beach quadrangle (Washington). Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1981-01-01

No uranium anomalies meet the minimum statistical requirements as defined. There is no Uranium Anomaly Interpretation Map for the Copalis Beach quadrangle. Potassium (%K), equivalent Uranium (ppM eU), equivalent Thorium (ppM eT), eU/eT, eU/K, eT/K, and magnetic pseudo-contour maps are presented in Appendix E. Stacked Profiles showing geologic strip maps along each flight-line, together with sensor data, and ancillary data are presented in Appendix F. All maps and profiles were prepared on a scale of 1:250,000, but have been reduced to 1:500,000 for presentation.

Gravity and magnetic anomaly data analysis

NASA Technical Reports Server (NTRS)

Braile, L. W.; Hinze, W. J.; Vonfrese, R. R. B. (Principal Investigator)

1982-01-01

Progress on the analysis MAGSAT data is reported. The MAGSAT data from 40 deg S to 70 deg N latitude and 30 deg W to 60 E longitude was reduced to radial polarization. In addition, gravity anomaly data from this area were processed and a variety of filtered maps were prepared for combined interpretation of the gravity and magnetic data in conjunction with structural and tectonic maps of the area. The VERSATEC listings and cross-reference maps of variable and array names for the spherical Earth analysis programs NVERTSM, SMFLD, NVERTG, and GFLD were also prepared.

Complete Bouguer gravity anomaly map of the state of Colorado

USGS Publications Warehouse

Abrams, Gerda A.

1993-01-01

The Bouguer gravity anomaly map is part of a folio of maps of Colorado cosponsored by the National Mineral Resources Assessment Program (NAMRAP) and the National Geologic Mapping Program (COGEOMAP) and was produced to assist in studies of the mineral resource potential and tectonic setting of the State. Previous compilations of about 12,000 gravity stations by Behrendt and Bajwa (1974a,b) are updated by this map. The data was reduced at a 2.67 g/cm3 and the grid contoured at 3 mGal intervals. This map will aid in the mineral resource assessment by indicating buried intrusive complexes, volcanic fields, major faults and shear zones, and sedimentary basins; helping to identify concealed geologic units; and identifying localities that might be hydrothermically altered or mineralized.

Hierarchical Kohonenen net for anomaly detection in network security.

PubMed

Sarasamma, Suseela T; Zhu, Qiuming A; Huff, Julie

2005-04-01

A novel multilevel hierarchical Kohonen Net (K-Map) for an intrusion detection system is presented. Each level of the hierarchical map is modeled as a simple winner-take-all K-Map. One significant advantage of this multilevel hierarchical K-Map is its computational efficiency. Unlike other statistical anomaly detection methods such as nearest neighbor approach, K-means clustering or probabilistic analysis that employ distance computation in the feature space to identify the outliers, our approach does not involve costly point-to-point computation in organizing the data into clusters. Another advantage is the reduced network size. We use the classification capability of the K-Map on selected dimensions of data set in detecting anomalies. Randomly selected subsets that contain both attacks and normal records from the KDD Cup 1999 benchmark data are used to train the hierarchical net. We use a confidence measure to label the clusters. Then we use the test set from the same KDD Cup 1999 benchmark to test the hierarchical net. We show that a hierarchical K-Map in which each layer operates on a small subset of the feature space is superior to a single-layer K-Map operating on the whole feature space in detecting a variety of attacks in terms of detection rate as well as false positive rate.

Identification of active fault using analysis of derivatives with vertical second based on gravity anomaly data (Case study: Seulimeum fault in Sumatera fault system)

NASA Astrophysics Data System (ADS)

Hududillah, Teuku Hafid; Simanjuntak, Andrean V. H.; Husni, Muhammad

2017-07-01

Gravity is a non-destructive geophysical technique that has numerous application in engineering and environmental field like locating a fault zone. The purpose of this study is to spot the Seulimeum fault system in Iejue, Aceh Besar (Indonesia) by using a gravity technique and correlate the result with geologic map and conjointly to grasp a trend pattern of fault system. An estimation of subsurface geological structure of Seulimeum fault has been done by using gravity field anomaly data. Gravity anomaly data which used in this study is from Topex that is processed up to Free Air Correction. The step in the Next data processing is applying Bouger correction and Terrin Correction to obtain complete Bouger anomaly that is topographically dependent. Subsurface modeling is done using the Gav2DC for windows software. The result showed a low residual gravity value at a north half compared to south a part of study space that indicated a pattern of fault zone. Gravity residual was successfully correlate with the geologic map that show the existence of the Seulimeum fault in this study space. The study of earthquake records can be used for differentiating the active and non active fault elements, this gives an indication that the delineated fault elements are active.

Photointerpretation of Skylab 2 multispectral camera (S-190A) data: Advance report of significant results

NASA Technical Reports Server (NTRS)

Jensen, M. L. (Principal Investigator)

1973-01-01

The author has identified the following significant results. A significant and possible major economic example of the practical value of Skylab photographs was provided by locating on Skylab Camera Station Number 4, frame 010, SL-2, an area of exposures of limestone rocks which were thought to be completely covered by volcanic rocks based upon prior mapping. The area is located less than 12 miles north of the Ruth porphyry copper deposit, White Pine County, Nevada. This is a major copper producing open pit mine owned by Kennecott Copper Corporation. Geophysical maps consisting of gravity and aeromagnetic studies have been published indicating three large positive magnetic anomalies located at the Ruth ore deposits, the Ward Mountain, not a mineralized area, and in the area previously thought to be completely covered by post-ore volcanics. Skylab photos indicate, however, that erosion has removed volcanic cover in specific sites sufficient to expose the underlying older rocks suggesting, therefore, that the volcanic rocks may not be the cause of the aeromagnetic anomaly. Field studies have verified the initial interpretations made from the Skylab photos. The potential significance of this study is that the large positive aeromagnetic anomaly suggests the presence of cooled and solidified magma below the anomalies, in which ore-bearing solutions may have been derived forming possible large ore deposits.

Free-air and Bouguer gravity anomalies and the Martian crustal dichotomy

NASA Technical Reports Server (NTRS)

Frey, Herbert; Bills, Bruce G.; Kiefer, Walter S.; Nerem, R. Steven; Roark, James H.; Zuber, Maria T.

1993-01-01

Free-air and Bouguer gravity anomalies from a 50x50 field, derived from re-analysis of Viking Orbiter and Mariner 9 tracking data and using a 50x50 expansion of the current Mars topography and the GSFC degree 50 geoid as the equipotential reference surface, with the Martian crustal dichotomy are compared. The spherical harmonic topography used has zero mean elevation, and differs from the USGS maps by about 2 km. In this field the dichotomy boundary in eastern Mars lies mostly at -1 to -2 km elevation. Bouguer gravity anomalies are shown on a map of Noachian, Hesperian, and Amazonian age terrains, simplified from current geologic maps. The map is centered at 300 deg W to show the continuity of the dichotomy boundary. Contour interval is 100 mgals. Gravity and topography were compared along approximately 40 profiles oriented parallel to the dichotomy boundary topographic gradient, to determine how the geophysical character of the boundary changes along its length and what this implies for its origin and development.

A statistical investigation of z test and ROC curve on seismo-ionospheric anomalies in TEC associated earthquakes in Taiwan during 1999-2014

NASA Astrophysics Data System (ADS)

Shih, A. L.; Liu, J. Y. G.

2015-12-01

A median-based method and a z test are employed to find characteristics of seismo-ionospheric precursor (SIP) of the total electron content (TEC) in global ionosphere map (GIM) associated with 129 M≥5.5 earthquakes in Taiwan during 1999-2014. Results show that both negative and positive anomalies in the GIM TEC with the statistical significance of the z test appear few days before the earthquakes. The receiver operating characteristic (ROC) curve is further applied to see whether the SIPs exist in Taiwan.

Utility of Satellite Magnetic Observations for Estimating Near-Surface Magnetic Anomalies

NASA Technical Reports Server (NTRS)

Kim, Hyung Rae; vonFrese, Ralph R. B.; Taylor, Patrick T.; Kim, Jeong Woo; Park, Chan Hong

2003-01-01

Regional to continental scale magnetic anomaly maps are becoming increasingly available from airborne, shipborne, and terrestrial surveys. Satellite data are commonly considered to fill the coverage gaps in regional compilations of these near-surface surveys. For the near-surface Antarctic magnetic anomaly map being produced by the Antarctic Digital Magnetic Anomaly Project (ADMAP), we show that near-surface magnetic anomaly estimation is greatly enhanced by the joint inversion of the near-surface data with the satellite observations relative to the conventional technique such as minimum curvature. Orsted observations are especially advantageous relative to the Magsat data that have order-of-magnitude greater measurement errors, albeit at much lower orbital altitudes. CHAMP is observing the geomagnetic field with the same measurement accuracy as the Orsted mission, but at the lower orbital altitudes covered by Magsat. Hence, additional significant improvement in predicting near-surface magnetic anomalies can result as these CHAMP data are available. Our analysis also suggests that considerable new insights on the magnetic properties of the lithosphere may be revealed by a further order-of-magnitude improvement in the accuracy of the magnetometer measurements at minimum orbital altitude.

Euro-African MAGSAT anomaly-tectonic observations

NASA Technical Reports Server (NTRS)

Hinze, W. J.; Olivier, R.; Vonfrese, R. R. B.

1985-01-01

Preliminary satellite (MAGSAT) scalar magnetic anomaly data are compiled and differentially reduced to radial polarization by equivalent point source inversion for comparison with tectonic data of Africa, Europe and adjacent marine areas. A number of associations are evident to constrain analyses of the tectonic features and history of the region. The Precambrian shields of Africa and Europe exhibit varied magnetic signatures. All shields are not magnetic highs and, in fact, the Baltic shield is a marked minimum. The reduced-to-the-pole magnetic map shows a marked tendency for northeasterly striking anomalies in the eastern Atlantic and adjacent Africa, which is coincident to the track of several hot spots for the past 100 million years. However, there is little consistency in the sign of the magnetic anomalies and the track of the hot spots. Comparison of the radially polarized anomalies of Africa and Europe with other reduced-to-the-pole magnetic satellite anomaly maps of the Western Hemisphere support the reconstruction of the continents prior to the origin of the present-day Atlantic Ocean in the Mesozoic Era.

Euro-african MAGSAT Anomaly-tectonic Observations

NASA Technical Reports Server (NTRS)

Hinze, W. J.; Vonfrese, R. R. B. (Principal Investigator); Olivier, R.

1984-01-01

Preliminary satellite (MAGSAT) scalar magnetic anomaly data are compiled and differentially reduced to radial polarization by equivalent point source inversion for comparison with tectonic data of Africa, Europe and adjacent marine areas. A number of associations are evident to constrain analyses of the tectonic features and history of the region. The Precambrian shields of Africa and Europe exhibit varied magnetic signatures. All shields are not magnetic highs and, in fact, the Baltic shield is a marked minimum. The reduced-to-the-pole magnetic map shows a marked tendency for northeasterly striking anomalies in the eastern Atlantic and adjacent Africa, which is coincident to the track of several hot spots for the past 100 million years. However, there is little consistency in the sign of the magnetic anomalies and the track of the hot spots. Comparison of the radially polarized anomalies of Africa and Europe with other reduced-to-the-pole magnetic satellite anomaly maps of the Western Hemisphere support the reconstruction of the continents prior to the origin of the present-day Atlantic Ocean in the Mesozoic Era.

Snake River Plain Geothermal Play Fairway Analysis - Phase 1 Raster Files

DOE Data Explorer

John Shervais

2015-10-09

Snake River Plain Play Fairway Analysis - Phase 1 CRS Raster Files. This dataset contains raster files created in ArcGIS. These raster images depict Common Risk Segment (CRS) maps for HEAT, PERMEABILITY, AND SEAL, as well as selected maps of Evidence Layers. These evidence layers consist of either Bayesian krige functions or kernel density functions, and include: (1) HEAT: Heat flow (Bayesian krige map), Heat flow standard error on the krige function (data confidence), volcanic vent distribution as function of age and size, groundwater temperature (equivalue interval and natural breaks bins), and groundwater T standard error. (2) PERMEABILTY: Fault and lineament maps, both as mapped and as kernel density functions, processed for both dilational tendency (TD) and slip tendency (ST), along with data confidence maps for each data type. Data types include mapped surface faults from USGS and Idaho Geological Survey data bases, as well as unpublished mapping; lineations derived from maximum gradients in magnetic, deep gravity, and intermediate depth gravity anomalies. (3) SEAL: Seal maps based on presence and thickness of lacustrine sediments and base of SRP aquifer. Raster size is 2 km. All files generated in ArcGIS.

An aeromagnetic interpretation of eleven map sheets, scale 1:250,000, in the southern Najd and part of the southern Tuwayq quadrangles, Kingdom of Saudi Arabia

USGS Publications Warehouse

Griscom, Andrew

1983-01-01

Eleven magnetic interpretation maps (scale 1:250,000) have been prepared for the area .of. exposed crystalline rocks in the Southern Najd and part of the Southern Tuwayq quadrangles (scale 1:500,000) from available published data. Boundaries of a variety of rock units that produce distinctive magnetic anomalies .or anomaly patterns are delineated. In some cases these magnetic boundaries correspond with previously mapped geologic contacts, and in other cases they indicate the possibility of additional, as yet unmapped, geologic contacts. The magnetic boundaries also allow the extrapolation of geologic contacts across areas covered by Quaternary deposits. Many boundaries are identified as part of the Najd fault system, and offset magnetic anomalies may be correlated across certain fault zones. Approximate dips were calculated for a few boundaries that represent igneous contacts, faults, or unconformities. Some characteristic anomalies appear to be associated in a general way with areas of gold mineralization and thus provide a guide for further prospecting.

Remote sensing revealed drainage anomalies and related tectonics of South India

NASA Astrophysics Data System (ADS)

Ramasamy, SM.; Kumanan, C. J.; Selvakumar, R.; Saravanavel, J.

2011-03-01

Drainages have characteristic pattern and life histories with youthful stage in hilly areas, mature stage in plains and old stage in the coastal zones. The deviations from their normal life histories, especially aberrations in their flow pattern in the form of various drainage anomalies have been inferred to be the indications of dominantly the Eustatic and Isostatic changes. This, especially after the advent of Earth Observing Satellites, has attracted the geoscientists from all over the world, for studying such drainage anomalies. In this connection, a study has been undertaken in parts of South India falling south of 14° south latitude to comprehensively map some drainage anomalies like deflected drainages, eyed drainages and compressed meanders and to evolve the tectonic scenario therefrom. The mapping of such mega drainage anomalies and the related lineaments/faults from the satellite digital data and the integration of such lineaments/faults with the overall lineament map of South India showed that the study area is marked by active N-S block faults and NE-SW sinistral and NW-SE dextral strike slip faults. Such an architecture of active tectonic grains indicates that the northerly directed compressive force which has originally drifted the Indian plate towards northerly is still active and deforming the Indian plate.

Satellite-Altitude Geopotential Study of the Kursk Magnetic Anomaly (KMA)

NASA Technical Reports Server (NTRS)

Taylor, Patrick T.; Kim, Hyung Rae; vonFrese, Ralph R. B.; Potts, Laramie V.; Frawley, James J.

2003-01-01

With the successful launch of the Orsted, SAC-C and CHAMP satellites we are able to make both magnetic and gravity anomaly maps of the Earth's crust; magnetic from all three missions and gravity with CHAMP. We have used these data to study the KMA area of Russia. This is an important region for several reasons: (1) we have already made satellite magnetic anomaly maps of this region and they can be integrated with the gravity data from CHAMP for a comprehensive interpretation; (2) KMA contains the largest know reserves of iron-ore in the world; and (3) there are significant ground truth data available for this region from aeromagnetic, balloon surveys and geophysical mapping, including extensive rock magnetic/paleo-magnetic and geologic studies. Utilizing the gravity observations, collocated with the magnetic data enabled us to make a joint interpretation. While there is a high amplitude magnetic anomaly recorded over the KMA the gravity anomaly at satellite altitude revealed by CHAMP is only around 3-6 mGal but is not centered on the magnetic high. This would indicate that despite the fact that in the region of the KMA the rocks have a higher percentage of iron than in the surrounding formations the entire area is Archean-Proterozoic in age and therefore very dense.

Iowa magnetic and gravity maps and data: a web site for distribution of data

USGS Publications Warehouse

Kucks, Robert P.; Hill, Patricia L.

2005-01-01

Magnetic anomalies are due to variations in the Earth's magnetic field caused by the uneven distribution of magnetic minerals (primarily magnetite) in the rocks that make up the upper part of the Earth's crust. The features and patterns of the magnetic anomalies can be used to delineate details of subsurface geology, including the locations of buried faults and magnetite-bearing rocks and the depth to the base of sedimentary basins. This information is valuable for mineral exploration, geologic mapping, and environmental studies. The Iowa magnetic map is constructed from grids that combine information collected in nine separate magnetic surveys conducted between 1953 and 1972. The data from these surveys are of varying quality. The design and specifications (terrain clearance, sampling rates, line spacing, and reduction procedures) varied from survey to survey depending on the purpose of the project and the technology of that time. Every attempt was made to acquire the data in digital form. All survey grids have been continued to 305 m (1,000 ft) above ground and merged together to form the State compilation.

Statistical Analysis of TEC Anomalies Prior to M6.0+ Earthquakes During 2003-2014

NASA Astrophysics Data System (ADS)

Zhu, Fuying; Su, Fanfan; Lin, Jian

2018-04-01

There are many studies on the anomalous variations of the ionospheric TEC prior to large earthquakes. However, whether or not the morphological characteristics of the TEC anomalies in the daytime and at night are different is rarely studied. In the present paper, based on the total electron content (TEC) data from the global ionosphere map (GIM), we carry out a statistical survey on the spatial-temporal distribution of TEC anomalies before 1339 global M6.0+ earthquakes during 2003-2014. After excluding the interference of geomagnetic disturbance, the temporal and spatial distributions of ionospheric TEC anomalies prior to the earthquakes in the daytime and at night are investigated and compared. Except that the nighttime occurrence rates of the pre-earthquake ionospheric anomalies (PEIAs) are higher than those in the daytime, our analysis has not found any statistically significant difference in the spatial-temporal distribution of PEIAs in the daytime and at night. Moreover, the occurrence rates of pre-earthquake ionospheric TEC both positive anomalies and negative anomalies at night tend to increase slightly with the earthquake magnitude. Thus, we suggest that monitoring the ionospheric TEC changes at night might be a clue to reveal the relation between ionospheric disturbances and seismic activities.

Satellite Gravity Drilling the Earth

NASA Technical Reports Server (NTRS)

vonFrese, R. R. B.; Potts, L. V.; Leftwich, T. E.; Kim, H. R.; Han, S.-H.; Taylor, P. T.; Ashgharzadeh, M. F.

2005-01-01

Analysis of satellite-measured gravity and topography can provide crust-to-core mass variation models for new insi@t on the geologic evolution of the Earth. The internal structure of the Earth is mostly constrained by seismic observations and geochemical considerations. We suggest that these constraints may be augmented by gravity drilling that interprets satellite altitude free-air gravity observations for boundary undulations of the internal density layers related to mass flow. The approach involves separating the free-air anomalies into terrain-correlated and -decorrelated components based on the correlation spectrum between the anomalies and the gravity effects of the terrain. The terrain-decorrelated gravity anomalies are largely devoid of the long wavelength interfering effects of the terrain gravity and thus provide enhanced constraints for modeling mass variations of the mantle and core. For the Earth, subcrustal interpretations of the terrain-decorrelated anomalies are constrained by radially stratified densities inferred from seismic observations. These anomalies, with frequencies that clearly decrease as the density contrasts deepen, facilitate mapping mass flow patterns related to the thermodynamic state and evolution of the Earth's interior.

Anomaly Detection and Comparative Analysis of Hydrothermal Alteration Materials Trough Hyperspectral Multisensor Data in the Turrialba Volcano

NASA Astrophysics Data System (ADS)

Rejas, J. G.; Martínez-Frías, J.; Bonatti, J.; Martínez, R.; Marchamalo, M.

2012-07-01

The aim of this work is the comparative study of the presence of hydrothermal alteration materials in the Turrialba volcano (Costa Rica) in relation with computed spectral anomalies from multitemporal and multisensor data adquired in spectral ranges of the visible (VIS), short wave infrared (SWIR) and thermal infrared (TIR). We used for this purposes hyperspectral and multispectral images from the HyMAP and MASTER airborne sensors, and ASTER and Hyperion scenes in a period between 2002 and 2010. Field radiometry was applied in order to remove the atmospheric contribution in an empirical line method. HyMAP and MASTER images were georeferenced directly thanks to positioning and orientation data that were measured at the same time in the acquisition campaign from an inertial system based on GPS/IMU. These two important steps were allowed the identification of spectral diagnostic bands of hydrothermal alteration minerals and the accuracy spatial correlation. Enviromental impact of the volcano activity has been studied through different vegetation indexes and soil patterns. Have been mapped hydrothermal materials in the crater of the volcano, in fact currently active, and their surrounding carrying out a principal components analysis differentiated for a high and low absorption bands to characterize accumulations of kaolinite, illite, alunite and kaolinite+smectite, delimitating zones with the presence of these minerals. Spectral anomalies have been calculated on a comparative study of methods pixel and subpixel focused in thermal bands fused with high-resolution images. Results are presented as an approach based on expert whose main interest lies in the automated identification of patterns of hydrothermal altered materials without prior knowledge or poor information on the area.

Integrated study of basins in the Four Corners region

NASA Astrophysics Data System (ADS)

Fagbola, Olamide Olawumi

2007-12-01

This dissertation is an integrated study of basins in the four corners area of the central part of the Colorado Plateau. The Colorado Plateau is a structurally unique part of the Rocky Mountain region because it has only been moderately deformed when compared to the more intensely deformed areas around it. The Colorado Plateau covers a portion of Utah, Colorado, New Mexico and Arizona. The study area extends from latitude 34°N-40°N to longitude 106°W-111W° encompassing a series of major basins and uplifts: the San Juan, Black Mesa, Paradox, and the Blanding basins; and the Zuni, Defiance, Four Corners, Monument uplifts and the San Juan dome and volcanic field. An analysis of gravity anomalies, basement and crustal structure for basins in the four corners region was carried out. This involved using gravity, magnetic, well, outcrop, seismic estimates of crustal thickness, and geologic data in an integrated fashion. Six filtered gravity and three filtered magnetic maps were generated to aid in the interpretation of the gravity and magnetic anomalies in the study area. A detailed comparison of these maps was carried out. The results show a deep seated mafic structure in the basement acting as a crustal boundary separating the high gravity anomalies from the low. These maps also show that the sources of these anomalies are quite shallow resulting from the upper crust in the study area. The structures in the study area are characterized by northwest and northeast trends which correspond to the Precambrian and the Late Paleozoic structures, respectively. A crustal thickness map of the area was also constructed from seismic estimates of crustal thickness. A comparison was done between the crustal thickness map and the 45 km upward continuation Bouguer anomaly map. The result of this comparison shows that areas of thicker ix crust corresponded to low gravity while areas of thinner crust means mantle material is closer to the surface, thereby producing a high gravity anomaly. The thinnest crust encountered is about 32 km while the thickest crust is about 50 km. Seven gravity models were constructed and these include three crustal-scale profiles crisscrossing the study area and four local profiles. The gravity profiles were modeled using well data, structural thickness maps, cross section data, geologic maps and previous gravity models as constraints. Basement inhomogeneities beneath the basins and the uplifts were delineated by the gravity modeling. One of results from this study reveals that the basement beneath the Four Corners area is highly inhomogeneous. This study reveals that there is a high density deep seated mafic intrusion present in the basement which is responsible for the high gravity and magnetic anomaly in A. This dissertation has also shown that the Four Corners region does not possess a single crustal signature as shown by the different crustal trends in San Juan basin trending northeast and the east-west trending Uncompahgre uplift. The 45 km upward continuation gravity map was also found to correlate with seismic estimates of crustal thickness. The Precambrian basement in this region is also not homogeneous as shown by the necessity of inserting exotic bodies into the basement to compensate for high gravity anomalies and lastly an attempt was made to better define Tweto's (1980) outline of geologic features in the study area. On integrating gravity, magnetics, well and outcrop data, the relief of the Defiance uplift is not as high as delineated by Tweto's (1980) outline.

Airborne gamma-ray spectrometer and magnetometer survey: Victoria quadrangle (Washington). Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1981-01-01

One uranium anomaly meets the minimum statistical requirements. Potassium (%K), equivalent Uranium (ppM eU), equivalent Thorium (ppM eT), eU/eT, eU/K, eT/K, and magnetic pseudo-contour maps are presented. Stacked Profiles showing geologic strip maps along each flight-line, together with sensor data, and ancillary data are presented. All maps and profiles were prepared on a scale of 1:250,000, but have been reduced to 1:500,000 for presentation. Anomaly number 1 is over an exposure of the Permian Shuksan metamorphic suite which is predominantly phyllite (Trps).

Identification of large geomorphological anomalies based on 2D discrete wavelet transform

NASA Astrophysics Data System (ADS)

Doglioni, A.; Simeone, V.

2012-04-01

The identification and analysis based on quantitative evidences of large geomorphological anomalies is an important stage for the study of large landslides. Numerical geomorphic analyses represent an interesting approach to this kind of studies, allowing for a detailed and pretty accurate identification of hidden topographic anomalies that may be related to large landslides. Here a geomorphic numerical analyses of the Digital Terrain Model (DTM) is presented. The introduced approach is based on 2D discrete wavelet transform (Antoine et al., 2003; Bruun and Nilsen, 2003, Booth et al., 2009). The 2D wavelet decomposition of the DTM, and in particular the analysis of the detail coefficients of the wavelet transform can provide evidences of anomalies or singularities, i.e. discontinuities of the land surface. These discontinuities are not very evident from the DTM as it is, while 2D wavelet transform allows for grid-based analysis of DTM and for mapping the decomposition. In fact, the grid-based DTM can be assumed as a matrix, where a discrete wavelet transform (Daubechies, 1992) is performed columnwise and linewise, which basically represent horizontal and vertical directions. The outcomes of this analysis are low-frequency approximation coefficients and high-frequency detail coefficients. Detail coefficients are analyzed, since their variations are associated to discontinuities of the DTM. Detailed coefficients are estimated assuming to perform 2D wavelet transform both for the horizontal direction (east-west) and for the vertical direction (north-south). Detail coefficients are then mapped for both the cases, thus allowing to visualize and quantify potential anomalies of the land surface. Moreover, wavelet decomposition can be pushed to further levels, assuming a higher scale number of the transform. This may potentially return further interesting results, in terms of identification of the anomalies of land surface. In this kind of approach, the choice of a proper mother wavelet function is a tricky point, since it conditions the analysis and then their outcomes. Therefore multiple levels as well as multiple wavelet analyses are guessed. Here the introduced approach is applied to some interesting cases study of south Italy, in particular for the identification of large anomalies associated to large landslides at the transition between Apennine chain domain and the foredeep domain. In particular low Biferno valley and Fortore valley are here analyzed. Finally, the wavelet transforms are performed on multiple levels, thus trying to address the problem of which is the level extent for an accurate analysis fit to a specific problem. Antoine J.P., Carrette P., Murenzi R., and Piette B., (2003), Image analysis with two-dimensional continuous wavelet transform, Signal Processing, 31(3), pp. 241-272, doi:10.1016/0165-1684(93)90085-O. Booth A.M., Roering J.J., and Taylor Perron J., (2009), Automated landslide mapping using spectral analysis and high-resolution topographic data: Puget Sound lowlands, Washington, and Portland Hills, Oregon, Geomorphology, 109(3-4), pp. 132-147, doi:10.1016/j.geomorph.2009.02.027. Bruun B.T., and Nilsen S., (2003), Wavelet representation of large digital terrain models, Computers and Geoscience, 29(6), pp. 695-703, doi:10.1016/S0098-3004(03)00015-3. Daubechies, I. (1992), Ten lectures on wavelets, SIAM.

Global Mapping of Oceanic and Continental Shelf Crustal Thickness and Ocean-Continent Transition Structure

NASA Astrophysics Data System (ADS)

Kusznir, Nick; Alvey, Andy; Roberts, Alan

2017-04-01

The 3D mapping of crustal thickness for continental shelves and oceanic crust, and the determination of ocean-continent transition (OCT) structure and continent-ocean boundary (COB) location, represents a substantial challenge. Geophysical inversion of satellite derived free-air gravity anomaly data incorporating a lithosphere thermal anomaly correction (Chappell & Kusznir, 2008) now provides a useful and reliable methodology for mapping crustal thickness in the marine domain. Using this we have produced the first comprehensive maps of global crustal thickness for oceanic and continental shelf regions. Maps of crustal thickness and continental lithosphere thinning factor from gravity inversion may be used to determine the distribution of oceanic lithosphere, micro-continents and oceanic plateaux including for the inaccessible polar regions (e.g. Arctic Ocean, Alvey et al.,2008). The gravity inversion method provides a prediction of continent-ocean boundary location which is independent of ocean magnetic anomaly and isochron interpretation. Using crustal thickness and continental lithosphere thinning factor maps with superimposed shaded-relief free-air gravity anomaly, we can improve the determination of pre-breakup rifted margin conjugacy and sea-floor spreading trajectory during ocean basin formation. By restoring crustal thickness & continental lithosphere thinning to their initial post-breakup configuration we show the geometry and segmentation of the rifted continental margins at their time of breakup, together with the location of highly-stretched failed breakup basins and rifted micro-continents. For detailed analysis to constrain OCT structure, margin type (i.e. magma poor, "normal" or magma rich) and COB location, a suite of quantitative analytical methods may be used which include: (i) Crustal cross-sections showing Moho depth and crustal basement thickness from gravity inversion. (ii) Residual depth anomaly (RDA) analysis which is used to investigate OCT bathymetric anomalies with respect to expected oceanic values. This includes flexural backstripping to produce bathymetry corrected for sediment loading. (iii) Subsidence analysis which is used to determine the distribution of continental lithosphere thinning. (iv) Joint inversion of time-domain deep seismic reflection and gravity anomaly data which is used to determine lateral variations in crustal basement density and velocity across the OCT, and to validate deep seismic reflection interpretations of Moho depth. The combined interpretation of these independent quantitative measurements is used to determine crustal thickness and composition across the ocean-continent-transition. This integrated approach has been validated on the Iberian margin where ODP drilling provides ground-truth of ocean-continent-transition crustal structure, continent-ocean-boundary location and magmatic type.

Crustal structure of the Churchill-Superior boundary zone between 80 and 98 deg W longitude from Magsat anomaly maps and stacked passes

NASA Technical Reports Server (NTRS)

Hall, D. H.; Millar, T. W.; Noble, I. A.

1985-01-01

A modeling technique using spherical shell elements and equivalent dipole sources has been applied to Magsat signatures at the Churchill-Superior boundary in Manitoba, Ontario, and Ungava. A large satellite magnetic anomaly (12 nT amplitude) on POGO and Magsat maps near the Churchill-Superior boundary was found to be related to the Richmond Gulf aulacogen. The averaged crustal magnetization in the source region is 5.2 A/m. Stacking of the magnetic traces from Magsat passes reveals a magnetic signature (10 nT amplitude) at the Churchill-Superior boundary in an area studied between 80 deg W and 98 deg W. Modeling suggests a steplike thickening of the crust on the Churchill side of the boundary in a layer with a magnetization of 5 A/m. Signatures on aeromagnetic maps are also found in the source areas for both of these satellite anomalies.

An Adaptive Network-based Fuzzy Inference System for the detection of thermal and TEC anomalies around the time of the Varzeghan, Iran, (Mw = 6.4) earthquake of 11 August 2012

NASA Astrophysics Data System (ADS)

Akhoondzadeh, M.

2013-09-01

Anomaly detection is extremely important for forecasting the date, location and magnitude of an impending earthquake. In this paper, an Adaptive Network-based Fuzzy Inference System (ANFIS) has been proposed to detect the thermal and Total Electron Content (TEC) anomalies around the time of the Varzeghan, Iran, (Mw = 6.4) earthquake jolted in 11 August 2012 NW Iran. ANFIS is the famous hybrid neuro-fuzzy network for modeling the non-linear complex systems. In this study, also the detected thermal and TEC anomalies using the proposed method are compared to the results dealing with the observed anomalies by applying the classical and intelligent methods including Interquartile, Auto-Regressive Integrated Moving Average (ARIMA), Artificial Neural Network (ANN) and Support Vector Machine (SVM) methods. The duration of the dataset which is comprised from Aqua-MODIS Land Surface Temperature (LST) night-time snapshot images and also Global Ionospheric Maps (GIM), is 62 days. It can be shown that, if the difference between the predicted value using the ANFIS method and the observed value, exceeds the pre-defined threshold value, then the observed precursor value in the absence of non seismic effective parameters could be regarded as precursory anomaly. For two precursors of LST and TEC, the ANFIS method shows very good agreement with the other implemented classical and intelligent methods and this indicates that ANFIS is capable of detecting earthquake anomalies. The applied methods detected anomalous occurrences 1 and 2 days before the earthquake. This paper indicates that the detection of the thermal and TEC anomalies derive their credibility from the overall efficiencies and potentialities of the five integrated methods.

Maps showing geology, structure, and geophysics of the central Black Hills, South Dakota

USGS Publications Warehouse

Redden, Jack A.; DeWitt, Ed

2008-01-01

This 1:100,000-scale digital geologic map details the complex Early Proterozoic granitic rocks, Early Proterozoic supracrustal metamorphic rocks, and Archean crystalline basement of the Black Hills. The granitic rocks host pegmatite deposits renowned for their feldspar, mica, spodumene, and beryl. The supracrustal rocks host the Homestake gold mine, which produced more than 40 million ounces of gold over a 125-year lifetime. The map documents the Laramide deformation of Paleozoic and Mesozoic cover rocks; and shows the distribution of Laramide plutonic rocks associated with precious-metals deposits. Four 1:300,000-scale maps summarize Laramide structures; Early Proterozoic structures; aeromagnetic anomalies; and gravity anomalies. Three 1:500,000-scale maps show geophysical interpretations of buried Early Proterozoic to Archean rocks in western South Dakota and eastern Wyoming.

Do MAGSAT anomalies contain a record of past and present-day mantle convection under South America?

NASA Technical Reports Server (NTRS)

Hastings, D. A.

1985-01-01

Global anomaly maps from the National Aeronautics and Space Administration's Magnetic Field Satellite (MAGSAT) have been spatially filtered to reduce the prominence of long-wavelength east-west bands and to improve the discrimination of anomalies within structural provinces. Previous research suggested a correlation between total-field MAGSAT anomaly lows in equatorial regions with crustal bodies of relatively high average magnetic susceptibility (such as Archaean shields), and of anomaly highs with bodies of low susceptibility (such as deep parts of basins). These correlations reverse at higher latitudes.

Modeling of the Foca-Uzunada magnetic anomaly and thermal structure in the gulf of Izmir, western Turkey

NASA Astrophysics Data System (ADS)

Aydemir, Attila; Bilim, Funda; Cifci, Gunay; Okay, Seda

2018-05-01

The Gulf of Izmir (GoI) is one of the largest gulfs in the Aegean Sea, Turkey. There is a large magnetic anomaly extending in the NE-SW direction between Foca and Uzunada (Uzun Island) in the gulf. Previously, Curie Point Depth (CPD), geothermal gradient, heat-flow and radiogenic heat production maps of the onshore part of the Aegean region were constructed from the aeromagnetic data. In this study, the same maps except radiogenic heat production map are presented for the offshore part and the largest magnetic anomaly in the northern part of the gulf is focused, particularly. As a result, the thermal structure of GoI is clearly defined and according to the results of this study, CPD values were found from 7 km in the NE of Foca to 10 km through the south of the gulf. The geothermal gradient values vary between 50 and 80 °C/km. Maximum heat flow values around the anomaly are calculated as 200 and 215 mW/m2 according to the thermal conductivity coefficients of 2.5 W m-1 K-1 and 2.7 W m-1 K-1, respectively. Although the anomaly is located in the Izmir Gulf; CPD, geothermic gradient, heat flow anomalies are shifted through the north of Foca and Aliaga towns in the Candarli Bay. This prominent anomaly in the Gulf of Izmir is associated with the magmatics that were encountered at 969 m in the Foca-1 well although it was drilled about 2 km away from the outermost closed contour of the magnetic anomaly. The anomaly is also modeled three dimensionally (3D) in this study. In the model map, the top of the causative body is completely located in the outer part of the gulf, and is very shallow at about 0.5 km while its bottom is inclined through the west of Cigli and Menemen. From this viewpoint, it is possible to suggest that the causative body is inclined through the Foca Peninsula. However, its closed contours are in the NE direction, through the Candarli Bay. Top depth of the causative body is also calculated from the basement horizon on the seismic sections crossing this anomaly. Depth calculations are consistent in these sections and confirm the top depths from the modeling study. The basement geometry in the seismic sections also reflects the shape of 3D model geometry, and bottom depth of the magmatics is also verified by the basement depth calculations in seismic sections.

Bangui Anomaly

NASA Technical Reports Server (NTRS)

Taylor, Patrick T.

2004-01-01

Bangui anomaly is the name given to one of the Earth s largest crustal magnetic anomalies and the largest over the African continent. It covers two-thirds of the Central African Republic and therefore the name derives from the capitol city-Bangui that is also near the center of this feature. From surface magnetic survey data Godivier and Le Donche (1962) were the first to describe this anomaly. Subsequently high-altitude world magnetic surveying by the U.S. Naval Oceanographic Office (Project Magnet) recorded a greater than 1000 nT dipolar, peak-to-trough anomaly with the major portion being negative (figure 1). Satellite observations (Cosmos 49) were first reported in 1964, these revealed a 40nT anomaly at 350 km altitude. Subsequently the higher altitude (417-499km) POGO (Polar Orbiting Geomagnetic Observatory) satellite data recorded peak-to-trough anomalies of 20 nT these data were added to Cosmos 49 measurements by Regan et al. (1975) for a regional satellite altitude map. In October 1979, with the launch of Magsat, a satellite designed to measure crustal magnetic anomalies, a more uniform satellite altitude magnetic map was obtained. These data, computed at 375 km altitude recorded a -22 nT anomaly (figure 2). This elliptically shaped anomaly is approximately 760 by 1000 km and is centered at 6%, 18%. The Bangui anomaly is composed of three segments; there are two positive anomalies lobes north and south of a large central negative field. This displays the classic pattern of a magnetic anomalous body being magnetized by induction in a zero inclination field. This is not surprising since the magnetic equator passes near the center of this body.

Anomalous variation in GPS based TEC measurements prior to the 30 September 2009 Sumatra Earthquake

NASA Astrophysics Data System (ADS)

Karia, Sheetal; Pathak, Kamlesh

This paper investigates the features of pre-earthquake ionospheric anomalies in the total elec-tron content (TEC) data obtained on the basis of regular GPS observations from the GPS receiver at SVNIT Surat (21.16 N, 72.78 E Geog) located at the northern crest of equatorial anomaly region. The data has been analysed for 5 different earthquakes that occurred during 2009 in India and its neighbouring regions. Our observation shows that for the cases of the earthquake, in which the preparation area lies between the crests of the equatorial anomaly close to the geomagnetic equator the enhancement in TEC was followed by a depletion in TEC on the day of earthquake, which may be connected to the equatorial anomaly shape distortions. For the analysis of the ionospheric effects of one of such case-the 30 September 2009 Sumatra earthquake, Global Ionospheric Maps of TEC were used. The possible influence of the earth-quake preparation processes on the main low-latitude ionosphere peculiarity—the equatorial anomaly—is discussed.

Geological and geochemical studies in the Wadi Bidah District, Kingdom of Saudi Arabia

USGS Publications Warehouse

Smith, C.W.; Waters, B.C.; Naqvi, M.; Worl, R.G.; Helaby, A.M.; Flanigan, V.J.; Sadek, H.S.; Samater, R.M.

1983-01-01

Geological and geochemical followup studies of airborne electromagnetic anomalies in the Wadi Bidah district, southwestern Saudi Arabia, did not reveal metals of economic grade. Investigation of an anomaly enclosing the Rabathan ancient mine disclosed tightly folded and sheared Proterozoic tuffaceous rocks interlayered mostly with chert, dolomite, carbonaceous rocks, and volcanic wacke including cherty iron-manganese formations slightly anomalous in copper and zinc. Three drill holes placed to test anomalies within these formations yielded negative results. Studies of a long, narrow anomaly north of the Rabathan area indicated a similar geological environment. This northern area also contains limited zones that are highly anomalous in copper and zinc and extensive zones that are slightly anomalous in those metals. Drilling was not undertaken in this area. The Bilajimah airborne electromagnetic anomaly west of Wadi Bidah coincides with a broad synclinorium of layered felsic turfs and gossans. Geochemical studies indicated slightly anomalous copper, zinc, and silver values in gossans within the anomaly area. Two drill holes intersected carbonaceous rock that contained approximately 15 percent pyrrhotite and traces of sphalerite and chalcopyrite. Two geophysically anomalous areas west of Wadi Bidah surround ancient mines at Mahawiyah and Khayal al Masna'ah. Results of geochemical sampling at these workings were positive. An airborne electromagnetic anomaly located in the Assifar area in the southwestern corner of the Wadi Bidah district is underlain principally by metasedimentary rocks that include large linear zones of cherty iron-manganese formation and a few gossans .containing secondary base metal minerals. Detailed mapping and sampling of the Mulhal ancient mine, located west of Wadi Bidah, revealed two types of polymetallic gossans : (1) stratiform deposits interlayered with ignimbrites and mafic volcanic rocks and (2) barite-bearing gossanous material in shear zones that grade into hydrothermally altered shear zones and extend beyond the mine area. The gossans and gossanous shear zones contain anomalous amounts of gold, silver, lead, copper, zinc, barium, and selenium. Two gossans west of Wadi Bidah were mapped and sampled in detail; both gossans are interlayered, with siliceous volcanic rocks. Although the gossan at Jabal Mohr covers a large area, it contains low amounts of precious and base metals. The gossan at Mulhal No. 2 contains moderate to high amounts of gold, silver, copper, lead, and zinc.

Relation of the lunar volcano complexes lying on the identical linear gravity anomaly

NASA Astrophysics Data System (ADS)

Yamamoto, K.; Haruyama, J.; Ohtake, M.; Iwata, T.; Ishihara, Y.

2015-12-01

There are several large-scale volcanic complexes, e.g., Marius Hills, Aristarchus Plateau, Rumker Hills, and Flamsteed area in western Oceanus Procellarum of the lunar nearside. For better understanding of the lunar thermal history, it is important to study these areas intensively. The magmatisms and volcanic eruption mechanisms of these volcanic complexes have been discussed from geophysical and geochemical perspectives using data sets acquired by lunar explorers. In these data sets, precise gravity field data obtained by Gravity Recovery and Interior Laboratory (GRAIL) gives information on mass anomalies below the lunar surface, and useful to estimate location and mass of the embedded magmas. Using GRAIL data, Andrews-Hanna et al. (2014) prepared gravity gradient map of the Moon. They discussed the origin of the quasi-rectangular pattern of narrow linear gravity gradient anomalies located along the border of Oceanus Procellarum and suggested that the underlying dikes played important roles in magma plumbing system. In the gravity gradient map, we found that there are also several small linear gravity gradient anomaly patterns in the inside of the large quasi-rectangular pattern, and that one of the linear anomalies runs through multiple gravity anomalies in the vicinity of Aristarchus, Marius and Flamstead volcano complexes. Our concern is whether the volcanisms of these complexes are caused by common factors or not. To clarify this, we firstly estimated the mass and depth of the embedded magmas as well as the directions of the linear gravity anomalies. The results were interpreted by comparing with the chronological and KREEP distribution maps on the lunar surface. We suggested providing mechanisms of the magma to these regions and finally discussed whether the volcanisms of these multiple volcano complex regions are related with each other or not.

Mapping lacustrine syn-rift reservoir distribution using spectral attributes: A case study of the Pematang Brownshale Central Sumatra Basin

NASA Astrophysics Data System (ADS)

Haris, A.; Yustiawan, R.; Riyanto, A.; Ramadian, R.

2017-07-01

Pematang Brownshale is the lake sediment, which is proven as the main source rock in Malacca Strait Area. So far Brownshale is only considered as source rock, but the well data show intercalated sand layers encountered within the Pematang Brownshale, where several downhole tests proved this series as a potential hydrocarbon reservoir. Pematang formation is a syn-rift sequent deposited in Malacca Strait following the opening of central Sumatra basin during a late cretaceous to early Oligocene, which is proven as potential source rock and reservoir. The aim of the study is to identify the distribution of sandstone reservoir in Pematang Brownshale using spectral attributes. These works were carried out by integrating log data analysis and frequency maps extracted from spectral attributes Continuous Wavelet Transform (CWT). All these data are used to delineate reservoir distribution in Pematang Brownshale. Based on CWT analysis the anomalies are only visible on the frequency of I5 and I0 Hz maps, which are categorized as low frequencies. Low-frequency shadow anomaly is commonly used as an indication of the presence of hydrocarbons. The distribution of these anomalies is covering an area of approximately 3840.66 acres or equal to I554.25 sq. km, where the low-frequency pattern is interpreted as a deltaic lacustrine feature. By considering the Pematang Brown Shale of Malacca Strait area as a potential reservoir, it would open new play to another basin that has similar characteristics.

Aeromagnetic Study of the Nortern Acambay Graben and Amealco Caldera, Central Mexican Volcanic Belt

NASA Astrophysics Data System (ADS)

Gonzalez, T.

2011-12-01

The Mexican Volcanic Belt (MVB) is characterized by E-W striking faults which form a series of en echelon graben along its length. In the central region of the MVB is located the Acambay graben an intra-arc tectonic depression structure, of apparent Quaternary age, which gives rise to pronounced scarps over a distance of about 80 Km. and 15 to 35 Km wide. The general arrangement of the faults that constitute the Acambay graben shows E-W trend which defines the fronts of the graben exhibits a major fault discontinuity. The graben is limited of the north by the Acambay- Tixmadeje and Epitafio Huerta faults and in the south by the Pastores and Venta de Bravo faults.. In the northern wall in the graben is located the Amealco caldera. This volcanic center (approximately 10 km in diameter) was formed by several discrete volcanic events, which produced an ignimbrite which covers the area. It is partially cut by a regional fault and the southern portion of the Amealco Caldera was displaced by a normal faulting along a segment of the Epitafio Huerta system. Continued tectonic activity in the Acambay area is confirmed by recent seismic episodes The Amealco tuff is the most important volcanic unit because of its volume and distribution. Aeromagnetic data was obtained and analyzed the anomalies. The anomaly map was compared with the surface geology and larger anomalies were correlated with major volcanic features. Since our main interest was in mapping the subsurface intrusive and volcanic bodies, the total field magnetic anomalies were reduced to the pole by using the double integral Fourier method. The reduced to the pole anomaly map results in a simplified pattern of isolated positive and negative anomalies, which show an improved correlation with all major volcanic structures. For the analysis and interpretation of the anomalies, the reduced to the pole anomalies were continued upward at various reference levels. These operations result in smoothing of the anomaly field by the filtering of high frequency anomalies that may be related to shallow sources.

Oxygen-17 anomaly in soil nitrate: A new precipitation proxy for desert landscapes

NASA Astrophysics Data System (ADS)

Wang, Fan; Ge, Wensheng; Luo, Hao; Seo, Ji-Hye; Michalski, Greg

2016-03-01

The nitrogen cycle in desert soil ecosystems is particularly sensitive to changes in precipitation, even of relatively small magnitude and short duration, because it is already under water stress. This suggests that desert soils may have preserved past evidence of small variations in continental precipitation. We have measured nitrate (NO3-) concentrations in soils from the Atacama (Chile), Kumtag (China), Mojave (US), and Thar (India) deserts, and stable nitrogen and oxygen isotope (15N, 17O, and 18O) abundances of the soil NO3-. 17O anomalies (Δ17O), the deviations from the mass-independent isotopic fractionation, were detected in soil NO3- from almost all sites of these four deserts. There was a strong negative correlation between the mean annual precipitation (MAP) and soil NO3- Δ17O values (Δ

Heat Flux and Fluid Flow in the Terrebonne Basin, Northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Meazell, K.; Flemings, P. B.

2016-12-01

We use a three-dimensional seismic survey to map the gas hydrate stability zone within a mid-slope salt-withdrawal minibasin in the northern Gulf of Mexico and identify anomalous regions within the basin where fluids may modify the hydrate stability zone. A discontinuous bottom-simulating reflector (BSR) marks the base of the hydrate stability zone and suggests an average geothermal gradient of 18.1 C/km based on the calculated temperature at the BSR assuming seawater salinity, hydrostatic pressure, and a seafloor temperature of 4 C. When compared to our model of the predicted base of gas hydrate stability assuming a basin-wide geothermal gradient of 18.1 C, two anomalies are found where the BSR is observed significantly shallower than expected. The southern anomaly has a lateral influence of 1500 m from the salt, and a maximum shoaling of 800 m. This anomaly is likely the result of increased salinity or heat from a rising salt diapir along the flank of the basin. A local geothermal gradient of 67.31 C/km or a salinity of 17.5 wt % can explain the observed position of the BSR at the southern anomaly. The northern anomaly is associated with active cold seep vents. In this area, the pluming BSR is crescent shaped, which we interpret as the result of warm and or salty fluids migrating up through a fault. This anomaly has a lateral influence of 1500 m, and a maximum shoaling of 600 m above the predicted base of gas hydrate stability. A local geothermal gradient of 35.45 C/km or a salinity of 14.7 wt % is required to adjust the position of the BSR to that which is observed at the northern anomaly. Active fluid migration suggests a combination of both heat and salinity is responsible for the altered position of the BSR.

Decomposing Worldwide Complete Spherical Bouguer Gravity Anomaly Using 2-D Empirical Method

NASA Astrophysics Data System (ADS)

Firdaus, Ruhul; Mey Ekawati, Gestin

2017-04-01

Currently available worldwide gravity anomaly data provides a high-resolution (2’×2’) of Complete Spherical Bouguer Anomaly (CSBA) based on the available information of the Earth gravity field from surface and satellite measurements. The data has not only been provided and processed thoroughly but it also has been claimed to be appropriate for various geophysical applications. Therefore, the analysis of gravity anomaly is becoming increasingly significant for the earth sciences as a whole and assisting both shallow and deep geological problems. Earth gravity anomaly has to be analyzed carefully as it has very complex data due to anomaly mixing of the density masses spread over the Earth horizontally and vertically. The bigger the spatial coverage of data (e.g. global scale data), the more severe the data from anomaly mixing due to various wavelength. BEMD is an empirical method supposedly suitable with highly oscillation-mixing data. It can effectively isolate each local anomaly in details and is analogized as successively reverse moving average with local windowing. BEMD is designed to reduce multi-component, non-linear gravity field data to a series of single local anomaly contributions. Anomaly from a single body was assumed as a mono-component signal. The main advantage of BEMD processing techniques is to present the subtle details in the data which are not clearly identified in anomaly maps, without specifying any prior information about the nature of the source bodies. As the result, we have identified regional anomalies due to the drift of continental and oceanic masses considered as crust-regional anomaly (CRA). We remove the CRA from the CBA to provide surface-residual anomaly (SRA) where shallow geologic bodies reveal. Meanwhile, the CRA itself can be used as reference to reduce this high magnitude anomaly from any measurement data to exhibit only shallow body anomaly. Further analysis can be carried out to build a general understanding of the details and parameters of the shallower or deeper causative body distributions.

Improving the geological interpretation of magnetic and gravity satellite anomalies

NASA Technical Reports Server (NTRS)

Hinze, W. J.; Braile, L. W. (Principal Investigator); Vonfrese, R. R. B.

1985-01-01

Current limitations in the quantitative interpretation of satellite-elevation geopotential field data and magnetic anomaly data were investigated along with techniques to overcome them. A major result was the preparation of an improved scalar magnetic anomaly map of South America and adjacent marine areas directly from the original MAGSAT data. In addition, comparisons of South American and Euro-African data show a strong correlation of anomalies along the Atlantic rifted margins of the continents.

Teleconnection of the 1997 El Nino Observed by Spaceborne Sensors and the Dacadal Anomalies in the Northeast Pacific

NASA Technical Reports Server (NTRS)

Liu, W.; Hu, H.; Xie, X.

1999-01-01

Liu et al.[1998] (hereafter referred as LTH), superimposed wind velocity anomalies observed by the NASA Scatterometer (NSCAT) on the map of sea surface temperature (SST) anomalies observed by the Advanced Very High Resolution Radiometer (AVHRR) in the Pacific at the end of May 1997, and illustrated that the three regions of anomalous warming in the North Pacific Ocean are related to wind anomalies through different mechanisms.

Lithospheric structure of Taiwan from gravity modelling and sequential inversion of seismological and gravity data

NASA Astrophysics Data System (ADS)

Masson, F.; Mouyen, M.; Hwang, C.; Wu, Y.-M.; Ponton, F.; Lehujeur, M.; Dorbath, C.

2012-11-01

Using a Bouguer anomaly map and a dense seismic data set, we have performed two studies in order to improve our knowledge of the deep structure of Taiwan. First, we model the Bouguer anomaly along a profile crossing the island using simple forward modelling. The modelling is 2D, with the hypothesis of cylindrical symmetry. Second we present a joint analysis of gravity anomaly and seismic arrival time data recorded in Taiwan. An initial velocity model has been obtained by local earthquake tomography (LET) of the seismological data. The LET velocity model was used to construct an initial 3D gravity model, using a linear velocity-density relationship (Birch's law). The synthetic Bouguer anomaly calculated for this model has the same shape and wavelength as the observed anomaly. However some characteristics of the anomaly map are not retrieved. To derive a crustal velocity/density model which accounts for both types of observations, we performed a sequential inversion of seismological and gravity data. The variance reduction of the arrival time data for the final sequential model was comparable to the variance reduction obtained by simple LET. Moreover, the sequential model explained about 80% of the observed gravity anomaly. New 3D model of Taiwan lithosphere is presented.

Aeromagnetic maps with geologic interpretations for the Tularosa Valley, south-central New Mexico

USGS Publications Warehouse

Bath, G.D.

1977-01-01

An aeromagnetic survey of the Tularosa Valley in south-central New Mexico has provided information on the igneous rocks that are buried beneath alluvium and colluvium. The data, compiled as residual magnetic anomalies, are shown on twelve maps at a scale of 1:62,500. Measurements of magnetic properties of samples collected in the valley and adjacent highlands give a basis for identifying the anomaly-producing rocks. Precambrian rocks of the crystalline basement have weakly induced magnetizations and produce anomalies having low magnetic intensities and low magnetic gradients. Late Cretaceous and Cenozoic intrusive rocks have moderately to strongly induced magnetizations. Precambrian rocks produce prominent magnetic anomalies having higher amplitudes and higher gradients. The Quaternary basalt has a strong remanent magnetization of normal polarity and produces narrow anomalies having high-magnetic gradients. Interpretations include an increase in elevation to the top of buried Precambrian rock in the northern part of the valley, a large Late Cretaceous and Cenozoic intrusive near Alamogordo, and a southern extension of the intrusive rock exposed in the Jarilla Mountains. Evidence for the southern extension comes from a quantitative analysis of the magnetic anomalies..

Seismic evidence for broad attenuation anomalies in the asthenosphere beneath the Pacific Ocean

NASA Astrophysics Data System (ADS)

Adenis, Alice; Debayle, Eric; Ricard, Yanick

2017-06-01

We present QADR17, a global model of Rayleigh-wave attenuation based on a massive surface wave data set (372 629 frequency-dependent attenuation curves in the period range 50-260 s). We correct for focusing-defocusing effects and geometrical spreading, and perform a stringent selection to only keep robust observations. Then, data with close epicentres recorded at the same station are clustered, as they sample the same Earth's structure. After this pre-selection, our data set consists of about 35 000 curves that constrain the Rayleigh-wave intrinsic attenuation in the upper mantle. The logarithms of the attenuation along the individual rays are then inverted to obtain global maps of the logarithm of the local attenuation. After a first inversion, outliers are rejected and a second inversion yields a variance reduction of about 45 per cent. Our attenuation maps present strong agreement with surface tectonics at periods lower than 200 s, with low attenuation under continents and high attenuation under oceans. Over oceans, attenuation decreases with increasing crustal ages, but at periods sensitive to the uppermost 150 km, mid-ocean ridges are not characterized by a very localized anomaly, in contrast to what is commonly observed for seismic velocity models. Attenuation is rather well correlated with hotspots, especially in the Pacific ocean, where a strong attenuating anomaly is observed in the long wavelength component of our signal at periods sampling the oceanic asthenosphere. We suggest that this anomaly results from the horizontal spreading of several thermal plumes within the asthenosphere. Strong velocity reductions associated with high attenuation anomalies of moderate amplitudes beneath the East Pacific Rise, the Red Sea and the eastern part of Asia may require additional mechanisms, such as partial melting.

Isostatic gravity map of the Nevada Test Site and vicinity, Nevada

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ponce, D.A.; Harris, R.N.; Oliver, H.W.

1988-12-31

The isostatic gravity map of the Nevada Test Site (NTS) and vicinity is based on about 16,000 gravity stations. Principal facts of the gravity data were listed by Harris and others (1989) and their report included descriptions of base stations, high-precision and absolute gravity stations, and data accuracy. Observed gravity values were referenced to the International Gravity Standardization Net 1971 gravity datum described by Morelli (1974) and reduced using the Geodetic Reference System 1967 formula for the normal gravity on the ellipsoid (International Union of Geodesy and Geophysics, 1971). Free-air, Bouguer, curvature, and terrain corrections for a standard reduction densitymore » of 2.67 g/cm{sup 3} were made to compute complete Bouguer anomalies. Terrain corrections were made to a radial distance of 166.7 km from each station using a digital elevation model and a computer procedure by Plouff (1977) and, in general, include manually estimated inner-zone terrain corrections. Finally, isostatic corrections were made using a procedure by Simpson and others (1983) based on an Airy-Heiskanen model with local compensation (Heiskanen and Moritz, 1967) with an upper-crustal density of 2.67 g/cm{sup 3}, a crustal thickness of 25 km, and a density contrast between the lower-crust and upper-mantle of 0.4 g/cm{sup 3}. Isostatic corrections help remove the effects of long-wavelength anomalies related to topography and their compensating masses and, thus, enhance short- to moderate-wavelength anomalies caused by near surface geologic features. 6 refs.« less

Planetary radar studies

NASA Technical Reports Server (NTRS)

Thompson, T. W.; Cutts, J. A.

1981-01-01

A catalog of lunar and radar anomalies was generated to provide a base for comparison with Venusian radar signatures. The relationships between lunar radar anomalies and regolith processes were investigated, and a consortium was formed to compare lunar and Venusian radar images of craters. Time was scheduled at the Arecibo Observatory to use the 430 MHz radar to obtain high resolution radar maps of six areas of the lunar suface. Data from 1978 observations of Mare Serenitas and Plato are being analyzed on a PDP 11/70 computer to construct the computer program library necessary for the eventual reduction of the May 1981 and subsequent data acquisitions. Papers accepted for publication are presented.

Spatial distribution of soil radon as a tool to recognize active faulting on an active volcano: the example of Mt. Etna (Italy).

PubMed

Neri, Marco; Giammanco, Salvatore; Ferrera, Elisabetta; Patanè, Giuseppe; Zanon, Vittorio

2011-09-01

This study concerns measurements of radon and thoron emissions from soil carried out in 2004 on the eastern flank of Mt. Etna, in a zone characterized by the presence of numerous seismogenic and aseismic faults. The statistical treatment of the geochemical data allowed recognizing anomaly thresholds for both parameters and producing distribution maps that highlighted a significant spatial correlation between soil gas anomalies and tectonic lineaments. The seismic activity occurring in and around the study area during 2004 was analyzed, producing maps of hypocentral depth and released seismic energy. Both radon and thoron anomalies were located in areas affected by relatively deep (5-10 km depth) seismic activity, while less evident correlation was found between soil gas anomalies and the released seismic energy. This study confirms that mapping the distribution of radon and thoron in soil gas can reveal hidden faults buried by recent soil cover or faults that are not clearly visible at the surface. The correlation between soil gas data and earthquakes depth and intensity can give some hints on the source of gas and/or on fault dynamics. Copyright © 2011 Elsevier Ltd. All rights reserved.

Magnetic and gravity anomalies in the Americas

NASA Technical Reports Server (NTRS)

Braile, L. W.; Hinze, W. J.; Vonfrese, R. R. B. (Principal Investigator)

1981-01-01

The cleaning and magnetic tape storage of spherical Earth processing programs are reported. These programs include: NVERTSM which inverts total or vector magnetic anomaly data on a distribution of point dipoles in spherical coordinates; SMFLD which utilizes output from NVERTSM to compute total or vector magnetic anomaly fields for a distribution of point dipoles in spherical coordinates; NVERTG; and GFLD. Abstracts are presented for papers dealing with the mapping and modeling of magnetic and gravity anomalies, and with the verification of crustal components in satellite data.

Identification and Evaluation of Submerged Anomalies, Mobile Harbor, Alabama.

DTIC Science & Technology

1984-10-01

Bay Waters , 1864-1865 APPENDIX B: Description of Maps in National ill Archives Collection V LIST OF FIGURES Figure Page cover Torpedo Raft in Mobile Bay...Anomaly D-E 51 13 Magnetometer Chart, Anomaly F 53 14 Sketch of Steel Wreckage Found at Anomaly F 54 15 Approaches to Mobile City by Water (Merrill...Osage (1863-65) 84 30 CSS Albemarle, Prototype for the Huntsville 86 31 Magnolia, CSA-Utilized Vessel 109 32 Approaches to Mobile City by Water (1864

Crustal analysis of the Ulleung Basin in the East Sea (Japan Sea) from enhanced gravity mapping

NASA Astrophysics Data System (ADS)

Park, Chan Hong; Kim, Jeong Woo; Isezaki, Nobuhiro; Roman, Daniel R.; von Frese, Ralph R. B.

2006-12-01

To facilitate geological analyses of the Ulleung Basin in the East Sea (Japan Sea) between Korea and Japan, shipborne and satellite altimetry-derived gravity data are combined to derive a regionally coherent anomaly field. The 2-min gridded satellite altimetry-based gravity predicted by Sandwell and Smith [Sandwell DT, Smith WHF (1997) J Geophys Res 102(B5):10,039-10,054] are used for making cross-over adjustments that reduce the errors between track segments and at the cross-over points of shipborne gravity profiles. Relative to the regionally more homogeneous satellite gravity anomalies, the longer wavelength components of the shipborne anomalies are significantly improved with minimal distortion of their shorter wavelength components. The resulting free-air gravity anomaly map yields a more coherent integration of short and long wavelength anomalies compared to that obtained from either the shipborne or satellite data sets separately. The derived free-air anomalies range over about 140 mGals or more in amplitude and regionally correspond with bathymetric undulations in the Ulleung Basin. The gravity lows and highs along the basin’s margin indicate the transition from continental to oceanic crust. However, in the northeastern and central Ulleung Basin, the negative regional correlation between the central gravity high and bathymetric low suggests the presence of shallow denser mantle beneath thinned oceanic crust. A series of gravity highs mark seamounts or volcanic terranes from the Korean Plateau to Oki Island. Gravity modeling suggests underplating by mafic igneous rocks of the northwestern margin of the Ulleung Basin and the transition between continental and oceanic crust. The crust of the central Ulleung Basin is about a 14-15 km thick with a 4-5 km thick sediment cover. It may also include a relatively weakly developed buried fossil spreading ridge with approximately 2 km of relief.

Shallow gas in Cenozoic sediments of the Southern North Sea

NASA Astrophysics Data System (ADS)

Trampe, Anna F.; Lutz, Rüdiger; Franke, Dieter; Thöle, Hauke; Arfai, Jashar

2013-04-01

Shallow petroleum systems in the southern North Sea are known for several decades but they were not actively explored for a long time. In recent years these unconventional shallow petroleum systems are studied in greater detail and one shallow gas field (A-12) is in production in the Netherlands. Additionally, oil was encountered in Miocene sandstones in the southern Danish North Sea (Lille John well) just north of the Danish-German border. Seismic amplitude anomalies are an indication for hydrocarbons in sediments. Therefore we have mapped the occurrence of seismic amplitude anomalies in the German North Sea based on more than 25.000 km of 2D seismic data and around 4.000 km2 of 3D seismic data. Amplitude anomalies are ubiquitous phenomena in the study area. These anomalies are not only caused by hydrocarbons but also by changing lithologies e.g. peat or fluid migration. Therefore several classes of seismic anomalies, e.g. bright spots, chimneys, blanking areas and velocity pull-down were mapped. Examples for these classes were studied with AVO (amplitude variation with offset) analyses to verify the existence or non-existence of gas in the sediments. Shallow gas can be produced and transported through the dense pipeline grid of the southern and central North Sea or it could be burned offshore close to wind parks in small power plants and the electric energy then transported through the existing power connections of the wind parks. Thus enabling a continuous energy supply during calm wind periods. This study is carried out within the framework of the project "Geoscientific Potential of the German North Sea (GPDN)" in which the Cenozoic sedimentary system was mapped in great detail. A detailed model of delta evolution (Baltic river system) was developed which serves as a structural framework. The studied interval is time equivalent to the Utsira formation which is used offshore Norway for sequestration of CO2. These different possibilities of using or exploiting the underground emphasize the need for detailed knowledge on the underground for sound decisions on the future use of this area.

Investigation of antarctic crust and upper mantle using MAGSAT and other geophysical data. M.S. Thesis. Final Report, Sep. 1979 - Aug. 1983

NASA Technical Reports Server (NTRS)

Bentley, C. R.; Ritzwoller, M. H.

1983-01-01

Data selection and reduction procedures are described by which scalar and vector magnetic anomaly maps are constructed. The scalar and vertical magnetic anomalies are believed to be generated mainly in the Earth's crust. The horizontal anomalies are believed to be mainly due to short-period field-aligned currents. The correlation of scalar magnetic anomalies with known oceanic structure is remarkable -- magnetic highs are associated with oceanic ridges and magnetic lows with abyssal plains. The correlation between anomalies and continental geology is not so clear.

Provisional maps of thermal areas in Yellowstone National Park, based on satellite thermal infrared imaging and field observations

USGS Publications Warehouse

Vaughan, R. Greg; Heasler, Henry; Jaworowski, Cheryl; Lowenstern, Jacob B.; Keszthelyi, Laszlo P.

2014-01-01

Maps that define the current distribution of geothermally heated ground are useful toward setting a baseline for thermal activity to better detect and understand future anomalous hydrothermal and (or) volcanic activity. Monitoring changes in the dynamic thermal areas also supports decisions regarding the development of Yellowstone National Park infrastructure, preservation and protection of park resources, and ensuring visitor safety. Because of the challenges associated with field-based monitoring of a large, complex geothermal system that is spread out over a large and remote area, satellite-based thermal infrared images from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) were used to map the location and spatial extent of active thermal areas, to generate thermal anomaly maps, and to quantify the radiative component of the total geothermal heat flux. ASTER thermal infrared data acquired during winter nights were used to minimize the contribution of solar heating of the surface. The ASTER thermal infrared mapping results were compared to maps of thermal areas based on field investigations and high-resolution aerial photos. Field validation of the ASTER thermal mapping is an ongoing task. The purpose of this report is to make available ASTER-based maps of Yellowstone’s thermal areas. We include an appendix containing the names and characteristics of Yellowstone’s thermal areas, georeferenced TIFF files containing ASTER thermal imagery, and several spatial data sets in Esri shapefile format.

Detailed petrophysical characterization enhances geological mapping of a buried substratum using aeromagnetic and gravity data; application to the southwestern Paris basin

NASA Astrophysics Data System (ADS)

Baptiste, Julien; Martelet, Guillaume; Faure, Michel; Beccaletto, Laurent; Chen, Yan; Reninger, Pierre-Alexandre

2016-04-01

Mapping the geometries (structure and lithology) of a buried basement is a key for targeting resources and for improving the regional geological knowledge. The Paris basin is a Mesozoic to Cenozoic intraplate basin set up on a Variscan substratum, which crops out in the surrounding massifs. We focus our study on the southwestern part of the Paris basin at its junction with the Aquitaine basin. This Mezo-Cenozoic cover separates the Armorican Massif and the Massif Central which compose of several litho-tectonic units bounded by crustal-scale shear zones. In spite of several lithological and structural correlations between various domains of the two massifs, their geological connection, hidden below the Paris basin sedimentary cover, is still largely debated. Potential field geophysics have proven effective for mapping buried basin/basement interfaces. In order to enhance the cartographic interpretation of these data, we have set up a detailed petrophysical library (field magnetic susceptibility data and density measurements on rock samples) of the Paleozoic rocks outcropping in the Variscan massifs. The combination of aeromagnetic and gravity data supported by the petrophysical signatures and field/borehole geological information, is carried out to propose a new map of the architecture of the Variscan substratum. The new synthetic map of geophysical signature of the Paris basin basement combines: i) the magnetic anomaly reduced to the pole, ii) the vertical gradient of the Bouguer anomaly and iii) the tilt derivative of the magnetic anomaly reduced to the pole. Based on this information, the Eastern extension of the major shear zones below the sedimentary cover is assessed. The petrophysical signatures were classified in three classes of magnetic susceptibility and density: low, intermediate and high. Basic rocks have high magnetization and density values whereas granite, migmatite and orthogneiss show low magnetization and density values, Proterozoic and Paleozoic sediments, micaschists and metagrauwackes have intermediate to low magnetization and density values. Detailed lithological attribution of geophysical anomalies was achieved separately for each geological sub-domain (in between 2 major structures). This methodology will be generalized at the scale of the entire Paris basin in order to propose a tectonic reconstruction of this segment of the Variscan belt, and provide guides for the exploration of hidden resources.

Effect of Varying Crustal Thickness on CHAMP Geopotential Data

NASA Technical Reports Server (NTRS)

Taylor, Patrick T.; Kis, Karoly I.; vonFrese, Ralph R. B.; Korhonen, Juha V.; Wittmann, Geza; Kim, Hyung Rae; Potts, Larmie V.

2003-01-01

Tn determine the effect of crustal thickness variation on satellite-altitude geopotential anomalies we compared two regions of Europe with vastly different values, South and Central Finland and the Pannonian Basin. In our study regions, crustal thickness exceeds 44 km in Finland and is less than 26 km in the Pannonian Basin. Heat-flow data indicate that the thinner and more active crust of the Pannonian Basin has a value nearly three times that of the Finnish Svecofennian Province. An ovoid positive CHAMP gravity anomaly (-4 mGal) is quasi-coincidental with the CHAMP magnetic anomaly traverses the Pannonian Basin while ground based gravity mapping in Hungary shows that the free-air gravity anomalies across the Pannonian Basin are near 0 to +20 mGal with shorter wavelength anomalies from +40 to less than +60 mGal and some 0 to greater than -20 mGal. Larger anomalies are detected in the mountainous areas. The minor value anomalies can indicate the isostatic equilibrium for Hungary (the central part of the Pannonian Basin). Gravity data over Finland bear overprint of de-glaciation. CHAMP gravity data indicates a west-east positive gradient of less than 4 mGal across South and Central Finland. CHAMP magnetic data (400 km) reveal elongated semi-circular negative anomalies for both regions with South-Central Finland having larger amplitude (less than -6 nT) than that over the Pannonian Basin, Hungary (less than -5 nT). In the latter subducted oceanic lithosphere has been proposed as the anomalous body.

Preliminary correlations of MAGSAT anomalies with tectonic features of Africa

USGS Publications Warehouse

Hastings, David A.

1982-01-01

An overview of the MAGSAT scalar anomaly map for Africa has suggested a correlation of MAGSAT anomalies with major crustal blocks of uplift or depression and different degrees of regional metamorphism. The strongest MAGSAT anomalies in Africa are closely correlated spatially with major tectonic features. Although a magnetic anomaly caused by a rectangular crustal block would be offset from the block's center by the effects of magnetic inclination, an anomaly caused by real crustal blocks of varying uplift, depression, and degree of regional metamorphism would be located nearer to the locus of greatest vertical movement and highest grade of metamorphism. Thus, the Bangui anomaly may be caused by a central old Precambrian shield, flanked to the north and south by two relatively young sedimentary basins.

The impact of the 17 March 2015- St. Patrick's Day storm on the evolutionary pattern of Equatorial Ionization Anomaly over the Indian longitudes using high resolution spatio-temporal TEC maps - New insights

NASA Astrophysics Data System (ADS)

Yadav, S.; Sunda, S.; Sridharan, R.

2016-12-01

The impact of the St. Patrick's Day storm (17 March 2015) on the major equatorial electro-dynamical process viz., the Equatorial Ionization Anomaly (EIA) has been assessed using 2D (lat. x long.) total electron content (TEC) maps generated from the ground based SBAS (Satellite Based Augmentation System) enabled receiver data. The various aspects of EIA viz., i) evolution/devolution, ii) longitudinal structure, and iii) its variability during different phases of a geomagnetic storm have been brought out. These 2D TEC maps, which have a large latitudinal (5̊ S-45° N) and longitudinal (55-110° E) coverage, show the complete reversal in the longitudinal structure of EIA during the recovery phase of the storm as compared to the quiet day. These results have been explained in the light of the combined effects of the storm associated processes viz., i) the penetration electric fields of magnetosphere origin, ii) storm induced thermospheric winds, and iii) activation of the consequent disturbance dynamo, effectively distorting the longitudinal wave number 4 (WN4) structure of the EIA. It has been shown unambiguously that even a separation of few degrees in longitude ( 30̊) could experience significantly different forcings. The relevance and the far reaching consequences of the study in the light of the current trends and requirements for reliable satellite based navigation are highlighted.

Non-supervised method for early forest fire detection and rapid mapping

NASA Astrophysics Data System (ADS)

Artés, Tomás; Boca, Roberto; Liberta, Giorgio; San-Miguel, Jesús

2017-09-01

Natural hazards are a challenge for the society. Scientific community efforts have been severely increased assessing tasks about prevention and damage mitigation. The most important points to minimize natural hazard damages are monitoring and prevention. This work focuses particularly on forest fires. This phenomenon depends on small-scale factors and fire behavior is strongly related to the local weather. Forest fire spread forecast is a complex task because of the scale of the phenomena, the input data uncertainty and time constraints in forest fire monitoring. Forest fire simulators have been improved, including some calibration techniques avoiding data uncertainty and taking into account complex factors as the atmosphere. Such techniques increase dramatically the computational cost in a context where the available time to provide a forecast is a hard constraint. Furthermore, an early mapping of the fire becomes crucial to assess it. In this work, a non-supervised method for forest fire early detection and mapping is proposed. As main sources, the method uses daily thermal anomalies from MODIS and VIIRS combined with land cover map to identify and monitor forest fires with very few resources. This method relies on a clustering technique (DBSCAN algorithm) and on filtering thermal anomalies to detect the forest fires. In addition, a concave hull (alpha shape algorithm) is applied to obtain rapid mapping of the fire area (very coarse accuracy mapping). Therefore, the method leads to a potential use for high-resolution forest fire rapid mapping based on satellite imagery using the extent of each early fire detection. It shows the way to an automatic rapid mapping of the fire at high resolution processing as few data as possible.

Elevation Difference and Bouguer Anomaly Analysis Tool (EDBAAT) User's Guide

USGS Publications Warehouse

Smittle, Aaron M.; Shoberg, Thomas G.

2017-06-16

This report describes a software tool that imports gravity anomaly point data from the Gravity Database of the United States (GDUS) of the National Geospatial-Intelligence Agency and University of Texas at El Paso along with elevation data from The National Map (TNM) of the U.S. Geological Survey that lie within a user-specified geographic area of interest. Further, the tool integrates these two sets of data spatially and analyzes the consistency of the elevation of each gravity station from the GDUS with TNM elevation data; it also evaluates the consistency of gravity anomaly data within the GDUS data repository. The tool bins the GDUS data based on user-defined criteria of elevation misfit between the GDUS and TNM elevation data. It also provides users with a list of points from the GDUS data, which have Bouguer anomaly values that are considered outliers (two standard deviations or greater) with respect to other nearby GDUS anomaly data. “Nearby” can be defined by the user at time of execution. These outputs should allow users to quickly and efficiently choose which points from the GDUS would be most useful in reconnaissance studies or in augmenting and extending the range of individual gravity studies.

Tularosa Basin Play Fairway Analysis: Weights of Evidence; Mineralogy, and Temperature Anomaly Maps

DOE Data Explorer

Adam Brandt

2015-11-15

This submission has two shapefiles and a tiff image. The weights of evidence analysis was applied to data representing heat of the earth and fracture permeability using training sites around the Southwest; this is shown in the tiff image. A shapefile of surface temperature anomalies was derived from the statistical analysis of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) thermal infrared data which had been converted to surface temperatures; these anomalies have not been field checked. The second shapefile shows outcrop mineralogy which originally mapped by the New Mexico Bureau of Geology and Mineral Resources, and supplemented with mineralogic information related to rock fracability risk for EGS. Further metadata can be found within each file.

The search for crustal resources - MAGSAT and beyond

NASA Technical Reports Server (NTRS)

Taylor, P. T.; Hinze, W. J.; Ravat, D. N.

1992-01-01

In the decade since global satellite magnetic field data have been available from MAGSAT, notable progress has been made in processing these data for purposes of mapping crustal anomalies. Several regional magnetic anomaly maps compiled using these new techniques (e.g. Kursk region, U.S.S.R.; central Africa; Kiruna, Sweden; and the U.S.A. midcontinent) provide insight into the nature and tectonic evolution of the crust that contribute to conceptual crustal models useful in regional resource exploration. A recent mail survey of geopotential-field specialists involved in resource exploration indicates interest in MAGSAT data and future satellite missions with improved resolution. It is apparent that magnetic anomalies derived from satellite observations can aid in the search for crustal resources.

An investigation of MAGSAT and complementary data emphasizing precambrian shields and adjacent areas of West Africa and South America

NASA Technical Reports Server (NTRS)

Hastings, D. A. (Principal Investigator)

1982-01-01

The problems associated with the use of an interactive magnetic modeling program are reported and a publication summarizing the MAGSAT anomaly results for Africa and the possible tectonic associations of these anomalies is provided. An overview of the MAGSAT scalar anomaly map for Africa suggested a correlation of MAGSAT anomalies with major crustal blocks of uplift or depression and different degrees of regional metamorphism. The strongest MAGSAT anomalies in Africa are closely correlated spatially with major tectonic features. Results indicate that the Bangui anomaly may be caused by a central old Precambrian shield, flanked to the north and south by two relatively young sedimentary basins.

Application of the Geo-Anomaly Unit Concept in Quantitative Delineation and Assessment of Gold Ore Targets in Western Shandong Uplift Terrain, Eastern China

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen Yongqing, E-mail: ydonglai@mail.cgs.gov.cn; Zhao Pengda; Chen Jianguo

2001-03-15

A number of large and giant ore deposits have been discovered within the relatively small areas of lithospheric structure anomalies, including various boundary zones of tectonic plates. The regions have become the well-known intercontinental ore-forming belts, such as the circum-Pacific gold-copper, copper-molybdenum, and tungsten-tin metallogenic belts. These belts are typical geological anomalous areas. An investigation into the hydrothermal ore deposits in different regions in the former Soviet Union illustrated that the geologic structures of ore fields of almost all major commercial deposits have distinct features compared with the neighboring areas. These areas with distinct features are defined as geo-anomalies. Amore » geo-anomaly refers to such a geologic body or a combination of bodies that their composition, texture-structure, and genesis are significantly different from those of their surroundings. A geo-anomaly unit (GU) is an area containing distinct features that can be delineated with integrated ore-forming information using computer techniques on the basis of the geo-anomaly concept. Herein, the GU concept is illustrated by a case study of delineating the gold ore targets in the western Shandong uplift terrain, eastern China. It includes: (1) analyses of gold ore-forming factors; (2) compilation of normalized regional geochemical map and extraction of geochemical anomalies; (3) compilation of gravitational and aeromagnetic tectonic skeleton map and extraction of gravitational and aeromagnetic anomalies; (4) extraction of circular and linear anomalies from remote-sensing Landsat TM images; (5) establishment of a geo-anomaly conceptual model associated with known gold mineralization; (6) establishment of gold ore-forming favorability by computing techniques; and (7) delineation and assessment of ore-forming units. The units with high favorability are suggested as ore targets.« less

Developing an automatic classification system of vegetation anomalies for early warning with the ASAP (Anomaly hot Spots of Agricultural Production) system

NASA Astrophysics Data System (ADS)

Meroni, M.; Rembold, F.; Urbano, F.; Lemoine, G.

2016-12-01

Anomaly maps and time profiles of remote sensing derived indicators relevant to monitor crop and vegetation stress can be accessed online thanks to a rapidly growing number of web based portals. However, timely and systematic global analysis and coherent interpretation of such information, as it is needed for example for SDG 2 related monitoring, remains challenging. With the ASAP system (Anomaly hot Spots of Agricultural Production) we propose a two-step analysis to provide monthly warning of production deficits in water-limited agriculture worldwide. The first step is fully automated and aims at classifying each administrative unit (1st sub-national level) into a number of possible warning levels, ranging from "none" to "watch" and up to "extended alarm". The second step involves the verification of the automatic warnings and integration into a short national level analysis by agricultural analysts. In this paper we describe the methodological development of the automatic vegetation anomaly classification system. Warnings are triggered only during the crop growing season, defined by a remote sensing based phenology. The classification takes into consideration the fraction of the agricultural and rangelands area for each administrative unit that is affected by a severe anomaly of two rainfall-based indicators (the Standardized Precipitation Index (SPI), computed at 1 and 3-month scale) and one biophysical indicator (the cumulative NDVI from the start of the growing season). The severity of the warning thus depends on the timing, the nature and the number of indicators for which an anomaly is detected. The prototype system is using global NDVI images of the METOP sensor, while a second version is being developed based on 1km Modis NDVI with temporal smoothing and near real time filtering. Also a specific water balance model is under development to include agriculture water stress information in addition to the SPI. The monthly warning classification and crop condition assessment will be made available on a website and will strengthen the JRC support to information products based on consensus assessment such as the GEOGLAM Crop Monitor for Early Warning.

Chapter 3: Circum-Arctic mapping project: New magnetic and gravity anomaly maps of the Arctic

USGS Publications Warehouse

Gaina, C.; Werner, S.C.; Saltus, R.; Maus, S.; Aaro, S.; Damaske, D.; Forsberg, R.; Glebovsky, V.; Johnson, Kevin; Jonberger, J.; Koren, T.; Korhonen, J.; Litvinova, T.; Oakey, G.; Olesen, O.; Petrov, O.; Pilkington, M.; Rasmussen, T.; Schreckenberger, B.; Smelror, M.

2011-01-01

New Circum-Arctic maps of magnetic and gravity anomalies have been produced by merging regional gridded data. Satellite magnetic and gravity data were used for quality control of the long wavelengths of the new compilations. The new Circum-Arctic digital compilations of magnetic, gravity and some of their derivatives have been analyzed together with other freely available regional and global data and models in order to provide a consistent view of the tectonically complex Arctic basins and surrounding continents. Sharp, linear contrasts between deeply buried basement blocks with different magnetic properties and densities that can be identified on these maps can be used, together with other geological and geophysical information, to refine the tectonic boundaries of the Arctic domain. ?? 2011 The Geological Society of London.

Regional magnetic and gravity features of the Gibson Dome area and surrounding region, Paradox Basin, Utah : a preliminary report

USGS Publications Warehouse

Hildenbrand, T.G.; Kucks, R.P.

1983-01-01

Analyses of regional gravity and magnetic anomaly maps have been carried out to assist in the evaluation of the Gibson Dome area as a possible repository site for high-level radioactive waste. Derivative, wavelength-filtered, and trend maps were compiled to aid in properly locating major geophysical trends corresponding to faults, folds, and lithologic boundaries. The anomaly maps indicate that Paradox Basin is characterized by a heterogeneous Precambrian basement, essentially a metamorphic complex of gneisses and schist intruded by granitic rocks and mafic to ultramafic bodies. Interpreted Precambrian structures trend predominantly northwest and northeast although east-west trending features are evident. Prominent gravity lows define the salt anticlines. Structural and lithologic trends in the Gibson Dome area are closely examined. Of greatest interest is a series of circular magnetic highs trending west-northwest into the Gibson Dome area. Further study of the exact definition and geologic significance of this series of anomalies is warranted.

Soil-Gas Radon Anomaly Map of an Unknown Fault Zone Area, Chiang Mai, Northern Thailand

NASA Astrophysics Data System (ADS)

Udphuay, S.; Kaweewong, C.; Imurai, W.; Pondthai, P.

2015-12-01

Soil-gas radon concentration anomaly map was constructed to help detect an unknown subsurface fault location in San Sai District, Chiang Mai Province, Northern Thailand where a 5.1-magnitude earthquake took place in December 2006. It was suspected that this earthquake may have been associated with an unrecognized active fault in the area. In this study, soil-gas samples were collected from eighty-four measuring stations covering an area of approximately 50 km2. Radon in soil-gas samples was quantified using Scintrex Radon Detector, RDA-200. The samplings were conducted twice: during December 2014-January 2015 and March 2015-April 2015. The soil-gas radon map obtained from this study reveals linear NNW-SSE trend of high concentration. This anomaly corresponds to the direction of the prospective fault system interpreted from satellite images. The findings from this study support the existence of this unknown fault system. However a more detailed investigation should be conducted in order to confirm its geometry, orientation and lateral extent.

Use of MAGSAT anomaly data for crustal structure and mineral resources in the US Midcontinent

NASA Technical Reports Server (NTRS)

Carmichael, R. S. (Principal Investigator)

1981-01-01

The analysis and preliminary interpretation of investigator-B MAGSAT data are addressed. The data processing included: (1) removal of spurious data points; (2) statistical smoothing along individual data tracks, to reduce the effect of geomagnetic transient disturbances; (3) comparison of data profiles spatially coincident in track location but acquired at different times; (4) reduction of data by weighted averaging to a grid with 1 deg xl deg latitude/longitude spacing, and with elevations interpolated and weighted to a common datum of 400 km; (5) wavelength filtering; and (6) reduction of the anomaly map to the magnetic pole. Agreement was found between a magnitude data anomaly map and a reduce-to-the-pole map supporting the general assumption that, on a large scale (long wavelength), it is induced crustal magnetization which is responsible for major anamalies. Anomalous features are identified and explanations are suggested with regard to crustal structure, petrologic characteristics, and Curie temperature isotherms.

Aeromagnetic survey map of the central California Coast Ranges

USGS Publications Warehouse

Langenheim, V.E.; Jachens, R.C.; Moussaoui, K.

2009-01-01

This aeromagnetic survey was flown as part of a Cooperative Research and Development Agreement (CRADA) with the Pacific Gas and Electric Company and is intended to promote further understanding of the geology and structure in the central California Coast Ranges by serving as a basis for geophysical interpretations and by supporting geological mapping, mineral and water resource investigations, and other topical studies. Local spatial variations in the Earth's magnetic field (evident as anomalies on aeromagnetic maps) reflect the distribution of magnetic minerals, primarily magnetite, in the underlying rocks. In many cases the volume content of magnetic minerals can be related to rock type, and abrupt spatial changes in the amount of magnetic minerals can commonly mark lithologic or structural boundaries. Bodies of serpentinite and other mafic and ultramafic rocks tend to produce the most intense magnetic anomalies, but such generalizations must be applied with caution because rocks with more felsic compositions, such as the porphyritic granodiorite-granite of the La Panza Range, and even some sedimentary units, also can cause measurable magnetic anomalies.

A Geophysical Atlas for Interpretation of Satellite-derived Data

NASA Technical Reports Server (NTRS)

Lowman, P. D., Jr. (Editor); Frey, H. V. (Editor); Davis, W. M.; Greenberg, A. P.; Hutchinson, M. K.; Langel, R. A.; Lowrey, B. E.; Marsh, J. G.; Mead, G. D.; Okeefe, J. A.

1979-01-01

A compilation of maps of global geophysical and geological data plotted on a common scale and projection is presented. The maps include satellite gravity, magnetic, seismic, volcanic, tectonic activity, and mantle velocity anomaly data. The Bibliographic references for all maps are included.

New digital magnetic anomaly database for North America

USGS Publications Warehouse

Finn, C.A.; Pilkington, M.; Cuevas, A.; Hernandez, I.; Urrutia, J.

2001-01-01

The Geological Survey of Canada (GSC), U.S. Geological Survey (USGS), and Consejo de Recursos Minerales of Mexico (CRM) are compiling an upgraded digital magnetic anomaly database and map for North America. This trinational project is expected to be completed by late 2002.

Heat Flow and Magnetization in the Oceanic Lithosphere. Ph.D. ThesisSemiannual Report, Nov. 1987 - Apr. 1988

NASA Technical Reports Server (NTRS)

Hayling, Kjell Lennart

1988-01-01

Two aspects of the processing and interpretation of satellite measurements of the geomagnetic field are described. One deals with the extraction of the part of the geomagnetic field that originates from sources in the earth's atmosphere. The other investigates the possibility of using the thermal state of the oceanic lithosphere to further constrain modelling and interpretation of magnetic anomalies. It is shown that some of the magnetic signal in crustal anomaly maps can be an artifact of the mathematical algorithms that have been used to separate the crustal field from the observed data. Strong magnetic anomalies can be distorted but are probably real, but weak magnetic anomalies can arise from leakage of power from short wavelengths, and will also appear in anomaly maps as repetitions of the strong crustal anomaly. The distortion and the ghost anomalies follow the magnetic dip lines in a way that is similar to actual MAGSAT anomaly fields. This phenomenon will also affect the lower degree spherical harmonic terms in the power spectrum of the crustal field. A model of the magnetic properties of the oceanic crust that has been derived from direct measurements of the rock magnetic properties of oceanic rocks is presented. The average intensity of magnetization in the oceanic crust is not strong enough to explain magnetic anomalies observed over oceanic areas. This is the case for both near surface observations (ship and aeromagnetic data) and satellite altitude observations. It is shown that magnetic sources in the part of the upper mantle that is situated above the Curie isotherm, if sufficiently strong, can produce satellite magnetic anomalies that are comparable to MAGSAT data. The method developed for the study of depth to the Curie isotherm and magnetic anomalies can also be used in inverse modelling of satellite magnetic anomalies when the model is to be adjusted with an annihilator.

Gravimetry contributions to the study of the complex western Haouz aquifer (Morocco): Structural and hydrogeological implications

NASA Astrophysics Data System (ADS)

Chouikri, Ibtissam; el Mandour, Abdennabi; Jaffal, Mohammed; Baudron, Paul; García-Aróstegui, José-Luis; Manar, Ahmed; Casas, Albert

2016-03-01

This study provides new elements that illustrate the benefits of combining gravity, structural, stratigraphic and piezometric data for hydrogeological purposes. A combined methodology was applied to the western Haouz aquifer (Morocco), one of the main sources of water for irrigation and human consumption in the Marrakech region. First, a residual anomaly map was calculated from the Bouguer anomaly data. The computed map provided information on the ground density variation, revealing a strong control by a regional gradient. We then used various filtering techniques to delineate the major geological structures such as faults and basins: vertical and horizontal derivatives and upward continuation. This technique highlighted news structures and provided information on their dip. The gravity anomalies perfectly delineated the basement uplifts and the sedimentary thickening in depressions and grabens. The interpretation of gravimetric filtering, geological and hydrogeological data then highlighted two types of groundwater reservoirs, an unconfined aquifer hosted in conglomeratic mio-pliocene and quaternary rocks, covering the entire western Haouz and a deep confined aquifer contained in cenomanian-turonian limestone and eocene dolomitic formations in the south. Combining piezometric and residual anomaly maps revealed that groundwater flow and storage was in perfect agreement with the structures showing a negative anomaly, while structures with positive anomalies corresponded to groundwater divides. The study of gravity gradient zones by contact analysis enhanced the existing structural pattern of the study area and highlighted new structures, mainly oriented N70 and N130. The results of this study present a common framework and provide a notable step forward in the knowledge of the geometry and the groundwater flow pattern of the western Haouz aquifer, and will serve as a solid basis for a better water resource management.

Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet Anomaly in NGC 5548 with X-Ray Spectroscopy

NASA Astrophysics Data System (ADS)

Mathur, S.; Gupta, A.; Page, K.; Pogge, R. W.; Krongold, Y.; Goad, M. R.; Adams, S. M.; Anderson, M. D.; Arévalo, P.; Barth, A. J.; Bazhaw, C.; Beatty, T. G.; Bentz, M. C.; Bigley, A.; Bisogni, S.; Borman, G. A.; Boroson, T. A.; Bottorff, M. C.; Brandt, W. N.; Breeveld, A. A.; Brown, J. E.; Brown, J. S.; Cackett, E. M.; Canalizo, G.; Carini, M. T.; Clubb, K. I.; Comerford, J. M.; Coker, C. T.; Corsini, E. M.; Crenshaw, D. M.; Croft, S.; Croxall, K. V.; Dalla Bontà, E.; Deason, A. J.; Denney, K. D.; De Lorenzo-Cáceres, A.; De Rosa, G.; Dietrich, M.; Edelson, R.; Ely, J.; Eracleous, M.; Evans, P. A.; Fausnaugh, M. M.; Ferland, G. J.; Filippenko, A. V.; Flatland, K.; Fox, O. D.; Gates, E. L.; Gehrels, N.; Geier, S.; Gelbord, J. M.; Gorjian, V.; Greene, J. E.; Grier, C. J.; Grupe, D.; Hall, P. B.; Henderson, C. B.; Hicks, S.; Holmbeck, E.; Holoien, T. W.-S.; Horenstein, D.; Horne, Keith; Hutchison, T.; Im, M.; Jensen, J. J.; Johnson, C. A.; Joner, M. D.; Jones, J.; Kaastra, J.; Kaspi, S.; Kelly, B. C.; Kelly, P. L.; Kennea, J. A.; Kim, M.; Kim, S.; Kim, S. C.; King, A.; Klimanov, S. A.; Kochanek, C. S.; Korista, K. T.; Kriss, G. A.; Lau, M. W.; Lee, J. C.; Leonard, D. C.; Li, M.; Lira, P.; Ma, Z.; MacInnis, F.; Manne-Nicholas, E. R.; Malkan, M. A.; Mauerhan, J. C.; McGurk, R.; McHardy, I. M.; Montouri, C.; Morelli, L.; Mosquera, A.; Mudd, D.; Muller-Sanchez, F.; Musso, R.; Nazarov, S. V.; Netzer, H.; Nguyen, M. L.; Norris, R. P.; Nousek, J. A.; Ochner, P.; Okhmat, D. N.; Ou-Yang, B.; Pancoast, A.; Papadakis, I.; Parks, J. R.; Pei, L.; Peterson, B. M.; Pizzella, A.; Poleski, R.; Pott, J.-U.; Rafter, S. E.; Rix, H.-W.; Runnoe, J.; Saylor, D. A.; Schimoia, J. S.; Schnülle, K.; Sergeev, S. G.; Shappee, B. J.; Shivvers, I.; Siegel, M.; Simonian, G. V.; Siviero, A.; Skielboe, A.; Somers, G.; Spencer, M.; Starkey, D.; Stevens, D. J.; Sung, H.-I.; Tayar, J.; Tejos, N.; Turner, C. S.; Uttley, P.; Van Saders, J.; Vestergaard, M.; Vican, L.; Villanueva, S., Jr.; Villforth, C.; Weiss, Y.; Woo, J.-H.; Yan, H.; Young, S.; Yuk, H.; Zheng, W.; Zhu, W.; Zu, Y.

2017-09-01

During the Space Telescope and Optical Reverberation Mapping Project observations of NGC 5548, the continuum and emission-line variability became decorrelated during the second half of the six-month-long observing campaign. Here we present Swift and Chandra X-ray spectra of NGC 5548 obtained as part of the campaign. The Swift spectra show that excess flux (relative to a power-law continuum) in the soft X-ray band appears before the start of the anomalous emission-line behavior, peaks during the period of the anomaly, and then declines. This is a model-independent result suggesting that the soft excess is related to the anomaly. We divide the Swift data into on- and off-anomaly spectra to characterize the soft excess via spectral fitting. The cause of the spectral differences is likely due to a change in the intrinsic spectrum rather than to variable obscuration or partial covering. The Chandra spectra have lower signal-to-noise ratios, but are consistent with the Swift data. Our preferred model of the soft excess is emission from an optically thick, warm Comptonizing corona, the effective optical depth of which increases during the anomaly. This model simultaneously explains all three observations: the UV emission-line flux decrease, the soft-excess increase, and the emission-line anomaly.

Stream gradient Hotspot and Cluster Analysis (SL-HCA) for improving the longitudinal profiles metrics

NASA Astrophysics Data System (ADS)

Troiani, Francesco; Piacentini, Daniela; Seta Marta, Della

2016-04-01

Many researches successfully focused on stream longitudinal profiles analysis through Stream Length-gradient (SL) index for detecting, at different spatial scales, either tectonic structures or hillslope processes. The analysis and interpretation of spatial variability of SL values, both at a regional and local scale, is often complicated due to the concomitance of different factors generating SL anomalies, including the bedrock composition. The creation of lithologically-filtered SL maps is often problematic in areas where homogeneously surveyed geological maps, with a sufficient resolution are unavailable. Moreover, both the SL map classification and the unbiased anomaly detection are rather difficult. For instance, which is the best threshold to define the anomalous SL values? Further, is there a minimum along-channel extent of anomalous SL values for objectively defining over-steeped segments on long-profiles? This research investigates the relevance and potential of a new approach based on Hotspot and Cluster Analysis of SL values (SL-HCA) for detecting knickzones on long-profiles at a regional scale and for fine-tuning the interpretation of their geological-geomorphological meaning. We developed this procedure within a 2800 km2-wide area located in the mountainous sector of the Northern Apennines of Italy. The Getis-Ord Gi∗ statistic is applied for the SL-HCA approach. The value of SL, calculated starting from a 5x5 m Digital Elevation Model, is used as weighting factor and the Gi∗ index is calculated for each 50 m-long channel segment for the whole fluvial system. The outcomes indicate that high positive Gi∗ values imply the clustering of SL anomalies, thus the occurrence of knickzones on the stream long-profiles. Results show that high and very high Gi* values (i.e. values beyond two standard deviations from the mean) correlate well with the principal knickzones detected with existent lithologically-filtered SL maps. Field checks and remote sensing analysis conducted on 52 clusters of high and very high Gi* values indicate that mass movement of slope material represents the dominant process producing over-steeped long-profiles along connected streams, whereas the litho-structure accounts for the main anomalies along disconnected steams. Tectonic structures generally provide to the largest clusters. Our results demonstrate that SL-HCA maps have the same potential of lithologically-filtered SL maps for detecting knickzones due to hillslope processes and/or tectonic structures. The reduced-complexity model derived from SL-HCA approach highly improve the readability of the morphometric outcomes, thus the interpretation at a regional scale of the geological-geomorphological meaning of over-steeped segments on long-profiles. SL-HCA maps are useful to investigate and better interpret knickzones within regions poorly covered by geological data and where field surveys are difficult to be performed.

In situ chemical sensing for hydrothermal plume mapping and modeling

NASA Astrophysics Data System (ADS)

Fukuba, T.; Kusunoki, T.; Maeda, Y.; Shitashima, K.; Kyo, M.; Fujii, T.; Noguchi, T.; Sunamura, M.

2012-12-01

Detection, monitoring, and mapping of biogeochemical anomalies in seawater such as temperature, salinity, turbidity, oxidation-reduction potential, and pH are essential missions to explore undiscovered hydrothermal sites and to understand distribution and behavior of hydrothermal plumes. Utilization of reliable and useful in situ sensors has been widely accepted as a promised approach to realize a spatiotemporally resolved mapping of anomalies without water sampling operations. Due to remarkable progresses of sensor technologies and its relatives, a number of highly miniaturized and robust chemical sensors have been proposed and developed. We have been developed, evaluated, and operated a compact ISFET (Ion-Sensitive Field-Effect Transistor)-based chemical sensors for ocean environmental sensing purposes. An ISFET has advantages against conventional glass-based electrodes on its faster response, robustness, and potential on miniaturization, and thus variety of chemical sensors has been already on the market. In this study, ISFET-based standalone pH sensors with a solid-state Cl-ISE as a reference electrode were mounted on various platforms and operated to monitor the pH anomalies in deep-sea environment at the Kairei, Edmond, and surrounding hydrothermal sites in the southern Central Indian Ridge area during KH10-06 scientific cruise (Nov. 2010), supported by project TAIGA (Trans-crustal Advection and In situ biogeochemical processes of Global sub-seafloor Aquifer). Up to three pH sensors were mounted on a wire-lined CTD/RMS (Rosette Multiple Sampler), dredge sampler, a series of MTD plankton nets, and VMPS (Vertical Multiple-operating Plankton Sampler). A standalone temperature sensor was bundled and operated with the pH sensor when they were mounted on the dredge sampler, MTD plankton nets, and VMPS. An AUV equipped with the pH sensor was also operated for hydrothermal activity survey operations. As a result of Tow-Yo intersect operations of the CTD/RMS, distribution of pH anomalies were successfully visualized at the Kairei site. During the operations with the dredge sampler, MTD nets, and VMPS, the pH sensors successfully worked except for a few failures of measurements due to a problem on a sensor cable. The pH sensor mounted on the AUV "R2D4" recoded a weak low-pH anomaly during a dive at the Yokoniwa site. Representative of the pH data obtained at southern Central Indian Ride will be shown visually on the poster. The spatiotemporally resolved data can be also utilized to develop reliable numerical models to estimate fluxes of energy and matters from geologically active sites. An example of optimization of a numerical model for hydrothermal plume study using 4D pH data obtained at a back-arc hydrothermal system (the Hatoma-knoll, the Okinawa Trough, Japan) will be also presented.

Regional magnetic anomaly constraints on continental breakup

DOE Office of Scientific and Technical Information (OSTI.GOV)

von Frese, R.R.B.; Hinze, W.J.; Olivier, R.

1986-01-01

Continental lithosphere magnetic anomalies mapped by the Magsat satellite are related to tectonic features associated with regional compositional variations of the crust and upper mantle and crustal thickness and thermal perturbations. These continental-scale anomaly patterns when corrected for varying observation elevation and the global change in the direction and intensity of the geomagnetic field show remarkable correlation of regional lithospheric magnetic sources across rifted continental margins when plotted on a reconstruction of Pangea. Accordingly, these anomalies provide new and fundamental constraints on the geologic evolution and dynamics of the continents and oceans.

Airborne gamma-ray spectrometer and magnetometer survey, Seattle quadrangle (Washington). Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1981-01-01

One uranium anomaly meets the minimum statistical requirements as defined. This anomaly is over the potassium (%K) contact area between undifferentiated Tertiary rocks and Pleistocene glacial deposits. Equivalent uranium (ppM eU), equivalent thorium (ppM eT), eU/eT, eU/eK, eT,K, and magnetic pseudo-contour maps are presented in Appendix E. Stacked profiles showing geologic strip maps along each flight-line, together with sensor data, and ancillary data are presented in Appendix F. All maps and profiles were prepared on a scale of 1:250,000, but have been reduced to 1:500,000 for presentation in this report.

An Unsupervised Anomalous Event Detection and Interactive Analysis Framework for Large-scale Satellite Data

NASA Astrophysics Data System (ADS)

LIU, Q.; Lv, Q.; Klucik, R.; Chen, C.; Gallaher, D. W.; Grant, G.; Shang, L.

2016-12-01

Due to the high volume and complexity of satellite data, computer-aided tools for fast quality assessments and scientific discovery are indispensable for scientists in the era of Big Data. In this work, we have developed a framework for automated anomalous event detection in massive satellite data. The framework consists of a clustering-based anomaly detection algorithm and a cloud-based tool for interactive analysis of detected anomalies. The algorithm is unsupervised and requires no prior knowledge of the data (e.g., expected normal pattern or known anomalies). As such, it works for diverse data sets, and performs well even in the presence of missing and noisy data. The cloud-based tool provides an intuitive mapping interface that allows users to interactively analyze anomalies using multiple features. As a whole, our framework can (1) identify outliers in a spatio-temporal context, (2) recognize and distinguish meaningful anomalous events from individual outliers, (3) rank those events based on "interestingness" (e.g., rareness or total number of outliers) defined by users, and (4) enable interactively query, exploration, and analysis of those anomalous events. In this presentation, we will demonstrate the effectiveness and efficiency of our framework in the application of detecting data quality issues and unusual natural events using two satellite datasets. The techniques and tools developed in this project are applicable for a diverse set of satellite data and will be made publicly available for scientists in early 2017.

MODELING THE ANOMALY OF SURFACE NUMBER DENSITIES OF GALAXIES ON THE GALACTIC EXTINCTION MAP DUE TO THEIR FIR EMISSION CONTAMINATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kashiwagi, Toshiya; Suto, Yasushi; Taruya, Atsushi

The most widely used Galactic extinction map is constructed assuming that the observed far-infrared (FIR) fluxes come entirely from Galactic dust. According to the earlier suggestion by Yahata et al., we consider how FIR emission of galaxies affects the SFD map. We first compute the surface number density of Sloan Digital Sky Survey (SDSS) DR7 galaxies as a function of the r-band extinction, A {sub r,} {sub SFD}. We confirm that the surface densities of those galaxies positively correlate with A {sub r,} {sub SFD} for A {sub r,} {sub SFD} < 0.1, as first discovered by Yahata et al.more » for SDSS DR4 galaxies. Next we construct an analytical model to compute the surface density of galaxies, taking into account the contamination of their FIR emission. We adopt a log-normal probability distribution for the ratio of 100 μm and r-band luminosities of each galaxy, y ≡ (νL){sub 100} {sub μm}/(νL) {sub r}. Then we search for the mean and rms values of y that fit the observed anomaly, using the analytical model. The required values to reproduce the anomaly are roughly consistent with those measured from the stacking analysis of SDSS galaxies. Due to the limitation of our statistical modeling, we are not yet able to remove the FIR contamination of galaxies from the extinction map. Nevertheless, the agreement with the model prediction suggests that the FIR emission of galaxies is mainly responsible for the observed anomaly. Whereas the corresponding systematic error in the Galactic extinction map is 0.1-1 mmag, it is directly correlated with galaxy clustering and thus needs to be carefully examined in precision cosmology.« less

Construction of Improved Maps of Mercury's Crustal Magnetic Field at Northern Midlatitudes

NASA Astrophysics Data System (ADS)

Hood, L. L.; Oliveira, J. S.

2017-12-01

We report progress toward the construction of a refined version of the northern midlatitude crustal magnetic field map of Hood [GRL, 2016], extended to cover latitudes from 35N to 80N and all longitudes. The main improvements include: (1) Combining MESSENGER magnetometer data from August and September of 2014 with that from February, March, and April of 2015 to provide the best overall input data set for mapping and the largest possible area of coverage; (2) improving the elimination of external and core field contamination by using a model for Mercury's core field and a more conservative high-pass filter length; and (3) improving the equivalent source dipole (ESD) mapping technique using an equidistant equivalent source dipole array and varying the depth, orientation, and resolution of the array to minimize the overall root mean square misfit. Combining data from the two time intervals allows the total latitude range of the final map to be increased by at least 5 degrees to 35N - 80N. Also, previous mapping has concentrated on the hemisphere from 90E to 270E; inclusion of all available data will allow the final maps to be extended to all longitudes, more than doubling the coverage reported by Hood [2016]. Previous work has demonstrated a concentration of relatively strong magnetic anomalies near and within the Caloris impact basin. A secondary concentration near Sobkou Planitia, which contains an older impact basin, was also found. The existence of anomalies within the Caloris rim implies that a steady magnetizing field, i.e., a core dynamo, was present when this basin formed. A major application of the improved map will be to investigate whether anomalies are concentrated near and within other impact basins. If some basins are found not to have concentrations of magnetic anomalies, this could imply a role of impactor composition (e.g., iron content) in producing the crustal materials that are most strongly magnetized, as has previously been proposed to be the case on the Moon [Wieczorek et al., Science, 2012].

A Computer-Based Atlas of Global Instrumental Climate Data (DB1003)

DOE Data Explorer

Bradley, Raymond S.; Ahern, Linda G.; Keimig, Frank T.

1994-01-01

Color-shaded and contoured images of global, gridded instrumental data have been produced as a computer-based atlas. Each image simultaneously depicts anomaly maps of surface temperature, sea-level pressure, 500-mbar geopotential heights, and percentages of reference-period precipitation. Monthly, seasonal, and annual composites are available in either cylindrical equidistant or northern and southern hemisphere polar projections. Temperature maps are available from 1854 to 1991, precipitation from 1851 to 1989, sea-level pressure from 1899 to 1991, and 500-mbar heights from 1946 to 1991. The source of data for the temperature images is Jones et al.'s global gridded temperature anomalies. The precipitation images were derived from Eischeid et al.'s global gridded precipitation percentages. Grids from the Data Support Section, National Center for Atmospheric Research (NCAR) were the sources for the sea-level-pressure and 500-mbar geopotential-height images. All images are in GIF files (1024 × 822 pixels, 256 colors) and can be displayed on many different computer platforms. Each annual subdirectory contains 141 images, each seasonal subdirectory contains 563 images, and each monthly subdirectory contains 1656 images. The entire atlas requires approximately 340 MB of disk space, but users may retrieve any number of images at one time.

Aeromagnetometry of the El Papalote H12A-13 Chart Northwestern Sonora, México: Relationships to Regional Geology and Mineral Deposits

NASA Astrophysics Data System (ADS)

Martinez-Retama, S.; Pérez-Segura, E.; Vega-Granillo, R.

2014-12-01

This study is focused in obtaining a geophysical-geological characterization of magnetic anomalies associated with outcropping or buried rock bodies and its possible relation to ore deposits. To do this, total field aeromagnetic data from the Mexican Geological Survey were processed. Reduction to pole and residual anomaly maps show two main elongated dipolar high-amplitude anomalies, a first NE-SW directed, which is located in the NW portion of the card, and a second corresponding to a belt with NW-SE direction that is located SW of the chart, near the eastern region of the "El Elegante" volcano. Above structures have not been mapped in the surface; however, the well-defined magnetic anomalies indicate its existence below Quaternary sediments. The geology of the chart is only partially known. The outcropping units, mostly in the Sierra de Los Tanques, are Paleoproterozoic igneous and metamorphic rocks; Permian-Triassic granitoids; and Jurassic and Tertiary volcanic and volcanosedimentary rocks. About 50% of the card is covered by Quaternary sediments, there the interest of these geophysical studies. The NW-SE oriented deep magnetic anomaly follows the same direction as the Sierra San Francisco (SSF) located south of Los Norteños chart H12A-2. This mountain is composed of Paleoproterozoic metamorphic rocks intruded by Upper Cretaceous granitoids. Numerous mineral manifestations of orogenic gold type occurred in that range. This anomaly can be interpreted in 2 ways: first: as a NW extension of a landform similar to the SSF, which dips to NW or that is more erosionated; or; second: as an extension of the SSF to the NW displaced by a normal fault oriented ~N60E, roughly following the Palo Fierro creek indicated on the map. Either of the two possible interpretations, the magnetic anomaly indicates an interesting target in the search of orogenic gold deposits that could be buried in the area.

Saliency U-Net: A regional saliency map-driven hybrid deep learning network for anomaly segmentation

NASA Astrophysics Data System (ADS)

Karargyros, Alex; Syeda-Mahmood, Tanveer

2018-02-01

Deep learning networks are gaining popularity in many medical image analysis tasks due to their generalized ability to automatically extract relevant features from raw images. However, this can make the learning problem unnecessarily harder requiring network architectures of high complexity. In case of anomaly detection, in particular, there is often sufficient regional difference between the anomaly and the surrounding parenchyma that could be easily highlighted through bottom-up saliency operators. In this paper we propose a new hybrid deep learning network using a combination of raw image and such regional maps to more accurately learn the anomalies using simpler network architectures. Specifically, we modify a deep learning network called U-Net using both the raw and pre-segmented images as input to produce joint encoding (contraction) and expansion paths (decoding) in the U-Net. We present results of successfully delineating subdural and epidural hematomas in brain CT imaging and liver hemangioma in abdominal CT images using such network.

Detection and characterization of buried lunar craters with GRAIL data

NASA Astrophysics Data System (ADS)

Sood, Rohan; Chappaz, Loic; Melosh, Henry J.; Howell, Kathleen C.; Milbury, Colleen; Blair, David M.; Zuber, Maria T.

2017-06-01

We used gravity mapping observations from NASA's Gravity Recovery and Interior Laboratory (GRAIL) to detect, characterize and validate the presence of large impact craters buried beneath the lunar maria. In this paper we focus on two prominent anomalies detected in the GRAIL data using the gravity gradiometry technique. Our detection strategy is applied to both free-air and Bouguer gravity field observations to identify gravitational signatures that are similar to those observed over buried craters. The presence of buried craters is further supported by individual analysis of regional free-air gravity anomalies, Bouguer gravity anomaly maps, and forward modeling. Our best candidate, for which we propose the informal name of Earhart Crater, is approximately 200 km in diameter and forms part of the northwestern rim of Lacus Somniorum, The other candidate, for which we propose the informal name of Ashoka Anomaly, is approximately 160 km in diameter and lies completely buried beneath Mare Tranquillitatis. Other large, still unrecognized, craters undoubtedly underlie other portions of the Moon's vast mare lavas.

Ionospheric total electron content anomalies due to Typhoon Nakri on 29 May 2008: A nonlinear principal component analysis

NASA Astrophysics Data System (ADS)

Lin, Jyh-Woei

2012-09-01

This paper uses Nonlinear Principal Component Analysis (NLPCA) and Principal Component Analysis (PCA) to determine Total Electron Content (TEC) anomalies in the ionosphere for the Nakri Typhoon on 29 May, 2008 (UTC). NLPCA, PCA and image processing are applied to the global ionospheric map (GIM) with transforms conducted for the time period 12:00-14:00 UT on 29 May 2008 when the wind was most intense. Results show that at a height of approximately 150-200 km the TEC anomaly using NLPCA is more localized; however its intensity increases with height and becomes more widespread. The TEC anomalies are not found by PCA. Potential causes of the results are discussed with emphasis given to vertical acoustic gravity waves. The approximate position of the typhoon's eye can be detected if the GIM is divided into fine enough maps with adequate spatial-resolution at GPS-TEC receivers. This implies that the trace of the typhoon in the regional GIM is caught using NLPCA.

Gravity study through the Tualatin Mountains, Oregon: Understanding crustal structure and earthquake hazards in the Portland urban area

USGS Publications Warehouse

Blakely, R.J.; Beeson, M.H.; Cruikshank, K.; Wells, R.E.; Johnson, Aaron H.; Walsh, K.

2004-01-01

A high-resolution gravity survey through the Tualatin Mountains (Portland Nills) west of downtown Portland exhibits evidence of faults previously identified from surface geologic and aeromagnetic mapping. The gravity survey was conducted in 1996 along the 4.5-km length of a twin-bore tunnel, then under construction and now providing light-rail service between downtown Portland and communities west of the Portland Hills. Gravitational attraction gradually increases from west to east inside the tunnel, which reflects the tunnel's location between low-density sedimentary deposits of the Tualatin basin to the west and high-density, mostly concealed Eocene basalt to the east. Superimposed on this gradient are several steplike anomalies that we interpret as evidence for faulted contacts between rocks of contrasting density. The largest of these anomalies occurs beneath Sylvan Creek, where a fault had previously been mapped inside the tunnel. Another occurs 1200 m from the west portal, at the approximate intersection of the tunnel with an aeromagnetic anomaly associated with the Sylvan fault (formerly called the Oatfield fault). Lithologic cross sections based on these gravity data show that the steplike anomalies are consistent with steeply dipping reverse faults, although strike-slip displacements also may be important. Three gravity lows correspond with topographic lows directly overhead and may reflect zones of shearing. Several moderate earthquakes (M ??? 3.5) occurred near the present-day location of the tunnel in 1991, suggesting that some of these faults or other faults in the Portland Hills fault zone are seismically active.

Recent Weather Extremes and Impacts on Agricultural Production and Vector-Borne Disease Outbreak Patterns

NASA Technical Reports Server (NTRS)

Anyamba, Assaf; Small, Jennifer L.; Britch, Seth C.; Tucker, Compton J.; Pak, Edwin W.; Reynolds, Curt A.; Crutchfield, James; Linthicum, Kenneth J.

2014-01-01

We document significant worldwide weather anomalies that affected agriculture and vector-borne disease outbreaks during the 2010-2012 period. We utilized 2000-2012 vegetation index and land surface temperature data from NASA's satellite-based Moderate Resolution Imaging Spectroradiometer (MODIS) to map the magnitude and extent of these anomalies for diverse regions including the continental United States, Russia, East Africa, Southern Africa, and Australia. We demonstrate that shifts in temperature and/or precipitation have significant impacts on vegetation patterns with attendant consequences for agriculture and public health. Weather extremes resulted in excessive rainfall and flooding as well as severe drought, which caused,10 to 80% variation in major agricultural commodity production (including wheat, corn, cotton, sorghum) and created exceptional conditions for extensive mosquito-borne disease outbreaks of dengue, Rift Valley fever, Murray Valley encephalitis, and West Nile virus disease. Analysis of MODIS data provided a standardized method for quantifying the extreme weather anomalies observed during this period. Assessments of land surface conditions from satellite-based systems such as MODIS can be a valuable tool in national, regional, and global weather impact determinations.

Recent weather extremes and impacts on agricultural production and vector-borne disease outbreak patterns.

PubMed

Anyamba, Assaf; Small, Jennifer L; Britch, Seth C; Tucker, Compton J; Pak, Edwin W; Reynolds, Curt A; Crutchfield, James; Linthicum, Kenneth J

2014-01-01

We document significant worldwide weather anomalies that affected agriculture and vector-borne disease outbreaks during the 2010-2012 period. We utilized 2000-2012 vegetation index and land surface temperature data from NASA's satellite-based Moderate Resolution Imaging Spectroradiometer (MODIS) to map the magnitude and extent of these anomalies for diverse regions including the continental United States, Russia, East Africa, Southern Africa, and Australia. We demonstrate that shifts in temperature and/or precipitation have significant impacts on vegetation patterns with attendant consequences for agriculture and public health. Weather extremes resulted in excessive rainfall and flooding as well as severe drought, which caused ∼10 to 80% variation in major agricultural commodity production (including wheat, corn, cotton, sorghum) and created exceptional conditions for extensive mosquito-borne disease outbreaks of dengue, Rift Valley fever, Murray Valley encephalitis, and West Nile virus disease. Analysis of MODIS data provided a standardized method for quantifying the extreme weather anomalies observed during this period. Assessments of land surface conditions from satellite-based systems such as MODIS can be a valuable tool in national, regional, and global weather impact determinations.

Petrologic model of the northern Mississippi Embayment based on satellite magnetic and ground-based geophysical data

NASA Technical Reports Server (NTRS)

Thomas, H. H.

1984-01-01

A petrologic model of the northern Mississippi Embayment, derived from gravity, seismic and rift data, is evaluated by converting the model to a magnetization model which is compared with satellite magnetic anomaly models. A magnetization contrast of approximately -0.54 A/m, determined from the petrologic model of the embayment compares favorably to values of -0.62 A/m and -0.45 A/m from a Magsat United States Apparent Magnetization Contrast Map and a published POGO magnetization contrast model, respectively. The petrologic model suggests that the magnetic anomaly low associated with the Mississippi Embayment may be largely due to the intrusion under non-oxidizing conditions of low Curie temperature gabbroic material at the base of the crust of the embayment. Near-surface mafic plutons, bordering the Mississippi Valley Graben, appear from aeromagnetic data to have higher magnetizations than the deeper gabbroic material; however, it is impossible to ascertain if this is due to compositional differences or similar material at shallower (lower temperature) depths. These results indicate that variations in the Curie temperatures of intrusions accompanying rifting may account for a large part of the wide range of magnetic anomalies associated with presently inactive rifts with normal heat flow.

A strategy for mineral and energy resource independence

USGS Publications Warehouse

Carter, W.D.

1983-01-01

Data acquired by Landsats 1, 2, and 3, are beginning to provide the information on which an improved mineral and energy resource exploration strategy can be based. Landsat 4 is expected to augment this capability with its higher resolution (30 m) and additional spectral bands in the Thematic Mapper (TM) designed specifically to discriminate clay minerals associated with mineral alteration. In addition, a new global magnetic anomaly map, derived from the recent Magsat mission, has recently been compiled by the National Aeronautics and Space Administration (NASA), the U.S. Geological Survey (USGS), and others. Preliminary, extremely small-scale renditions of this map indicate that global coverage is nearly complete and that the map will improve upon a previous one derived from Polar Orbiting Geophysical Observatory (POGO) data. Digital processing of the Landsat image data and Magsat geophysical data can be used to create three-dimensional stereoscopic models for which Landsat images provide surface reference to deep structural anomalies. Comparative studies of national Landsat lineament maps, Magsat stereoscopic models, and metallogenic information derived from the Computerized Resources Information Bank (CRIB) inventory of U.S. mineral resources, provide a way of identifying and selecting exploration areas that have mineral resource potential. Landsat images and computer-compatible tapes can provide new and better mosaics and also provide the capability for a closer look at promising sites. ?? 1983.

Crustal controls on magmatic-hydrothermal systems: A geophysical comparison of White River, Washington, with Goldfield, Nevada

USGS Publications Warehouse

Blakely, R.J.; John, D.A.; Box, S.E.; Berger, B.R.; Fleck, R.J.; Ashley, R.P.; Newport, G.R.; Heinemeyer, G.R.

2007-01-01

The White River altered area, Washington, and the Goldfield mining district, Nevada, are nearly contemporaneous Tertiary (ca.20 Ma) calc-alkaline igneous centers with large exposures of shallow (<1 km depth) magmatic-hydrothermal, acid-sulfate alteration. Goldfield is the largest known high-sulfidation gold deposit in North America. At White River, silica is the only commodity exploited to date, but, based on its similarities with Goldfield, White River may have potential for concealed precious and/or base metal deposits at shallow depth. Both areas are products of the ancestral Cascade arc Goldfield lies within the Great Basin physiographic province in an area of middle Miocene and younger Basin and Range and Walker Lane faulting, whereas White River is largely unaffected by young faults. However, west-northwest-striking magnetic anomalies at White River do correspond with mapped faults synchronous with magmatism, and other linear anomalies may reflect contemporaneous concealed faults. The White River altered area lies immediately south of the west-northwest-striking White River fault zone and north of a postulated fault with similar orientation. Structural data from the White River altered area indicate that alteration developed synchronously with an anomalous stress field conducive to left-lateral, strike-slip displacement on west-north-west-striking faults. Thus, the White River alteration may have developed in a transient transtensional region between the two strike-slip faults, analogous to models proposed for Goldfield and other mineral deposits in transverse deformational zones. Gravity and magnetic anomalies provide evidence for a pluton beneath the White River altered area that may have provided heat and fluids to overlying volcanic rocks. East- to east- northeast-striking extensional faults and/or fracture zones in the step-over region, also expressed in magnetic anomalies, may have tapped this intrusion and provided vertical and lateral transport of fluids to now silicified areas. By analogy to Goldfield, geophysical anomalies at the White River altered area may serve as proxies for geologic mapping in identifying faults, fractures, and intrusions relevant to hydrothermal alteration and ore formation in areas of poor exposure. ?? 2006 Geological Society of America.

MX Siting Investigation. Gravity Survey - Sevier Desert Valley, Utah.

DTIC Science & Technology

1981-01-24

Cheyenne, Wyoming. DMAHTC reduces the data to Simple Bouguer Anomaly (see Section A1.4, Appendix Al.0). The Defense Mapping Agency Aerospace Center...Desert Valley, Utah ......... 2 2 Topographic Setting - Sevier Desert Valley, Utah . 3 LIST OF DRAWINGS Drawing Number 1 Complete Bouguer Anomaly...gravity stations were distributed throughout the valley at an approxi- mate interval of 1.4 miles (2.3 km). Drawing 1 is a Complete Bouguer Anomaly

Regional TEC model under quiet geomagnetic conditions and low-to-moderate solar activity based on CODE GIMs

NASA Astrophysics Data System (ADS)

Feng, Jiandi; Jiang, Weiping; Wang, Zhengtao; Zhao, Zhenzhen; Nie, Linjuan

2017-08-01

Global empirical total electron content (TEC) models based on TEC maps effectively describe the average behavior of the ionosphere. However, the accuracy of these global models for a certain region may not be ideal. Due to the number and distribution of the International GNSS Service (IGS) stations, the accuracy of TEC maps is geographically different. The modeling database derived from the global TEC maps with different accuracy is likely one of the main reasons that limits the accuracy of the new models. Moreover, many anomalies in the ionosphere are geographic or geomagnetic dependent, and as such the accuracy of global models can deteriorate if these anomalies are not fully incorporated into the modeling approach. For regional models built in small areas, these influences on modeling are immensely weakened. Thus, the regional TEC models may better reflect the temporal and spatial variations of TEC. In our previous work (Feng et al., 2016), a regional TEC model TECM-NEC is proposed for northeast China. However, this model is only directed against the typical region of Mid-latitude Summer Nighttime Anomaly (MSNA) occurrence, which is meaningless in other regions without MSNA. Following the technique of TECM-NEC model, this study proposes another regional empirical TEC model for other regions in mid-latitudes. Taking a small area BeiJing-TianJin-Tangshan (JJT) region (37.5°-42.5° N, 115°-120° E) in China as an example, a regional empirical TEC model (TECM-JJT) is proposed using the TEC grid data from January 1, 1999 to June 30, 2015 provided by the Center for Orbit Determination in Europe (CODE) under quiet geomagnetic conditions. The TECM-JJT model fits the input CODE TEC data with a bias of 0.11TECU and a root mean square error of 3.26TECU. Result shows that the regional model TECM-JJT is consistent with CODE TEC data and GPS-TEC data.

Mapping Subsurface Structure at Guar Kepah by using Ground Penetrating Radar

NASA Astrophysics Data System (ADS)

Mansor, Hafizuddin; Rosli, Najmiah; Ismail, N. A.; Saidin, M.; Masnan, S. S. K.

2018-04-01

A Ground Penetrating Radar (GPR) survey was conducted at Guar Kepah to detect buried object before commencement of archaeological gallery construction. The study area covered around 20 m length and 14 m width. 15 GPR lines were constructed from north to south with 20 m length, 1 m spacing and parallel to each other. The 500 MHz closed antenna had been used in this study. The surface findings were noticed before started GPR survey. The data was analysed and interpreted by using Groundvision software and several filters were applied to radargrams to enhance the data. Based on the result, several anomalies were detected. The surface findings also detected by GPR which cause hyperbolic curve in radargrams. The subsurface layer was detected by GPR survey. The anomalies are assigned to several classes based on the pattern of signals obtained in radargrams.

Preliminary Aeromagnetic Map of Joshua Tree National Park and Vicinity, Southern California

USGS Publications Warehouse

Langenheim, V.E.; Hill, P.L.

2010-01-01

This aeromagnetic map of Joshua Tree National Park and vicinity is intended to promote further understanding of the geology and structure in the region by serving as a basis for geophysical interpretations and by supporting geological mapping, water-resource investigations, and various topical studies. Local spatial variations in the Earth's magnetic field (evident as anomalies on aeromagnetic maps) reflect the distribution of magnetic minerals, primarily magnetite, in the underlying rocks. In many cases the volume content of magnetic minerals can be related to rock type, and abrupt spatial changes in the amount of magnetic minerals commonly mark lithologic or structural boundaries. Bodies of mafic and ultramafic rocks tend to produce the most intense magnetic anomalies, but such generalizations must be applied with caution because rocks with more felsic compositions, or even some sedimentary units, also can cause measurable magnetic anomalies. The database includes two ASCII files containing new aeromagnetic data and two ASCII files with point locations of the local maximum horizontal gradient derived from the aeromagnetic data. This metadata file describes the horizontal gradient locations derived from new and existing aeromagnetic data. This aeromagnetic map identifies magnetic features as a basis for geophysical interpretations; the gradients help define the edges of magnetic sources. This database updates geophysical information originally presented in smaller-scale formats and includes detailed aeromagnetic data collected by EON Geosciences, Inc.

Reconnaissance geologic mapping of a portion of the rain‐forest‐covered Guiana Shield, Northwestern Brazil, using SIR-B and digital aeromagnetic data

USGS Publications Warehouse

Pellon de Miranda, Fernando; McCafferty, Anne E.; Taranik, James V.

1994-01-01

This paper documents the result of an integrated analysis of spaceborne radar (SIR-B) and digital aeromagnetic data carried out in the heavily forested Guiana Shield. The objective of the research is to interpret the geophysical data base to its limit to produce a reconnaissance geologic map as an aid to ground work planning in a worst‐case setting. Linear geomorphic features were identified based on the interpretation of the SIR-B image. Digital manipulation of aeromagnetic data allowed the development of a color‐shaded relief map of reduced‐to‐pole magnetic anomalies, a terrace‐magnetization map, and a map showing the location of maximum values of the horizontal component of the pseudogravity gradient (magnetization boundary lines). The resultant end product was a reconnaissance geologic map where broad terrane categories were delineated and geologic faults with both topographic and magnetic expression were defined. The availability of global spaceborne radar coverage in the 1990s and the large number of existing digital aeromagnetic surveys in northwestern Brazil indicate that this approach can be potentially useful for reconnaissance geologic mapping elsewhere in the Guiana Shield.

Viscous remanent magnetization model for the Broken Ridge satellite magnetic anomaly

NASA Technical Reports Server (NTRS)

Johnson, B. D.

1985-01-01

An equivalent source model solution of the satellite magnetic field over Australia obtained by Mayhew et al. (1980) showed that the satellite anomalies could be related to geological features in Australia. When the processing and selection of the Magsat data over the Australian region had progressed to the point where interpretation procedures could be initiated, it was decided to start by attempting to model the Broken Ridge satellite anomaly, which represents one of the very few relatively isolated anomalies in the Magsat maps, with an unambiguous source region. Attention is given to details concerning the Broken Ridge satellite magnetic anomaly, the modeling method used, the Broken Ridge models, modeling results, and characteristics of magnetization.

Underwater Gravity Survey of Northern Monterey Bay.

DTIC Science & Technology

stations were occupied just above the swash zone. A complete Bouguer anomaly map was drawn and tied in with the previous land surveys and with one...covering the southern half of the bay. The isolines of the complete Bouguer anomaly indicate the relative vertical position of the basement complex Santa

Standardized Analysis for UXO Demonstration Sites

DTIC Science & Technology

2008-04-01

is a time-domain electromagnetic instrument designed to detect shallow ferrous and nonferrous metallic objects. The applicability of the EM61 for UXO...or spots show EMI field anomalies caused by buried metal objects, both UXO and clutter. Anomaly maps for APG are shown in Figure 5. The Blind Grid

New aerogravity and aeromagnetic anomaly data over Lomonosov Ridge and adjacent areas for bathymetric and tectonic mapping

NASA Astrophysics Data System (ADS)

Dossing, A.; Olesen, A. V.; Forsberg, R.

2010-12-01

Results of an 800 x 800 km aero-gravity and aeromagnetic survey (LOMGRAV) of the southern Lomonosov Ridge and surrounding area are presented. The survey was acquired by the Danish National Space Center, DTU in cooperation with National Resources Canada in spring 2009 as a net of ~NE-SW flight lines spaced 8-10 km apart. Nominal flight level was 2000 ft. We have compiled a detailed 2.5x2.5 km gravity anomaly grid based on the LOMGRAV data and existing data from the southern Arctic Ocean (NRL98/99) and the North Greenland continental margin (KMS98/99). The gravity grid reveals detailed, elongated high-low anomaly patterns over the Lomonosov Ridge which is interpreted as the presence of narrow ridges and subbasins. Distinct local topography is also interpreted over the southernmost part of the Lomonosov Ridge where existing bathymetry compilations suggest a smooth topography due to the lack of data. A new bathymetry model is presented for the region predicted by formalized inversion of the available gravity data. Finally, a detailed magnetic anomaly grid has been compiled from the LOMGRAV data and existing NRL98/99 and PMAP data. New tectonic features are revealed, particularly in the Amerasia Basin, compared with existing magnetic anomaly data from the region.

Analysis of the nature of excessive cosmic radiation in the area of the Brazilian magnetic anomaly at altitudes 250-500km, from Kosmos-225 satellite data

NASA Technical Reports Server (NTRS)

Raychenko, L. V.

1974-01-01

Results are presented from a study of the region of anomalous cosmic radiation in the area of the Brazilian magnetic anomaly at the altitudes 250-500 km, using data measurements taken on the Kosmos-225 satellite (14-29 June 1968). The existence of a stable intensity anomaly discovered in the experiments on the second and third Soviet spacecraft-satellites is confirmed. The total vector of the geomagnetic field at different altitudes was compared with isoline maps. An altitude profile of the South Atlantic anomaly of radiation intensity was obtained, using data from the same instrument. The nature of the anomalies in cosmic radiation intensity over the regions of negative magnetic anomalies is discussed.

The characteristic analysis of Korean August rainfall using Self-Organizing Maps

NASA Astrophysics Data System (ADS)

Lee, S. H.; Seo, K. H.; Kim, J.

2016-12-01

The characteristics of the low-level pressure pattern during Korean August rainfall have been investigated using a neural network-based cluster analysis called self-organizing map (SOM). On the basis of various SOM mode analyses, five major phases of low-level pressure pattern are dynamically identified. The first mode occurs with a distinct circulation state corresponding to a strengthened subtropical high to the south of Korea and migratory low passing though north of Korea. The cold, dry inflow from the north by the cyclonic anomaly and warm, moist air produced by the WNPSH demonstrate the convective instability that provides reasonably intense precipitation over the Korean Peninsula. The second mode represents that low-level anticyclonic anomaly is located to the south of Korea and low-level anticyclonic anomaly is located over the Sea of Okhotsk. The two high pressure pattern conflict with each other forming front, which is identified as the frontal precipitation. The third mode represents local instability with no specific large-scale environmental condition; weak low-level jets, weak upper-level jets, no front, and no typhoon. The fourth mode is typhoon near Taiwan suppling a lot of water vapor in the Korean peninsula to be unloaded precipitation. This can be represented as an indirect-typhoon mode. The fifth mode can be classified as direct-typhoon mode, which typhoon passes though the Korea.

A Review of Aeromagnetic Anomalies in the Sawatch Range, Central Colorado

USGS Publications Warehouse

Bankey, Viki

2010-01-01

This report contains digital data and image files of aeromagnetic anomalies in the Sawatch Range of central Colorado. The primary product is a data layer of polygons with linked data records that summarize previous interpretations of aeromagnetic anomalies in this region. None of these data files and images are new; rather, they are presented in updated formats that are intended to be used as input to geographic information systems, standard graphics software, or map-plotting packages.

MX Siting Investigation Gravity Survey - Wah Wah Valley, Utah.

DTIC Science & Technology

1981-05-15

Bouguer Anomaly (see Section A1.4, Appendix A1.0). The Defense Mapping Agency Aerospace Center (DMAAC), St. Louis, Missouri, calculates outer zone...Utah .... 12 LIST OF DRAWINGS Drawing Number 1 Complete Bouguer Anomaly Contours In Pocket at 2 Deptn to Rock - Interpreted from End of Report...DMAHTC/GSS obtained the basic observations for the new stations and reduced them to Simple Bouguer Anomalies (SBA) as described in Appendix A1.0. Up to

Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet Anomaly in NGC 5548 with X-Ray Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mathur, S.; Gupta, A.; Page, K.

During the Space Telescope and Optical Reverberation Mapping Project observations of NGC 5548, the continuum and emission-line variability became decorrelated during the second half of the six-month-long observing campaign. Here we present Swift and Chandra X-ray spectra of NGC 5548 obtained as part of the campaign. The Swift spectra show that excess flux (relative to a power-law continuum) in the soft X-ray band appears before the start of the anomalous emission-line behavior, peaks during the period of the anomaly, and then declines. This is a model-independent result suggesting that the soft excess is related to the anomaly. We divide themore » Swift data into on- and off-anomaly spectra to characterize the soft excess via spectral fitting. The cause of the spectral differences is likely due to a change in the intrinsic spectrum rather than to variable obscuration or partial covering. The Chandra spectra have lower signal-to-noise ratios, but are consistent with the Swift data. Our preferred model of the soft excess is emission from an optically thick, warm Comptonizing corona, the effective optical depth of which increases during the anomaly. In conclusion, this model simultaneously explains all three observations: the UV emission-line flux decrease, the soft-excess increase, and the emission-line anomaly.« less

Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet Anomaly in NGC 5548 with X-Ray Spectroscopy

DOE PAGES

Mathur, S.; Gupta, A.; Page, K.; ...

2017-08-31

During the Space Telescope and Optical Reverberation Mapping Project observations of NGC 5548, the continuum and emission-line variability became decorrelated during the second half of the six-month-long observing campaign. Here we present Swift and Chandra X-ray spectra of NGC 5548 obtained as part of the campaign. The Swift spectra show that excess flux (relative to a power-law continuum) in the soft X-ray band appears before the start of the anomalous emission-line behavior, peaks during the period of the anomaly, and then declines. This is a model-independent result suggesting that the soft excess is related to the anomaly. We divide themore » Swift data into on- and off-anomaly spectra to characterize the soft excess via spectral fitting. The cause of the spectral differences is likely due to a change in the intrinsic spectrum rather than to variable obscuration or partial covering. The Chandra spectra have lower signal-to-noise ratios, but are consistent with the Swift data. Our preferred model of the soft excess is emission from an optically thick, warm Comptonizing corona, the effective optical depth of which increases during the anomaly. In conclusion, this model simultaneously explains all three observations: the UV emission-line flux decrease, the soft-excess increase, and the emission-line anomaly.« less

Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet Anomaly in NGC 5548 with X-Ray Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mathur, S.; Pogge, R. W.; Adams, S. M.

During the Space Telescope and Optical Reverberation Mapping Project observations of NGC 5548, the continuum and emission-line variability became decorrelated during the second half of the six-month-long observing campaign. Here we present Swift and Chandra X-ray spectra of NGC 5548 obtained as part of the campaign. The Swift spectra show that excess flux (relative to a power-law continuum) in the soft X-ray band appears before the start of the anomalous emission-line behavior, peaks during the period of the anomaly, and then declines. This is a model-independent result suggesting that the soft excess is related to the anomaly. We divide themore » Swift data into on- and off-anomaly spectra to characterize the soft excess via spectral fitting. The cause of the spectral differences is likely due to a change in the intrinsic spectrum rather than to variable obscuration or partial covering. The Chandra spectra have lower signal-to-noise ratios, but are consistent with the Swift data. Our preferred model of the soft excess is emission from an optically thick, warm Comptonizing corona, the effective optical depth of which increases during the anomaly. This model simultaneously explains all three observations: the UV emission-line flux decrease, the soft-excess increase, and the emission-line anomaly.« less

An attempt to obtain a detailed declination chart from the United States magnetic anomaly map

USGS Publications Warehouse

Alldredge, L.R.

1989-01-01

Modern declination charts of the United States show almost no details. It was hoped that declination details could be derived from the information contained in the existing magnetic anomaly map of the United States. This could be realized only if all of the survey data were corrected to a common epoch, at which time a main-field vector model was known, before the anomaly values were computed. Because this was not done, accurate declination values cannot be determined. In spite of this conclusion, declination values were computed using a common main-field model for the entire United States to see how well they compared with observed values. The computed detailed declination values were found to compare less favourably with observed values of declination than declination values computed from the IGRF 1985 model itself. -from Author

New Mars free-air and Bouguer gravity: Correlation with topography, geology and large impact basins

NASA Technical Reports Server (NTRS)

Frey, Herbert; Bills, Bruce G.; Kiefer, Walter S.; Nerem, R. Steven; Roark, James H.; Zuber, Maria T.

1993-01-01

Free-air and Bouguer gravity anomalies from a 50x50 field (MGM635), derived at the Goddard Space Flight Center, with global topography, geology, and the distribution of large impact basins was compared. The free-air gravity anomalies were derived from re-analysis of Viking Orbiter and Mariner 9 tracking data and have a spatial resolution of 250-300 km. Bouguer anomalies were calculated using a 50x50 expansion of the current Mars topography and the GSFC degree 50 geoid as the equipotential reference surface. Rotational flattening was removed using a moment of inertia of 0.365 and the corrections from Table B2 of Sleep and Phillips. Crustal density and mean density were assumed to be 2.9 and 3.93 gm/cm(sup 3). The spherical harmonic topography used has zero mean elevation, and differs from the USGS maps by about 2 km. Comparisons with global geology use a simplified map with about 1/3 the number of units on the current maps. For correlation with impact basins, the recent compilation by Schultz and Frey was used.

Gravity Survey of the Carson Sink - Data and Maps

DOE Data Explorer

Faulds, James E.

2013-12-31

A detailed gravity survey was carried out for the entire Carson Sink in western Nevada (Figure 1) through a subcontract to Zonge Engineering, Inc. The Carson Sink is a large composite basin containing three known, blind high-temperature geothermal systems (Fallon Airbase, Stillwater, and Soda Lake). This area was chosen for a detailed gravity survey in order to characterize the gravity signature of the known geothermal systems and to identify other potential blind systems based on the structural setting indicated by the gravity data. Data: Data were acquired at approximately 400, 800, and 1600 meter intervals for a total of 1,243 stations. The project location and station location points are presented in Figure 14. The station distribution for this survey was designed to complete regional gravity coverage in the Carson Sink area without duplication of available public and private gravity coverage. Gravity data were acquired using a Scintrex CG-5 gravimeter and a LaCoste and Romberg (L&R) Model-G gravimeter. The CG-5 gravity meter has a reading resolution of 0.001 milligals and a typical repeatability of less than 0.005 milligals. The L&R gravity meter has a reading resolution of 0.01 milligals and a typical repeatability of 0.02 milligals. The basic processing of gravimeter readings to calculate through to the Complete Bouguer Anomaly was made using the Gravity and Terrain Correction software version 7.1 for Oasis Montaj by Geosoft LTD. Results: The gravity survey of the Carson Sink yielded the following products. Project location and station location map (Figure 14). Complete Bouguer Anomaly @ 2.67 gm/cc reduction density. Gravity Complete Bouguer Anomaly at 2.50 g/cc Contour Map (Figure 15). Gravity Horizontal Gradient Magnitude Shaded Color Contour Map. Gravity 1st Vertical Derivative Color Contour Map. Interpreted Depth to Mesozoic Basement (Figure 16), incorporating drill-hole intercept values. Preliminary Interpretation of Results: The Carson Sink is a complex composite basin with several major depocenters (Figures 15 and 16). Major depocenters are present in the south-central, east-central, and northeastern parts of the basin. The distribution of gravity anomalies suggests a complex pattern of faulting in the subsurface of the basin, with many fault terminations, step-overs, and accommodation zones. The pattern of faulting implies that other, previously undiscovered blind geothermal systems are likely in the Carson Sink. The gravity survey was completed near the end of this project. Thus, more thorough analysis of the data and potential locations of blind geothermal systems is planned for future work.

Salient features of the dayside low latitude ionospheric response to the main phase step-I of the 17 March 2015 geomagnetic storm

NASA Astrophysics Data System (ADS)

Bagiya, Mala S.; Sunil, A. S.; Chakrabarty, D.; Sunda, Surendra

2017-10-01

Based on TEC observations by India's GPS Aided GEO Augmented Navigation (GAGAN) GPS network, we report the dayside low latitude ionospheric variations over the Indian region during the moderate main phase step-I of the 17 March 2015 geomagnetic storm. In addition, we assess the efficacy of GPS inferred TEC maps by International GNSS service (IGS) in capturing large scale diurnal features of equatorial ionization anomaly (EIA) over the Indian region during this period. Following the prompt penetration electric field (PPE) at ∼0605 UT, equatorial electrojet (EEJ) enhances by ∼55 nT over 75 ± 3oE longitudes where main phase step-I is coincided with local noon. Initial moderate EIA gradually strengthens with the storm commencement. Although GAGAN TEC exhibits more intense EIA evolution compare to IGS TEC maps, latitudinal extent of EIA are comparable in both. The enhanced EEJ reverses by ∼0918 UT under the effect of overshielding electric field, the later is accompanied by northward turning of interplanetary magnetic field (IMF) Bz. The weakening of well evolved EIA reflects in IGS TEC maps after ∼45 min of the overshielding occurrence. In contrary, GAGAN TEC shows the corresponding feature after ∼0115 h. Resurgence of EIA, following the PPE ∼1115 UT, shows up in GAGAN TEC but IGS TEC maps fails in capturing this feature. The observed low latitude TEC variations and EIA modulations are explained in terms of the varying storm time disturbance electric fields. The anomalies between the GAGAN TEC and IGS TEC maps are discussed in terms of the possible limitations of the IGS TEC maps in capturing storm time EIA variability over the Indian region.

Further Mapping of Mercury's Crustal Magnetic Field Using MESSENGER Magnetometer Data

NASA Astrophysics Data System (ADS)

Hood, L. L.; Oliveira, J. S.; Spudis, P. D.; Galluzzi, V.

2018-05-01

Further mapping of Mercury's crustal magnetic field shows that anomalies are associated with some impact craters but not others. Differences in impactor composition (e.g., iron content) may be indicated by this new observation.

Verification of Geosat sea surface topography in the Gulf Stream extension with surface drifting buoys and hydrographic measurements

NASA Astrophysics Data System (ADS)

Willebrand, J.; KäSe, R. H.; Stammer, D.; Hinrichsen, H.-H.; Krauss, W.

1990-03-01

Altimeter data from Geosat have been analyzed in the Gulf Stream extension area. Horizontal maps of the sea surface height anomaly relative to an annual mean for various 17-day intervals were constructed using an objective mapping procedure. The mean sea level was approximated by the dynamic topography from climatological hydrographic data. Geostrophic surface velocities derived from the composite maps (mean plus anomaly) are significantly correlated with surface drifter velocities observed during an oceanographie experiment in the spring of 1987. The drifter velocities contain much energy on scales less than 100 km which are not resolved in the altimetric maps. It is shown that the composite sea surface height also agrees well with ground verification from hydrographic data along sections in a triangle between the Azores, Newfoundland, and Bermuda, except in regions of high mean gradients.

Continental and oceanic magnetic anomalies: Enhancement through GRM

NASA Technical Reports Server (NTRS)

Vonfrese, R. R. B.; Hinze, W. J.

1985-01-01

In contrast to the POGO and MAGSAT satellites, the Geopotential Research Mission (GRM) satellite system will orbit at a minimum elevation to provide significantly better resolved lithospheric magnetic anomalies for more detailed and improved geologic analysis. In addition, GRM will measure corresponding gravity anomalies to enhance our understanding of the gravity field for vast regions of the Earth which are largely inaccessible to more conventional surface mapping. Crustal studies will greatly benefit from the dual data sets as modeling has shown that lithospheric sources of long wavelength magnetic anomalies frequently involve density variations which may produce detectable gravity anomalies at satellite elevations. Furthermore, GRM will provide an important replication of lithospheric magnetic anomalies as an aid to identifying and extracting these anomalies from satellite magnetic measurements. The potential benefits to the study of the origin and characterization of the continents and oceans, that may result from the increased GRM resolution are examined.

A large-scale anomaly in Enceladus' microwave emission

NASA Astrophysics Data System (ADS)

Ries, Paul A.; Janssen, Michael

2015-09-01

The Cassini spacecraft flew by Enceladus on 6 November 2011, configured to acquire synthetic aperture RADAR imaging of most of the surface with the RADAR instrument. The pass also recorded microwave thermal emission from most of the surface. We report on global patterns of thermal emission at 2.17 cm based on this data set in the context of additional unresolved data both from the ground and from Cassini. The observed thermal emission is consistent with dielectric constants of pure water or methane ice, but cannot discriminate between the two. The emissivity is similar to those of other icy satellites (≈ 0.7), consistent with volume scattering. The most intriguing result, however, is an anomaly in the thermal emission of Enceladus' leading hemisphere. Evidence presented here suggests the anomaly is buried at depths on the order of a few meters. This anomaly is located in similar geographic location to anomalies previously detected with the CIRS and ISS instruments on Mimas, Tethys, and Dione (Howett, C.J.A. et al. [2011]. Icarus 216, 221-226; Howett, C.J.A. et al. [2012]. Icarus 221, 1084-1088; Howett, C.J.A. et al. [2014]. Icarus 241, 239-247; Schenk, P. et al. [2011]. Icarus 211, 740-757), but also corresponds with a geological feature on Enceladus' leading terrain (Crow-Willard, E., Pappalardo, R.T. [2011]. Global geological mapping of Enceladus. In: EPSC-DPS Joint Meeting 2011. p. 635). Simple models show that the Crow-Willard and Pappalardo (Crow-Willard, E., Pappalardo, R.T. [2011]. Global geological mapping of Enceladus. In: EPSC-DPS Joint Meeting 2011. p. 635) model is a better fit to the data. Our best-supported hypothesis is that the leading hemisphere smooth terrain is young enough (<75-200 Myr old) that the micrometeorite impact gardening depth is shallower than the electromagnetic skin depth of the observations (≈ 3-5 m), a picture consistent with ground and space radar measurements, which show no variation at 2 cm, but an increase in albedo in the anomaly region at 13 cm.

Correlation of spatial climate/weather maps and the advantages of using the Mahalanobis metric in predictions

NASA Astrophysics Data System (ADS)

Stephenson, D. B.

1997-10-01

The skill in predicting spatially varying weather/climate maps depends on the definition of the measure of similarity between the maps. Under the justifiable approximation that the anomaly maps are distributed multinormally, it is shown analytically that the choice of weighting metric, used in defining the anomaly correlation between spatial maps, can change the resulting probability distribution of the correlation coefficient. The estimate of the numbers of degrees of freedom based on the variance of the correlation distribution can vary from unity up to the number of grid points depending on the choice of weighting metric. The (pseudo-) inverse of the sample covariance matrix acts as a special choice for the metric in that it gives a correlation distribution which has minimal kurtosis and maximum dimension. Minimal kurtosis suggests that the average predictive skill might be improved due to the rarer occurrence of troublesome outlier patterns far from the mean state. Maximum dimension has a disadvantage for analogue prediction schemes in that it gives the minimum number of analogue states. This metric also has an advantage in that it allows one to powerfully test the null hypothesis of multinormality by examining the second and third moments of the correlation coefficient which were introduced by Mardia as invariant measures of multivariate kurtosis and skewness. For these reasons, it is suggested that this metric could be usefully employed in the prediction of weather/climate and in fingerprinting anthropogenic climate change. The ideas are illustrated using the bivariate example of the observed monthly mean sea-level pressures at Darwin and Tahitifrom 1866 1995.

Early Opening of Seychelles and India: the Gop Basin Revisited

NASA Astrophysics Data System (ADS)

Dyment, J.; Vadakkeyakath, Y.; Bhattacharya, G.

2012-12-01

The deep offshore region located between the India-Pakistan continental margin and the Laxmi Ridge continental sliver contains valuable imprints of the early oceanic opening phase between India and the Seychelles. The acquisition of wide-angle deep seismic data by British scientists in 2003 provided new information about the deep structure and nature of the crust [1,2]. These data complement the large amount of seismic reflection profiles, altimetry-derived gravity and marine magnetic data which allow mapping the structure and determining the age of the oceanic crust [3,4,5]. Although these authors all agree on the oceanic nature of the Gop Basin, they surprisingly differ on the extent of the oceanic crust, the location of the extinct spreading center and the age of the basin. Here we re-evaluate published interpretations of the Gop Basin in light of all available data. The major discrepancy between [1,2,4] and [5] is the location of the extinct spreading center. [1,2,4] place it on an unnamed basement high located at 19°55'N, whereas [5] identify it with the Palitana Ridge at 19°25'N. Checking the location of the basement high of [1,2,4] on the basement isobath map of [3], based on many seismic reflection profiles, reveals that this basement high actually is an isolated feature of limited extent, which at best can be considered as part of a NE-SW trending basement high zone. This basement high locally coincides with a strong positive magnetic anomaly and a narrow gravity anomaly low but the trend of these anomalies is E-W, in contrast to the NE-SW trend of the basement in this area. For these reasons, this basement high probably is not the location of the Gop Basin extinct spreading center. Conversely, on the basement isobath map of [3], the Palitana Ridge appears as a prominent E-W high, located in the middle of a broad E-W graben, the Gop Basin. It extends over 200 km and is flanked on both sides by basement 2000 m deeper. On free air gravity anomaly maps, the Palitana Ridge lies in the center of the broad gravity high that delineates the Gop Basin. It corresponds, to the west, to a narrow gravity low, a typical signature of fossil spreading centers. The crustal structure determined by the wide angle seismic data of [1,2] shows that the base of the lower crust, the best seismically constrained interface (according to the ray diagram of [1]), is flat in the Arabian Basin, deeper under the Laxmi Ridge, shallower in the Gop Basin under the Palitana Ridge, and deeper again further north. For these reasons, the Palitana Ridge probably is the location of the Gop Basin extinct spreading centre. Further, the Gop Basin, being narrow, does not exhibit long sequences of magnetic anomalies, thereby making their interpretation difficult. Many models may fit the observed anomalies, so [4] and [5] each proposed different hypotheses. We note, however, that [4] consider a plausible (and preferred) model with "initial" spreading rates, i.e. just after break up, as fast as 68 mm/yr half-rate, which implies the Gop Basin to form in 1 Myr. Such a fast initial rate appears unrealistic, considering that initial spreading rates are usually much slower, about one fourth of that rate. [1] Minshull et al., Nature Geo., 2008 [2] Collier et al., JGR, 2009 [3] Malod et al., Tectonophys., 1997 [4] Collier et al., EPSL, 2008 [5] Yatheesh et al., EPSL, 2009

Does Terrestrial Drought Explain Global CO2 Flux Anomalies Induced by El Nino?

NASA Technical Reports Server (NTRS)

Schwalm. C. R.; Williams, C. A.; Schaefer, K.; Baker, I.; Collatz, G. J.; Roedenbeck, C.

2011-01-01

The El Nino Southern Oscillation is the dominant year-to-year mode of global climate variability. El Nino effects on terrestrial carbon cycling are mediated by associated climate anomalies, primarily drought, influencing fire emissions and biotic net ecosystem exchange (NEE). Here we evaluate whether El Nino produces a consistent response from the global carbon cycle. We apply a novel bottom-up approach to estimating global NEE anomalies based on FLUXNET data using land cover maps and weather reanalysis. We analyze 13 years (1997-2009) of globally gridded observational NEE anomalies derived from eddy covariance flux data, remotely-sensed fire emissions at the monthly time step, and NEE estimated from an atmospheric transport inversion. We evaluate the overall consistency of biospheric response to El Nino and, more generally, the link between global CO2 flux anomalies and El Nino-induced drought. Our findings, which are robust relative to uncertainty in both methods and time-lags in response, indicate that each event has a different spatial signature with only limited spatial coherence in Amazonia, Australia and southern Africa. For most regions, the sign of response changed across El Nino events. Biotic NEE anomalies, across 5 El Nino events, ranged from -1.34 to +0.98 Pg Cyr(exp -1, whereas fire emissions anomalies were generally smaller in magnitude (ranging from -0.49 to +0.53 Pg C yr(exp -1). Overall drought does not appear to impose consistent terrestrial CO2 flux anomalies during El Ninos, finding large variation in globally integrated responses from 11.15 to +0.49 Pg Cyr(exp -1). Despite the significant correlation between the CO2 flux and El Nino indices, we find that El Nino events have, when globally integrated, both enhanced and weakened terrestrial sink strength, with no consistent response across events

Archeogeophysical Studies in Nitovikla Settlement, Karpaz/ Karpasia Peninsula, Cyprus

NASA Astrophysics Data System (ADS)

Kızılduman, Bülent; Ahmet Yüksel, Fethi; Avci, Kerim

2017-04-01

The island of Cyprus, which played a significant role in connecting different cultures in the Eastern Mediterranean; moreover it has always played a significant role in the Mediterranean due to its strategical and geographical location (as located between Egypt, Palestine, Syria, Anatolia and the Aegean) became the cradle of an authentic and peculiar culture both in prehistoric and historic times. In particular, the Karpaz/ Karpasia Peninsula, located on the northeasternmost corner of the island, still retains valuable traces of this indigenous culture. One of the reasons of this peculiarity lies on the fact that the peninsula perched on the Eastern Mediterranean trade routes and boasted abundant copper deposits. The structure of the fortress had probably fallen into ruins and lost its functionality in the Cyprus Late Bronze Age IIB. According to the 2D and 3D georadar cross sections and Self Potantial (SP) with cubic model obtained from georadar mesurements to define the locations and directions of fortress sections and the foundation of the castle walls georadar measurements have been made on 8 areas in Nitovikla Region based on the purpose of archaeogeophysics. Linear geometrically distributed anomalies were also identified as they consistently extend over 6 metres deep (at least in some areas) these seem to be related to each other however possessing an individual architectural coherence. Anomalies and Self Potential anomaly distribution map are identified after examining the 3D diagrams (top view) and post processual data analysis as well as interpretation of GPR measurements were also included in the newly drawn layout plan. Fortress locations and foundations of caste walls have mapped by interpretation of 2D and 3D images. these have also revealed linear anomalies have surround the research site. Key Words: Cyprus, Karpaz/ Karpasia, Nitovikla, Archaeology, Archeogeophysic, GPR, SP

A Bottom Gravity Survey of the Continental Shelf Between Point Lobos and Point Sur, California.

DTIC Science & Technology

From an occupation of 68 ocean bottom and 38 land gravity stations between Pt. Lobos and Pt. Sur, California, a complete Bouguer anomaly map was...produced and analyzed. The steps in data reduction leading to the complete Bouguer anomaly field are presented, unique features of which are associated

Errors in MR-based attenuation correction for brain imaging with PET/MR scanners

NASA Astrophysics Data System (ADS)

Rota Kops, Elena; Herzog, Hans

2013-02-01

AimAttenuation correction of PET data acquired by hybrid MR/PET scanners remains a challenge, even if several methods for brain and whole-body measurements have been developed recently. A template-based attenuation correction for brain imaging proposed by our group is easy to handle and delivers reliable attenuation maps in a short time. However, some potential error sources are analyzed in this study. We investigated the choice of template reference head among all the available data (error A), and possible skull anomalies of the specific patient, such as discontinuities due to surgery (error B). Materials and methodsAn anatomical MR measurement and a 2-bed-position transmission scan covering the whole head and neck region were performed in eight normal subjects (4 females, 4 males). Error A: Taking alternatively one of the eight heads as reference, eight different templates were created by nonlinearly registering the images to the reference and calculating the average. Eight patients (4 females, 4 males; 4 with brain lesions, 4 w/o brain lesions) were measured in the Siemens BrainPET/MR scanner. The eight templates were used to generate the patients' attenuation maps required for reconstruction. ROI and VOI atlas-based comparisons were performed employing all the reconstructed images. Error B: CT-based attenuation maps of two volunteers were manipulated by manually inserting several skull lesions and filling a nasal cavity. The corresponding attenuation coefficients were substituted with the water's coefficient (0.096/cm). ResultsError A: The mean SUVs over the eight templates pairs for all eight patients and all VOIs did not differ significantly one from each other. Standard deviations up to 1.24% were found. Error B: After reconstruction of the volunteers' BrainPET data with the CT-based attenuation maps without and with skull anomalies, a VOI-atlas analysis was performed revealing very little influence of the skull lesions (less than 3%), while the filled nasal cavity yielded an overestimation in cerebellum up to 5%. ConclusionsThe present error analysis confirms that our template-based attenuation method provides reliable attenuation corrections of PET brain imaging measured in PET/MR scanners.

On gravity from SST, geoid from SEASAT, and plate age and fracture zones in the Pacific

NASA Technical Reports Server (NTRS)

Marsh, B. D.; Marsh, J. G.; Williamson, R. G.

1983-01-01

Data from an additional 50 satellite-to-satellite tracking (SST) passes were combined with earlier measurements of the high degree and order (n, m, 12) gravity in the central Pacific. A composite map was produced which shows good agreement with conventional GEM models. Data from the SEASAT altimeter was reduced and found to agree well with both the SST and the GEM fields. The maps are dominated especially in the east, by a pattern of roughly east-west anomalies with a transverse wavelength of about 2000 km. Further comparison with regional bathymetric data shows a remarkably close correlation with plate age. Each anomaly band is framed by those major fracture zones having large offsets. The regular spacing of these fractures seems to account for the fabric in the gravity fields. Other anomalies are accounted for by hot spots. The source of part of these anomalies is in the lithosphere itself. The possible plume size and ascent velocity necessary to supply deep mantle material to the upper mantel without complete thermal equilibration is considered.

The Crustal Structure of the North-South Earthquake Belt in China Revealed from Deep Seismic Soundings and Gravity Data

NASA Astrophysics Data System (ADS)

Zhao, Yang; Guo, Lianghui; Shi, Lei; Li, Yonghua

2018-01-01

The North-South earthquake belt (NSEB) is one of the major earthquake regions in China. The studies of crustal structure play a great role in understanding tectonic evolution and in evaluating earthquake hazards in this region. However, some fundamental crustal parameters, especially crustal interface structure, are not clear in this region. In this paper, we reconstructed the crustal interface structure around the NSEB based on both the deep seismic sounding (DSS) data and the gravity data. We firstly reconstructed the crustal structure of crystalline basement (interface G), interface between upper and lower crusts (interface C) and Moho in the study area by compiling the results of 38 DSS profiles published previously. Then, we forwardly calculated the gravity anomalies caused by the interfaces G and C, and then subtracted them from the complete Bouguer gravity anomalies, yielding the regional gravity anomalies mainly due to the Moho interface. We then utilized a lateral-variable density interface inversion technique with constraints of the DSS data to invert the regional anomalies for the Moho depth model in the study area. The reliability of our Moho depth model was evaluated by comparing with other Moho depth models derived from other gravity inversion technique and receiver function analysis. Based on our Moho depth model, we mapped the crustal apparent density distribution in the study area for better understanding the geodynamics around the NSEB.

Data-driven modeling of surface temperature anomaly and solar activity trends

USGS Publications Warehouse

Friedel, Michael J.

2012-01-01

A novel two-step modeling scheme is used to reconstruct and analyze surface temperature and solar activity data at global, hemispheric, and regional scales. First, the self-organizing map (SOM) technique is used to extend annual modern climate data from the century to millennial scale. The SOM component planes are used to identify and quantify strength of nonlinear relations among modern surface temperature anomalies (<150 years), tropical and extratropical teleconnections, and Palmer Drought Severity Indices (0–2000 years). Cross-validation of global sea and land surface temperature anomalies verifies that the SOM is an unbiased estimator with less uncertainty than the magnitude of anomalies. Second, the quantile modeling of SOM reconstructions reveal trends and periods in surface temperature anomaly and solar activity whose timing agrees with published studies. Temporal features in surface temperature anomalies, such as the Medieval Warm Period, Little Ice Age, and Modern Warming Period, appear at all spatial scales but whose magnitudes increase when moving from ocean to land, from global to regional scales, and from southern to northern regions. Some caveats that apply when interpreting these data are the high-frequency filtering of climate signals based on quantile model selection and increased uncertainty when paleoclimatic data are limited. Even so, all models find the rate and magnitude of Modern Warming Period anomalies to be greater than those during the Medieval Warm Period. Lastly, quantile trends among reconstructed equatorial Pacific temperature profiles support the recent assertion of two primary El Niño Southern Oscillation types. These results demonstrate the efficacy of this alternative modeling approach for reconstructing and interpreting scale-dependent climate variables.

Anomaly Detection of Electromyographic Signals.

PubMed

Ijaz, Ahsan; Choi, Jongeun

2018-04-01

In this paper, we provide a robust framework to detect anomalous electromyographic (EMG) signals and identify contamination types. As a first step for feature selection, optimally selected Lawton wavelets transform is applied. Robust principal component analysis (rPCA) is then performed on these wavelet coefficients to obtain features in a lower dimension. The rPCA based features are used for constructing a self-organizing map (SOM). Finally, hierarchical clustering is applied on the SOM that separates anomalous signals residing in the smaller clusters and breaks them into logical units for contamination identification. The proposed methodology is tested using synthetic and real world EMG signals. The synthetic EMG signals are generated using a heteroscedastic process mimicking desired experimental setups. A sub-part of these synthetic signals is introduced with anomalies. These results are followed with real EMG signals introduced with synthetic anomalies. Finally, a heterogeneous real world data set is used with known quality issues under an unsupervised setting. The framework provides recall of 90% (± 3.3) and precision of 99%(±0.4).

The south-central United States magnetic anomaly

NASA Technical Reports Server (NTRS)

Hinze, W. J.; Braile, L. W. (Principal Investigator); Starich, P. J.

1984-01-01

The South-Central United States Magnetic Anomaly is the most prominent positive feature in the MAGSAT scalar magnetic field over North America. The anomaly correlates with increased crustal thickness, above average crustal velocity, negative free air gravity anomalies and an extensive zone of Middle Proterozoic anorogenic felsic basement rocks. Spherical dipole source inversion of the MAGSAT scalar data and subsequent calculation of reduced to pole and derivative maps provide constraints for a crustal magnetic model which corresponds geographically to the extensive Middle Proterozoic felsic rocks trending northeasterly across the United States. These felsic rocks contain insufficient magnetization or volume to produce the anomaly, but are rather indicative of a crustal zone which was disturbed during a Middle Proterozoic thermal event which enriched magnetic material deep in the crust.

Magnetic space-based field measurements

NASA Technical Reports Server (NTRS)

Langel, R. A.

1981-01-01

Satellite measurements of the geomagnetic field began with the launch of Sputnik 3 in May 1958 and have continued sporadically in the intervening years. A list of spacecraft that have made significant contributions to an understanding of the near-earth geomagnetic field is presented. A new era in near-earth magnetic field measurements began with NASA's launch of Magsat in October 1979. Attention is given to geomagnetic field modeling, crustal magnetic anomaly studies, and investigations of the inner earth. It is concluded that satellite-based magnetic field measurements make global surveys practical for both field modeling and for the mapping of large-scale crustal anomalies. They are the only practical method of accurately modeling the global secular variation. Magsat is providing a significant contribution, both because of the timeliness of the survey and because its vector measurement capability represents an advance in the technology of such measurements.

Crustal structure of the Pannonian-Carpathian region, Central Europe, from ambient noise tomography

NASA Astrophysics Data System (ADS)

Ren, Y.; Stuart, G. W.; Houseman, G. A.; Carpathian Basins Project Working Group

2010-12-01

The Pannonian Basin of Central Europe is a major extensional basin surrounded by the Carpathian Mountains. During the evolution of the Carpathian-Pannonian region, extension of the crust and lithosphere created several inter-related basins of which the Pannonian basin is the largest. Imaging the seismic velocity structure of the crust and the upper mantle may help us understand the structure and geodynamic evolution of this part of central Europe. Here, we use ambient noise tomography to investigate the crust and uppermost mantle structure in the region. We have collected and processed continuous data from 56 temporary stations deployed in the Carpathian Basins Project (CBP) for 16 months (2005-2007) and 41 permanent broadband stations; this dataset enables the most well-resolved images of the S-wave structure of the region yet obtained. We computed the cross-correlation between vertical component seismograms from pairs of stations and stacked the correlated waveforms over 1-2 years to estimate the Rayleigh wave Green’s function. Frequency-time analysis is used to measure the group velocity dispersion curves, which are then inverted for the group velocity maps. Our 4-10 s group velocity maps exhibit low velocity anomalies which clearly defined the major sediment depo-centers in the Carpathian region. A broad low velocity anomaly in the center of the 5 s group velocity map can be associated with the Pannonian Basin, whereas an anomaly in the southeastern region is related to the Moesian platform. Further east, the Vienna Basin can also be seen on our maps. A fast anomaly in the central region can be associated with the Mid-Hungarian line. At periods from 18 to 24 seconds, group velocities become increasingly sensitive to crustal thickness. The maps also reveal low-velocity anomalies associated with the Carpathians. The low velocity anomalies are probably caused by deeper crustal roots beneath the mountain ranges which occur due to isostatic compensation. CBP working group: G. Houseman, G. Stuart, Y. Ren, B. Dando, P. Lorinczi, School of Earth and Environment, University of Leeds, UK; E. Hegedus, A. Kovács, I. Török, I. László, R. Csabafi, Eötvös Loránd Geophysical Institute, Budapest, Hungary; E. Brüeckl, H. Hausmann, W. Loderer, T-U Wien, Vienna, Austria; S. Radovanovic, V. Kovacevic, D. Valcic, S. Petrovic-Cacic, G. Krunic, Seismological Survey of Serbia, Belgrade, Serbia; A. Brisbourne, D. Hawthorn, A. Horleston, V. Lane, SEIS-UK, Leicester University, UK.

Thermal surveillance of active volcanoes. [infrared scanner recordings of thermal anomalies of Mt. Baker volcano

NASA Technical Reports Server (NTRS)

Friedman, J. D. (Principal Investigator)

1974-01-01

The author has identified the following significant results. By the end of 1973, aerial infrared scanner traverses for thermal anomaly recordings of all Cascade Range volcanoes were essentially completed. Amplitude level slices of the Mount Baker anomalies were completed and compiled at a scale of 1:24,000, thus producing, for the first time, an accurate map of the distribution and intensity of thermal activity on Mount Baker. The major thermal activity is concentrated within the crater south of the main summit and although it is characterized by intensive solfataric activity and warm ground, it is largely subglacial, causing the development of sizable glacier perforation features. The outgoing radiative flux from the east breach anomalies is sufficient to account for the volume of ice melted to form the glacier perforations. DCP station 6251 has been monitoring a thermally anomalous area on the north slope of Mount Baker. The present thermal activity of Mount Baker accounts for continuing hydrothermal alteration in the crater south of the main summit and recurrent debris avalanches from Sherman Peak on its south rim. The infrared anomalies mapped as part of the experiment SR 251 are considered the basic evidence of the subglacial heating which was the probable triggering mechanism of an avalanche down Boulder Glacier on August 20-21, 1973.

Mapping the Extent of the Lovejoy Basalt Beneath the Sacramento Valley, CA, Using Aeromagnetic Data

NASA Astrophysics Data System (ADS)

Langenheim, V. E.; Sweetkind, D. S.; Springhorn, S.

2014-12-01

The Lovejoy Basalt is a distinctive Miocene (~16 Ma) unit that erupted from Thompson Peak in the northeast Sierra Nevada, flowed southwest across the Sierra Nevada into the Sacramento Valley. It crops out in a few places in Sacramento Valley: (1) near Chico and Oroville on the east side of the valley, (2) Orland Buttes on the west side, and (3) Putnam Peak, some 250 km southwest of Thompson Peak. The basalt is also encountered in drill holes, but its extent is not entirely known. The Lovejoy Basalt is strongly magnetic and, in general, reversely magnetized, making it an excellent target for aeromagnetic mapping. Recently acquired aeromagnetic data (flight line spacing 800 m at an altitude of 240 m) indicate a characteristic, sinuous, short-wavelength magnetic pattern associated with outcrops and known subcrops of Lovejoy Basalt. Filtering of these data to enhance negative, short-wavelength anomalies defines two large bands of negative anomalies that trend southwest of Chico and Oroville and appear to coalesce about 25 km north of Sutter Buttes. Another band of negative anomalies extends north of the junction roughly along the Sacramento River 40 km to Deer Creek. The anomalies become more subdued to the north, suggesting that the Lovejoy thins to the north. Aeromagnetic data also indicate a large subcrop of Lovejoy Basalt that extends 25 km north-northeast from exposures at Orland Buttes. Driller logs from gas and water wells confirm our mapping of Lovejoy within these areas. The sinuous magnetic lows are not continuous south of Sutter Buttes, but form isolated patches that are aligned in a north-south direction south of the concealed Colusa Dome to Putnam Peak and an east-west, 20-km-long band about 15 km south of Sutter Buttes. Other reversed anomalies in the Sacramento Valley coincide with volcanic necks in the Sutter Buttes and Colusa Dome; these produce semicircular anomalies that are distinct from those caused by the Lovejoy Basalt.

Lunar Gravity Studies from the Lunar Prospector Line-of-Sight Acceleration Data: Isostatic Compensation of Medium Sized Craters

NASA Astrophysics Data System (ADS)

Sugano, T.; Heki, K.

2002-12-01

Direct estimation of mass distribution on the lunar nearside surface using the Lunar Prospector (LP) line-of-sight (LOS) acceleration data has several merits over conventional methods to estimate Stokes' coefficients of the lunar gravity field, such as (1) high resolution gravity anomaly recovery without introducing Kaula's constraint, (2) fast inversion calculation by stepwise estimation of parameter sets enabled by small correlation between parameters sets. Resolution of the lunar free-air gravity anomaly map obtained here, is as high as a gravity model complete to degree/order 225, and yet less noisy than the recent models. Next we performed terrain correction for the raw LOS acceleration data using lunar topography model from the Clementine laser altimetry data and the average crustal density of 2.9 g/cm3. By conducting the same inversion for the data after the correction, we obtained the map of Bouguer gravity anomaly that mainly reflects the MOHO topography. By comparing maps we notice that signatures of medium-sized (80-300 km in diameter) craters visible as topographic depression and negative free air anomaly, disappear in the Bouguer anomaly. The absence of mass deficits in the Bouguer anomaly suggests that the MOHO beneath them is flat. Generally speaking, longer wavelength topographic features have to be supported by MOHO topography (Airy isostatic compensation) while small scale topographic features are supported by lithospheric strength. The boundary between these two modes constrains the lithosphere thickness, and hence thermal structure near the surface. Larger craters are known to have become Mascons; mantle plugs and high-density mare basalts cause positive gravity anomalies there. The smallest Mascon has diameters a little larger than 300 km (e.g. Schiller-Zuccius), and the boundary between the two compensation status seems to lie around 300 km. Thermal evolution history of the Moon suggests temporally increasing thickness of lithosphere over its entire history, and the lithosphere as thick as 50-100 km around 4.0 Ga. This is consistent with the isostatic compensation status of the craters studied here, and a model describing the degree of lithospheric supports for various wavelength topographies.

Surveying the South Pole-Aitken basin magnetic anomaly for remnant impactor metallic iron

USGS Publications Warehouse

Cahill, Joshua T.S.; Hagerty, Justin J.; Lawrence, David M.; Klima, Rachel L.; Blewett, David T.

2014-01-01

The Moon has areas of magnetized crust ("magnetic anomalies"), the origins of which are poorly constrained. A magnetic anomaly near the northern rim of South Pole-Aitken (SPA) basin was recently postulated to originate from remnant metallic iron emplaced by the SPA basin-forming impactor. Here, we remotely examine the regolith of this SPA magnetic anomaly with a combination of Clementine and Lunar Prospector derived iron maps for any evidence of enhanced metallic iron content. We find that these data sets do not definitively detect the hypothesized remnant metallic iron within the upper tens of centimeters of the lunar regolith.

Identifying Resistivity Anomalies of Sungai Batu Ancient River using 3D Contour Map

NASA Astrophysics Data System (ADS)

Yusoh, R.; Saad, R.; Saidin, M.; Muhammad, S. B.; Anda, S. T.; Ismail, M. A. M.; Hazreek, Z. A. M.

2018-04-01

Electrical resistivity method was undertaken at archeological site at Sungai Batu in Lembah Bujang, located at Sungai Merbok in northwestern of Malaysia. The survey was implemented near the excavation site. This paper shows the results of 5 ground resistivity survey line was carry out using SAS4000 equipment. The wenner-schlumberger array was applied for measurement. Resistivity data are used to obtain valuable information to identify the remain buried archeology. The ground resistivity data were presented in contour map for various depth by using Surfer 13 software visualized clearly the anomalies evidenced for every single depth section. The results from the survey has found the appearance of sedimentation formation that believe happen long time ago after ancient river was buried by sediment from weathering process due to increasing sea level. Otherwise, another anomaly was found in the middle of the survey area which shows high resistivity value about 1000 – 2000 ohm.m

Magnetic map of the Irish Hills and surrounding areas, San Luis Obispo County, central California

USGS Publications Warehouse

Langenheim, V.E.; Watt, J.T.; Denton, K.M.

2012-01-01

A magnetic map of the Irish Hills and surrounding areas was created as part of a cooperative research and development agreement with the Pacific Gas and Electric Company and is intended to promote further understanding of the areal geology and structure by serving as a basis for geophysical interpretations and by supporting geological mapping, mineral and water resource investigations, and other topical studies. Local spatial variations in the Earth's magnetic field (evident as anomalies on magnetic maps) reflect the distribution of magnetic minerals, primarily magnetite, in the underlying rocks. In many cases the volume content of magnetic minerals can be related to rock type, and abrupt spatial changes in the amount of magnetic minerals can be related to either lithologic or structural boundaries. Magnetic susceptibility measurements from the area indicate that bodies of serpentinite and other mafic and ultramafic rocks tend to produce the most intense magnetic anomalies, but such generalizations must be applied with caution because some sedimentary units also can produce measurable magnetic anomalies. Remanent magnetization does not appear to be a significant source for magnetic anomalies because it is an order of magnitude less than the induced magnetization. The map is a mosaic of three separate surveys collected by (1) fixed-wing aircraft at a nominal height of 305 m, (2) by boat with the sensor at sea level, and (3) by helicopter. The helicopter survey was flown by New-Sense Geophysics in October 2009 along flight lines spaced 150-m apart and at a nominal terrain clearance of 50 to 100 m. Tie lines were flown 1,500-m apart. Data were adjusted for lag error and diurnal field variations. Further processing included microleveling using the tie lines and subtraction of the reference field defined by International Geomagnetic Reference Field (IGRF) 2005 extrapolated to August 1, 2008.

Recalculation of regional and detailed gravity database from Slovak Republic and qualitative interpretation of new generation Bouguer anomaly map

NASA Astrophysics Data System (ADS)

Pasteka, Roman; Zahorec, Pavol; Mikuska, Jan; Szalaiova, Viktoria; Papco, Juraj; Krajnak, Martin; Kusnirak, David; Panisova, Jaroslava; Vajda, Peter; Bielik, Miroslav

2014-05-01

In this contribution results of the running project "Bouguer anomalies of new generation and the gravimetrical model of Western Carpathians (APVV-0194-10)" are presented. The existing homogenized regional database (212478 points) was enlarged by approximately 107 500 archive detailed gravity measurements. These added gravity values were measured since the year 1976 to the present, therefore they need to be unified and reprocessed. The improved positions of more than 8500 measured points were acquired by digitizing of archive maps (we recognized some local errors within particular data sets). Besides the local errors (due to the wrong positions, heights or gravity of measured points) we have found some areas of systematic errors probably due to the gravity measurement or processing errors. Some of them were confirmed and consequently corrected by field measurements within the frame of current project. Special attention is paid to the recalculation of the terrain corrections - we have used a new developed software as well as the latest version of digital terrain model of Slovakia DMR-3. Main improvement of the new terrain corrections evaluation algorithm is the possibility to calculate it in the real gravimeter position and involving of 3D polyhedral bodies approximation (accepting the spherical approximation of Earth's curvature). We have realized several tests by means of the introduction of non-standard distant relief effects introduction. A new complete Bouguer anomalies map was constructed and transformed by means of higher derivatives operators (tilt derivatives, TDX, theta-derivatives and the new TDXAS transformation), using the regularization approach. A new interesting regional lineament of probably neotectonic character was recognized in the new map of complete Bouguer anomalies and it was confirmed also by realized in-situ field measurements.

Recent Weather Extremes and Impacts on Agricultural Production and Vector-Borne Disease Outbreak Patterns

PubMed Central

Anyamba, Assaf; Small, Jennifer L.; Britch, Seth C.; Tucker, Compton J.; Pak, Edwin W.; Reynolds, Curt A.; Crutchfield, James; Linthicum, Kenneth J.

2014-01-01

We document significant worldwide weather anomalies that affected agriculture and vector-borne disease outbreaks during the 2010–2012 period. We utilized 2000–2012 vegetation index and land surface temperature data from NASA's satellite-based Moderate Resolution Imaging Spectroradiometer (MODIS) to map the magnitude and extent of these anomalies for diverse regions including the continental United States, Russia, East Africa, Southern Africa, and Australia. We demonstrate that shifts in temperature and/or precipitation have significant impacts on vegetation patterns with attendant consequences for agriculture and public health. Weather extremes resulted in excessive rainfall and flooding as well as severe drought, which caused ∼10 to 80% variation in major agricultural commodity production (including wheat, corn, cotton, sorghum) and created exceptional conditions for extensive mosquito-borne disease outbreaks of dengue, Rift Valley fever, Murray Valley encephalitis, and West Nile virus disease. Analysis of MODIS data provided a standardized method for quantifying the extreme weather anomalies observed during this period. Assessments of land surface conditions from satellite-based systems such as MODIS can be a valuable tool in national, regional, and global weather impact determinations. PMID:24658301

An app for climate-based Chikungunya risk monitoring and mapping

NASA Astrophysics Data System (ADS)

Soebiyanto, R. P.; Rama, X.; Jepsen, R.; Bijoria, S.; Linthicum, K. J.; Anyamba, A.

2017-12-01

There is an increasing concern for reemergence and spread of chikungunya in the last 10 years in Africa, the Indian Ocean, and Asia, and range expansion that now reaches the Caribbean, South America and threatens North America. The outbreak of Chikungunya in 2013 and its spread throughout the Americas has so far resulted in more than 1.7 million suspected cases. This has demonstrated the importance of readiness in assessing potential risk of the emergence of vector-borne diseases. Climate and ecological conditions are now recognized as major contributors to the emergence and re-emergence of various vector-borne diseases including Chikungunya. Variations and persistence of extreme climate conditions provide suitable environment for the increase of certain disease vector populations, which then further amplify vector-borne disease transmission. This highlights the importance of climate anomaly information in assessing regions at risk for Chikungunya. In order to address such issue, we are developing a climate-based app, CHIKRISK, which will help decision makers to answer three critical questions: (i) Where has Chikungunya activity occurred; (ii) Where it is occurring now; (iii) Which regions are currently at risk for Chikungunya. We first develop a database of historical Chikungunya outbreak locations compiled from publicly available information. These records are used to map where Chikungunya activity has occurred over time. We leverage on various satellite-based climate data records - such as rainfall, land surface and near surface temperature to characterize evolving conditions prior to and during Chikungunya activity. Chikungunya outbreak data, climate and ancillary (i.e. population and elevation) data are used to develop analytics capability that will produce risk maps. The CHIKRISK app has the capability to visualize historical Chikungunya activity locations, climate anomaly conditions and Chikungunya risk maps. Currently, the focus of the development is on the Caribbean and South America regions. The capability will be expanded in phased manner to the entire world.

Shear wave velocity, seismic attenuation, and thermal structure of the continental upper mantle

USGS Publications Warehouse

Artemieva, I.M.; Billien, M.; Leveque, J.-J.; Mooney, W.D.

2004-01-01

Seismic velocity and attenuation anomalies in the mantle are commonly interpreted in terms of temperature variations on the basis of laboratory studies of elastic and anelastic properties of rocks. In order to evaluate the relative contributions of thermal and non-thermal effects on anomalies of attenuation of seismic shear waves, QS-1, and seismic velocity, VS, we compare global maps of the thermal structure of the continental upper mantle with global QS-1 and Vs maps as determined from Rayleigh waves at periods between 40 and 150 S. We limit the comparison to three continental mantle depths (50, 100 and 150 km), where model resolution is relatively high. The available data set does not indicate that, at a global scale, seismic anomalies in the upper mantle are controlled solely by temperature variations. Continental maps have correlation coefficients of <0.56 between VS and T and of <0.47 between QS and T at any depth. Such low correlation coefficients can partially be attributed to modelling arrefacts; however, they also suggest that not all of the VS and QS anomalies in the continental upper mantle can be explained by T variations. Global maps show that, by the sign of the anomaly, VS and QS usually inversely correlate with lithospheric temperatures: most cratonic regions show high VS and QS and low T, while most active regions have seismic and thermal anomalies of the opposite sign. The strongest inverse correlation is found at a depth of 100 km, where the attenuation model is best resolved. Significantly, at this depth, the contours of near-zero QS anomalies approximately correspond to the 1000 ??C isotherm, in agreement with laboratory measurements that show a pronounced increase in seismic attenuation in upper mantle rocks at 1000-1100 ??C. East-west profiles of VS, QS and T where continental data coverage is best (50??N latitude for North America and 60??N latitude for Eurasia) further demonstrate that temperature plays a dominant, but non-unique, role in determining the value of lithospheric VS and QS. At 100 km depth, where the resolution of seismic models is the highest, we compare observed seismic VS and QS with theoretical VST and QST values, respectively, that are calculated solely from temperature anomalies and constrained by experimental data on temperature dependencies of velocity and attenuation. This comparison shows that temperature variations alone are sufficient to explain seismic VS and QS in ca 50 per cent of continental regions. We hypothesize that compositional anomalies resulting from Fe depletion can explain the misfit between seismic and theoretical VS in cratonic lithosphere. In regions of active tectonics, temperature effects alone cannot explain seismic VS and QS in the lithosphere. It is likely that partial melts and/or fluids may affect seismic parameters in these regions. This study demonstrates that lithospheric temperature plays the dominant role in controlling VS and QS anomalies, but other physical parameters, such as compositional variations, fluids, partial melting and scattering, may also play a significant role in determining VS and QS variations in the continental mantle. ?? 2004 RAS.

ISHM Anomaly Lexicon for Rocket Test

NASA Technical Reports Server (NTRS)

Schmalzel, John L.; Buchanan, Aubri; Hensarling, Paula L.; Morris, Jonathan; Turowski, Mark; Figueroa, Jorge F.

2007-01-01

Integrated Systems Health Management (ISHM) is a comprehensive capability. An ISHM system must detect anomalies, identify causes of such anomalies, predict future anomalies, help identify consequences of anomalies for example, suggested mitigation steps. The system should also provide users with appropriate navigation tools to facilitate the flow of information into and out of the ISHM system. Central to the ability of the ISHM to detect anomalies is a clearly defined catalog of anomalies. Further, this lexicon of anomalies must be organized in ways that make it accessible to a suite of tools used to manage the data, information and knowledge (DIaK) associated with a system. In particular, it is critical to ensure that there is optimal mapping between target anomalies and the algorithms associated with their detection. During the early development of our ISHM architecture and approach, it became clear that a lexicon of anomalies would be important to the development of critical anomaly detection algorithms. In our work in the rocket engine test environment at John C. Stennis Space Center, we have access to a repository of discrepancy reports (DRs) that are generated in response to squawks identified during post-test data analysis. The DR is the tool used to document anomalies and the methods used to resolve the issue. These DRs have been generated for many different tests and for all test stands. The result is that they represent a comprehensive summary of the anomalies associated with rocket engine testing. Fig. 1 illustrates some of the data that can be extracted from a DR. Such information includes affected transducer channels, narrative description of the observed anomaly, and the steps used to correct the problem. The primary goal of the anomaly lexicon development efforts we have undertaken is to create a lexicon that could be used in support of an associated health assessment database system (HADS) co-development effort. There are a number of significant byproducts of the anomaly lexicon compilation effort. For example, (1) Allows determination of the frequency distribution of anomalies to help identify those with the potential for high return on investment if included in automated detection as part of an ISHM system, (2) Availability of a regular lexicon could provide the base anomaly name choices to help maintain consistency in the DR collection process, and (3) Although developed for the rocket engine test environment, most of the anomalies are not specific to rocket testing, and thus can be reused in other applications.

Structural Control and Groundwater Flow in the Nubian Aquifer

NASA Astrophysics Data System (ADS)

Fathy, K.; Sultan, M.; Ahmed, M.; Save, H.; Emil, M. K.; Elkaliouby, B.

2017-12-01

An integrated research approach (remote sensing, field, geophysics) was conducted to investigate the structural control on groundwater flow in large aquifers using the less studied Nubian Sandstone Aquifer System (NSAS) of NE Africa as a test site. The aquifer extends over 2.2 x 106 km2 in Egypt, Libya, Chad, and Sudan and consists of thick (> 3 kms), water-bearing, Paleozoic and Mesozoic sandstone with intercalations of Tertiary shale and clay. It is subdivided into three sub-basins (Northern Sudan Platform [NSP], Dakhla [DAS], and Kufra) that are separated by basement uplifts (e.g., E-W trending Uweinat-Aswan uplift that separates DAS from the NSP). Aquifer recharge occurs in the south (NSP and southern Kufra) where the aquifer is unconfined and precipitation is high (Average Annual Precipitation [AAP]: 117 mm/yr.) and discharge is concentrated in the north (DAS and northern Kufra). Our approach is a three-fold exercise. Firstly, we compared GOCE-based Global Geopotential Models (GGMs) to terrestrial gravity anomalies for 21262 sites to select the optimum model for deriving Bouguer gravity anomalies. Secondly, structures and uplifts were mapped using hill shade images and their extension in the subsurface were mapped using the Eigen_6C4 model-derived Bouguer anomalies and their Tilt Derivative products (TDR). Thirdly, hydrological analysis was conducted using GRACE CSR 1° x 1° mascon solutions to investigate the mass variations in relation to the mapped structures. Our findings include: (1) The Eigen-6C4 is the optimum model having the lowest deviation (9.122 mGal) from the terrestrial gravity anomalies; (2) the surface expressions of structures matched fairly well with their postulated extensions in the subsurface; (3) identified fault systems include: Red Sea rift-related N-S to NW-SE trending grabens formed by reactivating basement structures during Red Sea opening and Syrian arc-related NE-SW trending dextral shear systems; (4) TWS patterns are uniform throughout the length (hundreds of kilometers) of the identified shear systems but are dissimilar from those extracted in areas proximal to, but outside of, the shear zones; and (5) basement uplifts impede or redirect the groundwater flow.

Hydrocarbon Reservoir Identification in Volcanic Zone by using Magnetotelluric and Geochemistry Information

NASA Astrophysics Data System (ADS)

Firda, S. I.; Permadi, A. N.; Supriyanto; Suwardi, B. N.

2018-03-01

The resistivity of Magnetotelluric (MT) data show the resistivity mapping in the volcanic reservoir zone and the geochemistry information for confirm the reservoir and source rock formation. In this research, we used 132 data points divided with two line at exploration area. We used several steps to make the resistivity mapping. There are time series correction, crosspower correction, then inversion of Magnetotelluric (MT) data. Line-2 and line-3 show anomaly geological condition with Gabon fault. The geology structure from the resistivity mapping show the fault and the geological formation with the geological rock data mapping distribution. The geochemistry information show the maturity of source rock formation. According to core sample analysis information, we get the visual porosity for reservoir rock formation in several geological structure. Based on that, we make the geological modelling where the potential reservoir and the source rock around our interest area.

Interpretation of Local Gravity Anomalies in Northern New York

NASA Astrophysics Data System (ADS)

Revetta, F. A.

2004-05-01

About 10,000 new gravity measurements at a station spacing of 1 to 2 Km were made in the Adirondack Mountains, Lake Champlain Valley, St. Lawrence River Valley and Tug Hill Plateau. These closely spaced gravity measurements were compiled to construct computer contoured gravity maps of the survey areas. The gravity measurements reveal local anomalies related to seismicity, faults, mineral resources and gas fields that are not seen in the regional gravity mapping. In northern New York gravity and seismicity maps indicate epicenters are concentrated in areas of the most pronounced gravity anomalies along steep gravity gradients. Zones of weakness along the contacts of these lithologies of different density could possibly account for the earthquakes in this high stress area. Also, a computer contoured gravity map of the 5.3 magnitude Au Sable Forks earthquake of April 20, 2002 indicates the epicenter lies along a north-south trending gravity gradient produced by a high angle fault structure separating a gravity low in the west from high gravity in the east. In the St. Lawrence Valley, the Carthage-Colton Mylonite Zone, a major northeast trending structural boundary between the Adirondack Highlands and Northwest Lowlands, is represented as a steep gravity gradient extending into the eastern shore of Lake Ontario. At Russell, New York near the CCMZ, a small circular shaped gravity high coincides with a cluster of earthquakes. The coincidence of the epicenters over the high may indicate stress amplification at the boundary of a gabbro pluton. The Morristown fault located in the Morristown Quadrangle in St. Lawrence County produces both gravity and magnetic anomalies due to Precambrian Basement faulting. This faulting indicates control of the Morristown fault in the overlying Paleozoics by the Precambrian faults. Gravity and magnetic anomalies also occur over proposed extensions of the Gloucester and Winchester Springs faults into northern New York. Gravity and magnetic surveys were conducted at the closed Benson Mines magnetite mine and the Zinc Mines at Balmat, New York. The gravity and magnetic anomalies at Benson Mines indicate that significant amounts of magnetite remain in the subsurface and the steep gradients indicate a shallow depth. A gravity high of 35 gravity units in the Sylvia Lake Zinc District at Balmat, New York occurs over the upper marble and a 100 gu anomaly occurs just northeast of the zinc district. Abandoned natural gas fields exist along the southern and southwestern boundary of the Tug Hill Plateau. Gravity surveys were conducted in the vicinity of three of these gas fields in the Tug Hill Plateau (Camden, Sandy Creek and Pulaski). The Tug Hill Plateau is thought to be an uplifted-fault-bounded block which, if correct, might account for the existence of those gas fields. The trends of the gravity contours on the gravity maps lends credence to the fault interpretation. Also gravity and magnetic traverses were conducted across faults in the Trenton-Black River. These traverses show gravity anomalies across the faults which indicate control by faulting in the Precambrian.

Venus - Ishtar gravity anomaly

NASA Technical Reports Server (NTRS)

Sjogren, W. L.; Bills, B. G.; Mottinger, N. A.

1984-01-01

The gravity anomaly associated with Ishtar Terra on Venus is characterized, comparing line-of-sight acceleration profiles derived by differentiating Pioneer Venus Orbiter Doppler residual profiles with an Airy-compensated topographic model. The results are presented in graphs and maps, confirming the preliminary findings of Phillips et al. (1979). The isostatic compensation depth is found to be 150 + or - 30 km.

Post-Metamorphic Thermal Anomaly across the Nacimiento Block, Central California: a Hydrothermal Overprint?

NASA Astrophysics Data System (ADS)

Lacroix, B.; Hughes, J.; Lahfid, A.; Delchini, S.

2017-12-01

The thermal history of the Nacimiento block located within the Franciscan Complex (California, USA) has been previously proposed based on both vitrinite reflectance (Rm) and illite cristallinity methods (Underwood et al., 1995). These authors suggest that the Nacimiento block is locally perturbed by a thermal anomaly (up to 300ºC), probably caused by post-metamorphic hydrothermal activity linked to the emplacement of an Au-deposit: the Los Burros Gold deposit. Although both thermal anomaly and deposit seem spatially correlated, their relationship is still poorly constrained. Detailed geological and structural mapping within the Los Burros Mining District (LBMD) coupled with a thermal study was conducted to better understand processes responsible for the anomalous temperatures recorded near the deposit. The regional maximum temperature reached by metasediments from the Nacimiento block have been first investigated using the Raman Spectroscopy of Carbonaceous Materials (RSCM) method. In addition, through careful fluid-inclusion and stable isotopes (O and C) studies on the deposit, the temperature and the potential source of the fluid responsible for the Los Burros Au-deposit emplacement were investigated. RSCM technique confirms the presence of a thermal anomaly in the range 260-320ºC near LBMD. However, our structural and petrographic results suggest that the thermal anomaly is not correlated to a post-metamorphic hydrothermal overprint but rather to a late, transpressive deformation uplifting buried metamorphic rocks.

Marine magnetic anomalies in the NE Indian Ocean: the Wharton and Central Indian basins revisited

NASA Astrophysics Data System (ADS)

Jacob, J.; Dyment, J.; Yatheesh, V.; Bhattacharya, G. C.

2009-04-01

The North-eastern Indian Ocean has recently received a renewed interest. The disastrous earthquakes and tsunamis of Dec. 2004 off Sumatra have triggered a large international effort including several oceanographic cruises. The Ninetyeast Ridge, a long submarine ridge which extends NS on more than 4000 km, has been the focus of a recent cruise aiming to study the interaction of a hotspot with the oceanic lithosphere and spreading centres. Both the study of the seismogenic zone under Sumatra and the Ninetyeast Ridge formation require accurate determination of the age and structure of the oceanic lithosphere in the Wharton and Central Indian Basins. First we delineate tectonic elements such as the Sunda Trench, the Ninetyeast Ridge, and the fracture zones of the Wharton and Central Indian basins from a recent version of the free-air gravity anomaly deduced from satellite altimetry and available multibeam bathymetric data. We use all available magnetic data to identify magnetic anomalies and depict seafloor spreading isochrons in order to build a tectonic map of the Wharton Basin. To do so, we apply the analytic signal method to unambiguously determine the location of the magnetic picks. The new tectonic map shows more refinements than previous ones, as expected from a larger data set. The fossil ridge in the Wharton Basin is clearly defined; spreading ceased at anomaly 18 young (38.5 Ma), and, perhaps, as late as anomaly 15 (35 Ma). Symmetric anomalies are observed on both flanks of the fossil ridge up to anomaly 24 (54 Ma), preceded by a slight reorganization of the spreading compartments between anomalies 28 and 25 (64 - 56 Ma) and a more stable phase of spreading between anomalies 34 and 29 (83 - 64 Ma). Earlier, a major change of spreading direction is clearly seen in the bending fracture zones; interpolating in the Cretaceous Quiet Zone between anomaly 34 in the Wharton Basin and anomaly M0 off Australia leads to an age of ~100 Ma for this reorganization. Anomalies 20 to 34 are clearly identified in the western part of the Central Indian Basin. The interpretation is more difficult in the compartments located immediately west of the Ninetyeast Ridge, where multiple ridge jumps have been proposed to explain complex anomaly patterns. In a different way, we recognize a continuous sequence of anomalies 20 to 34, although the anomalies 25 to 29 seem to be wider and display complex boundaries.

An investigation of MAGSAT and complementary data emphasizing precambrian shields and adjacent areas of West Africa and South America

NASA Technical Reports Server (NTRS)

Hastings, D. A. (Principal Investigator)

1981-01-01

Several possible causes for the east-west striping of the MAGSAT anomaly maps are listed and discussed including: (1) the inadequacy of the field model used for core-crustal separation of geomagnetic anomalies; (2) external field noise remaining in the available maps; (3) east-west trends of crustal uplift and depression; (4) east-west trends to convection patterns in the mantle; (5) bands of crustal materials of similar metamorphic grade; (6) variations in the depth of the Curie isotherm; and (7) the data processing techniques used to overcome the absence of tie lines and orbital path of MAGSAT.

Research for Key Techniques of Geophysical Recognition System of Hydrocarbon-induced Magnetic Anomalies Based on Hydrocarbon Seepage Theory

NASA Astrophysics Data System (ADS)

Zhang, L.; Hao, T.; Zhao, B.

2009-12-01

Hydrocarbon seepage effects can cause magnetic alteration zones in near surface, and the magnetic anomalies induced by the alteration zones can thus be used to locate oil-gas potential regions. In order to reduce the inaccuracy and multi-resolution of the hydrocarbon anomalies recognized only by magnetic data, and to meet the requirement of integrated management and sythetic analysis of multi-source geoscientfic data, it is necessary to construct a recognition system that integrates the functions of data management, real-time processing, synthetic evaluation, and geologic mapping. In this paper research for the key techniques of the system is discussed. Image processing methods can be applied to potential field images so as to make it easier for visual interpretation and geological understanding. For gravity or magnetic images, the anomalies with identical frequency-domain characteristics but different spatial distribution will reflect differently in texture and relevant textural statistics. Texture is a description of structural arrangements and spatial variation of a dataset or an image, and has been applied in many research fields. Textural analysis is a procedure that extracts textural features by image processing methods and thus obtains a quantitative or qualitative description of texture. When the two kinds of anomalies have no distinct difference in amplitude or overlap in frequency spectrum, they may be distinguishable due to their texture, which can be considered as textural contrast. Therefore, for the recognition system we propose a new “magnetic spots” recognition method based on image processing techniques. The method can be divided into 3 major steps: firstly, separate local anomalies caused by shallow, relatively small sources from the total magnetic field, and then pre-process the local magnetic anomaly data by image processing methods such that magnetic anomalies can be expressed as points, lines and polygons with spatial correlation, which includes histogram-equalization based image display, object recognition and extraction; then, mine the spatial characteristics and correlations of the magnetic anomalies using textural statistics and analysis, and study the features of known anomalous objects (closures, hydrocarbon-bearing structures, igneous rocks, etc.) in the same research area; finally, classify the anomalies, cluster them according to their similarity, and predict hydrocarbon induced “magnetic spots” combined with geologic, drilling and rock core data. The system uses the ArcGIS as the secondary development platform, inherits the basic functions of the ArcGIS, and develops two main sepecial functional modules, the module for conventional potential-field data processing methods and the module for feature extraction and enhancement based on image processing and analysis techniques. The system can be applied to realize the geophysical detection and recognition of near-surface hydrocarbon seepage anomalies, provide technical support for locating oil-gas potential regions, and promote geophysical data processing and interpretation to advance more efficiently.

On the interpretation of satellite-derived gravity and magnetic data for studies of crustal geology and metallogenesis

NASA Technical Reports Server (NTRS)

Hastings, D. A.

1985-01-01

Satellite-derived global gravity and magnetic maps have been shown to be useful in large-scale studies of the Earth's crust, despite the relative infancy of such studies. Numerous authors have made spatial associations of gravity or magnetic anomalies with geological provinces. Gravimetric interpretations are often made in terms of isostasy, regional variations of density, or of geodesy in general. Interpretations of satellite magnetic anomalies often base assumptions of overall crustal magnetism on concepts of the vertical and horizontal distribution of magnetic susceptibility, then make models of these assumed distributions. The opportunity of improving our satellite gravity and magnetic data through the proposed Geopotential Research Mission should considerably improve the scientific community's ability to analyze and interpret global magnetic and gravity data.

Gravity Anomalies

NASA Image and Video Library

2015-04-15

Analysis of radio tracking data have enabled maps of the gravity field of Mercury to be derived. In this image, overlain on a mosaic obtained by MESSENGER's Mercury Dual Imaging System and illuminated with a shape model determined from stereo-photoclinometry, Mercury's gravity anomalies are depicted in colors. Red tones indicate mass concentrations, centered on the Caloris basin (center) and the Sobkou region (right limb). Such large-scale gravitational anomalies are signatures of subsurface structure and evolution. The north pole is near the top of the sunlit area in this view. http://photojournal.jpl.nasa.gov/catalog/PIA19285

Surface Temperature Anomalies Derived from Night Time ASTER Data Corrected for Solar and Topographic Effects, Archuleta County

DOE Data Explorer

Khalid Hussein

2012-02-01

This map shows areas of anomalous surface temperature in Alamosa and Saguache Counties identified from ASTER thermal data and spatial based insolation model. The temperature is calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas that had temperature greater than 2o were considered ASTER modeled "very warm modeled surface temperature" are shown in red on the map. Areas that had temperatures between 1o and 2o were considered ASTER modeled "warm modeled surface temperature" are shown in yellow on the map. This map also includes the locations of shallow temperature survey points, locations of springs or wells with favorable geochemistry, faults, transmission lines, and areas of modeled basement weakness "fairways." Note: 'o' is used in this description to represent lowercase sigma.

Surface Temperature Anomalies Derived from Night Time ASTER Data Corrected for Solar and Topographic Effects, San Miguel County, Colorado

DOE Data Explorer

Khalid Hussein

2012-02-01

This map shows areas of anomalous surface temperature in Alamosa and Saguache Counties identified from ASTER thermal data and spatial based insolation model. The temperature is calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas that had temperature greater than 2o were considered ASTER modeled "very warm modeled surface temperature" are shown in red on the map. Areas that had temperatures between 1o and 2o were considered ASTER modeled "warm modeled surface temperature" are shown in yellow on the map. This map also includes the locations of shallow temperature survey points, locations of springs or wells with favorable geochemistry, faults, transmission lines, and areas of modeled basement weakness "fairways." Note: 'o' is used in this description to represent lowercase sigma.

Surface Temperature Anomalies Derived from Night Time ASTER Data Corrected for Solar and Topographic Effects, Fremont County, Colorado

DOE Data Explorer

Khalid Hussein

2012-02-01

This map shows areas of anomalous surface temperature in Alamosa and Saguache Counties identified from ASTER thermal data and spatial based insolation model. The temperature is calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas that had temperature greater than 2o were considered ASTER modeled "very warm modeled surface temperature" are shown in red on the map. Areas that had temperatures between 1o and 2o were considered ASTER modeled "warm modeled surface temperature" are shown in yellow on the map. This map also includes the locations of shallow temperature survey points, locations of springs or wells with favorable geochemistry, faults, transmission lines, and areas of modeled basement weakness "fairways." Note: 'o' is used in this description to represent lowercase sigma.

Surface Temperature Anomalies Derived from Night Time ASTER Data Corrected for Solar and Topographic Effects, Routt County, Colorado

DOE Data Explorer

Khalid Hussein

2012-02-01

This map shows areas of anomalous surface temperature in Alamosa and Saguache Counties identified from ASTER thermal data and spatial based insolation model. The temperature is calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas that had temperature greater than 2o were considered ASTER modeled "very warm modeled surface temperature" are shown in red on the map. Areas that had temperatures between 1o and 2o were considered ASTER modeled"warm modeled surface temperature" are shown in yellow on the map. This map also includes the locations of shallow temperature survey points, locations of springs or wells with favorable geochemistry, faults, transmission lines, and areas of modeled basement weakness "fairways." Note: 'o' is used in this description to represent lowercase sigma.

Surface Temperature Anomalies Derived from Night Time ASTER Data Corrected for Solar and Topographic Effects, Alamosa and Saguache Counties, Colorado

DOE Data Explorer

Khalid Hussein

2012-02-01

This map shows areas of anomalous surface temperature in Alamosa and Saguache Counties identified from ASTER thermal data and spatial based insolation model. The temperature is calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas that had temperature greater than 2o were considered ASTER modeled "very warm modeled surface temperature" are shown in red on the map. Areas that had temperatures between 1o and 2o were considered ASTER modeled "warm modeled surface temperature" are shown in yellow on the map. This map also includes the locations of shallow temperature survey points, locations of springs or wells with favorable geochemistry, faults, transmission lines, and areas of modeled basement weakness "fairways." Note: 'o' is used in this description to represent lowercase sigma.

Surface Temperature Anomalies Derived from Night Time ASTER Data Corrected for Solar and Topographic Effects, Dolores County

DOE Data Explorer

Khalid Hussein

2012-02-01

This map shows areas of anomalous surface temperature in Alamosa and Saguache Counties identified from ASTER thermal data and spatial based insolation model. The temperature is calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas that had temperature greater than 2o were considered ASTER modeled "very warm modeled surface temperature" are shown in red on the map. Areas that had temperatures between 1o and 2o were considered ASTER modeled "warm modeled surface temperature" are shown in yellow on the map. This map also includes the locations of shallow temperature survey points, locations of springs or wells with favorable geochemistry, faults, transmission lines, and areas of modeled basement weakness "fairways." Note: 'o' is used in this description to represent lowercase sigma.

An investigation of MAGSAT and complementary data emphasizing precambrian shields and adjacent areas of West Africa and South America

NASA Technical Reports Server (NTRS)

Hastings, D. A. (Principal Investigator)

1981-01-01

Accomplishments with regard to the mapping and analysis of MAGSAT data for the investigation of correlations between the magnetic field characteristics of South American and African shields are reported. Significant results in the interpretation of the global total-field anomalies and the anomaly patterns of Africa and South America are discussed. The central position of the Brazilian shield tends to form a negative total-field anomaly, consistent with findings for shields in equatorial Africa. Sedimentary sequences in the Amazon basin and in the Rio de Janeiro-Sao Paolo areas exhibit positive anomalies, also consistent with equatorial Africa. Results for the Caribbean Sea and Guyana regions are also described.

Doppler-Zeeman mapping of the magnetic CP star HD 215441

NASA Astrophysics Data System (ADS)

Khokhlova, V. L.; Vasilchenko, D. V.; Stepanov, V. V.; Tsymbal, V. V.

1997-07-01

The method of Vasilchenko et al. (1996) is used to obtain a Doppler-Zeeman map of the magnetic CP star HD 215441. The magnetic field is approximated by a magnetic dipole that is arbitrarily shifted from the star center. The solution of the inverse problem yields the dipole parameters and the maps of Si, Ti, Cr, and Fe abundance anomalies; the coordinates of local magnetic vectors on the star surface are computed. A comparison of the distribution of abundance anomalies and the magnetic-field configuration reveals that in the region where the magnetic-field lines are vertical (near the magnetic pole), Si, Ti and Cr are highly deficient, while the Fe enhancement is strongest. In the regions where the magnetic-field lines are horizontal (near the magnetic equator), Si, Ti and Cr show the greatest overabundance. In these regions, the Fe abundance is also slightly enhanced and exhibits, as it were, a secondary maximum. The factors that limit the accuracy of Doppler-Zeeman mapping are reviewed.

Detection of alteration associated with a porphyry copper deposit in southern Arizona

NASA Technical Reports Server (NTRS)

Abrams, M. J.; Siegal, B. S.

1977-01-01

Computer processing of Landsat MSS data was performed using contrast stretching and band-to-band ratioing. A false color ratio composite picture showed color anomalies which coincided with known areas of alteration on and about Red Mountain. A helicopter survey of the study area was undertaken using a portable field reflectance spectrometer. One hundred fifty-six spectra were obtained in the 0.4 to 2.5 micrometer wavelength region. The spectra were digitized, and contour maps for 24 wavelength intervals were produced; no spectral anomalies were evident for the known altered areas. A contour map produced from the 1.6 and 2.2 micrometer ratio generally delineated the alteration areas. The 1.3, 1.6, and 2.2 micrometer wavelength data were canonically transformed using a transformation empirically derived from discriminant function analysis of altered and unaltered materials for the Goldfield, Nevada region, and a contour map was produced for the first canonical variable. The known areas of alteration were clearly defined on the contour map.

Effect of attractive interactions on the water-like anomalies of a core-softened model potential.

PubMed

Pant, Shashank; Gera, Tarun; Choudhury, Niharendu

2013-12-28

It is now well established that water-like anomalies can be reproduced by a spherically symmetric potential with two length scales, popularly known as core-softened potential. In the present study we aim to investigate the effect of attractive interactions among the particles in a model fluid interacting with core-softened potential on the existence and location of various water-like anomalies in the temperature-pressure plane. We employ extensive molecular dynamic simulations to study anomalous nature of various order parameters and properties under isothermal compression. Order map analyses have also been done for all the potentials. We observe that all the systems with varying depth of attractive wells show structural, dynamic, and thermodynamic anomalies. As many of the previous studies involving model water and a class of core softened potentials have concluded that the structural anomaly region encloses the diffusion anomaly region, which in turn, encloses the density anomaly region, the same pattern has also been observed in the present study for the systems with less depth of attractive well. For the systems with deeper attractive well, we observe that the diffusion anomaly region shifts toward higher densities and is not always enclosed by the structural anomaly region. Also, density anomaly region is not completely enclosed by diffusion anomaly region in this case.

Seismo-ionospheric anomalies in ionospheric TEC and plasma density before the 17 July 2006 M7.7 south of Java earthquake

NASA Astrophysics Data System (ADS)

Tao, Dan; Cao, Jinbin; Battiston, Roberto; Li, Liuyuan; Ma, Yuduan; Liu, Wenlong; Zhima, Zeren; Wang, Lanwei; Wray Dunlop, Malcolm

2017-04-01

In this paper, we report significant evidence for preseismic ionospheric anomalies in total electron content (TEC) of the global ionosphere map (GIM) and plasma density appearing on day 2 before the 17 July 2006 M7.7 south of Java earthquake. After distinguishing other anomalies related to the geomagnetic activities, we found a temporal precursor around the epicenter on day 2 before the earthquake (15 July 2006), which agrees well with the spatial variations in latitude-longitude-time (LLT) maps. Meanwhile, the sequences of latitude-time-TEC (LTT) plots reveal that the TECs on epicenter side anomalously decrease and lead to an anomalous asymmetric structure with respect to the magnetic equator in the daytime from day 2 before the earthquake. This anomalous asymmetric structure disappears after the earthquake. To further confirm these anomalies, we studied the plasma data from DEMETER satellite in the earthquake preparation zone (2046.4 km in radius) during the period from day 45 before to day 10 after the earthquake, and also found that the densities of both electron and total ion in the daytime significantly increase on day 2 before the earthquake. Very interestingly, O+ density increases significantly and H+ density decreases, while He+ remains relatively stable. These results indicate that there exists a distinct preseismic signal (preseismic ionospheric anomaly) over the epicenter.

InfoSequia: the first operational remote sensing-based Drought Monitoring System of Spain

NASA Astrophysics Data System (ADS)

Contreras, Sergio; Hunink, Johannes E.

2016-04-01

We present a satellite-based Drought Monitoring System that provides weekly updates of maps and bulletins with vegetation drought indices over the Iberian Peninsula. The web portal InfoSequía (http://infosequia.es) aims to complement the current Spanish Drought Monitoring System which relies on a hydrological drought index computed at the basin level using data on river flows and water stored in reservoirs. Drought indices computed by InfoSequia are derived from satellite data provided by MODIS sensors (TERRA and AQUA satellites), and report the relative anomaly observed in the Normalized Difference Vegetation Index (NDVI), Land Surface Temperature (LST), and in an additive combination of both. Similar to the U.S. Drought Monitoring System by NOAA, the indices include the Vegetation Condition Index (VCI, relative NDVI anomaly), the Temperature Condition Index (TCI, relative LST anomaly) and the Vegetation Health Index (VHI, relative NDVI-LST anomaly). Relative anomalies are codified into four warning levels, and all of them are provided for short periods of time (8-day windows), or longer periods (e.g. 1 year) in order to capture the cumulative effects of droughts in the state variables. Additionally, InfoSequia quantifies the seasonal trajectories of the cumulative deviation of the observed NDVI in relation with the averaged seasonal trajectory observed over a reference period. Through the weekly bulletins, the Drought Monitoring System InfoSequia aims to provide practical information to stakeholders on the sensitivity and resilience of native ecosystems and rainfed agrosystems during drought periods. Also, the remote sensed indices can be used as drought impact indicator to evaluate the skill of seasonal agricultural drought forecasting systems. InfoSequia is partly funded by the Spanish Ministry of Economy and Competiveness through a Torres-Quevedo grant.

Risk of congenital anomalies around a municipal solid waste incinerator: a GIS-based case-control study

PubMed Central

Vinceti, Marco; Malagoli, Carlotta; Fabbi, Sara; Teggi, Sergio; Rodolfi, Rossella; Garavelli, Livia; Astolfi, Gianni; Rivieri, Francesca

2009-01-01

Background Waste incineration releases into the environment toxic substances having a teratogenic potential, but little epidemiologic evidence is available on this topic. We aimed at examining the relation between exposure to the emissions from a municipal solid waste incinerator and risk of birth defects in a northern Italy community, using Geographical Information System (GIS) data to estimate exposure and a population-based case-control study design. By modelling the incinerator emissions, we defined in the GIS three areas of increasing exposure according to predicted dioxins concentrations. We mapped the 228 births and induced abortions with diagnosis of congenital anomalies observed during the 1998–2006 period, together with a corresponding series of control births matched for year and hospital of birth/abortion as well as maternal age, using maternal address in the first three months of pregnancy to geocode cases and controls. Results Among women residing in the areas with medium and high exposure, prevalence of anomalies in the offspring was substantially comparable to that observed in the control population, nor dose-response relations for any of the major categories of birth defects emerged. Furthermore, odds ratio for congenital anomalies did not decrease during a prolonged shut-down period of the plant. Conclusion Overall, these findings do not lend support to the hypothesis that the environmental contamination occurring around an incineration plant such as that examined in this study may induce major teratogenic effects. PMID:19208225

Integrated GRASS GIS based techniques to identify thermal anomalies on water surface. Taranto case study.

NASA Astrophysics Data System (ADS)

Massarelli, Carmine; Matarrese, Raffaella; Felice Uricchio, Vito

2014-05-01

In the last years, thermal images collected by airborne systems have made the detection of thermal anomalies possible. These images are an important tool to monitor natural inflows and legal or illegal dumping in coastal waters. By the way, the potential of these kinds of data is not well exploited by the Authorities who supervises the territory. The main reason is the processing of remote sensing data that requires very specialized operators and softwares which are usually expensive and complex. In this study, we adopt a simple methodology that uses GRASS, a free open-source GIS software, which has allowed us to map surface water thermal anomalies and, consequently, to identify and locate coastal inflows, as well as manmade or natural watershed drains or submarine springs (in italian citri) in the Taranto Sea (South of Italy). Taranto sea represents a coastal marine ecosystem that has been gradually modified by mankind. One of its inlet, the Mar Piccolo, is a part of the National Priority List site identified by the National Program of Environmental Remediation and Restoration because of the size and high presence of industrial activities, past and present, that have had and continue to seriously compromise the health status of the population and the environment. In order to detect thermal anomalies, two flights have been performed respectively on March 3rd and on April 7th, 2013. A total of 13 TABI images have been acquired to map the whole Mar Piccolo with 1m of spatial resolution. TABI-320 is an airborne thermal camera by ITRES, with a continuous spectral range between 8 and 12 microns. On July 15th, 2013, an in-situ survey was carried out along the banks to retrieve clear visible points of natural or artificial inflows, detecting up to 72 of discharges. GRASS GIS (Geographic Resources Analysis Support System), is a free and open source Geographic Information System (GIS) software suite used for geospatial data management and analysis, image processing, graphics and maps production, spatial modeling, and visualization. In this study, we used three GRASS modules: r.clump, r.contour and v.generalize. The first module recategorizes data by grouping cells in discrete areas into a unique category preserving category distinctions in the input raster map layer. R.contour transforms an input surface raster data into an isolines vector data. The third module simplifies and smoothes the lines, reducing the complexity of vector features. As result, we produced a map of thermal anomalies around the coast surprisingly coincident with the inflows detected during the survey. Furthermore, the use of airborne images allowed us to identify other discharges in areas impossible to reach with the boat, due to the presence of algae, mussel-culture or forbidden military zones. With this study we demonstrated how it is possible to use GRASS GIS modules in a new combination in order to process remote sensed data achieving the same results of the expensive and complex specialized softwares. This work was funded by Regional Agency for Environmental Protection and Prevention in the Puglia region (ARPA Puglia).

The magnetic low of central Europe: analysis and interpretation by a multi scale approach.

NASA Astrophysics Data System (ADS)

Milano, Maurizio; Fedi, Maurizio

2016-04-01

The objective of this work is an interpretation of the European magnetic low (EML) which is the main magnetic anomaly characterizing the magnetic field of central Europe at high-altitude, extending from the eastern France to Poland and placed above the main geological boundary of Europe, the Trans European Suture Zone (TESZ), that separates the western and thinner Paleozoic platform from the eastern and thicker Precambrian platform. In particular, the EML has a relative magnetic high north-east of it, showing a reverse dipolar behavior that many authors tried to interpret in past also by high-altitude satellite exploration. We used an aeromagnetic dataset and employed a level-to-level upward continuation from 1 km up to 200 km, following a multiscale approach thanks to which the anomalies generated by sources placed at different depths can be discriminated. Low-altitude magnetic maps show a complex pattern of high-frequency anomalies up to an altitude of 50 km; then, increasing the altitude up to 200 km, the field simplifies gradually. In order to interpret the anomalies we generated the maps of the total gradient (|T|) of the field at each upward continued altitude, thanks to its property in localizing in a very simple way the edges of the sources and their horizontal position without specifying a priori information about source parameters. From the total gradient maps at low altitude we obtained information about the position of shallow and localized sources producing patterns of small anomalies. In central Europe, most of them have a reverse dipolar behavior, being related probably to metasedimentary rocks in the upper crust containing pyrrhotite and a strong remament component. At higher altitude the total gradient maps has been useful to give a more complex explanation of the EML taking in consideration the results obtained in previous studies. The maps at 150-200 km show that the maximum amplitude of |T| is exactly localized along the TESZ in the NW-SE direction. So, a simple contact model was performed in order to demonstrate that the main source that generates the EML is the complex fault system of the TESZ. However, the |T| maxima are positioned not only along the suture zone, but also in Central Europe, showing that the contributions to the EML derive also from sources placed in the Paleozoic platform with a reverse dipolar aspect. From these results it appears that the contributions responsible for the nature of this anomaly are to be reconnected first to the presence of the TESZ, which puts in contact two different platforms with different thicknesses, and also to the presence of bodies with a strong remanent component, which characterize part of the Central European crust.

Soil anomaly mapping using a caesium magnetometer: Limits in the low magnetic amplitude case

NASA Astrophysics Data System (ADS)

Mathé, Vivien; Lévêque, François; Mathé, Pierre-Etienne; Chevallier, Claude; Pons, Yves

2006-03-01

Caesium magnetometers are new tools for soil property mapping with a decimetric resolution [Mathé, V., Lévêque, F., 2003. High resolution magnetic survey for soil monitoring: detection of drainage and soil tillage effects. Earth and Planetary Science Letters 212 (1-2), 241-251]. However, when the magnetic anomalies are only a few nanoteslas (nT), the geologic and pedogenic signal must first be isolated from magnetic disturbances for this method to be useful. This paper investigates the instrumental artifacts and environmental disturbances to adapt the survey protocol to slightly magnetic soils. Among the possible instrumental sources of disturbances listed and quantified, the most significant are: 1) The battery effect upon sensors 2 m away (classic protocol, about ± 0.15 nT) while increasing this distance up to 10 m cancelled it; 2) The noise level of magnetometers and sensors, which, according to tests on two magnetometers and three sensors, rarely and randomly exceeds 0.1 nT, but seems to increase with the electronic component age. Among the environmental disturbances, temporal variations such as diurnal variation or fluctuations linked to the moving of metallic masses play a major role, although the pseudogradient or base-station methods have commonly cancelled them. The efficiency of the latter is strongly dependent on the source nature. However, the ground currents and electromagnetic fields propagating in soils cause more problems. As a first step to better understand such disturbance sources, uncommon magnetic signal variations supposedly due to electromagnetic wave conversions and likely linked to the railway traffic are presented. Based on previous results, an adapted protocol using one magnetometer and two caesium sensors (0.3 and 1.6 m above the surface) is proposed to increase the signal / noise ratio. At first, to maintain an accurate horizontal and vertical location of the sensors, the latter are affixed to a wooden handcart running on plastic rails. Rails adapt to micro-topography, thereby decreasing strongly the soil-sensors distance variations. Anomalies due to topography rarely exceed 0.1 nT. Finally, a method to remove diurnal variations from high-resolution magnetic maps is proposed. Parallel profiles performed successively are adjusted by a cross-profile. Assuming that the temporal variations during each profile are negligible (less than 0.05 nT), this technique, contrary to the pseudogradient, preserves both the decimetric and the metric anomalies (gain of more than 1 nT).

Engima of a thermal anomaly - A TM/AVHRR study of the volcanic Arabian highlands

NASA Technical Reports Server (NTRS)

Blodget, H. W.; Andre, C. G.; Masuoka, P. M.

1987-01-01

Discovery of a large thermal anomaly in the western Arabian highlands on Landsat TM imagery is reported. The anomaly, 15 C warmer than surroundings, forms a 2-km-wide arc around the southern flank of Jebel Chada, a volcano active in 1256 AD. It is recorded by AVHRR imagery as well, despite the 1.1-km spatial resolution of this sensor. Air photos and geologic maps show no bedrock unit that corresponds to the anomaly. Digital techniques were applied to the TM and AVHRR data, including contrast enhancement, density slicing, principal components analysis, and construction of multiband composite images. It is concluded that the anomaly results from a thin cover of volcanic ash or cinder that is optically indistinguishable from underlying basalt, rather than from internal (volcanic or hydrologic) heat sources.

Venus - Global gravity and topography

NASA Technical Reports Server (NTRS)

Mcnamee, J. B.; Borderies, N. J.; Sjogren, W. L.

1993-01-01

A new gravity field determination that has been produced combines both the Pioneer Venus Orbiter (PVO) and the Magellan Doppler radio data. Comparisonsbetween this estimate, a spherical harmonic model of degree and order 21, and previous models show that significant improvements have been made. Results are displayed as gravity contours overlaying a topographic map. We also calculate a new spherical harmonic model of topography based on Magellan altimetry, with PVO altimetry included where gaps exist in the Magellan data. This model is also of degree and order 21, so in conjunction with the gravity model, Bouguer and isostatic anomaly maps can be produced. These results are very consistent with previous results, but reveal more spatial resolution in the higher latitudes.

Model parameter estimations from residual gravity anomalies due to simple-shaped sources using Differential Evolution Algorithm

NASA Astrophysics Data System (ADS)

Ekinci, Yunus Levent; Balkaya, Çağlayan; Göktürkler, Gökhan; Turan, Seçil

2016-06-01

An efficient approach to estimate model parameters from residual gravity data based on differential evolution (DE), a stochastic vector-based metaheuristic algorithm, has been presented. We have showed the applicability and effectiveness of this algorithm on both synthetic and field anomalies. According to our knowledge, this is a first attempt of applying DE for the parameter estimations of residual gravity anomalies due to isolated causative sources embedded in the subsurface. The model parameters dealt with here are the amplitude coefficient (A), the depth and exact origin of causative source (zo and xo, respectively) and the shape factors (q and ƞ). The error energy maps generated for some parameter pairs have successfully revealed the nature of the parameter estimation problem under consideration. Noise-free and noisy synthetic single gravity anomalies have been evaluated with success via DE/best/1/bin, which is a widely used strategy in DE. Additionally some complicated gravity anomalies caused by multiple source bodies have been considered, and the results obtained have showed the efficiency of the algorithm. Then using the strategy applied in synthetic examples some field anomalies observed for various mineral explorations such as a chromite deposit (Camaguey district, Cuba), a manganese deposit (Nagpur, India) and a base metal sulphide deposit (Quebec, Canada) have been considered to estimate the model parameters of the ore bodies. Applications have exhibited that the obtained results such as the depths and shapes of the ore bodies are quite consistent with those published in the literature. Uncertainty in the solutions obtained from DE algorithm has been also investigated by Metropolis-Hastings (M-H) sampling algorithm based on simulated annealing without cooling schedule. Based on the resulting histogram reconstructions of both synthetic and field data examples the algorithm has provided reliable parameter estimations being within the sampling limits of M-H sampler. Although it is not a common inversion technique in geophysics, it can be stated that DE algorithm is worth to get more interest for parameter estimations from potential field data in geophysics considering its good accuracy, less computational cost (in the present problem) and the fact that a well-constructed initial guess is not required to reach the global minimum.

GIS-based rare events logistic regression for mineral prospectivity mapping

NASA Astrophysics Data System (ADS)

Xiong, Yihui; Zuo, Renguang

2018-02-01

Mineralization is a special type of singularity event, and can be considered as a rare event, because within a specific study area the number of prospective locations (1s) are considerably fewer than the number of non-prospective locations (0s). In this study, GIS-based rare events logistic regression (RELR) was used to map the mineral prospectivity in the southwestern Fujian Province, China. An odds ratio was used to measure the relative importance of the evidence variables with respect to mineralization. The results suggest that formations, granites, and skarn alterations, followed by faults and aeromagnetic anomaly are the most important indicators for the formation of Fe-related mineralization in the study area. The prediction rate and the area under the curve (AUC) values show that areas with higher probability have a strong spatial relationship with the known mineral deposits. Comparing the results with original logistic regression (OLR) demonstrates that the GIS-based RELR performs better than OLR. The prospectivity map obtained in this study benefits the search for skarn Fe-related mineralization in the study area.

Analysis of LANDSAT-4 TM Data for Lithologic and Image Mapping Purpose

NASA Technical Reports Server (NTRS)

Podwysocki, M. H.; Salisbury, J. W.; Bender, L. V.; Jones, O. D.; Mimms, D. L.

1984-01-01

Lithologic mapping techniques using the near infrared bands of the Thematic Mapper onboard the LANDSAT 4 satellite are investigated. These methods are coupled with digital masking to test the capability of mapping geologic materials. Data are examined under medium to low Sun angle illumination conditions to determine the detection limits of materials with absorption features. Several detection anomalies are observed and explained.

Tropical Pacific sea surface salinity variability derived from SMOS data: Comparison with in-situ observations.

NASA Astrophysics Data System (ADS)

Ballabrera, Joaquim; Hoareau, Nina; Umbert, Marta; Martínez, Justino; Turiel, Antonio

2013-04-01

Prediction of El Niño/Southern Oscillation (ENSO), and its relation with global climate anomalies, continues to be an important research effort in short-term climate forecasting. This task has become even more challenging as researchers are becoming more and more convinced that there is not a single archetypical El Niño (or La Niña) pattern, but several. During some events (called now Standard or East Pacific), the largest temperature anomalies are located at the eastern part of the Pacific. However, during some of the most recent events, the largest anomalies are restricted to the central part of the Pacific Ocean, and are now called Central Pacific or Modoki (a Japanese word for "almost") events. Although the role of salinity in operational ENSO forecasting was initially neglected (in contrast with temperature, sea level, or surface winds), recent studies have shown that salinity does play a role in the preconditioning of ENSO. Moreover, some researchers suggest that sea surface salinity might play a role (through the modulation of the western Pacific barrier layer) to favor the Standard or the Modoki nature of each event. Sea Surface Salinity maps are being operationally generated from microwave (L-band, 1.4 Ghz) brightness temperature maps. The L-band frequency was chosen because is the optimal one for ocean salinity measurements. However, after three years of satellite data, it has been found that noise in brightness temperatures (due to natural and artificial sources) is larger than expected. Moreover, the retrieval of SSS information requires special care because of the low sensitivity of the brightness temperature to SSS: from 0.2-0.8 K per salinity unit. Despite of all these facts, current accuracy of SS maps ranges from 0.2-0.4, depending on the processing level and the region being considered. We present here our study about the salinity variability in the tropical Pacific Ocean from the 9-day, 0.25 bins salinity maps derived from the SMOS reprocessing campaign released to the SMOS user community on March 2011. During the period under study, the equatorial Pacific has been in a quasi-continuous La Niña state. During the cold phases of ENSO, positive anomalies of SSS are expected with the largest anomalous values in the western warm-fresh pool. The anomalies derived from the SMOS data do indeed display a positive anomaly. The persistence of the feature, its geographical pattern, the time modulation of the anomaly amplitude indicate, and its resemblance with in situ observations indicate this novel observation technology is currently able to capture seasonal and interannual signatures of climate interest.

Investigation from Japanese MAGSAT Team. Part A. Crustal structure near Japan and in Antarctic station. Part B. Electric currents and hydromagnetic waves in the ionosphere and the magnetosphere

NASA Technical Reports Server (NTRS)

Fukushima, N. (Principal Investigator)

1981-01-01

Preliminary results of MAGSAT data analysis are described. Regional anomaly maps (deviations from the MGST model field) for X,Y,Z, and F in the area of 115 to 155 deg E and 20 to 60 deg N were obtained. A similar map for the geomagnetic total force anomaly in the vicinity of Japan showed that the observed anomaly can be explained by the difference in crustal magnetization between the Japan Sea and the Japan Island, which reflects a difference of 25 km in the thickness of the magnetized layer. The MAGSAT record of a sudden commencement of a magnetic storm above the South Atlantic Ocean showed a reverse impulse particularly in the D-component. Results relating to toroidal currents in the ionosphere, transverse and parallel perturbations over the polar regions, the relationship between field aligned currents and precipitating electrons, and the calculation of the subsatellite electric field are also discussed.

Seismic properties of the crust and uppermost mantle of North America

NASA Technical Reports Server (NTRS)

Braile, L. W.; Hinze, W. J.; Vonfrese, R. R. B.; Keller, G. R.

1983-01-01

Seismic refraction profiles for the North American continent were compiled. The crustal models compiled data on the upper mantle seismic velocity (P sub n), the crustal thickness (H sub c) and the average seismic velocity of the crystalline crust (V sub p). Compressional wave parameters were compared with shear wave data derived from surface wave dispersion models and indicate an average value for Poisson's ratio of 0.252 for the crust and of 0.273 for the uppermost mantle. Contour maps illustrate lateral variations in crustal thickness, upper mantle velocity and average seismic velocity of the crystalline crust. The distribution of seismic parameters are compared with a smoothed free air anomaly map of North America and indicate that a complidated mechanism of isostatic compensation exists for the North American continent. Several features on the seismic contour maps also correlate with regional magnetic anomalies.

Aeromagnetic anomaly patterns reveal buried faults along the eastern margin of the Wilkes Subglacial Basin (East Antarctica)

USGS Publications Warehouse

Armadillo, E.; Ferraccioli, F.; Zunino, A.; Bozzo, E.

2007-01-01

The Wilkes Subglacial Basin (WSB) is the major morphological feature recognized in the hinterland of the Transantarctic Mountains. The origin of this basin remains contentious and relatively poorly understood due to the lack of extensive geophysical exploration. We present a new aeromagnetic anomaly map over the transition between the Transantarctic Mountains and the WSB for an area adjacent to northern Victoria Land. The aeromagnetic map reveals the existence of subglacial faults along the eastern margin of the WSB. These inferred faults connect previously proposed fault zones over Oates Land with those mapped along the Ross Sea Coast. Specifically, we suggest a link between the Matusevich Frature Zone and the Priestley Fault during the Cenozoic. The new evidence for structural control on the eastern margin of the WSB implies that a purely flexural origin for the basin is unlikely.

Strong Water Isotopic Anomalies in the Martian Atmosphere: Probing Current and Ancient Reservoirs

NASA Technical Reports Server (NTRS)

Villanueva, G. L.; Mumma, M. J.; Novak, R. E.; Käufl, H. U.; Hartogh, P.; Encrenaz, T.; Tokunaga, A.; Khayat, A.; Smith, M. D.

2015-01-01

We measured maps of atmospheric water (H2O) and its deuterated form (HDO) across the martian globe, showing strong isotopic anomalies and a significant high deuterium/hydrogen (D/H) enrichment indicative of great water loss. The maps sample the evolution of sublimation from the north polar cap, revealing that the released water has a representative D/H value enriched by a factor of about 7 relative to Earth's ocean [Vienna standard mean ocean water (VSMOW)]. Certain basins and orographic depressions show even higher enrichment, whereas high-altitude regions show much lower values (1 to 3 VSMOW). Our atmospheric maps indicate that water ice in the polar reservoirs is enriched in deuterium to at least 8 VSMOW, which would mean that early Mars (4.5 billion years ago) had a global equivalent water layer at least 137 meters deep.

Strong water isotopic anomalies in the martian atmosphere: probing current and ancient reservoirs.

PubMed

Villanueva, G L; Mumma, M J; Novak, R E; Käufl, H U; Hartogh, P; Encrenaz, T; Tokunaga, A; Khayat, A; Smith, M D

2015-04-10

We measured maps of atmospheric water (H2O) and its deuterated form (HDO) across the martian globe, showing strong isotopic anomalies and a significant high deuterium/hydrogen (D/H) enrichment indicative of great water loss. The maps sample the evolution of sublimation from the north polar cap, revealing that the released water has a representative D/H value enriched by a factor of about 7 relative to Earth's ocean [Vienna standard mean ocean water (VSMOW)]. Certain basins and orographic depressions show even higher enrichment, whereas high-altitude regions show much lower values (1 to 3 VSMOW). Our atmospheric maps indicate that water ice in the polar reservoirs is enriched in deuterium to at least 8 VSMOW, which would mean that early Mars (4.5 billion years ago) had a global equivalent water layer at least 137 meters deep. Copyright © 2015, American Association for the Advancement of Science.

EMAG2: A 2-arc min resolution Earth Magnetic Anomaly Grid compiled from satellite, airborne, and marine magnetic measurements

USGS Publications Warehouse

Maus, S.; Barckhausen, U.; Berkenbosch, H.; Bournas, N.; Brozena, J.; Childers, V.; Dostaler, F.; Fairhead, J.D.; Finn, C.; von Frese, R.R.B; Gaina, C.; Golynsky, S.; Kucks, R.; Lu, Hai; Milligan, P.; Mogren, S.; Muller, R.D.; Olesen, O.; Pilkington, M.; Saltus, R.; Schreckenberger, B.; Thebault, E.; Tontini, F.C.

2009-01-01

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. ?? 2009 by the American Geophysical Union.

Regional geochemical studies in the Patagonia Mountains, Santa Cruz County, Arizona

USGS Publications Warehouse

Chaffee, M.A.; Hill, R.H.; Sutley, S.J.; Watterson, J.R.

1981-01-01

The Patagonia Mountains in southern Arizona contain the deeply buried porphyry copper system at Red Mountain as well as a number of other base- and precious-metal mines and prospects. The range contains complex Basin and Range geology with units ranging in age from Precambrian to Holocene. Rock types present include igneous intrusive and extrusive units as well as sedimentary and metamorphic units, most of which have been tectonically disturbed. A total of 264 stream-sediment samples were collected and analyzed for 32 elements. Geochemical maps for Sb, Ag, Pb, Te, B, Mn, Au, Zn, Cu (total), Cu (cold-extractable), and Mo, as well as for Cu (cold-extractable)/Cu (total) and Fe/Mn, are presented. Anomaly patterns for these elements generally occur over the Red Mountain deposit and (or) along a north-northwest trend parallel to the major Harshaw Creek Fault. Much of the entire area sampled contains widespread anomalies for Pb, Te, and Cu; the other elements are only locally anomalous. Various plots of ratios of Cu (cold-extractable) to Cu (total) did not produce any new information not readily apparent on either one of the two copper maps. A plot of ratios of Fe to Mn delineated many areas of pyrite mineralization. Several of these areas may represent the pyritic halos around deeply buried porphyry copper systems. The best ore guide for the Red Mountain porphyry system is the coincidence of positive anomalies of Mo, Pb, and Te and a negative anomaly of Mn. Other areas with anomalies of the same suite of elements are present within the Patagonia Mountains. It is concluded that geochemical sampling, even in a highly contaminated area, can be useful in delineating major geologic features, such as porphyry copper belts and major faults. Multielement geochemical surveys on a regional scale can effectively locate large, deeply buried, zoned mineral systems such as that at Red Mountain. Plots of element ratios, where adequately understood, can provide geochemical information not readily discernible from plots of single elements alone. ?? 1981.

Crop yield monitoring in the Sahel using root zone soil moisture anomalies derived from SMOS soil moisture data assimilation

NASA Astrophysics Data System (ADS)

Gibon, François; Pellarin, Thierry; Alhassane, Agali; Traoré, Seydou; Baron, Christian

2017-04-01

West Africa is greatly vulnerable, especially in terms of food sustainability. Mainly based on rainfed agriculture, the high variability of the rainy season strongly impacts the crop production driven by the soil water availability in the soil. To monitor this water availability, classical methods are based on daily precipitation measurements. However, the raingauge network suffers from the poor network density in Africa (1/10000km2). Alternatively, real-time satellite-derived precipitations can be used, but they are known to suffer from large uncertainties which produce significant error on crop yield estimations. The present study proposes to use root soil moisture rather than precipitation to evaluate crop yield variations. First, a local analysis of the spatiotemporal impact of water deficit on millet crop production in Niger was done, from in-situ soil moisture measurements (AMMA-CATCH/OZCAR (French Critical Zone exploration network)) and in-situ millet yield survey. Crop yield measurements were obtained for 10 villages located in the Niamey region from 2005 to 2012. The mean production (over 8 years) is 690 kg/ha, and ranges from 381 to 872 kg/ha during this period. Various statistical relationships based on soil moisture estimates were tested, and the most promising one (R>0.9) linked the 30-cm soil moisture anomalies from mid-August to mid-September (grain filling period) to the crop yield anomalies. Based on this local study, it was proposed to derive regional statistical relationships using 30-cm soil moisture maps over West Africa. The selected approach was to use a simple hydrological model, the Antecedent Precipitation Index (API), forced by real-time satellite-based precipitation (CMORPH, PERSIANN, TRMM3B42). To reduce uncertainties related to the quality of real-time rainfall satellite products, SMOS soil moisture measurements were assimilated into the API model through a Particular Filter algorithm. Then, obtained soil moisture anomalies were compared to 17 years of crop yield estimates from the FAOSTAT database (1998-2014). Results showed that the 30-cm soil moisture anomalies explained 89% of the crop yield variation in Niger, 72% in Burkina Faso, 82% in Mali and 84% in Senegal.

Publications - GPR 2014-4 | Alaska Division of Geological & Geophysical

Science.gov Websites

Geologic Mapping Advisory Board STATEMAP Publications Geophysics Program Information Geophysical Survey content DGGS GPR 2014-4 Publication Details Title: Farewell and Middle Styx survey areas: Project report , Inc., 2015, Farewell and Middle Styx survey areas: Project report, interpretation maps, EM anomalies

NCEP SST Analysis

Science.gov Websites

Branches Global Climate & Weather Modeling Mesoscale Modeling Marine Modeling and Analysis Contact EMC , state and local government Web resources and services. Real-time, global, sea surface temperature (RTG_SST_HR) analysis For a regional map, click the desired area in the global SST analysis and anomaly maps

Satellite monitoring temperature conditions spawning area of the Northeast Arctic cod in the Norwegian Sea and assessment its abundance

NASA Astrophysics Data System (ADS)

Vanyushin, George; Bulatova, Tatiana; Klochkov, Dmitriy; Troshkov, Anatoliy; Kruzhalov, Michail

2013-04-01

In this study, the attempt to consider the relationship between sea surface anomalies of temperature (SST anomalies °C) in spawning area of the Norwegian Arctic cod off the Lofoten islands in coastal zone of the Norwegian Sea and modern cod total stock biomass including forecasting assessment of future cod generation success. Continuous long-term database of the sea surface temperature (SST) was created on the NOAA satellites data. Mean monthly SST and SST anomalies are computed for the selected area on the basis of the weekly SST maps for the period of 1998-2012. These maps were plotted with the satellite SST data, as well as information of vessels, byoies and coastal stations. All data were classified by spawning seasons (March-April) and years. The results indicate that poor and low middle generations of cod (2001, 2006, 2007) occurred in years with negative or extremely high positive anomalies in the spawning area. The SST anomalies in years which were close to normal or some more normal significances provide conditions for appearance strong or very strong generations of cod (1998, 2000, 2002, 2004, 2005, 2006, 2008, 2009). Temperature conditions in concrete years influence on different indexes of cod directly. So, the mean temperature in spawning seasons in years 1999-2005 was ≈5,0°C and SST anomaly - +0,35°C, by the way average year significances indexes of cod were: total stock biomass - 1425,0 th.t., total spawning biomass - 460,0 th.t., recruitment (age 3+) - 535,0 mln. units and landings - 530,0 th.t. In spawning seasons 2006-2012 years the average data were following: mean SST ≈6,0°C, SST anomaly - +1,29°C, total stock biomass - 2185,0 th.t., total spawning biomass - 1211,0 th.t., recruitment (age 3+) - 821,0 mln. units and landings - 600,0 th.t. The SST and SST anomalies (the NOAA satellite data) characterize increase of decrease in input of warm Atlantic waters which form numerous eddies along the flows of the main warm currents thus creating favorable conditions for development of the cod larvae and fry and provide them with food stock, finally, direct influence on forming total stock biomass of cod and helping its population forecast. Key words: satellite monitoring of SST, Northeast Arctic cod, spawning area, maps of SST, prognosis.

Equivalent magnetization over the World's Ocean and the World Digital Magnetic Anomaly Map

NASA Astrophysics Data System (ADS)

Dyment, Jerome; Choi, Yujin; Hamoudi, Mohamed; Thébault, Erwan; Quesnel, Yoann; Roest, Walter; Lesur, Vincent

2014-05-01

As a by-product of our recent work to build a candidate model over the oceans for the second version of the World Digital Magnetic Anomaly Map (WDMAM), we derived global distributions of the equivalent magnetization in oceanic domains. In a first step, we use classic point source forward modeling on a spherical Earth to build a forward model of the marine magnetic anomalies at sea-surface. We estimate magnetization vectors using the age map of the ocean floor, the relative plate motions, the apparent polar wander path for Africa, and a geomagnetic reversal time scale. We assume two possible magnetized source geometry, involving both a 1 km-thick layer bearing a 10 A/m magnetization either on a regular spherical shell with a constant, 5 km-deep, bathymetry (simple geometry) or following the topography of the oceanic basement as defined by the bathymetry and sedimentary thickness (realistic geometry). Adding a present-day geomagnetic field model allows the computation of our initial magnetic anomaly model. In a second step, we adjust this model to the existing marine magnetic anomaly data, in order to make it consistent with these data. To do so, we extract synthetic magnetic along the ship tracks for which real data are available and we compare quantitatively the measured and computed anomalies on 100, 200 or 400 km-long sliding windows (depending the spreading rate). Among the possible comparison criteria, we discard the maximal range - too dependent on local values - and the correlation and coherency - the geographical adjustment between model and data being not accurate enough - to favor the standard deviation around the mean value. The ratio between the standard deviations of data and model on each sliding window represent an estimate of the magnetization ratio causing the anomalies, which we interpolate to adjust the initial magnetic anomaly model to the data and therefore compute a final model to be included in our WDMAM candidate over the oceanic regions lacking data. The above ratio, after division by the magnetization of 10 A/m used in the model, represents an estimate of the equivalent magnetization under the considered magnetized source geometry. The resulting distributions of equivalent magnetization are further discussed in terms of mid-ocean ridges, presence of hotspots and oceanic plateaus, and the age of the oceanic lithosphere. Global marine magnetic data sets and models represent a useful tool to assess first order magnetic properties of the oceanic lithosphere.

Crustal Structure of the Flood Basalt Province of Ethiopia from Constrained 3-D Gravity Inversion

NASA Astrophysics Data System (ADS)

Mammo, Tilahun

2013-12-01

The Oligocene Afar mantle plume resulted in the eruption of a large volume of basaltic magma, including major sequences of rhyolitic ignimbrites, in a short span of time across Ethiopia. In order to assess the impact of these magmatic processes on the crust and to investigate the general crustal configuration beneath the Ethiopian plateau, northern part of the Main Ethiopian Rift and the Afar depression, analysis and modeling of the gravity field have been conducted. The Bouguer gravity map is dominated by long-wavelength anomalies that primarily arise from the isostatic compensation of the topography. Consequently, anomalies within the crust/upper mantle are masked and quantitative interpretation becomes difficult. The long-wavelength anomalies are approximated using admittance technique and subsequently removed from the Bouguer anomalies to obtain the residual isostatic anomalies. The residual map contains both short- and intermediate-wavelength anomalies related to geologic and tectonic features. The long-wavelength regional isostatic field is used to map the crust-mantle interface and the results are in good agreement with those determined by other geophysical methods. Seismic constrained gravity inversion was performed on the isostatic residual field and series of three-dimensional models have been constructed for the structures of the crust and upper mantle beneath the uplifted and rifted flood basalt province of northern Ethiopia. The inversion results have shown that the NW plateau has thick crust that rests on normal lithospheric mantle. Afar, On the other hand, is marked by thin stretched crust resting on a low-density upper mantle indicating a hotter thermal regime and partial melt. No lithospheric mantle is observed beneath Afar. The models further indicate the presence of an extensive sub-crustal thick (~12 km on average) and high-density (~3.06 gm/cc) mafic accreted igneous layer of fractionated cumulate (magmatic underplating) beneath the NW plateau. The study suggests that the underplate was fundamental to the accretion process and may have played a role in compensating most of the plateau uplift and in localizing stresses.

Seismo-ionospheric anomalies in total electron content of the GIM and electron density of DEMETER before the 27 February 2010 M8.8 Chile earthquake

NASA Astrophysics Data System (ADS)

Ho, Yi-Ying; Jhuang, Hau-Kun; Su, Yung-Chih; Liu, Jann-Yenq

2013-06-01

In this paper we examine the pre-earthquake ionospheric anomalies by the total electron content (TEC) extracted from GIM (global ionospheric map) and the electron density (Ne) observed by the DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite during the 2010 M8.8 Chile earthquake. Temporal variations show the nighttime TEC and Ne simultaneously increase 9-19 days before the earthquake. A cross-comparison of data recorded during the period of 1 February to 3 March in 2006-2010 confirms the above temporal anomalies specifically appear in 2010. The spatial analyses show that the anomalies tend to appear over the epicenter.

Total electron content anomalies associated with global VEI4 + volcanic eruptions during 2002-2015

NASA Astrophysics Data System (ADS)

Li, Wang; Guo, Jinyun; Yue, Jianping; Shen, Yi; Yang, Yang

2016-10-01

In previous studies, little attention has been paid to the total electron content (TEC) anomalies preceding the volcanic eruption. We analyze the coupling relationship between volcanic eruption and TEC anomalies, and discuss the spatial distribution of TEC anomalies associated with volcanic geographical location. We utilize the global ionosphere map (GIM) data from the Center for Orbit Determination in Europe (CODE) to analyze TEC variations before the global volcanic eruptions indicated by VEI (Volcanic Explosivity Index) 4 + from 2002 to 2015 with the sliding interquartile range method. The results indicate the occurrence rate of TEC anomalies before great volcanic eruptions is related with the volcanic type and geographical position. The occurrence rate of TEC anomalies before stratovolcano and caldera eruptions is higher than that before shield and pyroclastic shield eruptions, and the occurrence rate of TEC anomalies has a descending trend from low latitudes to high latitudes. The TEC anomalies before the volcanic eruptions in low-mid latitudes are within the volcanic affected areas, but do not coincide with the volcanic foci. The corresponding TEC anomalies could be observed in the conjugated region, and all the TEC anomalies in the volcanic affected areas are usually close to bounds of equatorial anomaly zones. However, the TEC anomalies preceding these eruptions in high latitudes usually surround the volcano, and no TEC anomalies appear in the conjugated region. These conclusions have potential applications to the prediction of great volcanic eruptions in the future.

Surface Wave Tomography with Spatially Varying Smoothing Based on Continuous Model Regionalization

NASA Astrophysics Data System (ADS)

Liu, Chuanming; Yao, Huajian

2017-03-01

Surface wave tomography based on continuous regionalization of model parameters is widely used to invert for 2-D phase or group velocity maps. An inevitable problem is that the distribution of ray paths is far from homogeneous due to the spatially uneven distribution of stations and seismic events, which often affects the spatial resolution of the tomographic model. We present an improved tomographic method with a spatially varying smoothing scheme that is based on the continuous regionalization approach. The smoothness of the inverted model is constrained by the Gaussian a priori model covariance function with spatially varying correlation lengths based on ray path density. In addition, a two-step inversion procedure is used to suppress the effects of data outliers on tomographic models. Both synthetic and real data are used to evaluate this newly developed tomographic algorithm. In the synthetic tests, when the contrived model has different scales of anomalies but with uneven ray path distribution, we compare the performance of our spatially varying smoothing method with the traditional inversion method, and show that the new method is capable of improving the recovery in regions of dense ray sampling. For real data applications, the resulting phase velocity maps of Rayleigh waves in SE Tibet produced using the spatially varying smoothing method show similar features to the results with the traditional method. However, the new results contain more detailed structures and appears to better resolve the amplitude of anomalies. From both synthetic and real data tests we demonstrate that our new approach is useful to achieve spatially varying resolution when used in regions with heterogeneous ray path distribution.

Mineral resource potential map of the Raywood Flat Roadless Areas, Riverside and San Bernardino counties, California

USGS Publications Warehouse

Matti, Jonathan C.; Cox, Brett F.; Iverson, Stephen R.

1983-01-01

The area having moderate potential for base-metal resources forms a small zone in the eastern part of the recommended wilderness (A5-187). Within this zone, evidence provided by stream-sediment geochemistry suggests that crystalline bedrocks in several drainages contain concentrations of metallic elements. Because the terrain is inaccessible and covered with dense brush, most of the bedrock in the specific drainages containing the geochemical anomalies could not be examined. Thus, although we infer that mineral occurrences exist in the drainage basins, we have little data on which to base an estimate of their extent and quality. Locally, the crystalline rocks probably contain hydrothermal veins or disseminated occurrences where lead, copper, molybdenum, tin, cobalt, bismuth, and arsenic have been concentrated. However, the geochemical anomalies for these metals are small, and the stream drainages also are relatively small. Therefore, the inferred occurrences of metallic minerals probably are small scale, scattered, and low grade. There is only low probability that the inferred mineral occurrences are large scale.

Gravity anomaly and geoid undulation results in local areas from GEOS-3 altimeter data

NASA Technical Reports Server (NTRS)

Rapp, R. H.

1979-01-01

The adjusted GEOS-3 altimeter data, taken as averages within a data frame, have been used to construct free air anomaly and geoid undulation profiles and maps in areas of geophysical interest. Profiles were constructed across the Philippine Trench (at a latitude of 6 deg) and across the Bonin Trench (at a latitude of 28 deg). In the latter case an anomaly variation of 443 mgals in 143 km was derived from the altimeter data. These variations agreed reasonably with terrestrial estimates, considering the predicted point accuracy was about + or - 27 mgals. An area over the Patton Sea mounts was also investigated with the altimeter anomaly field agreeing well with the terrestrial data except for the point directly over the top of the sea mount. It is concluded that the GEOS-3 altimeter data is valuable not only for determining 5 deg and 1 deg x 1 deg mean anomalies, but also can be used to describe more local anomaly variations.

High-resolution aeromagnetic mapping of volcanic terrain, Yellowstone National Park

USGS Publications Warehouse

Finn, C.A.; Morgan, L.A.

2002-01-01

High-resolution aeromagnetic data acquired over Yellowstone National Park (YNP) show contrasting patterns reflecting differences in rock composition, types and degree of alteration, and crustal structures that mirror the variable geology of the Yellowstone Plateau. The older, Eocene, Absaroka Volcanic Supergroup, a series of mostly altered, andesitic volcanic and volcaniclastic rocks partially exposed in mountains on the eastern margin of YNP, produces high-amplitude, positive magnetic anomalies, strongly contrasting with the less magnetic, younger, latest Cenozoic, Yellowstone Plateau Group, primarily a series of fresh and variably altered rhyolitic rocks covering most of YNP. The Yellowstone caldera is the centerpiece of the Yellowstone Plateau; part of its boundary can be identified on the aeromagnetic map as a series of discontinuous, negative magnetic anomalies that reflect faults or zones along which extensive hydrothermal alteration is localized. The large-volume rhyolitic ignimbrite deposits of the 0.63-Ma Lava Creek Tuff and the 2.1-Ma Huckleberry Ridge Tuff, which are prominent lithologies peripheral to the Yellowstone caldera, produce insignificant magnetic signatures. A zone of moderate amplitude positive anomalies coincides with the mapped extent of several post-caldera rhyolitic lavas. Linear magnetic anomalies reflect the rectilinear fault systems characteristic of resurgent domes in the center of the caldera. Peripheral to the caldera, the high-resolution aeromagnetic map clearly delineates flow unit boundaries of pre- and post-caldera basalt flows, which occur stratigraphically below the post-caldera rhyolitic lavas and are not exposed extensively at the surface. All of the hot spring and geyser basins, such as Norris, Upper and Lower Geyser Basins, West Thumb, and Gibbon, are associated with negative magnetic anomalies, reflecting hydrothermal alteration that has destroyed the magnetic susceptibility of minerals in the volcanic rocks. Within Yellowstone Lake, which is mostly within the Yellowstone caldera, aeromagnetic lows also are associated with known hydrothermal activity in the lake. Many of the magnetic lows extend beyond the areas of alteration and hot springs, suggesting a more extensive currently active or fossil hydrothermal system than is currently mapped. Steep magnetic gradients, suggesting faults or fractures, bound the magnetic lows. This implies that fractures localize the hot springs. Magnetic gradient trends reflect the mapped Basin and Range structural trends of north and northwest, as well as northeasterly trends that parallel the regional trend of the Snake River Plain and the track of the Yellowstone hot spot which follow the Precambrian structural grain. These trends are found both at small scales such as in hydrothermal basins and at more regional fault scales, which suggests that the regional stress field and reactivated older structures may exert some control on localization of hydrothermal activity. ?? 2002 Elsevier Science B.V. All rights reserved.

Ground penetrating radar imaging of cap rock, caliche and carbonate strata

USGS Publications Warehouse

Kruse, S.E.; Schneider, J.C.; Campagna, D.J.; Inman, J.A.; Hickey, T.D.

2000-01-01

Field experiments show ground penetrating radar (GPR) can be used to image shallow carbonate stratigraphy effectively in a variety of settings. In south Florida, the position and structure of cap rock cover on limestone can be an important control on surface water flow and vegetation, but larger scale outcrops (tens of meters) of cap rock are sparse. GPR mapping through south Florida prairie, cypress swamp and hardwood hammock resolves variations in thickness and structure of cap rock to ~3 m and holds the potential to test theories for cap rock-vegetation relationships. In other settings, carbonate strata are mapped to test models for the formation of local structural anomalies. A test of GPR imaging capabilities on an arid caliche (calcrete) horizon in southeastern Nevada shows depth penetration to ~2 m with resolution of the base of caliche. GPR profiling also succeeds in resolving more deeply buried (~5 m) limestone discontinuity surfaces that record subaerial exposure in south Florida. (C) 2000 Elsevier Science B.V. All rights reserved.Field experiments show ground penetrating radar (GPR) can be used to image shallow carbonate stratigraphy effectively in a variety of settings. In south Florida, the position and structure of cap rock cover on limestone can be an important control on surface water flow and vegetation, but larger scale outcrops (tens of meters) of cap rock are sparse. GPR mapping through south Florida prairie, cypress swamp and hardwood hammock resolves variations in thickness and structure of cap rock to approx. 3 m and holds the potential to test theories for cap rock-vegetation relationships. In other settings, carbonate strata are mapped to test models for the formation of local structural anomalies. A test of GPR imaging capabilities on an arid caliche (calcrete) horizon in southeastern Nevada shows depth penetration to approx. 2 m with resolution of the base of caliche. GPR profiling also succeeds in resolving more deeply buried (approx. 5 m) limestone discontinuity surfaces that record subaerial exposure in south Florida.

Remote detection of geobotanical anomalies associated with hydrocarbon microseepage

NASA Technical Reports Server (NTRS)

Rock, B. N.

1985-01-01

As part of the continuing study of the Lost River, West Virginia NASA/Geosat Test Case Site, an extensive soil gas survey of the site was conducted during the summer of 1983. This soil gas survey has identified an order of magnitude methane, ethane, propane, and butane anomaly that is precisely coincident with the linear maple anomaly reported previously. This and other maple anomalies were previously suggested to be indicative of anaerobic soil conditions associated with hydrocarbon microseepage. In vitro studies support the view that anomalous distributions of native tree species tolerant of anaerobic soil conditions may be useful indicators of methane microseepage in heavily vegetated areas of the United States characterized by deciduous forest cover. Remote sensing systems which allow discrimination and mapping of native tree species and/or species associations will provide the exploration community with a means of identifying vegetation distributional anomalies indicative of microseepage.

Experimental Investigation into the Radar Anomalies on the Surface of Venus

NASA Technical Reports Server (NTRS)

Kohler, E.; Gavin, P.; Chevrier, V.; Johnson, Natasha M.

2012-01-01

Radar mapping of thc surface of Venus shows areas of high reflectivity (low emissivity) in the Venusian highlands at altitudes between 2.5-4.75 kilometers. The origin of the radar anomalies found in the Venusian highlands remains unclear. Most explanations of the potential causes for these radar anomalies come from theoretical work. Previous studies suggest increased surface roughness or materials with higher dielectric constants as well as surface atmospheric interactions. Several possible candidates of high-dielectric materials are tellurium) ferroelectric materials, and lead or bismuth sulfides. While previous studies have been influential in determining possible sources for the Venus anomalies, only a very few hypotheses have been verified via experimentation. This work intends to experimentally constrain the source of the radar anomalies on Venus. This study proposes to investigate four possible materials that could potentially cause the high reflectivities on the surface of Venus and tests their behavior under simulated Venusian conditions.

Boundary conformal anomalies on hyperbolic spaces and Euclidean balls

NASA Astrophysics Data System (ADS)

Rodriguez-Gomez, Diego; Russo, Jorge G.

2017-12-01

We compute conformal anomalies for conformal field theories with free conformal scalars and massless spin 1/2 fields in hyperbolic space ℍ d and in the ball B^d , for 2≤d≤7. These spaces are related by a conformal transformation. In even dimensional spaces, the conformal anomalies on ℍ2 n and B^{2n} are shown to be identical. In odd dimensional spaces, the conformal anomaly on B^{2n+1} comes from a boundary contribution, which exactly coincides with that of ℍ2 n + 1 provided one identifies the UV short-distance cutoff on B^{2n+1} with the inverse large distance IR cutoff on ℍ2 n + 1, just as prescribed by the conformal map. As an application, we determine, for the first time, the conformal anomaly coefficients multiplying the Euler characteristic of the boundary for scalars and half-spin fields with various boundary conditions in d = 5 and d = 7.

The preliminary results: Seismic ambient noise Rayleigh wave tomography around Merapi volcano, central Java, Indonesia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trichandi, Rahmantara, E-mail: rachmantara.tri@gmail.com; Yudistira, Tedi; Nugraha, Andri Dian

Ambient noise tomography is relatively a new method for imaging the shallow structure of the Earth subsurface. We presents the application of this method to produce a Rayleigh wave group velocity maps around the Merapi Volcano, Central Java. Rayleigh waves group velocity maps were reconstructed from the cross-correlation of ambient noise recorded by the DOMERAPI array which consists 43 broadband seismometers. In the processing stage, we first filtered the observation data to separatethe noise from the signal that dominated by the strong volcanic activities. Next, we cross-correlate the filtered data and stack to obtain the Green’s function for all possiblemore » station pairs. Then we carefully picked the peak of each Green’s function to estimate the dispersion trend and appliedMultiple Filter Technique to obtain the dispersion curve. Inter-station group velocity curvesare inverted to produceRayleigh wave group velocity maps for periods 1 to 10 s. The resulted Rayleigh group velocity maps show the interesting features around the Merapi Volcano which generally agree with the previous studies. Merapi-Lawu Anomaly (MLA) is emerged as a relatively low anomaly in our group velocity maps.« less

Time series of GNSS-derived ionospheric maps to detect anomalies as possible precursors of high magnitude earthquakes

NASA Astrophysics Data System (ADS)

Barbarella, M.; De Giglio, M.; Galeandro, A.; Mancini, F.

2012-04-01

The modification of some atmospheric physical properties prior to a high magnitude earthquake has been recently debated within the Lithosphere-Atmosphere-Ionosphere (LAI) Coupling model. Among this variety of phenomena the ionization of air at the higher level of the atmosphere, called ionosphere, is investigated in this work. Such a ionization occurrences could be caused by possible leaking of gases from earth crust and their presence was detected around the time of high magnitude earthquakes by several authors. However, the spatial scale and temporal domain over which such a disturbances come into evidence is still a controversial item. Even thought the ionospheric activity could be investigated by different methodologies (satellite or terrestrial measurements), we selected the production of ionospheric maps by the analysis of GNSS (Global Navigation Satellite Data) data as possible way to detect anomalies prior of a seismic event over a wide area around the epicentre. It is well known that, in the GNSS sciences, the ionospheric activity could be probed by the analysis of refraction phenomena occurred on the dual frequency signals along the satellite to receiver path. The analysis of refraction phenomena affecting data acquired by the GNSS permanent trackers is able to produce daily to hourly maps representing the spatial distribution of the ionospheric Total Electron Content (TEC) as an index of the ionization degree in the upper atmosphere. The presence of large ionospheric anomalies could be therefore interpreted in the LAI Coupling model like a precursor signal of a strong earthquake, especially when the appearance of other different precursors (thermal anomalies and/or gas fluxes) could be detected. In this work, a six-month long series of ionospheric maps produced from GNSS data collected by a network of 49 GPS permanent stations distributed within an area around the city of L'Aquila (Abruzzi, Italy), where an earthquake (M = 6.3) occurred on April 6, 2009, were investigated. Basically, the proposed methodology is able to perform a time series analysis of the TEC maps and, eventually, define the spatial and temporal domains of ionospheric disturbances. This goal was achieved by a time series analysis of the spatial dataset able to compare a local pattern of ionospheric activity with its historical mean value and detect areas where the TEC content exhibits anomalous values. This data processing shows some 1 to 2 days long anomalies about 20 days before of the seismic event (confirming also results provided in recent studies by means of ionospheric soundings).

Multispectral thermal infrared mapping of the 1 October 1988 Kupaianaha flow field, Kilauea volcano, Hawaii

USGS Publications Warehouse

Realmuto, V.J.; Hon, K.; Kahle, A.B.; Abbott, E.A.; Pieri, D.C.

1992-01-01

Multispectral thermal infrared radiance measurements of the Kupaianaha flow field were acquired with the NASA airborne Thermal Infrared Multispectral Scanner (TIMS) on the morning of 1 October 1988. The TIMS data were used to map both the temperature and emissivity of the surface of the flow field. The temperature map depicted the underground storage and transport of lava. The presence of molten lava in a tube or tumulus resulted in surface temperatures that were at least 10?? C above ambient. The temperature map also clearly defined the boundaries of hydrothermal plumes which resulted from the entry of lava into the ocean. The emissivity map revealed the boundaries between individual flow units within the Kupaianaha field. In general, the emissivity of the flows varied systematically with age but the relationship between age and emissivity was not unique. Distinct spectral anomalies, indicative of silica-rich surface materials, were mapped near fumaroles and ocean entry sites. This apparent enrichment in silica may have resulted from an acid-induced leaching of cations from the surfaces of glassy flows. Such incipient alteration may have been the cause for virtually all of the emissivity variations observed on the flow field, the spectral anomalies representing areas where the acid attack was most intense. ?? 1992 Springer-Verlag.

The Ultramafic Complex of Reinfjord: from the Magnetic Petrology to the Interpretation of the Magnetic Anomalies

NASA Astrophysics Data System (ADS)

Pastore, Zeudia; McEnroe, Suzanne; Church, Nathan; Fichler, Christine; ter Maat, Geertje W.; Fumagalli, Patrizia; Oda, Hirokuni; Larsen, Rune B.

2017-04-01

A 3D model of the geometry of the Reinfjord complex integrating geological and petrophysical data with high resolution aeromagnetic, ground magnetic and gravity data is developed. The Reinfjord ultramafic complex in northern Norway is one of the major ultramafic complexes of the Neoproterozoic Seiland Igneous Province (SIP). This province, now embedded in the Caledonian orogen, was emplaced deep in the crust (30 km of depth) and is believed to represent a section of the deep plumbing system of a large igneous province. The Reinfjord complex consists of three magmatic series formed during multiple recharging events resulting in the formation of a cylindrically zoned complex with a slightly younger dunite core surrounded by wehrlite and lherzolite units. Gabbros and gneiss form the host rock. The ultramafic complex has several distinct magnetic anomalies which do not match the mapped lithological boundaries, but are correlated with changes in magnetic susceptibilities. In particular, the deviating densities and magnetic susceptibilities at the northern side of the complex are interpreted to be due to serpentinization. Detailed studies of magnetic anomalies and magnetic properties of samples can provide a powerful tool for mapping petrological changes. Samples can have wide range of magnetic properties depending on composition, amount of ferromagnetic minerals, grain sizes and microstructures. Later geological processes such as serpentinization can alter this signal. Therefore a micro-scale study of magnetic anomalies at the thin section scale was carried out to understand better the link between the magnetic petrology and the magnetic anomalies. Serpentinization can significantly enhance the magnetic properties and therefore change the nature of the magnetic anomaly. The detailed gravity and magnetic model here presented shows the subsurface structure of the ultramafic complex refining the geological interpretation of the magnetic sources within it, and the local effects of serpentinization.

On gravity from SST, geoid from Seasat, and plate age and fracture zones in the Pacific

NASA Technical Reports Server (NTRS)

Marsh, B. D.; Marsh, J. G.; Williamson, R. G. (Principal Investigator)

1984-01-01

A composite map produced by combining 90 passes of SST data show good agreement with conventional GEM models. The SEASAT altimeter data were deduced and found to agree with both the SST and GEM fields. The maps are dominated (especially in the east) by a pattern of roughly east-west anomalies with a transverse wavelength of about 2000 km. Comparison with regional bathymetric data shows a remarkedly close correlation with plate age. Most anomalies in the east half of the Pacific could be partly caused by regional differences in plate age. The amplitude of these geoid or gravity anomalies caused by age differences should decrease with absolute plate age, and large anomalies (approximately 3 m) over old, smooth sea floor may indicate a further deeper source within or perhaps below the lithosphere. The possible plume size and ascent velocity necessary to supply deep mantle material to the upper mantle without complete thermal equilibration was considered. A plume emanating from a buoyant layer 100 km thick and 10,000 times less viscous than the surrounding mantle should have a diameter of about 400 km and must ascend at about 10 cm/yr to arrive still anomalously hot in the uppermost mantle.

Aeromagnetic maps of the Uinta and Piceance Basins and vicinity, Utah and Colorado

USGS Publications Warehouse

Grauch, V.J.S.; Plesha, Joseph L.

1989-01-01

In order to understand the evolution of sedimentary basins, it is important to understand their tectonic setting. In a U.S. Geological Survey (USGS) study of the Uinta and Piceance basins in Utah and Colorado, this understanding is approached through characterization of subsurface structure and lithology of a large region encompassing the basins. An important tool for interpreting these subsurface features is aeromagnetic data. Aeromagnetic anomalies represent variations in the strength and direction of the Earth's magnetic field that are produced by rocks containing a significant number of magnetic minerals (commonly magnetite). The shape and magnitude of an anomaly produced by one body of rock are complexly related to the amount of magnetic minerals present, the magnetic properties of those minerals (determined by a number of factors, including the history of the rock), and the shape of the rock body. In the study area, only crystalline basement rocks and volcanic rocks are likely to contain enough magnetic minerals to produce anomalies; sedimentary rocks and metasediments are generally so poor in magnetic minerals that their magnetic effects cannot be detected by the types of surveys presented in this report. Patterns of anomalies on aeromagnetic maps can reveal not only lithologic differences related to magnetite content, but structural features as well, such as faults that have juxtaposed crystalline rocks against sedimentary rocks, and upwarps of crystalline basement underlying sedimentary sequences. Tectonic features of regional extent may not become apparent until a number of aeromagnetic surveys have been compiled and plotted at the same scale. Commonly the compilation involves piecing together data from surveys that were flown at different times and have widely disparate flight specifications and data reduction procedures. The data may be compiled into a composite map, where all the pieces are plotted onto one map without regard to the differences in flight elevation and datum, or they may be compiled into a merged map, where all survey data are analytically reduced to a common flight elevation and datum, and then digitally merged at the survey boundaries. The composite map retains the original resolution of all survey data, but computer methods to enhance or model regional features crossing the survey boundaries cannot be applied. On the other hand, these computer methods can be applied to the merged data, but the resolution of the data may be somewhat diminished. This report presents both composite and merged aeromagnetic maps for a large region that includes the Uinta Basin in Utah and the Piceance basin in Colorado (fig. 1).

Merging high resolution geophysical and geochemical surveys to reduce exploration risk at glass buttes, Oregon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walsh, Patrick; Fercho, Steven; Perkin, Doug

2015-06-01

The engineering and studies phase of the Glass Buttes project was aimed at reducing risk during the early stages of geothermal project development. The project’s inclusion of high resolution geophysical and geochemical surveys allowed Ormat to evaluate the value of these surveys both independently and in combination to quantify the most valuable course of action for exploration in an area where structure, permeability, and temperature are the most pressing questions. The sizes of the thermal anomalies at Glass Buttes are unusually large. Over the course of Phase I Ormat acquired high resolution LIDAR data to accurately map fault manifestations atmore » the surface and collected detailed gravity and aeromagnetic surveys to map subsurface structural features. In addition, Ormat collected airborne hyperspectral data to assist with mapping the rock petrology and mineral alteration assemblages along Glass Buttes faults and magnetotelluric (MT) survey to try to better constrain the structures at depth. Direct and indirect identification of alteration assemblages reveal not only the geochemical character and temperature of the causative hydrothermal fluids but can also constrain areas of upflow along specific fault segments. All five datasets were merged along with subsurface lithologies and temperatures to predict the most likely locations for high permeability and hot fluids. The Glass Buttes temperature anomalies include 2 areas, totaling 60 km2 (23 mi2) of measured temperature gradients over 165° C/km (10° F/100ft). The Midnight Point temperature anomaly includes the Strat-1 well with 90°C (194 °F) at 603 m (1981 ft) with a 164 °C/km (10°F/100ft) temperature gradient at bottom hole and the GB-18 well with 71°C (160 °F) at 396 m (1300 ft) with a 182°C/km (11°F/100ft) gradient. The primary area of alteration and elevated temperature occurs near major fault intersections associated with Brothers Fault Zone and Basin and Range systems. Evidence for faulting is observed in each data set as follows. Field observations include fault plane orientations, complicated fault intersections, and hydrothermal alteration apparently pre-dating basalt flows. Geophysical anomalies include large, linear gradients in gravity and aeromagnetic data with magnetic lows possibly associated with alteration. Resistivity low anomalies also appear to have offsets associated with faulting. Hyperspectral and XRF identified alteration and individual volcanic flow units, respectively. When incorporated into a 3D geologic model, the fault intersections near the highest proven temperature and geophysical anomalies provide the first priority targets at Midnight Point. Ormat geologists selected the Midnight Point 52-33 drilling target based on a combination of pre-existing drilling data, geologic field work, geophysical interpretation, and geochemical analysis. Deep temperatures of well 52-33 was lower than anticipated. Temperature gradients in the well mirrored those found in historical drilling, but they decreased below 1500 ft and were isothermal below 2000 ft.« less

A comparative study of linear and nonlinear anomaly detectors for hyperspectral imagery

NASA Astrophysics Data System (ADS)

Goldberg, Hirsh; Nasrabadi, Nasser M.

2007-04-01

In this paper we implement various linear and nonlinear subspace-based anomaly detectors for hyperspectral imagery. First, a dual window technique is used to separate the local area around each pixel into two regions - an inner-window region (IWR) and an outer-window region (OWR). Pixel spectra from each region are projected onto a subspace which is defined by projection bases that can be generated in several ways. Here we use three common pattern classification techniques (Principal Component Analysis (PCA), Fisher Linear Discriminant (FLD) Analysis, and the Eigenspace Separation Transform (EST)) to generate projection vectors. In addition to these three algorithms, the well-known Reed-Xiaoli (RX) anomaly detector is also implemented. Each of the four linear methods is then implicitly defined in a high- (possibly infinite-) dimensional feature space by using a nonlinear mapping associated with a kernel function. Using a common machine-learning technique known as the kernel trick all dot products in the feature space are replaced with a Mercer kernel function defined in terms of the original input data space. To determine how anomalous a given pixel is, we then project the current test pixel spectra and the spectral mean vector of the OWR onto the linear and nonlinear projection vectors in order to exploit the statistical differences between the IWR and OWR pixels. Anomalies are detected if the separation of the projection of the current test pixel spectra and the OWR mean spectra are greater than a certain threshold. Comparisons are made using receiver operating characteristics (ROC) curves.

Glacier mass balance in high-arctic areas with anomalous gravity

NASA Astrophysics Data System (ADS)

Sharov, A.; Rieser, D.; Nikolskiy, D.

2012-04-01

All known glaciological models describing the evolution of Arctic land- and sea-ice masses in changing climate treat the Earth's gravity as horizontally constant, but it isn't. In the High Arctic, the strength of the gravitational field varies considerably across even short distances under the influence of a density gradient, and the magnitude of free air gravity anomalies attains 100 mGal and more. On long-term base, instantaneous deviations of gravity can have a noticeable effect on the regime and mass budget of glaciological objects. At best, the gravity-induced component of ice mass variations can be determined on topographically smooth, open and steady surfaces, like those of arctic planes, regular ice caps and landfast sea ice. The present research is devoted to studying gravity-driven impacts on glacier mass balance in the outer periphery of four Eurasian shelf seas with a very cold, dry climate and rather episodic character of winter precipitation. As main study objects we had chosen a dozen Russia's northernmost insular ice caps, tens to hundreds of square kilometres in extent, situated in a close vicinity of strong gravity anomalies and surrounded with extensive fields of fast and/or drift ice for most of the year. The supposition about gravitational forcing on glacioclimatic settings in the study region is based on the results of quantitative comparison and joint interpretation of existing glacier change maps and available data on the Arctic gravity field and solid precipitation. The overall mapping of medium-term (from decadal to half-centennial) changes in glacier volumes and quantification of mass balance characteristics in the study region was performed by comparing reference elevation models of study glaciers derived from Russian topographic maps 1:200,000 (CI = 20 or 40 m) representing the glacier state as in the 1950s-1980s with modern elevation data obtained from satellite radar interferometry and lidar altimetry. Free-air gravity anomalies were graphically represented in the reference model geometry using Russian gravimetric maps 1:1000000 (1980s), ArcGP grid (2008) and GOCE gravity field data (Release 3, 2009-2011). 25-year long records of daily precipitation obtained from 38 coastal stations were involved in the causality analysis. Strong positive distance-weighted correlation was discovered between the magnitude of geopotential and gravity gradient on one hand and the precipitation amount, annual number of precipitation "events" and glacier elevation changes on the other, while it was noted that the correlation decreases in humid and mountainous areas. Relevant analytical and geophysical explanations were provided and tested using the basic concepts of hydrostatic stress, lapse rate and non-orographic gradient precipitation. It was concluded that the gravitational impact on the mass balance of arctic maritime ice caps is threefold. 1) Lateral variations of gravity influence directly the ambient lapse rate thereby modulating the atmospheric stability and leading to the increased intensity and frequency of heavy snowfalls over the areas with positive gravity anomalies. 2) Glacier ice deformation, flow, calving and meltwater runoff are gravity-driven phenomena, and the removal of glacier ice is closely interrelated with geopotential variations nearby. 3) Gravity anomalies affect processes of sea ice grow, drift and consolidation resulting in generally lower concentration and lesser thickness of the sea ice found in the aquatories with positive gravity. The advection of moist air to insular ice caps facilitates sea-effect snow events and makes glacier mass balance more positive. The effect is enhanced when the air mass advects toward the centre of positive anomaly. The idea about gradient (deviatoric) precipitation and related cryogravic processes does not contradict to the concept of gravity waves and has some analogy with the hypothesis on "ice lichens" devised by E.Gernet 80 years ago. Further analogies can be learned from another industry, e.g. technical chemistry. Several questions associated with the variability of evaporation, ice nucleation, aerosol deposition and snow redistribution in the heterogeneous field of gravity remain open.

Continental magnetic anomaly constraints on continental reconstruction

NASA Technical Reports Server (NTRS)

Vonfrese, R. R. B.; Hinze, W. J.; Olivier, R.; Bentley, C. R.

1985-01-01

Crustal magnetic anomalies mapped by the MAGSAT satellite for North and South America, Europe, Africa, India, Australia and Antarctica and adjacent marine areas were adjusted to a common elevation of 400 km and differentially reduced to the radial pole of intensity 60,000 nT. These radially polarized anomalies are normalized for differential inclination, declination and intensity effects of the geomagnetic field, so that in principle they directly reflected the geometric and magnetic polarization attributes of sources which include regional petrologic variations of the crust and upper mantle, and crustal thickness and thermal perturbations. Continental anomalies demonstrate remarkably detailed correlation of regional magnetic sources across rifted margins when plotted on a reconstruction of Pangea. Accordingly, they suggest further fundamental constraints on the geologic evolution of the continents and their reconstructions.

Midlatitude atmospheric responses to Arctic sensible heat flux anomalies in Community Climate Model, Version 4: Atmospheric Response to Arctic SHFs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mills, Catrin M.; Cassano, John J.; Cassano, Elizabeth N.

Possible linkages between Arctic sea ice loss and midlatitude weather are strongly debated in the literature. We analyze a coupled model simulation to assess the possibility of Arctic ice variability forcing a midlatitude response, ensuring consistency between atmosphere, ocean, and ice components. We work with weekly running mean daily sensible heat fluxes with the self-organizing map technique to identify Arctic sensible heat flux anomaly patterns and the associated atmospheric response, without the need of metrics to define the Arctic forcing or measure the midlatitude response. We find that low-level warm anomalies during autumn can build planetary wave patterns that propagatemore » downstream into the midlatitudes, creating robust surface cold anomalies in the eastern United States.« less

Petroleum system of Northwest Java basin based on gravity data analysis

NASA Astrophysics Data System (ADS)

Widianto, E.

2018-01-01

Energy management in the upstream oil and gas sector becomes very important for the country’s energy security. The renewal of energy resources and reserves becomes necessary and is a must. In the oil and gas industry, gravity data is usually used only for regional surveys, but with the development of instrumentation technology and gravity software development, this method can be used for assessing oil and gas survey stages from exploration to production. This study was conducted to evaluate aspects of petroleum system and exploration play concept in the part of Northwest Java Basin, covering source rock deposition regions (source kitchen area, migration direction), development of reservoirs, structural and stratigraphic trap, based on gravity data. This study uses data from Bouguer gravity anomaly map by filtering process to produce a residual map depicting sedimentation basin configuration. The mapping generated 20 sedimentary basins in Java Island with the total hydrocarbon resources of 113 BBOE (Billion Barrel of Oil Equivalent). The petroleum system analysis was conducted in the Northwest Basin section. The final map produced illustrates the condition of petroleum system and play concept that can be used as exploration direction, expectedly reducing the risk of drilling failure.

Mars topography harmonics and geophysical implications

NASA Technical Reports Server (NTRS)

Bills, B. G.; Ferrari, A. J.

1978-01-01

The paper describes an improved model of Martian global topography which has been obtained by fitting a sixteenth-degree harmonic series to occultation, radar, spectral, and photogrammetric measurements. Empirical elevation data based on photographic data are used to supplement the observations in areas without data. Values for the mean radius, the mean density, and the displacement of the center of the figure from the center of mass are presented. The reported geometric flattening is too great and the reported dynamic flattening is too small for Mars to be homogeneous and hydrostatic. Maps of the data distribution, global topography, and Bouguer gravity anomaly are interpreted in terms of a crustal thickness map which is consistent with gravity, topography, and recent preliminary Viking seismic results.

Characterization of Arctic Highly Magnetic Domains - the Geophysical Expression of Inferred Large Igneous Province(s)

NASA Astrophysics Data System (ADS)

Saltus, R. W.; Oakey, G.; Miller, E. L.; Jackson, R.

2012-12-01

The magnetic anomalies of the high arctic are dominated by a large domain (1000 x 1700 km; the High Arctic Magnetic High, HAMH) consisting of numerous high-amplitude magnetic high ridges with a complex set of orientations and by other smaller, but still fundamentally highly magnetic, domains. The magnetic potential anomaly field (also known as pseudogravity) of the HAMH shows a single large intensity high and underscores the crustal-scale thickness of this geophysical feature (which also forms a prominent anomaly on satellite magnetic maps). The seafloor morphology of this region includes the complex linear trends of the Alpha and Mendeleev ridges, but the magnetic expression of this domain extends beyond the complex bathymetry to include areas where Canada Basin sediments have covered the complex basement topography. The calculated magnetic effect of the bathymetric ridges matches some of the observed magnetic anomalies, but not others. We have analyzed and modeled the distinctive HAMH and other smaller magnetic high domains to generate estimates of their volume and to characterize the directionality of their component features. Complimentary processing and modeling of high arctic gravity anomalies allows characterization of the density component of these geophysical features. Spatially, the HAMH encompasses the Alpha and Mendeleev "ridges," that are considered to represent a major mafic igneous province. The term "Alpha-Mendeleev Large Igneous Province" is given to a domain mapped by tracing magnetic anomalies in a recent map published by AAPG (Grantz and others, 2009). On this map the province is described as "alkali basalt with ages between 120 and 90 Ma". New seismic and bathymetric data, collected as part of on-going research efforts for definition of extended continental shelf, are revealing new details about the Alpha ridge. One interesting development is the possible identification of a supervolcano that may represent a major locus of igneous activity. In the broader Arctic region, the term High Arctic Large Igneous Province (HALIP) refers to (now) scattered parts of a major plume-type basaltic eruption, many of which also show as magnetic highs on the current data compilation. Rocks that contribute to this province have been mapped in Arctic Canada, Greenland, Svalbard, Franz Josef Land and the DeLong Islands. Most HALIP volcanic rocks do not have reliable reported radiometric ages but seem to indicate two pulses of magmatism of around 130-120 Ma and 90-80 Ma. There are many fundamental open questions regarding the evolution of the Arctic, particularly for the opening and development of the Amerasian side. The mafic igneous rocks and their roots that make up large igneous provinces are a good target for regional magnetic interpretation. Our goal is to use a data-driven approach to characterize the geometries and volumes these features as the expression of major mafic (basaltic) elements to aid in tectonic reconstruction and understanding.

ADMAP-2: The next-generation Antarctic magnetic anomaly map

NASA Astrophysics Data System (ADS)

Golynsky, Alexander; Golynsky, Dmitry; Ferraccioli, Fausto; Jordan, Tom; Damaske, Detlef; Blankenship, Don; Holt, Jack; Young, Duncan; Ivanov, Sergey; Kiselev, Alexander; Jokat, Wilfried; Gohl, Karsten; Eagles, Graeme; Bell, Robin; Armadillo, Egidio; Bozzo, Emanuelle; Caneva, Giorgio; Finn, Carol; Forsberg, Rene; Aitken, Alan

2017-04-01

The Antarctic Digital Magnetic Anomaly Project compiled the first international magnetic anomaly map of the Antarctic region south of 60°S (ADMAP-1) some six years after its 1995 launch (Golynsky et al., 2001; Golynsky et al., 2007; von Frese et al., 2007). This magnetic anomaly compilation provided new insights into the structure and evolution of Antarctica, including its Proterozoic-Archaean cratons, Proterozoic-Palaeozoic orogens, Palaeozoic-Cenozoic magmatic arc systems, continental rift systems and rifted margins, large igneous provinces and the surrounding oceanic gateways. The international working group produced the ADMAP-1 database from more than 1.5 million line-kilometres of terrestrial, airborne, marine and satellite magnetic observations collected during the IGY 1957-58 through 1999. Since the publication of the first magnetic anomaly map, the international geomagnetic community has acquired more than 1.9 million line-km of new airborne and marine data. This implies that the amount of magnetic anomaly data over the Antarctic continent has more than doubled. These new data provide important constraints on the geology of the enigmatic Gamburtsev Subglacial Mountains and Prince Charles Mountains, Wilkes Land, Dronning Maud Land, and other largely unexplored Antarctic areas (Ferraccioli et al., 2011, Aitken et al., 2014¸ Mieth & Jokat, 2014, Golynsky et al., 2013). The processing of the recently acquired data involved quality assessments by careful statistical analysis of the crossover errors. All magnetic data used in the ADMAP-2 compilation were delivered as profiles, although several of them were in raw form. Some datasets were decimated or upward continued to altitudes of 4 km or higher with the higher frequency geological signals smoothed out. The line data used for the ADMAP-1 compilation were reprocessed for obvious errors and residual corrugations. The new near-surface magnetic data were corrected for the international geomagnetic reference field and diurnal effects, edited for high-frequency errors, and levelled to minimize line-correlated noise. The magnetic anomaly data collected mainly in the 21-st century clearly cannot be simply stitched together with the previous surveys. Thus, mutual levelling adjustments were required to accommodate overlaps in these surveys. The final compilation merged all the available aeromagnetic and marine grids to create the new composite grid of the Antarctic with minimal mismatch along the boundaries between the datasets. Regional coverage gaps in the composite grid will be filled with anomaly estimates constrained by both the near-surface data and satellite magnetic observations taken mainly from the CHAMP and Swarm missions. Magnetic data compilations are providing tantalizing new views into regional-scale subglacial geology and crustal architecture in interior of East and West Antarctica. The ADMAP-2 map provides a new geophysical foundation to better understand the geological structure and tectonic history of Antarctica and surrounding marine areas. In particular, it will provide improved constraints on the lithospheric transition of Antarctica to its oceanic basins, and thus enable improved interpretation of the geodynamic evolution of the Antarctic lithosphere that was a key component in the assembly and break-up of the Rodinia and Gondwana supercontinents. This work was supported by the Korea Polar Research Institute.

Performance metrics for state-of-the-art airborne magnetic and electromagnetic systems for mapping and detection of unexploded ordnance

NASA Astrophysics Data System (ADS)

Doll, William E.; Bell, David T.; Gamey, T. Jeffrey; Beard, Les P.; Sheehan, Jacob R.; Norton, Jeannemarie

2010-04-01

Over the past decade, notable progress has been made in the performance of airborne geophysical systems for mapping and detection of unexploded ordnance in terrestrial and shallow marine environments. For magnetometer systems, the most significant improvements include development of denser magnetometer arrays and vertical gradiometer configurations. In prototype analyses and recent Environmental Security Technology Certification Program (ESTCP) assessments using new production systems the greatest sensitivity has been achieved with a vertical gradiometer configuration, despite model-based survey design results which suggest that dense total-field arrays would be superior. As effective as magnetometer systems have proven to be at many sites, they are inadequate at sites where basalts and other ferrous geologic formations or soils produce anomalies that approach or exceed those of target ordnance items. Additionally, magnetometer systems are ineffective where detection of non-ferrous ordnance items is of primary concern. Recent completion of the Battelle TEM-8 airborne time-domain electromagnetic system represents the culmination of nearly nine years of assessment and development of airborne electromagnetic systems for UXO mapping and detection. A recent ESTCP demonstration of this system in New Mexico showed that it was able to detect 99% of blind-seeded ordnance items, 81mm and larger, and that it could be used to map in detail a bombing target on a basalt flow where previous airborne magnetometer surveys had failed. The probability of detection for the TEM-8 in the blind-seeded study area was better than that reported for a dense-array total-field magnetometer demonstration of the same blind-seeded site, and the TEM-8 system successfully detected these items with less than half as many anomaly picks as the dense-array total-field magnetometer system.

Cerium anomaly at microscale in fossils.

PubMed

Gueriau, Pierre; Mocuta, Cristian; Bertrand, Loïc

2015-09-01

Patterns in rare earth element (REE) concentrations are essential instruments to assess geochemical processes in Earth and environmental sciences. Excursions in the "cerium anomaly" are widely used to inform on past redox conditions in sediments. This proxy resources to the specificity of cerium to adopt both the +III and +IV oxidation states, while most rare earths are purely trivalent and share very similar reactivity and transport properties. In practical terms, the level of cerium anomaly is established through elemental point quantification and profiling. All these models rely on a supposed homogeneity of the cerium oxidation state within the samples. However, this has never been demonstrated, whereas the cerium concentration can significantly vary within a sample, as shown for fossils, which would vastly complicate interpretation of REE patterns. Here, we report direct micrometric mapping of Ce speciation through synchrotron X-ray absorption spectroscopy and production of local rare earth patterns in paleontological fossil tissues through X-ray fluorescence mapping. The sensitivity of the approach is demonstrated on well-preserved fishes and crustaceans from the Late Cretaceous (ca. 95 million years (Myr) old). The presence of Ce under the +IV form within the fossil tissues is attributed to slightly oxidative local conditions of burial and agrees well with the limited negative cerium anomaly observed in REE patterns. The [Ce(IV)]/[Ce(tot)] ratio appears remarkably stable at the microscale within each fossil and is similar between fossils from the locality. Speciation maps were obtained from an original combination of synchrotron microbeam X-ray fluorescence, absorption spectroscopy, and diffraction, together with light and electron microscopy. This work also highlights the need for more systematic studies of cerium geochemistry at the microscale in paleontological contexts, in particular across fossil histologies.

Temperature anomalies in the Lower Suwannee River and tidal creeks, Florida, 2005

USGS Publications Warehouse

Raabe, Ellen A.; Bialkowska-Jelinska, Elzbieta

2007-01-01

Temperature anomalies in coastal waters were detected with Thermal Infrared imagery of the Lower Suwannee River (LSR) and nearshore tidal marshes on Florida’s Gulf Coast. Imagery included 1.5-m-resolution day and night Thermal Infrared (TIR) and 0.75-m-resolution Color Infrared (CIR) imagery acquired on 2-3 March 2005. Coincident temperature readings were collected on the ground and used to calibrate the imagery. The Floridan aquifer is at or near the land surface in this area and bears a constant temperature signature of ~ 22 degrees Celsius. This consistent temperature contrasts sharply with ambient temperatures during winter and summer months. Temperature anomalies identified in the imagery during a late-winter cold spell may be correlated with aquifer seeps. Hot spots were identified as those areas exceeding ambient water temperature by 4 degrees Celsius or more. Warm-water plumes were also mapped for both day and night imagery. The plume from Manatee Spring, a first-order magnitude spring, influenced water temperature in the lower river. Numerous temperature anomalies were identified in small tributaries and tidal creeks from Shired Island to Cedar Key and were confirmed with field reconnaissance. Abundant warm-water features were identified along tidal creeks south of the Suwannee River and near Waccasassa Bay. Features were mapped in the tidal creeks north of the river but appear to be less common or have lower associated discharge. The imagery shows considerable promise in mapping coastal-aquifer seeps and understanding the underlying geology of the region. Detection of seep locations may aid research in groundwater/surface-water interactions and water quality, and in the management of coastal habitats.

Precambrian basement geologic map of Montana; an interpretation of aeromagnetic anomalies

USGS Publications Warehouse

Sims, P.K.; O'Neill, J. M.; Bankey, Viki; Anderson, E.

2004-01-01

Newly compiled aeromagnetic anomaly data of Montana, in conjunction with the known geologic framework of basement rocks, have been combined to produce a new interpretive geologic basement map of Montana. Crystalline basement rocks compose the basement, but are exposed only in the cores of mountain ranges in southwestern Montana. Principal features deduced from the map are: (1) A prominent northeast-trending, 200-km-wide zone of spaced negative anomalies, which extends more than 700 km from southwestern Montana's Beaverhead Mountains to the Canadian border and reflects suturing of the Archean Mexican Hat Block against the Archean Wyoming Province along the Paleoproterozoic Trans-Montana Orogen (new name) at about 1.9-1.8 Ga; (2) North-northwest-trending magnetic lows in northeastern Montana, which reflect the 1.9-1.8 Ga Trans-Hudson Orogen and truncate the older Trans-Montana Zone; and (3) Subtle northwest- and west-trending negative anomalies in central and western Montana, which represent the northernmost segment of brittle-ductile transcurrent faults of the newly recognized Mesoproterozoic Trans-Rocky Mountain fault system. Structures developed in the Proterozoic provided zones of crustal weakness reactivated during younger Proterozoic and Phanerozoic igneous and tectonic activity. For example, the Trans-Montana Zone guided basement involved thrust faulting in southwestern Montana during the Sevier Orogeny. The Boulder Batholith and associated ore deposits and the linear belt of alkaline intrusions to the northeast were localized along a zone of weakness between the Missouri River suture and the Dillon shear zone of the Trans-Montana Orogen. The northwest-trending faults of Trans-Rocky Mountain system outline depocenters for sedimentary rocks in the Belt Basin. This fault system provided zones of weakness that guided Laramide uplifts during basement crustal shortening. Northwest-trending zones have been locally reactivated during Neogene basin-range extension.

Use of MAGSAT anomaly data for crustal structure and mineral resources in the US midcontinent

NASA Technical Reports Server (NTRS)

Carmichael, R. S.

1983-01-01

Magnetic field data acquired by NASA's MAGSAT satellite is used to construct a long-wavelength magnetic anomaly map for the U.S. midcontinent. This aids in interpretation of gross crustal geology (structure, lithologic composition, resource potential) of the region. Magnetic properties of minerals and rocks are investigated and assessed, to help in evaluation and modelling of crustal magnetization sources and depth to the Curie-temperature isotherm.

Absolute Positioning Using The Earth’s Magnetic Anomaly Field

DTIC Science & Technology

2016-09-15

many of these limitations. We present a navigation filter which uses the Earth’s magnetic anomaly field as a navigation signal to aid an inertial...navigation system (INS) in an aircraft. The filter utilizes highly-accurate optically pumped cesium (OPC) magnetometers to make scalar intensity...measurements of the Earth’s magnetic field and compare them to a map using a marginalized particle filter approach. The accuracy of these mea- surements allows

Areas with Surface Thermal Anomalies as Detected by ASTER and LANDSAT Data around Pinkerton Hot Springs, Colorado

DOE Data Explorer

Khalid Hussein

2012-02-01

This map shows areas of anomalous surface temperature in northern Saguache Counties identified from ASTER and LANDSAT thermal data and spatial based insolation model. The temperature for the ASTER data was calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas having anomalous temperature in the ASTER data are shown in blue diagonal hatch, while areas having anomalous temperature in the LANDSAT data are shown in magenta on the map. Thermal springs and areas with favorable geochemistry are also shown. Springs or wells having non-favorable geochemistry are shown as blue dots.

Areas with Surface Thermal Anomalies as Detected by ASTER and LANDSAT Data in Northwest Delta, Colorado

DOE Data Explorer

Khalid Hussein

2012-02-01

This map shows areas of anomalous surface temperature in northern Saguache Counties identified from ASTER and LANDSAT thermal data and spatial based insolation model. The temperature for the ASTER data was calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas having anomalous temperature in the ASTER data are shown in blue diagonal hatch, while areas having anomalous temperature in the LANDSAT data are shown in magenta on the map. Thermal springs and areas with favorable geochemistry are also shown. Springs or wells having non-favorable geochemistry are shown as blue dots.

Areas with Surface Thermal Anomalies as Detected by ASTER and LANDSAT Data in Ouray, Colorado

DOE Data Explorer

Khalid Hussein

2012-02-01

This map shows areas of anomalous surface temperature in Ouray identified from ASTER and LANDSAT thermal data and spatial based insolation model. The temperature for the ASTER data was calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas having anomalous temperature in the ASTER data are shown in blue diagonal hatch, while areas having anomalous temperature in the LANDSAT data are shown in magenta on the map. Thermal springs and areas with favorable geochemistry are also shown. Springs or wells having non-favorable geochemistry are shown as blue dots.

Areas with Surface Thermal Anomalies as Detected by ASTER and LANDSAT Data in Southwest Steamboat Springs, Garfield County, Colorado

DOE Data Explorer

Khalid Hussein

2012-02-01

This map shows areas of anomalous surface temperature around south Steamboat Springs as identified from ASTER and LANDSAT thermal data and spatial based insolation model. The temperature for the ASTER data was calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas having anomalous temperature in the ASTER data are shown in blue diagonal hatch, while areas having anomalous temperature in the LANDSAT data are shown in magenta on the map. Thermal springs and areas with favorable geochemistry are also shown. Springs or wells having non-favorable geochemistry are shown as blue dots.

Areas with Surface Thermal Anomalies as Detected by ASTER and LANDSAT Data in Northern Saguache County, Colorado

DOE Data Explorer

Khalid Hussein

2012-02-01

This map shows areas of anomalous surface temperature in northern Saguache Counties identified from ASTER and LANDSAT thermal data and spatial based insolation model. The temperature for the ASTER data was calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas having anomalous temperature in the ASTER data are shown in blue diagonal hatch, while areas having anomalous temperature in the LANDSAT data are shown in magenta on the map. Thermal springs and areas with favorable geochemistry are also shown. Springs or wells having non-favorable geochemistry are shown as blue dots.

High resolution coherence domain depth-resolved nailfold capillaroscopy based on correlation mapping optical coherence tomography

NASA Astrophysics Data System (ADS)

Subhash, Hrebesh M.; O'Gorman, Sean; Neuhaus, Kai; Leahy, Martin

2014-03-01

In this paper we demonstrate a novel application of correlation mapping optical coherence tomography (cm-OCT) for volumetric nailfold capillaroscopy (NFC). NFC is a widely used non-invasive diagnostic method to analyze capillary morphology and microvascular abnormalities of nailfold area for a range of disease conditions. However, the conventional NFC is incapable of providing volumetric imaging, when volumetric quantitative microangiopathic parameters such as plexus morphology, capillary density, and morphologic anomalies of the end row loops most critical. cm-OCT is a recently developed well established coherence domain magnitude based angiographic modality, which takes advantage of the time-varying speckle effect, which is normally dominant in the vicinity of vascular regions compared to static tissue region. It utilizes the correlation coefficient as a direct measurement of decorrelation between two adjacent B-frames to enhance the visibility of depth-resolved microcirculation.

A nonlinear background removal method for seismo-ionospheric anomaly analysis under a complex solar activity scenario: A case study of the M9.0 Tohoku earthquake

NASA Astrophysics Data System (ADS)

He, Liming; Wu, Lixin; Pulinets, Sergey; Liu, Shanjun; Yang, Fan

2012-07-01

A precise determination of ionospheric total electron content (TEC) anomaly variations that are likely associated with large earthquakes as observed by global positioning system (GPS) requires the elimination of the ionospheric effect from irregular solar electromagnetic radiation. In particular, revealing the seismo-ionospheric anomalies when earthquakes occurred during periods of high solar activity is of utmost importance. To overcome this constraint, a multiresolution time series processing technique based on wavelet transform applicable to global ionosphere map (GIM) TEC data was used to remove the nonlinear effect from solar radiation for the earthquake that struck Tohoku, Japan, on 11 March, 2011. As a result, it was found that the extracted TEC have a good correlation with the measured solar extreme ultraviolet flux in 26-34 nm (EUV26-34) and the 10.7 cm solar radio flux (F10.7). After removing the influence of solar radiation origin in GIM TEC, the analysis results show that the TEC around the forthcoming epicenter and its conjugate were significantly enhanced in the afternoon period of 8 March 2011, 3 days before the earthquake. The spatial distributions of the TEC anomalous and extreme enhancements indicate that the earthquake preparation process had brought with a TEC anomaly area of size approximately 1650 and 5700 km in the latitudinal and longitudinal directions, respectively.

Atypical coordination of cortical oscillations in response to speech in autism

PubMed Central

Jochaut, Delphine; Lehongre, Katia; Saitovitch, Ana; Devauchelle, Anne-Dominique; Olasagasti, Itsaso; Chabane, Nadia; Zilbovicius, Monica; Giraud, Anne-Lise

2015-01-01

Subjects with autism often show language difficulties, but it is unclear how they relate to neurophysiological anomalies of cortical speech processing. We used combined EEG and fMRI in 13 subjects with autism and 13 control participants and show that in autism, gamma and theta cortical activity do not engage synergistically in response to speech. Theta activity in left auditory cortex fails to track speech modulations, and to down-regulate gamma oscillations in the group with autism. This deficit predicts the severity of both verbal impairment and autism symptoms in the affected sample. Finally, we found that oscillation-based connectivity between auditory and other language cortices is altered in autism. These results suggest that the verbal disorder in autism could be associated with an altered balance of slow and fast auditory oscillations, and that this anomaly could compromise the mapping between sensory input and higher-level cognitive representations. PMID:25870556

Mapping of radiation anomalies using UAV mini-airborne gamma-ray spectrometry.

PubMed

Šálek, Ondřej; Matolín, Milan; Gryc, Lubomír

2018-02-01

Localization of size-limited gamma-ray anomalies plays a fundamental role in uranium prospecting and environmental studies. Possibilities of a newly developed mini-airborne gamma-ray spectrometric equipment were tested on a uranium anomaly near the village of Třebsko, Czech Republic. The measurement equipment was based on a scintillation gamma-ray spectrometer specially developed for unmanned aerial vehicles (UAV) mounted on powerful hexacopter. The gamma-ray spectrometer has two 103 cm 3 BGO scintillation detectors of relatively high sensitivity. The tested anomaly, which is 80 m by 40 m in size, was investigated by ground gamma-ray spectrometric measurement in a detail rectangular measurement grid. Average uranium concentration is 25 mg/kg eU attaining 700 mg/kg eU locally. The mini-airborne measurement across the anomaly was carried out on three 100 m long parallel profiles at eight flight altitudes from 5 to 40 m above the ground. The resulting 1 s 1024 channel gamma-ray spectra, recorded in counts per second (cps), were processed to concentration units of K, U and Th, while total count (TC) was reported in cps. Increased gamma ray intensity of the anomaly was indicated by mini-airborne measurement at all profiles and altitudes, including the highest altitude of 40 m, at which the recorded intensity is close to the natural radiation background. The reported instrument is able to record data with comparable quality as standard airborne survey, due to relative sensitive detector, lower flight altitude and relatively low flight speed of 1 m/s. The presented experiment brings new experience with using unmanned semi-autonomous aerial vehicles and the latest mini-airborne radiometric instrument. The experiment has demonstrated the instrument's ability to localize size-limited uranium anomalies. Copyright © 2017 Elsevier Ltd. All rights reserved.

Assessment of ERTS-1 imagery as a tool for regional geological analysis in New York State. [Lake Ontario

NASA Technical Reports Server (NTRS)

Isachsen, Y. W. (Principal Investigator); Fakundiny, R. H.; Forster, S. W.

1974-01-01

The author has identified the following significant results. Linear anomalies dominate the new geological information derived from ERTS-1 imagery, total lengths now exceeding 26,500 km. Maxima on rose diagrams for ERTS-1 anomalies correspond well with those for mapped faults and topographic lineaments. Multi-scale analysis of linears shows that single topographic linears at 1:2,500,000 may become dashed linears at 1:1,000,000 aligned zones of shorter parallel, en echelon, or conjugate linears at 1:5000,000, and shorter linears lacking any conspicuous zonal alignment at 1:250,000. Field work in the Catskills suggests that the prominent new NNE lineaments may be surface manifestations of dip slip faulting in the basement, and that it may become possible to map major joint sets over extensive plateau regions directly on the imagery. Most circular features found were explained away by U-2 airfoto analysis but several remain as anomalies. Visible glacial features include individual drumlins, drumlinoids, eskers, ice-marginal drainage channels, glacial lake shorelines, sand plains, and end moraines.

Evaluation of ERTS-1 imagery for spectral geological mapping in diverse terranes of New York State

NASA Technical Reports Server (NTRS)

Isachsen, Y. W. (Principal Investigator); Fakundiny, R. H.; Forster, S. W.

1973-01-01

The author has identified the following significant results. Linear anomalies dominate the new geological information derived from ERTS-1 imagery, total lengths now exceeding 6000 km. Experimentation with a variety of viewing techniques suggest that conventional photogeologic analyses of band 7 results in the location of more than 97 percent of all linears found. Bedrock lithologic types are distinguishable only where they are topographically expressed or govern land use signatures. The maxima on rose diagrams for ERTS-1 anomalies correspond well with those for mapped faults and topographic lineaments. A multiscale analysis of linears showed that single topographic linears at 1:2,500,000 became dashed linears at 1:1,000,000 aligned zones of shorter parallel, en echelon, or conjugate linears at 1:500,00. Most circular features found were explained away by U-2 airphoto analysis but several remain as anomalies. Visible glacial features include individual drumlins, best seen in winter imagery, drumlinoids, eskers, ice-marginal drainage channels, glacial lake shorelines and sand plains, and end moraines.

Preliminary Gravity and Ground Magnetic Data in the Arbuckle Uplift near Sulphur, Oklahoma

USGS Publications Warehouse

Scheirer, Daniel S.; Aboud, Essam

2008-01-01

Improving knowledge of the geology and geophysics of the Arbuckle Uplift in south-central Oklahoma is a goal of the Framework Geology of Mid-Continent Carbonate Aquifers project sponsored by the United States Geological Survey (USGS) National Cooperative Geologic Mapping Program (NCGMP). In May 2007, we collected ground magnetic and gravity observations in the Hunton Anticline region of the Arbuckle Uplift, near Sulphur, Oklahoma. These observations complement prior gravity data collected for a project sponsored by the National Park Service and helicopter electromagnetic (HEM) and aeromagnetic data collected in March 2007 for the NCGMP project. This report describes the instrumentation and processing that was utilized in the May 2007 geophysical fieldwork, and it presents preliminary results as gravity anomaly maps and magnetic anomaly profiles. Digital tables of gravity and magnetic observations are provided as a supplement to this report. Future work will generate interpretive models of these anomalies and will involve joint analysis of these ground geophysical measurements with airborne and other geophysical and geological observations, with the goal of understanding the geological structures influencing the hydrologic properties of the Arbuckle-Simpson aquifer.

Exploring the Nature of Galaxies with Abundance Gradient Anomalies in the SDSS-IV/MaNGA Survey

NASA Astrophysics Data System (ADS)

Keith, Celeste; Tremonti, Christy; Pace, Zach; Schaefer, Adam

2018-01-01

Disk galaxies are known to have radial oxygen abundance gradients with their centers being more chemically enriched than their outskirts. The steepness of the abundance gradient has recently been shown to correlate with galaxy stellar mass, on average. However, individual galaxies sometimes show pronounced deviations from the expected trends, such as flatter or steeper slopes than expected for their mass, abrupt changes in slope, or azimuthal asymmetries. Here we report on a systematic search for galaxies with abundance gradient anomalies using 2-D spectroscopy from the Sloan Digital Sky Survey IV MaNGA. We construct nebular oxygen and nitrogen abundance maps for 300 moderately inclined non-interacting disk galaxies and use visual inspection to identify the most interesting cases. We use this training set to develop an automated pipeline to flag galaxies with abundance anomalies from the larger MaNGA dataset for visual inspection. We combine the metallicity maps with kinematic data and measurements of the galaxies' local environments to better understand the processes that shape the radial abundance gradients of disk galaxies.

Magnetic structure of Bayonnaise knoll caldera including Hakurei hydrothermal site obtained from near-bottom magnetic vector field mapping by autonomous underwater vehicle

NASA Astrophysics Data System (ADS)

Honsho, C.; Ura, T.; Kim, K.

2012-12-01

The Bayonnaise knoll caldera is one of the silicic submarine calderas in the Izu-Ogasawara Arc in Japan. In 2003, a large-scale hydrothermal deposit was found in the caldera, called the Hakurei deposit. The caldera had been explored by four surveys using autonomous underwater vehicles (AUVs) from 2008 to 2011, and the near-bottom magnetic field was mapped over about 75% of the caldera floor. We carried out detailed correction for the magnetic field produced by the vehicle body, which allowed us to take advantage of the vector anomaly instead of the total anomaly for the magnetic inversion. We applied the inversion method using the block model together with the Akaike's Bayesian information criterion (ABIC). One remarkable thing is that we recognized significant difference between the magnetic inversion result using the vector anomaly and that using the total anomaly: the latter result explains the observed total anomalies excellently, but does not explain the vector anomalies adequately. Except for a rare case where the vector anomaly is perpendicular to the main field throughout, the total anomaly should be sufficient for evaluating the entire field, provided that the data is collected in sufficiently high density. In fact, the track lines of our survey sometimes separate from each other by about twice the altitude of the vehicle (100 m), which can lead to considerable aliasing in the sampled field. The vector anomaly can provide vital information in such a situation. The obtained magnetization distribution is well correlated with the topography. The caldera rim and central cone have weak magnetization, which is consistent with the fact that they consist of dacite rocks. On the other hand, the caldera floor shows high magnetization, which implies the existence of basaltic rocks. The high magnetization appears to continue north and south beyond the caldera rim, forming an NS-trending high magnetization zone. Because the caldera floor is generally covered with sediment and pumice, the existence of basaltic rocks in the caldera floor has not yet been directly confirmed. As for the regional settings, however, there are NS-lined small knolls in the north and south of the caldera, which seem to continue across the caldera, and these knolls are known to consist of basaltic rocks. We postulate that the high magnetization zone of the caldera is due to basaltic volcanism, which formed the knoll chains and occurred after the formation of the silicic caldera. The Hakurei hydrothermal site is located on the southeastern rim of the caldera floor, near an inferred intersection of the caldera rim and the knoll chain. In the magnetization map, the Hakurei deposit is located near the edge of the high magnetization zone. We can clearly observe a zone of reduced magnetization associated with the deposit, probably caused by the high-temperature hydrothermal alteration of the host basaltic rock.

Geophysical Characterization of Some Terranes and the Geophysical Modeling of Candidate Suture Zones

NASA Technical Reports Server (NTRS)

Ravat, D.

1997-01-01

Indian participation in this project was terminated during the last year by a sudden withdrawal of support by the Department of Science and Technology, India, to the Indian Institute of Geomagnetism, Bombay. As a result, significant changes in the project focus had to be undertaken. Much of the work carried out at Southern Illinois University at Carbondale during the first year of the project anticipated the Indian participation and included development of computer programs to be used on gravity and magnetic data from the Indian subcontinent and preparations for fieldwork, tutorials, and workshops in India. Despite these setbacks, which were beyond our control, a number of significant tasks have been accomplished during the project period. These include: (1) Completion of digitization of the regional Bouguer gravity anomaly map of India and the regional ground total intensity magnetic anomaly map of India at an overdetermined spacing of 0.05 degrees. (2) We investigated and assessed the limitations of the Euler method using environmental examples because detailed aeromagnetic maps of parts of India were not available for interpretation by this method. (3) We also undertook an assessment of a suture zone between the Nyaza Craton (Archean) and the Mozambique Belt (Pan African) in the Kenya Rift, Africa, using gravity anomalies and the lithospheric seismological models. (4) We studied Magsat and high-altitude (approx. 4 km) aeromagnetic data over Canada.

Potential vorticity regimes over East Asia during winter

NASA Astrophysics Data System (ADS)

Huang, Wenyu; Chen, Ruyan; Wang, Bin; Wright, Jonathon S.; Yang, Zifan; Ma, Wenqian

2017-02-01

Nine potential vorticity (PV) regimes over East Asia are identified by applying a Self-Organizing Map and Hierarchical Ascendant Classification regime analysis to the daily PV reanalysis fields on the 300 K isentropic surface for December-March 1948-2014. According to the surface temperature anomalies over East Asia, these nine regimes are further classified into three classes, i.e., cold class (three regimes), warm class (four regimes), and neutral class (two regimes). The PV-based East Asian winter monsoon index (EAWMI) is used to study the relationship between PV distributions and the temperature anomalies. The magnitude of cold (warm) anomalies over the land areas of East Asia increases (decreases) quasi-linearly with the EAWMI. Regression analysis reveals that cold temperature anomalies preferentially occur when the EAWMI exceeds a threshold at ˜0.2 PVU (where 1 PVU ≡ 10-6 m2 K kg-1 s-1). PV inversion uncovers the mechanisms behind the relationships between the PV regimes and surface temperature anomalies and reveals that cold (warm) PV regimes are associated with significant warming (cooling) in the upper troposphere and lower stratosphere. On average, cold regimes have longer durations than warm regimes. Interclass transition probabilities are much higher for paths from warm/neutral regimes to cold regimes than for paths from cold regimes to warm/neutral regimes. Besides, intraclass transitions are rare within the warm or neutral regimes. The PV regime analysis provides insight into the causes of severe cold spells over East Asia, with blocking circulation patterns identified as the primary factor in initiating and maintaining these cold spells.

Regional Geological Mapping in the Graham Land of Antarctic Peninsula Using LANDSAT-8 Remote Sensing Data

NASA Astrophysics Data System (ADS)

Pour, A. B.; Hashim, M.; Park, Y.

2017-10-01

Geological investigations in Antarctica confront many difficulties due to its remoteness and extreme environmental conditions. In this study, the applications of Landsat-8 data were investigated to extract geological information for lithological and alteration mineral mapping in poorly exposed lithologies in inaccessible domains such in Antarctica. The north-eastern Graham Land, Antarctic Peninsula (AP) was selected in this study to conduct a satellite-based remote sensing mapping technique. Continuum Removal (CR) spectral mapping tool and Independent Components Analysis (ICA) were applied to Landsat-8 spectral bands to map poorly exposed lithologies at regional scale. Pixels composed of distinctive absorption features of alteration mineral assemblages associated with poorly exposed lithological units were detected by applying CR mapping tool to VNIR and SWIR bands of Landsat-8.Pixels related to Si-O bond emission minima features were identified using CR mapping tool to TIR bands in poorly mapped andunmapped zones in north-eastern Graham Land at regional scale. Anomaly pixels in the ICA image maps related to spectral featuresof Al-O-H, Fe, Mg-O-H and CO3 groups and well-constrained lithological attributions from felsic to mafic rocks were detectedusing VNIR, SWIR and TIR datasets of Landsat-8. The approach used in this study performed very well for lithological andalteration mineral mapping with little available geological data or without prior information of the study region.

Magnetic mapping of (carbonated) oceanic crust-mantle boundary: New insights from Linnajavri, northern Norway

NASA Astrophysics Data System (ADS)

Tominaga, M.; Beinlich, A.; Tivey, M.; Andrade Lima, E.; Weiss, B. P.

2012-12-01

The contribution of lower oceanic crust and upper mantle to marine magnetic anomalies has long been recognized, but the detailed magnetic character of this non-volcanic source layer remains to be fully defined. Here, we report preliminary results of a magnetic survey and source characterization of a "carbonated" oceanic Moho (petrological "Mohorovicic discontinuity") sequence observed at the Linnajavri Serpentinite Complex (LSC), northern Norway. The LSC is located at 67° 36'N and 16° 24'E within the upper Allochthon of the Norwegian Caledonides and represents a dismembered ophiolite. Particularly in the southern ("Ridoalggicohkka") area of the LSC, gabbro, serpentinite and its talc-carbonate (soapstone) and quartz-carbonate (listvenite) altered equivalents are extraordinarily well-exposed [1]. An intact oceanic Moho is exposed here, despite its complex tectonic setting. The small degree of arctic rock weathering (≤ 2 mm weathering surface) allowed for detailed regional-scale surface magnetic mapping across alteration fronts (serpentinite-soapstone; soapstone-listvenite) and lithological contacts (soapstone-gabbro). Magnetic mapping was conducted using a handheld 3-axis magnetometer, surface-towed resistivity meter and Teka surface magnetic susceptometer with sample spacing of 1 m. Geophysical field mapping was combined with petrological observations and scanning SQUID microscopy (SM) mapping conducted on thin sections from rock samples that were drilled along the survey lines. Regional scale magnetic mapping indicates that the total magnetic field across both the "carbonated" Moho and the soapstone-serpentinite interfaces show higher frequency changes in their magnetic anomaly character and amplitudes than the surface-towed resistivity data. SQUID microscopy mapping of both natural remanence magnetization (NRM) and anhysteretic remanence magnetization (ARM) on gabbro, serpentinite, soapstone, and listvenite samples, with a sensor-sample separation of ˜190 μm, show that the distribution of microscopically measurable ferromagnetic and possibly sulfide minerals produces a different bulk intensity for each of the rock types. SM vector magnetic field maps of these samples also reveal that the magnetization associated with these grains (observed as dipole-like fields in SM maps) is variable in direction from grain to grain, which may result from different alteration histories for each grain. These complex magnetization patterns acquired through thermal and chemical alteration history may explain the short wavelength magnetic anomalies observed along our traverse lines. [1] Beinlich, A., Plümper, O., Hövelmann, J., Austrheim, H. and Jamtveit, B. (2012), Terra Nova, in press.

Use of microcomputer in mapping depth of stratigraphic horizons in National Petroleum Reserve in Alaska

USGS Publications Warehouse

Payne, Thomas G.

1982-01-01

REGIONAL MAPPER is a menu-driven system in the BASIC language for computing and plotting (1) time, depth, and average velocity to geologic horizons, (2) interval time, thickness, and interval velocity of stratigraphic intervals, and (3) subcropping and onlapping intervals at unconformities. The system consists of three programs: FILER, TRAVERSER, and PLOTTER. A control point is a shot point with velocity analysis or a shot point at or near a well with velocity check-shot survey. Reflection time to and code number of seismic horizons are filed by digitizing tablet from record sections. TRAVERSER starts at a point of geologic control and, in traversing to another, parallels seismic events, records loss of horizons by onlap and truncation, and stores reflection time for geologic horizons at traversed shot points. TRAVERSER is basically a phantoming procedure. Permafrost thickness and velocity variations, buried canyons with low-velocity fill, and error in seismically derived velocity cause velocity anomalies that complicate depth mapping. Two depths to the top of the pebble is based shale are computed for each control point. One depth, designated Zs on seismically derived velocity. The other (Zw) is based on interval velocity interpolated linearly between wells and multiplied by interval time (isochron) to give interval thickness. Z w is computed for all geologic horizons by downward summation of interval thickness. Unknown true depth (Z) to the pebble shale may be expressed as Z = Zs + es and Z = Zw + ew where the e terms represent error. Equating the two expressions gives the depth difference D = Zs + Zw = ew + es A plot of D for the top of the pebble shale is readily contourable but smoothing is required to produce a reasonably simple surface. Seismically derived velocity used in computing Zs includes the effect of velocity anomalies but is subject to some large randomly distributed errors resulting in depth errors (es). Well-derived velocity used in computing Zw does not include the effect of velocity anomalies, but the error (ew) should reflect these anomalies and should be contourable (non-random). The D surface as contoured with smoothing is assumed to represent ew, that is, the depth effect of variations in permafrost thickness and velocity and buried canyon depth. Estimated depth (Zest) to each geologic horizon is the sum of Z w for that horizon and a constant e w as contoured for the pebble shale, which is the first highly continuous seismic horizon below the zone of anomalous velocity. Results of this 'depthing' procedure are compared with those of Tetra Tech, Inc., the subcontractor responsible for geologic and geophysical interpretation and mapping.

Challenges of using electrical resistivity method to locate karst conduits-A field case in the Inner Bluegrass Region, Kentucky

USGS Publications Warehouse

Zhu, J.; Currens, J.C.; Dinger, J.S.

2011-01-01

Conduits serve as major pathways for groundwater flow in karst aquifers. Locating them from the surface, however, is one of the most challenging tasks in karst research. Geophysical methods are often deployed to help locate voids by mapping variations of physical properties of the subsurface. Conduits can cause significant contrasts of some physical properties that can be detected; other subsurface features such as water-bearing fractures often yield similar contrasts, which are difficult to distinguish from the effects of the conduits. This study used electrical resistivity method to search for an unmapped karst conduit that recharges Royal Spring in the Inner Bluegrass karst region, Kentucky, USA. Three types of resistivity techniques (surface 2D survey, quasi-3D survey, and time-lapse survey) were used to map and characterize resistivity anomalies. Some of the major anomalies were selected as drilling targets to verify the existence of the conduits. Drilling near an anomaly identified by an electrical resistivity profile resulted in successful penetration of a major water-filled conduit. The drilling results also suggest that, in this study area, low resistivity anomalies in general are associated with water-bearing features. However, differences in the anomaly signals between the water-filled conduit and other water-bearing features such as water-filled fracture zones were undistinguishable. The electrical resistivity method is useful in conduit detection by providing potential drilling targets. Knowledge of geology and hydrogeology about the site and professional judgment also played important roles in locating the major conduit. ?? 2011 Elsevier B.V.

A two-dimensional analysis of the sensitivity of a pulse first break to wave speed contrast on a scale below the resolution length of ray tomography.

PubMed

Willey, Carson L; Simonetti, Francesco

2016-06-01

Mapping the speed of mechanical waves traveling inside a medium is a topic of great interest across many fields from geoscience to medical diagnostics. Much work has been done to characterize the fidelity with which the geometrical features of the medium can be reconstructed and multiple resolution criteria have been proposed depending on the wave-matter interaction model used to decode the wave speed map from scattering measurements. However, these criteria do not define the accuracy with which the wave speed values can be reconstructed. Using two-dimensional simulations, it is shown that the first-arrival traveltime predicted by ray theory can be an accurate representation of the arrival of a pulse first break even in the presence of diffraction and other phenomena that are not accounted for by ray theory. As a result, ray-based tomographic inversions can yield accurate wave speed estimations also when the size of a sound speed anomaly is smaller than the resolution length of the inversion method provided that traveltimes are estimated from the signal first break. This increased sensitivity however renders the inversion more susceptible to noise since the amplitude of the signal around the first break is typically low especially when three-dimensional anomalies are considered.

Magnetic Gradient Horizontal Operator (MHGO) useful for detecting objects buried at shallow depth: cultural heritage (Villa degli Antonini, Rota Rio)

NASA Astrophysics Data System (ADS)

Di Filippo, Michele; Di Nezza, Maria

2016-04-01

Several factors were taken into consideration in order to appropriately tailor the geophysical explorations at the cultural heritage. Given the fact that each site has been neglected for a long time and in recent times used as an illegal dumping area, we thoroughly evaluated for this investigation the advantages and limitations of each specific technique, and the general conditions and history of the site. We took into account the extension of the areas to be investigated and the need for rapid data acquisition and processing. Furthermore, the survey required instrumentation with sensitivity to small background contrasts and as little as possible affected by background noise sources. In order to ascertain the existence and location of underground buried walls, a magnetic gradiometer survey (MAG) was planned. The map of the magnetic anomalies is not computed to reduction at the pole (RTP), but with a magnetic horizontal gradient operator (MHGO). The magnetic horizontal gradient operator (MHGO) generates from a grid of vertical gradient a grid of steepest slopes (i.e. the magnitude of the gradient) at any point on the surface. The MHGO is reported as a number (rise over run) rather than degrees, and the direction is opposite to that of the slope. The MHGO is zero for a horizontal surface, and approaches infinity as the slope approaches the vertical. The gradient data are especially useful for detecting objects buried at shallow depth. The map reveals some details of the anomalies of the geomagnetic field. Magnetic anomalies due to walls are more evident than in the total intensity map, whereas anomalies due to concentrations of debris are very weak. In this work we describe the results of an investigation obtained with magnetometry investigation for two archaeological sites: "Villa degli Antonini" (Genzano, Rome) and Rota Ria (Mugnano in Teverina, Viterbo). Since the main goal of the investigation was to understand the nature of magnetic anomalies with cost-effective method, we have also detection and location of underground buried structures using different instruments and techniques geophysical were carried out (EMI, GPR and microgravity) and so far excavated only in a targeted sector of the area of the anomaly labeled in order to test the validity of the geophysical survey.

Mean gravity anomalies and sea surface heights derived from GEOS-3 altimeter data

NASA Technical Reports Server (NTRS)

Rapp, R. H.

1978-01-01

Approximately 2000 GEOS-3 altimeter arcs were analyzed to improve knowledge of the geoid and gravity field. An adjustment procedure was used to fit the sea surface heights (geoid undulations) in an adjustment process that incorporated cross-over constraints. The error model used for the fit was a one or two parameter model which was designed to remove altimeter bias and orbit error. The undulations on the adjusted arcs were used to produce geoid maps in 20 regions. The adjusted data was used to derive 301 5 degree equal area anomalies and 9995 1 x 1 degree anomalies in areas where the altimeter data was most dense, using least squares collocation techniques. Also emphasized was the ability of the altimeter data to imply rapid anomaly changes of up to 240 mgals in adjacent 1 x 1 degree blocks.

Aeromagnetic maps of the Colorado River region including the Kingman, Needles, Salton Sea, and El Centro 1 degree by 2 degrees quadrangles, California, Arizona, and Nevada

USGS Publications Warehouse

Mariano, John; Grauch, V.J.

1988-01-01

Aeromagnetic anomalies are produced by variations in the strength and direction of the magnetic field of rocks that include magnetic minerals, commonly magnetite. Patterns of anomalies on aeromagnetic maps can reveal structures - for example, faults which have juxtaposed magnetic rocks against non-magnetic rocks, or areas of alteration where magnetic minerals have been destroyed by hydrothermal activity. Tectonic features of regional extent may not become apparent until a number of aeromagnetic surveys have been compiled and plotted at the same scale. Commonly the compilation involves piecing together data from surveys that were flown at different times with widely disparate flight specifications and data reduction procedures. The data may be compiled into a composite map, where all the pieces are plotted onto one map without regard to the difference in flight elevation and datum, or they may be compiled into a merged map, where all survey data are analytically reduced to a common flight elevation and datum, and then digitally merged at the survey boundaries. The composite map retains the original resolution of all the survey data, but computer methods to enhance regional features crossing the survey boundaries may not be applied. On the other hand, computer methods can be applied to the merged data, but the accuracy of the data may be slightly diminished.

Investigating the early snowmelt of 2015 in the Cascade Mountains using new MODIS-based snowmelt timing maps

NASA Astrophysics Data System (ADS)

O'Leary, D., III; Hall, D. K.; Medler, M. J.; Flower, A.; Matthews, R.

2017-12-01

The spring of 2015 brought an alarmingly early snowmelt to the Cascade Mountains, impacting flora, fauna, watersheds, and wildfire activity. It is important that we understand these events because model-based projections suggest that snowmelt may arrive an average of 10-40 days earlier across the continental US by the year 2100. Available snow measurement methods including SNOTEL stations and stream gauges offer insights into point locations and individual watersheds, but lack the detail needed to assess snowmelt anomalies across the landscape. In this study we describe our new MODIS-based snowmelt timing maps (STMs), validate them with SNOTEL measurements, then use them to explore the spatial patterns of the 2015 snowmelt in the Cascades. We found that the Cascade Mountains experienced snowmelt 41 days earlier than the 2001-2015 average, with many areas melting >70 days early. Of concern to land managers, these events may be the `new normal' in the decades to come.

Utility of aeromagnetic studies for mapping of potentially active faults in two forearc basins: Puget Sound, Washington, and Cook Inlet, Alaska

USGS Publications Warehouse

Saltus, R.W.; Blakely, R.J.; Haeussler, Peter J.; Wells, R.E.

2005-01-01

High-resolution aeromagnetic surveys over forearc basins can detect faults and folds in weakly magnetized sediments, thus providing geologic constraints on tectonic evolution and improved understanding of seismic hazards in convergent-margin settings. Puget Sound, Washington, and Cook Inlet, Alaska, provide two case histories. In each lowland region, shallow-source magnetic anomalies are related to active folds and/or faults. Mapping these structures is critical for understanding seismic hazards that face the urban regions of Seattle, Washington, and Anchorage, Alaska. Similarities in aeromagnetic anomaly patterns and magnetic stratigraphy between the two regions suggest that we can expect the aeromagnetic method to yield useful structural information that may contribute to earth-hazard and energy resource investigations in other forearc basins.

Gravity anomaly detection: Apollo/Soyuz

NASA Technical Reports Server (NTRS)

Vonbun, F. O.; Kahn, W. D.; Bryan, J. W.; Schmid, P. E.; Wells, W. T.; Conrad, D. T.

1976-01-01

The Goddard Apollo-Soyuz Geodynamics Experiment is described. It was performed to demonstrate the feasibility of tracking and recovering high frequency components of the earth's gravity field by utilizing a synchronous orbiting tracking station such as ATS-6. Gravity anomalies of 5 MGLS or larger having wavelengths of 300 to 1000 kilometers on the earth's surface are important for geologic studies of the upper layers of the earth's crust. Short wavelength Earth's gravity anomalies were detected from space. Two prime areas of data collection were selected for the experiment: (1) the center of the African continent and (2) the Indian Ocean Depression centered at 5% north latitude and 75% east longitude. Preliminary results show that the detectability objective of the experiment was met in both areas as well as at several additional anomalous areas around the globe. Gravity anomalies of the Karakoram and Himalayan mountain ranges, ocean trenches, as well as the Diamantina Depth, can be seen. Maps outlining the anomalies discovered are shown.

Determination Gradients of the Earth's Magnetic Field from the Measurements of the Satellites and Inversion of the Kursk Magnetic Anomaly

NASA Technical Reports Server (NTRS)

Karoly, Kis; Taylor, Patrick T.; Geza, Wittmann

2014-01-01

We computed magnetic field gradients at satellite altitude, over Europe with emphasis on the Kursk Magnetic Anomaly (KMA). They were calculated using the CHAMP satellite total magnetic anomalies. Our computations were done to determine how the magnetic anomaly data from the new ESA/Swarm satellites could be utilized to determine the structure of the magnetization of the Earths crust, especially in the region of the KMA. Since the ten years of 2 CHAMP data could be used to simulate the Swarm data. An initial East magnetic anomaly gradient map of Europe was computed and subsequently the North, East and Vertical magnetic gradients for the KMA region were calculated. The vertical gradient of the KMA was determined using Hilbert transforms. Inversion of the total KMA was derived using Simplex and Simulated Annealing algorithms. Our resulting inversion depth model is a horizontal quadrangle with upper 300-329 km and lower 331-339 km boundaries.

Integrating gravity and magnetic field data to delineate structurally controlled gold mineralization in the Sefwi Belt of Ghana

NASA Astrophysics Data System (ADS)

Konadu Amoah, Bernard; Dadzie, Isaac; Takyi-Kyeremeh, Kwaku

2018-08-01

Gravity and magnetic surveys were used to delineate potential gold mineralization zones in the Sefwi belt of Ghana. The study area is an intrusive dominated area that hosts pockets of small scale mining operations locally referred to as Galamsey. These Galamsey operations are not guided by a scientific approach to back the trend of gold mineralization which is conventionally mined. The study aimed at mapping lithological units, structural setting and relating Galamsey sites to delineate potential zones of gold mineralization. A Scintrex CG5 gravimeter and GEM’s Overhauser magnetometer were used for gravity and magnetic data acquisition respectively. The magnetic data were corrected and enhancing filters such as reduction to the pole (RTP), analytical signal and first vertical derivative were applied using Oasis montaj 7.1. Gravity data were also reduced to the geoid using the Oasis montaj software to produce a complete Bouguer anomaly map. The regional/residual separation technique produced a residual gravity map. The RTP and analytical signal filters from the magnetic data and residual gravity anomaly map from the gravity data helped in mapping belt type (Dixcove) Birimian granitoids and mafic intrusive unit, interpreted as gabbro. The first vertical derivative filter was useful in mapping NE/SW minor faults and crosscutting dykes largely concentrated in the belt type Birimian granitoids. All the three mapped Galamsey sites fell on a minor fault and are associated with the belt type granitoids which were used in delineating four potential zones of gold mineralization.

Large-Angle Anomalies in the CMB

DOE PAGES

Copi, Craig J.; Huterer, Dragan; Schwarz, Dominik J.; ...

2010-01-01

We review the recently found large-scale anomalies in the maps of temperature anisotropies in the cosmic microwave background. These include alignments of the largest modes of CMB anisotropy with each other and with geometry and direction of motion of the solar ssystem, and the unusually low power at these largest scales. We discuss these findings in relation to expectation from standard inflationary cosmology, their statistical significance, the tools to study them, and the various attempts to explain them.

Mars gravity: high-resolution results from viking orbiter 2.

PubMed

Sjogren, W L

1979-03-09

Doppler radio-tracking data have provided detailed measurements for a martian gravity map extending from 30 degrees S to 65 degrees N in latitude and through 360 degrees of longitude. The feature resolution is approximately 500 kilometers, revealing a huge anomaly associated with Olympus Mons, a mascon in Isidis Planitia, and other anomalies correlated with volcanic structure. Olympus Mons has been modeled with a 600-kilometer surface disk having a mass of 8.7 x 1021grams.

A rapid method to map the crustal and lithospheric thickness using elevation, geoid anomaly and thermal analysis. Application to the Gibraltar Arc System, Atlas Mountains and adjacent zones

NASA Astrophysics Data System (ADS)

Fullea, J.; Fernàndez, M.; Zeyen, H.; Vergés, J.

2007-02-01

We present a method based on the combination of elevation and geoid anomaly data together with thermal field to map crustal and lithospheric thickness. The main assumptions are local isostasy and a four-layered model composed of crust, lithospheric mantle, sea water and the asthenosphere. We consider a linear density gradient for the crust and a temperature dependent density for the lithospheric mantle. We perform sensitivity tests to evaluate the effect of the variation of the model parameters and the influence of RMS error of elevation and geoid anomaly databases. The application of this method to the Gibraltar Arc System, Atlas Mountains and adjacent zones reveals the presence of a lithospheric thinning zone, SW-NE oriented. This zone affects the High and Middle Atlas and extends from the Canary Islands to the eastern Alboran Basin and is probably linked with a similarly trending zone of thick lithosphere constituting the western Betics, eastern Rif, Rharb Basin, and Gulf of Cadiz. A number of different, even mutually opposite, geodynamic models have been proposed to explain the origin and evolution of the study area. Our results suggest that a plausible slab-retreating model should incorporate tear and asymmetric roll-back of the subducting slab to fit the present-day observed lithosphere geometry. In this context, the lithospheric thinning would be caused by lateral asthenospheric flow. An alternative mechanism responsible for lithospheric thinning is the presence of a hot magmatic reservoir derived from a deep ancient plume centred in the Canary Island, and extending as far as Central Europe.

A stable downward continuation of airborne magnetic data: A case study for mineral prospectivity mapping in Central Iran

NASA Astrophysics Data System (ADS)

Abedi, Maysam; Gholami, Ali; Norouzi, Gholam-Hossain

2013-03-01

Previous studies have shown that a well-known multi-criteria decision making (MCDM) technique called Preference Ranking Organization METHod for Enrichment Evaluation (PROMETHEE II) to explore porphyry copper deposits can prioritize the ground-based exploratory evidential layers effectively. In this paper, the PROMETHEE II method is applied to airborne geophysical (potassium radiometry and magnetometry) data, geological layers (fault and host rock zones), and various extracted alteration layers from remote sensing images. The central Iranian volcanic-sedimentary belt is chosen for this study. A stable downward continuation method as an inverse problem in the Fourier domain using Tikhonov and edge-preserving regularizations is proposed to enhance magnetic data. Numerical analysis of synthetic models show that the reconstructed magnetic data at the ground surface exhibits significant enhancement compared to the airborne data. The reduced-to-pole (RTP) and the analytic signal filters are applied to the magnetic data to show better maps of the magnetic anomalies. Four remote sensing evidential layers including argillic, phyllic, propylitic and hydroxyl alterations are extracted from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images in order to map the altered areas associated with porphyry copper deposits. Principal component analysis (PCA) based on six Enhanced Thematic Mapper Plus (ETM+) images is implemented to map iron oxide layer. The final mineral prospectivity map based on desired geo-data set indicates adequately matching of high potential zones with previous working mines and copper deposits.

Understanding the Tectonic Features in the South China Sea By Analyzing Magnetic Anomalies

NASA Astrophysics Data System (ADS)

Guo, L.; Meng, X.; Shi, L.; Yao, C.

2011-12-01

The South China Sea (SCS) is surrounded by the Eurasia, Pacific and India-Australia plates. It formed during Late Oligocene-Early Miocene, and is one of the largest marginal seas in the Western Pacific. The collision of Indian subcontinent and Eurasian plate in the northwest, back-arc spreading in the centre and subduction beneath the Philippine plate along Manila trench in the east and along Palawan trough in the south had produced the complex tectonic features in the SCS that we can see today. In the past few decades, a variety of geophysical methods were conducted to study geological tectonics and evolution of the SCS. Here, we analyzed the magnetic data of this area using new data enhancement techniques to understand the regional tectonic features. We assembled the magnetic anomalies data with a resolution of two arc-minute from the World Digital Magnetic Anomaly Map, and then gridded the data on a regular grid. Then we used the method of reduction to the pole at low latitude with varying magnetic inclinations to stably reduce the magnetic anomalies. Then we used the preferential continuation method based on Wiener filtering and Green's equivalence principle to separate the reduced-to-pole (RTP) magnetic anomalies, and subsequently analyze the regional and residual anomalies. We also calculated the directional horizontal derivatives and the tilt-angle derivative of the data to derive clearer geological structures with more details. Then we calculated the depth of the magnetic basement surface in the area by 3D interface inversion. From the results of the preliminary processing, we analyzed the main faults, geological structures, magma distribution and tectonic features in the SCS. In the future, the integrated interpretation of the RTP magnetic anomalies, Bouguer gravity anomalies and other geophysical methods will be performed for better understanding the deep structure , the tectonic features and evolution of the South China Sea. Acknowledgment: We acknowledge the financial support of the SinoProbe project (201011039), the Fundamental Research Funds for the Central Universities (2010ZY26, 2011PY0184), and the National Natural Science Foundation of China (40904033, 41074095).

Infrared Microtransmission And Microreflectance Of Biological Systems

NASA Astrophysics Data System (ADS)

Hill, Steve L.; Krishnan, K.; Powell, Jay R.

1989-12-01

The infrared microsampling technique has been successfully applied to a variety of biological systems. A microtomed tissue section may be prepared to permit both visual and infrared discrimination. Infrared structural information may be obtained for a single cell, and computer-enhanced images of tissue specimens may be calculated from spectral map data sets. An analysis of a tissue section anomaly may gg suest eitherprotein compositional differences or a localized concentration of foreign matterp. Opaque biological materials such as teeth, gallstones, and kidney stones may be analyzed by microreflectance spectroscop. Absorption anomalies due to specular dispersion are corrected with the Kraymers-Kronig transformation. Corrected microreflectance spectra may contribute to compositional analysis and correlate diseased-related spectral differences to visual specimen anomalies.

Analysis of MAGSAT and surface data of the Indian region

NASA Technical Reports Server (NTRS)

Agarwal, G. C. (Principal Investigator)

1983-01-01

Techniques and significant results of an analysis of MAGSAT and surface data of the Indian region are described. Specific investigative tasks included: (1) use of the multilevel data at different altitudes to develop a model for variation of magnetic anomaly with altitude; (2) development of the regional model for the description of main geomagnetic field for the Indian sub-continent using MAGSAT and observatory data; (3) development of regional mathematical model of secular variations over the Indian sub-continent; and (4) downward continuation of the anomaly field obtained from MAGSAT and its combination with the existing observatory data to produce a regional anomaly map for elucidating tectonic features of the Indian sub-continent.

The Mystery of the Mars North Polar Gravity-Topography Correlation(Or Lack Thereof)

NASA Technical Reports Server (NTRS)

Phillips, R. J.; Sjogren, W. L.; Johnson, C. L.

1999-01-01

Maps of moderately high resolution gravity data obtained from the Mars Global Surveyor (MGS) gravity calibration orbit campaign and high precision topography obtained from the Mars Orbiter Laser Altimeter (MOLA) experiment reveal relationships between gravity and topography in high northern latitudes of Mars. Figure 1 shows the results of a JPL spherical harmonic gravity model bandpass filtered between degrees 6 and 50 contoured over a MOLA topographic image. A positive gravity anomaly exists over the main North Polar cap, but there are at least six additional positive gravity anomalies, as well as a number of smaller negative anomalies, with no obvious correlation to topography. Additional information is contained in the original extended abstract.

Study of ionospheric anomalies due to impact of typhoon using Principal Component Analysis and image processing

NASA Astrophysics Data System (ADS)

LIN, JYH-WOEI

2012-08-01

Principal Component Analysis (PCA) and image processing are used to determine Total Electron Content (TEC) anomalies in the F-layer of the ionosphere relating to Typhoon Nakri for 29 May, 2008 (UTC). PCA and image processing are applied to the global ionospheric map (GIM) with transforms conducted for the time period 12:00-14:00 UT on 29 May, 2008 when the wind was most intense. Results show that at a height of approximately 150-200 km the TEC anomaly is highly localized; however, it becomes more intense and widespread with height. Potential causes of these results are discussed with emphasis given to acoustic gravity waves caused by wind force.

Aeromagnetic map of the Fossil Springs Roadless Area, Yavapai, Gila, and Coconino counties, Arizona

USGS Publications Warehouse

Davis, W.E.; Weir, G.W.

1984-01-01

The magnetic anomalies and patterns on the aeromagnetic map reflect variations of magnetization in the underlying rocks. Basaltic rocks contain moderate amounts of magnetic minerals, mainly magnetite, and possess strong intensities of magnetization. The more silicic volcanic rocks have much lower magnetization intensities. Sedimentary rocks contain little or no magnetite and are virtually nonmagnetic.

Gravity anomaly map of Mars and Moon and analysis of Venus gravity field: New analysis procedures

NASA Technical Reports Server (NTRS)

1984-01-01

The technique of harmonic splines allows direct estimation of a complete planetary gravity field (geoid, gravity, and gravity gradients) everywhere over the planet's surface. Harmonic spline results of Venus are presented as a series of maps at spacecraft and constant altitudes. Global (except for polar regions) and local relations of gravity to topography are described.

Integration of satellite gravity data with ground-based geophysical data for a better understanding of the structural control of groundwater flow in the Nubian Sandstone Aquifer System

NASA Astrophysics Data System (ADS)

Fathy, K.; Sultan, M.; Bettadpur, S. V.; Save, H.; Ahmed, M.; Zahran, K. H.; Emil, M. K.; Helaly, A.; Abotalib, A. Z.; Ismaiel, A.

2016-12-01

The Nubian Sandstone Aquifer System (NSAS) extends beyond Egypt's political boundaries to cover eastern Libya, northern and central Sudan and northeast Chad. The optimum utilization of this resource requires a better understanding of the connectivity of the NSAS sub-basins and the structural control on groundwater flow throughout the system. We provide an integrated (geophysics, remote sensing and field) approach to address these issues. Firstly, we evaluated GOCE-based global Geopotential models (GGMs) compared to the terrestrial gravity anomalies for 21262 sites to select the optimum model for deriving Bouguer gravity datasets. The Eigen-6C4 was found to have the lowest deviation from the terrestrial gravity anomalies. Secondly, structures and uplifts were mapped on the surface and in the sub-surface. Extensive N-S to NW-SE trending grabens were delineated in areas proximal to the Nile Valley using Palsar-derived DEMs, and hill shade maps; these depressions are here interpreted as basement structures that were reactivated during the opening of the Red Sea and the Gulf of Suez. The sinistral E-W trending faults and shear zones of the Syrian Arc were mapped in northern Egypt from Sinai and across the Eastern and Western Deserts. These structures were mapped on the surface using hill shade images and their extension in the subsurface was successfully detected from Eigen-6C4 model-derived Bouguer and TDR maps. The E-W trending basement uplift (Uweinat-Aswan uplift) was mapped in southern Egypt and the N-S trending Uweinat-Howar uplift was delineated in western Sudan and eastern Chad using TDR maps. Thirdly, hydrological analysis was conducted using GRACE spherical harmonic solutions (RL05), and CSR 0.5° X 0.5°, and JPL Mascon solutions. These showed: (1) pronounced TWS depletion over the Dakhla basin (average of three solutions: -3.03 mm/yr); (2) the south to north groundwater flow from Sudan to Egypt is impeded by the E-W trending Uweinat-Aswan basement uplift, yet the southwest to northeast flow from Chad into Sudan is not obstructed by the Uweinat-Howar uplift, (3) the E-W trending faults and shear zones impede groundwater flow to the north and act as conduits for deep-seated groundwater discharge on the surface in natural depressions (e.g., Qattara) and in the overlying layers.

Trend analysis of vegetation in Louisiana's Atchafalaya river basin

USGS Publications Warehouse

O'Neil, Calvin P.; deSteiguer, J. Edward; North, Gary W.

1978-01-01

The purpose of the study was to determine vegetation succession trends; produce a current vegetation map of the basin; and to develop a mathematical model capable of predicting vegetation changes based on hydrologic factors. A statistical relationship of forests and hydrological variables with forest succession constraints predicted forest acreage totals for 16 forest categories within 70% or better of actual values in two-thirds of the cases. Using time-lapsed photography covering 42 years, 23 categories were described. The succession trend of vegetation since 1930, by sedimentation, had been toward mixed hardwoods, except for isolated areas. Satellite MSS Band 7 imagery was used to map the current vegetation into three main categories and for assessment of acreage. Additionally, a geological anomaly was recognized on satellite imagery indication an effect on drainage and sedimentation.

Joint geophysical investigation of a small scale magnetic anomaly near Gotha, Germany

NASA Astrophysics Data System (ADS)

Queitsch, Matthias; Schiffler, Markus; Goepel, Andreas; Stolz, Ronny; Guenther, Thomas; Malz, Alexander; Meyer, Matthias; Meyer, Hans-Georg; Kukowski, Nina

2014-05-01

In the framework of the multidisciplinary project INFLUINS (INtegrated FLUid Dynamics IN Sedimentary Basins) several airborne surveys using a full tensor magnetic gradiometer (FTMG) system were conducted in and around the Thuringian basin (central Germany). These sensors are based on highly sensitive superconducting quantum interference devices (SQUIDs) with a planar-type gradiometer setup. One of the main goals was to map magnetic anomalies along major fault zones in this sedimentary basin. In most survey areas low signal amplitudes were observed caused by very low magnetization of subsurface rocks. Due to the high lateral resolution of a magnetic gradiometer system and a flight line spacing of only 50m, however, we were able to detect even small magnetic lineaments. Especially close to Gotha a NW-SE striking strong magnetic anomaly with a length of 1.5 km was detected, which cannot be explained by the structure of the Eichenberg-Gotha-Saalfeld (EGS) fault zone and the rock-physical properties (low susceptibilities). Therefore, we hypothesize that the source of the anomaly must be related to an anomalous magnetization in the fault plane. To test this hypothesis, here we focus on the results of the 3D inversion of the airborne magnetic data set and compare them with existing structural geological models. In addition, we conducted several ground based measurements such as electrical resistivity tomography (ERT) and frequency domain electromagnetics (FDEM) to locate the fault. Especially, the geoelectrical measurements were able to image the fault zone. The result of the 2D electrical resistivity tomography shows a lower resistivity in the fault zone. Joint interpretation of airborne magnetics, geoelectrical and geological information let us propose that the source of the magnetization may be a fluid-flow induced impregnation with iron-oxide bearing minerals in the vicinity of the EGS fault plane.

The hydrocarbon accumulations mapping in crystalline rocks by mobile geophysical methods

NASA Astrophysics Data System (ADS)

Nesterenko, A.

2013-05-01

Sedimentary-migration origin theory of hydrocarbons dominates nowadays. However, a significant amount of hydrocarbon deposits were discovered in the crystalline rocks, which corroborates the theory of non-organic origin of hydrocarbons. During the solving of problems of oil and gas exploration in crystalline rocks and arrays so-called "direct" methods can be used. These methods include geoelectric methods of forming short-pulsed electromagnetic field (FSPEF) and vertical electric-resonance sounding (VERS) (FSPEF-VERS express-technology). Use of remote Earth sounding (RES) methods is also actual. These mobile technologies are extensively used during the exploration of hydrocarbon accumulations in crystalline rocks, including those within the Ukrainian crystalline shield. The results of explorations Four anomalous geoelectric zones of "gas condensate reservoir" type were quickly revealed as a result of reconnaissance prospecting works (Fig. 1). DTA "Obukhovychi". Anomaly was traced over a distance of 4 km. Approximate area is 12.0 km2. DTA"Korolevskaya". Preliminary established size of anomalous zone is 10.0 km2. The anomalous polarized layers of gas and gas-condensate type were determined. DTA "Olizarovskaya". Approximate size of anomaly is about 56.0 km2. This anomaly is the largest and the most intense. DTA "Druzhba". Preliminary estimated size of anomaly is 16.0 km2. Conclusions Long experience of a successful application of non-classical geoelectric methods for the solving of variety of practical tasks allow one to state their contribution to the development of a new paradigm of geophysical researches. Simultaneous usage of the remote sensing data processing and interpretation method and FSPEF and VERS technologies can essentially optimize and speed up geophysical work. References 1. S.P. Levashov. Detection and mapping of anomalies of "hydrocarbon deposit" type in the fault zones of crystalline arrays by geoelectric methods. / S.P. Levashov, N.A. Yakymchuk, I.N. Korchagin, V.V. Prilukov, J.N. Yakymchuk / / Oil. Gas. Novations. - 2011/4. - P. 10-17. Introduction. (in Russian); Fig. 1. The map of "gas condensate reservoir" type anomalous geoelectric zones on the area of human settlements Malin: 1 - a scale of the intensity of anomalous response, 2 - the zones of tectonic disturbances.

A magnetic anomaly of possible economic significance in southeastern Minnesota

USGS Publications Warehouse

Zietz, Isidore

1964-01-01

An aeromagnetic survey in southeastern Minnesota by the U. S. Geological Survey in cooperation with the State of Minnesota has revealed a high-amplitude, linear, and narrow magnetic feature that suggests a possible source of Precambrian iron-formation of economic value. For the past few years the U. S. Geological Survey has been conducting detailed geophysical studies of the midcontinent gravity anomaly--a broad, high-amplitude feature that extends from Lake Superior through the States of Minnesota, Iowa, Nebraska, and part of Kansas. As part of this study an aeromagnetic survey of the southern part of the State was made in cooperation with the State of Minnesota during the summer of 1963, in which a linear high-amplitude anomaly of the order of 4,000 gammas was discovered. Because of the high amplitude, the linearity, and the narrowness of the magnetic feature, it is believed the source may be Precambrian iron-formation of possible economic value. The anomalous area is in Fillmore County, approximately between the towns of Lanesboro and Peterson in the extreme southeastern part of the State. (See figures 1 and 2.) At the site of the anomaly, Cambrian sedimentary rocks occur in the valley of the Root River, and Ordovician rocks (nearly flat lying) mantle the upland areas. The uplands are largely covered by glacial deposits, which are relatively thin (Paul K. Sims, written communication, 1964). Depths to the Precambrian are estimated to range from 500 feet to 1,000 feet below the surface. The aeromagnetic map shown in figure 2 was compiled from continuous magnetic profiles made along east-west flight lines 1,000 feet above ground, and spaced approximately 1 mile apart. Contour intervals of 20, 100, and 500 gammas were used depending on the intensity. The instrument for the survey was a flux-gate type magnetometer (AN/ASQ-3A) which measures total-field variations. The contour map displays variations in magnetic pattern which are typical of shallow Precambrian rocks. Anomalies of the order of 1,000 gammas are shown along the east and west edges of the map. The outstanding feature is the previously mentioned linear positive anomaly that trends northeast and reaches a peak of 3,960 gammas. The positive anomaly is contoured from data on four consecutive profiles, but only two show high amplitudes. The high-amplitude anomalies along traverses 1 and 2 are shown in figure 3. Depth calculations suggest that the source of the anomaly lies about 1,000 feet below the surface. Assuming a dikelike source and magnetization resulting entirely from induction in the earth's field, several calculations were made in an attempt to fit the magnetic profile taken along the line AA' (see figs. 2 and 4), considered to be a typical cross-section of the magnetic anomaly. Comparisons are shown between observed and computed profiles. The fixed parameters used were (a) distance from detector to source of 2,000 ft; width of dike of 5,000 ft; dip of dike of 75?, 90?, 105? , and 120? , as shown. The best fit occurs when the dike is vertical or dips 75? to the southwest. For these cases, the susceptibility, k, is computed to be 0.016 c.g.s, units, and is comparable to k = 0.02+ calculated by Bath (1962) for the relatively unmetamorphosed iron-formation of the Main Megabi district in Minnesota where the induced magnetization was most likely the dominant magnetization. If the dominant magnetization for the anomaly in Fillmore County were remanent rather than induced, the economic importance of the anomaly would be greatly reduced. This anomaly seems sufficiently promising to warrant further geologic and geophysical investigation. Detailed ground magnetic and electrical studies would be useful to delineate the feature. In the final analysis, however, the presence of iron-formation can be determined only by the drill.

Tracking the Progress of EarthScope/USArray: The crust and upper mantle beneath the transition region between tectonic western US and cratonic eastern US

NASA Astrophysics Data System (ADS)

Shen, W.; Lin, F.; Ritzwoller, M. H.

2010-12-01

The transition region between the tectonic western US and the cratonic eastern US contains numerous significant geological regions (e.g., the Rocky Mountains, the Colorado Plateau, and the Rio Grande Rift), and also, unknowns (e.g, the location or extent of the east-west US dichotomy, the compensation of the high topography of the western Great Plains, the extensional mechanics of the Rio Grande Rift, and the structure of the mantle beneath the Colorado Plateau). The answers to these questions and others are critical to an understanding of the tectonics and tectonic history of this region and its impact on the cratonic eastern US. The recent deployments of seismic stations, particularly the EarthScope USArray Transportable Array (TA), provide an opportunity to construct a detailed 3-D structural model of the crust and upper mantle beneath this transition region, and thus allow us to address some of the questions listed above. We present results from ambient noise tomography (ANT) and teleseismic earthquake tomography by using data from TA stations within the western and central US. We processed continuous seismic noise data from ~600 TA stations from August 2008 to March 2010, which after data selection produces a data set with ~100,000 inter-station paths. Rayleigh wave phase speed maps between 6 and 40 sec period and Love wave phase speed maps between 8 and 30 sec with a resolution of ~60 km are constructed using eikonal tomography. In addition, we applied eikonal tomography (ET) to about 300 teleseismic earthquakes to obtain long-period (30 - 100 sec) Rayleigh wave phase speed maps and Love wave phase speeds maps (30 - 60 sec). By jointly inverting Rayleigh and Love phase speeds maps from ANT and earthquake tomography, we constructed a 3-D isotropic and radially anisotropic shear velocity model of the crust and upper mantle to ~150 km depth together with model uncertainties constrained by a Monte-Carlo inversion. The 3-D isotropic model reveals a variety of robust features in this transition region. In the uppermost crust, the main sedimentary basins (e.g., Green River, Uinta, Washakie, Powder River, Denver, Albuquerque, Permian, and Anadarko) are imaged. In the middle and lower crust where the low shear velocities from basins diminish, the Yellowstone hot spot becomes the main slow anomaly. In the uppermost mantle, high velocity anomalies are observed beneath the Colorado Plateau, the Wyoming craton, and the Great Plains. Although the Colorado Plateau shows more or less homogeneous shear velocity in its middle and towards its northern boundary, the other two main fast anomalies reveal inhomogeneous structures at depths deeper than 100 km. Two main low velocity anomalies are observed: one underlying the Snake River Plain which broadens and dips to the northeast and another U-shaped anomaly on the eastern margin of the Colorado Plateau. These velocity anomalies add to complexities at the transition between the tectonic western US and the stable eastern US. The location and uncertainty of the east-west shear velocity dichotomy also is constrained by this model.

Gravity field over the Sea of Galilee: Evidence for a composite basin along a transform fault

USGS Publications Warehouse

Ben-Avraham, Z.; ten Brink, Uri S.; Bell, R.; Reznikov, M.

1996-01-01

The Sea of Galilee (Lake Kinneret) is located at the northern portion of the Kinneret-Bet Shean basin, in the northern Dead Sea transform. Three hundred kilometers of continuous marine gravity data were collected in the lake and integrated with land gravity data to a distance of more than 20 km around the lake. Analyses of the gravity data resulted in a free-air anomaly map, a variable density Bouguer anomaly map, and a horizontal first derivative map of the Bouguer anomaly. These maps, together with gravity models of profiles across the lake and the area south of it, were used to infer the geometry of the basins in this region and the main faults of the transform system. The Sea of Galilee can be divided into two units. The southern half is a pull-apart that extends to the Kinarot Valley, south of the lake, whereas the northern half was formed by rotational opening and transverse normal faults. The deepest part of the basinal area is located well south of the deepest bathymetric depression. This implies that the northeastern part of the lake, where the bathymetry is the deepest, is a young feature that is actively subsiding now. The pull-apart basin is almost symmetrical in the southern part of the lake and in the Kinarot Valley south of the lake. This suggests that the basin here is bounded by strike-slip faults on both sides. The eastern boundary fault extends to the northern part of the lake, while the western fault does not cross the northern part. The main factor controlling the structural complexity of this area is the interaction of the Dead Sea transform with a subperpendicular fault system and rotated blocks.

Ionizing radiation environment for the TOMS mission

NASA Technical Reports Server (NTRS)

Lauriente, M.; Maloy, J. O.; Vampola, A. L.

1992-01-01

The Total Ozone Mapping Spectrometer (TOMS) will fly on several different spacecraft, each having an orbit which is approximately polar and 800-980 km in altitude. A description is given of the computer-based tools used for characterizing the spacecraft interactions with the ionizing radiation environment in orbit and the susceptibility requirements for ionizing radiation compatibility. The peak flux from the model was used to derive the expected radiation-induced noise in the South Atlantic Anomaly for the new TOMS instruments intended to fly on Advanced Earth Observatory System and Earth Probe.

Oceanic eddy detection and lifetime forecast using machine learning methods

NASA Astrophysics Data System (ADS)

Ashkezari, Mohammad D.; Hill, Christopher N.; Follett, Christopher N.; Forget, Gaël.; Follows, Michael J.

2016-12-01

We report a novel altimetry-based machine learning approach for eddy identification and characterization. The machine learning models use daily maps of geostrophic velocity anomalies and are trained according to the phase angle between the zonal and meridional components at each grid point. The trained models are then used to identify the corresponding eddy phase patterns and to predict the lifetime of a detected eddy structure. The performance of the proposed method is examined at two dynamically different regions to demonstrate its robust behavior and region independency.

Energy and remote sensing. [satellite exploration, monitoring, siting

NASA Technical Reports Server (NTRS)

Summers, R. A.; Smith, W. L.; Short, N. M.

1977-01-01

Exploration for uranium, thorium, oil, gas and geothermal activity through remote sensing techniques is considered; satellite monitoring of coal-derived CO2 in the atmosphere, and the remote assessment of strip mining and land restoration are also mentioned. Reference is made to color ratio composites based on Landsat data, which may aid in the detection of uranium deposits, and to computer-enhanced black and white airborne scanning imagery, which may locate geothermal anomalies. Other applications of remote sensing to energy resources management, including mapping of transportation networks and power plant siting, are discussed.

July 1973 ground survey of active Central American volcanoes

NASA Technical Reports Server (NTRS)

Stoiber, R. E. (Principal Investigator); Rose, W. I., Jr.

1973-01-01

The author has identified the following significant results. Ground survey has shown that thermal anomalies of various sizes associated with volcanic activity at several Central American volcanoes should be detectable from Skylab. Anomalously hot areas of especially large size (greater than 500 m in diameter) are now found at Santiaguito and Pacaya volcanoes in Guatemala and San Cristobal in Nicaragua. Smaller anomalous areas are to be found at least seven other volcanoes. This report is completed after ground survey of eleven volcanoes and ground-based radiation thermometry mapping at these same points.

Mapping and characterization from aeromagnetic data of the Foum Zguid dolerite Dyke (Anti-Atlas, Morocco) a member of the Central Atlantic Magmatic Province (CAMP)

NASA Astrophysics Data System (ADS)

Bouiflane, Mustapha; Manar, Ahmed; Medina, Fida; Youbi, Nasrrddine; Rimi, Abdelkrim

2017-06-01

A high-resolution aeromagnetic survey was carried out in the Anti- Atlas, Morocco covering the main areas traversed by the Great CAMP Foum Zguid dyke (FZD). This ;doleritic; dyke belongs to the Central Atlantic Magmatic Province (CAMP), a Large Igneous Province which is associated with the fragmentation of the supercontinent Pangaea and the initial stages of rifting of the Central Atlantic Ocean. It also coincides in time with the mass extinction of the Triassic - Jurassic boundary. Based on the study of geological maps and Google Earth satellite images, it appears that the FZD is poorly exposed and, often covered by Quaternary deposits. This work proposes aeromagnetic modelling and interpretation of the FZD in order to better constrain its structural extent. The data have allowed (i) mapping of the dyke over great distances, under the Quaternary deposits and through areas where it was poorly characterized on the geological map; (ii) identifying major tectonic lineaments interpreted as faults; (iii) recognizing magnetic anomalies related to mafic intrusive bodies; and (iv) informing about regional structural context.

Airborne gamma-ray spectrometer and magnetometer survey: Weed quadrangle, California. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1981-05-01

Volume II contains the flight path, radiometric multi-parameter stacked profiles, magnetic and ancillary parameter stacked profiles, histograms, and anomaly maps for the Weed Quadrangle in California.

MX Siting Investigation, Gravity Survey - Delamar Valley, Nevada.

DTIC Science & Technology

1981-07-20

reduces the data to Simple Bouguer Anomaly (see Section A1.4, Appendix A1.0). The Defense Mapping Agency Aerospace Center (DMAAC), St. Louis, Missouri...DRAWINGS Drawing Number 1 Complete Bouguer Anomaly Contours 2 Depth to Rock -Interpreted from In Pocket at Gravity Data End of Report iv E-TR-33-DM...ErtPX E-TR-3 3-DM 6 2.0 GRAVITY DATA REDUCTION DMAHTC/GSS obtained the basic observations for the new stations and reduced them to Simple Bouguer

Mapping the total electron content over Malaysia using Spherical Cap Harmonic Analysis

NASA Astrophysics Data System (ADS)

Bahari, S.; Abdullah, M.; Bouya, Z.; Musa, T. A.

2017-12-01

The ionosphere over Malaysia is unique because of her location which is in close proximity to the geomagnetic equator and is in the equatorial regions. In this region, the magnetic field is horizontally oriented from south to north and field aligned direction is in the meridional plane (ExB) which becomes the source of equatorial ionospheric anomaly occurrence such as plasma bubble, fountain effects and others. Until today, there is no model that has been developed over Malaysia to study the ionosphere. Due to that, the main objective of this paper is to develop a new technique for mapping the total electron content (TEC) from GPS measurements. Data by myRTKnet network of GPS receiver over Malaysia were used in this study. A new methodology, based on modified spherical cap harmonic analysis (SCHA), was developed to estimate diurnal vertical TEC over the region using GPS observations. The SCHA model is based on longitudinal expansion in Fourier series and fractional Legendre co-latitudinal functions over a spherical cap-like region. The TEC map with spatial resolution of 0.15 ° x 0.15 ° in latitude and longitude with the time resolution of 30 seconds are derived. TEC maps from the SCHA model were compared with the global ionospheric map and other regional models. Result shows that during low solar activity, SCHA model had a better mapping with the accuracy of less than 1 TECU compared to other regional models.

The reduction, verification and interpretation of MAGSAT magnetic data over Canada

NASA Technical Reports Server (NTRS)

Coles, R. L. (Principal Investigator); Haines, G. V.; Vanbeek, G. J.; Walker, J. K.; Newitt, L. R.; Nandi, A.

1982-01-01

Correlations between the MAGSAT scalar anomaly map produced at the Earth Physics ranch and other geophysical and geological data reveal relationships between high magnetic field and some metamorphic grade shields, as well as between low magnetic field and shield regions of lower metamorphic grade. An intriguing contrast exists between the broad low anomaly field over the Nasen-Gakkel Ridge (a spreading plate margin) and the high anomaly field over Iceland (part of a spreading margin). Both regions have high heat flow, and presumably thin magnetic crust. This indicates that Iceland is quite anomalous in its magnetic character, and possible similarities with the Alpha Ridge are suggested. Interesting correlations exist between MAGSAT anomalies around the North Atlantic, after reconstructing the fit of continents into a prerifting configuration. These correlations suggest that several orogenies in that region have not completely destroyed an ancient magnetization formed in high grade Precambrian rocks.

Eddy-induced Sea Surface Salinity changes in the tropical Pacific

NASA Astrophysics Data System (ADS)

Delcroix, T. C.; Chaigneau, A.; Soviadan, D.; Boutin, J.

2017-12-01

We analyse the Sea Surface Salinity (SSS) signature of westward propagating mesoscale eddies in the tropical Pacific by collocating 5 years (2010-2015) of SMOS (Soil Moisture and Ocean Salinity) SSS and altimetry-derived sea level anomalies. The main characteristics of mesoscale eddies are first identified in SLA maps. Composite analyses in the Central and Eastern ITCZ regions then reveal regionally dependent impacts with opposite SSS anomalies for the cyclonic and anticyclonic eddies. In the Central region (where we have the largest meridional SSS gradient), we found dipole-like SSS changes with maximum anomalies on the leading edge of the eddy. In the Eastern region (where we have the largest near-surface vertical salinity gradient) we found monopole-like SSS changes with maximum anomalies in the eddy centre. These dipole/monopole patterns and the rotational sense of eddies suggest the dominant role of horizontal and vertical advection in the Central and Eastern ITCZ regions, respectively.

Comparison of U-spatial statistics and C-A fractal models for delineating anomaly patterns of porphyry-type Cu geochemical signatures in the Varzaghan district, NW Iran

NASA Astrophysics Data System (ADS)

Ghezelbash, Reza; Maghsoudi, Abbas

2018-05-01

The delineation of populations of stream sediment geochemical data is a crucial task in regional exploration surveys. In this contribution, uni-element stream sediment geochemical data of Cu, Au, Mo, and Bi have been subjected to two reliable anomaly-background separation methods, namely, the concentration-area (C-A) fractal and the U-spatial statistics methods to separate geochemical anomalies related to porphyry-type Cu mineralization in northwest Iran. The quantitative comparison of the delineated geochemical populations using the modified success-rate curves revealed the superiority of the U-spatial statistics method over the fractal model. Moreover, geochemical maps of investigated elements revealed strongly positive correlations between strong anomalies and Oligocene-Miocene intrusions in the study area. Therefore, follow-up exploration programs should focus on these areas.

EMPACT 3D: an advanced EMI discrimination sensor for CONUS and OCONUS applications

NASA Astrophysics Data System (ADS)

Keranen, Joe; Miller, Jonathan S.; Schultz, Gregory; Sander-Olhoeft, Morgan; Laudato, Stephen

2018-04-01

We recently developed a new, man-portable, electromagnetic induction (EMI) sensor designed to detect and classify small, unexploded sub-munitions and discriminate them from non-hazardous debris. The ability to distinguish innocuous metal clutter from potentially hazardous unexploded ordnance (UXO) and other explosive remnants of war (ERW) before excavation can significantly accelerate land reclamation efforts by eliminating time spent removing harmless scrap metal. The EMI sensor employs a multi-axis transmitter and receiver configuration to produce data sufficient for anomaly discrimination. A real-time data inversion routine produces intrinsic and extrinsic anomaly features describing the polarizability, location, and orientation of the anomaly under test. We discuss data acquisition and post-processing software development, and results from laboratory and field tests demonstrating the discrimination capability of the system. Data acquisition and real-time processing emphasize ease-of-use, quality control (QC), and display of discrimination results. Integration of the QC and discrimination methods into the data acquisition software reduces the time required between sensor data collection and the final anomaly discrimination result. The system supports multiple concepts of operations (CONOPs) including: 1) a non-GPS cued configuration in which detected anomalies are discriminated and excavated immediately following the anomaly survey; 2) GPS integration to survey multiple anomalies to produce a prioritized dig list with global anomaly locations; and 3) a dynamic mapping configuration supporting detection followed by discrimination and excavation of targets of interest.

Geothermal Anomaly Mapping Using Landsat ETM+ Data in Ilan Plain, Northeastern Taiwan

NASA Astrophysics Data System (ADS)

Chan, Hai-Po; Chang, Chung-Pai; Dao, Phuong D.

2018-01-01

Geothermal energy is an increasingly important component of green energy in the globe. A prerequisite for geothermal energy development is to acquire the local and regional geothermal prospects. Existing geophysical methods of estimating the geothermal potential are usually limited to the scope of prospecting because of the operation cost and site reachability in the field. Thus, explorations in a large-scale area such as the surface temperature and the thermal anomaly primarily rely on satellite thermal infrared imagery. This study aims to apply and integrate thermal infrared (TIR) remote sensing technology with existing geophysical methods for the geothermal exploration in Taiwan. Landsat 7 (L7) Enhanced Thematic Mapper Plus (ETM+) imagery is used to retrieve the land surface temperature (LST) in Ilan plain. Accuracy assessment of satellite-derived LST is conducted by comparing with the air temperature data from 11 permanent meteorological stations. The correlation coefficient of linear regression between air temperature and LST retrieval is 0.76. The MODIS LST product is used for the cross validation of Landsat derived LSTs. Furthermore, Landsat ETM+ multi-temporal brightness temperature imagery for the verification of the LST anomaly results were performed. LST Results indicate that thermal anomaly areas appear correlating with the development of faulted structure. Selected geothermal anomaly areas are validated in detail by field investigation of hot springs and geothermal drillings. It implies that occurrences of hot springs and geothermal drillings are in good spatial agreement with anomaly areas. In addition, the significant low-resistivity zones observed in the resistivity sections are echoed with the LST profiles when compared with in the Chingshui geothermal field. Despite limited to detecting the surficial and the shallow buried geothermal resources, this work suggests that TIR remote sensing is a valuable tool by providing an effective way of mapping and quantifying surface features to facilitate the exploration and assessment of geothermal resources in Taiwan.

Geologic map of the Montoso Peak quadrangle, Santa Fe and Sandoval Counties, New Mexico

USGS Publications Warehouse

Thompson, Ren A.; Hudson, Mark R.; Shroba, Ralph R.; Minor, Scott A.; Sawyer, David A.

2011-01-01

The Montoso Peak quadrangle is underlain by volcanic rocks and associated sediments of the Cerros del Rio volcanic field in the southern part of the Española Basin that record volcanic, faulting, alluvial, colluvial, and eolian processes over the past three million years. The geology was mapped from 1997 to 1999 and modified in 2004 to 2008. The geologic mapping was carried out in support of the U.S. Geological Survey (USGS) Rio Grande Basin Project, funded by the USGS National Cooperative Geologic mapping Program. The mapped distribution of units is based primarily on interpretation of 1:16,000-scale, color aerial photographs taken in 1992, and 1:40,000-scale, black-and-white, aerial photographs taken in 1996. Most of the contacts on the map were transferred from the aerial photographs using a photogrammetric stereoplotter and subsequently field checked for accuracy and revised based on field determination of allostratigraphic and lithostratigraphic units. Determination of lithostratigraphic units in volcanic deposits was aided by geochemical data, 40Ar/39Ar geochronology, aeromagnetic and paleomagnetic data. Supplemental revision of mapped contacts was based on interpretation of USGS 1-meter orthoimagery. This version of the Montoso Peak quadrangle geologic map uses a traditional USGS topographic base overlain on a shaded relief base generated from 10-m digital elevation model (DEM) data from the USGS National Elevation Dataset (NED). Faults are identified with varying confidence levels in the map area. Recognizing and mapping faults developed near the surface in young, brittle volcanic rocks is difficult because (1) they tend to form fractured zones tens of meters wide rather than discrete fault planes, (2) the youth of the deposits has allowed only modest displacements to accumulate for most faults, and (3) many may have significant strike-slip components that do not result in large vertical offsets that are readily apparent in offset of sub-horizontal contacts. Those faults characterized as "certain" either have distinct offset of map units or had slip planes that were directly observed in the field. Faults classed as "inferred" were traced based on linear alignments of geologic, topographic and aerial photo features such as vents, lava flow edges, and drainages inferred to preferentially develop on fractured rock. Lineaments defined from magnetic anomalies form an additional constraint on potential fault locations.

A New Instrument for Magnetic Imaging of Rock Slabs at the Hand-Sample Scale

NASA Astrophysics Data System (ADS)

Brown, L. L.; Webber, J. R.; Williams, M. L.; Sweeney, J.

2015-12-01

Magnetic imaging techniques have provided a wealth of detailed information typically at two disparate spatial scales including the regional (e.g. satellite, airborne, and marine) and grain scales (e.g. Bitter colloid and magnetic force microscopy). However, there is a general lack of imaging techniques at the hand sample scale. We present a new instrument, procedure, and processing routine that automatically maps the magnetic flux density vector field above a slab of rock at a sub-millimeter resolution, which bridges the gap between the traditional magnetic mapping scales. This low-cost instrument consists of two linear axes that position and raster a stylus across the surface of a sample. Attached to the stylus is a MAG3110 triple axis magnetometer, which has an optimal spatial resolution of approximately 1 mm2. This technique has been particularly informative for metamorphic studies concerning the equilibria of ferrimagnetic minerals such as magnetite. For example, magnetic images have revealed complex anomalies within mafic granulites that indicate the heterogeneous production and removal of magnetite. Some mafic dikes display magnetic anomalies that are associated with partial retrograde metamorphism and hydration. Magnetic images of a sample of banded iron formation have documented sedimentary layering, as well as positive anomalies associated with the occurrence of leucosome. This association may provide key implications for anatectic redox reactions. Specimens extracted from various locations on slabs characterized by heterogeneous magnetic anomalies can be used to document disparate magnetic properties such as magnetic susceptibility, NRM, hysteresis, and coercivity distributions. As such, this technique may provide a context for targeted rock magnetic studies. The instrument provides a direct link for petrologic studies to magnetism that may be used as a small scale analog for regional and planetary magnetic anomalies.

Gravity anomalies of the Northern Hawaiian Islands: Implications on the shield evolutions of Kauai and Niihau

NASA Astrophysics Data System (ADS)

Flinders, Ashton F.; Ito, Garrett; Garcia, Michael O.

2010-08-01

New land and marine gravity data reveal two positive residual gravity anomalies in the Northern Hawaiian Islands: one over Kaua'i, the other between the islands of Kaua'i and Ni'ihau. These gravitational highs are similar in size and magnitude to those of other Hawaiian volcanoes, indicating local zones of high-density crust, attributed to olivine cumulates in solidified magma reservoirs. The residual gravity high over Kaua'i is located in the Līhu'e Basin, offset 8-12 km east of Kaua'i's geologically mapped caldera. This offset suggests that the mapped caldera is a collapsed feature later filled in with lava and not the long-term center of Kaua'i shield volcanism. A second residual gravity high, in the submarine channel between Kaua'i and Ni'ihau, marks the volcanic center of the Ni'ihau shield volcano. This second residual gravity anomaly implies that Ni'ihau's eastern boundary extended ˜20 km east of its present location. Through inversion, the residual gravity anomalies were modeled as being produced by two solidified magma reservoirs with average densities of 3100 kg/m3 and volumes between 2470 and 2540 km3. Considering the locations and sizes of the residual gravity anomalies/magma reservoirs, the extent of the two islands' paleoshorelines and potassium-argon dating of shield-stage lavas, we conclude that the two islands were not connected subaerially during their respective shield stages and that Ni'ihau's topographic summit was removed by an eastern flank collapse between 4.3 and 5.6 Ma. Continued constructional volcanism on western Kaua'i likely covered much of the submerged remains of eastern Ni'ihau.

Orbital studies of lunar magnetism

NASA Technical Reports Server (NTRS)

Mcleod, M. G.; Coleman, P. J., Jr.

1982-01-01

Limitations of present lunar magnetic maps are considered. Optimal processing of satellite derived magnetic anomaly data is also considered. Studies of coastal and core geomagnetism are discussed. Lunar remanent and induced lunar magnetization are included.

The Geopotential Research Mission - Mapping the near earth gravity and magnetic fields

NASA Technical Reports Server (NTRS)

Taylor, P. T.; Keating, T.; Smith, D. E.; Langel, R. A.; Schnetzler, C. C.; Kahn, W. D.

1983-01-01

The Geopotential Research Mission (GRM), NASA's low-level satellite system designed to measure the gravity and magnetic fields of the earth, and its objectives are described. The GRM will consist of two, Shuttle launched, satellite systems (300 km apart) that will operate simultaneously at a 160 km circular-polar orbit for six months. Current mission goals include mapping the global geoid to 10 cm, measuring gravity-field anomalies to 2 mgal with a spatial resolution of 100 km, detecting crustal magnetic anomalies of 100 km wavelength with 1 nT accuracy, measuring the vectors components to + or - 5 arc sec and 5 nT, and computing the main dipole or core field to 5 nT with a 2 nT/year secular variation detection. Resource analysis and exploration geology are additional applications considered.

Thermal Anomaly Engendered by the Emplacement of AN Au-DEPOSIT: Example from the Franciscan Complex

NASA Astrophysics Data System (ADS)

Lahfid, A.; Lacroix, B.; Delchini, S.; Hughes, J.

2016-12-01

The thermal history of the Lucia subterrane located within the Franciscan Complex (California, USA) has been previously proposed by Underwood et al. (1995). Based on both vitrinite reflectance (Rm) and illite cristallinity methods, these authors suggest that the Lucia subterrane is locally perturbed by a thermal anomaly (up to 300ºC), probably caused by the emplacement of an Au-deposit: the Los Burros Gold deposit. Although both the thermal anomaly and the deposit seem spatially correlated, their relationship is still poorly constrained. In order to better explain the anomalous temperatures recorded in the vicinity of the deposit and their possible link with mineralization processes, we first performed detailed geological and structural mapping within the Los Burros district coupled to a thermal study. The peak temperature reached by metasediments from the Lucia subterrane have been regionally investigated using Raman Spectroscopy of Carbonaceous Materials (RSCM) method. In addition, through a careful fluid-inclusion study of the deposit, the potential source and the temperature of the fluid responsible for the Los Burros Au-deposit emplacement are currently being investigated. Our preliminary results confirm the previous temperatures and the presence of the thermal anomaly in the range 260-320ºC as inferred by Underwood et al (1995). In addition, our structural interpretation shows that the Los Burros deposit was emplaced during a late tectonic event marked by local reorientation of the regional tectonic features and the emplacement of meter-wide, quartz-calcite-sulfide extension veins. The temperatures determined by both methods (RSCM thermometry and fluid inclusion microthermometry) are consistent and support that the thermal anomaly is likely generated by the emplacement of the Los Burros Au-deposit during a local tectonic event.

Three-dimensional seismic tomography from P wave and S wave microearthquake travel times and rock physics characterization of the Campi Flegrei Caldera

NASA Astrophysics Data System (ADS)

Vanorio, T.; Virieux, J.; Capuano, P.; Russo, G.

2005-03-01

The Campi Flegrei (CF) Caldera experiences dramatic ground deformations unsurpassed anywhere in the world. The source responsible for this phenomenon is still debated. With the aim of exploring the structure of the caldera as well as the role of hydrothermal fluids on velocity changes, a multidisciplinary approach dealing with three-dimensional delay time tomography and rock physics characterization has been followed. Selected seismic data were modeled by using a tomographic method based on an accurate finite difference travel time computation which simultaneously inverts P wave and S wave first-arrival times for both velocity model parameters and hypocenter locations. The retrieved P wave and S wave velocity images as well as the deduced Vp/Vs images were interpreted by using experimental measurements of rock physical properties on CF samples to take into account steam/water phase transition mechanisms affecting P wave and S wave velocities. Also, modeling of petrophysical properties for site-relevant rocks constrains the role of overpressured fluids on velocity. A flat and low Vp/Vs anomaly lies at 4 km depth under the city of Pozzuoli. Earthquakes are located at the top of this anomaly. This anomaly implies the presence of fractured overpressured gas-bearing formations and excludes the presence of melted rocks. At shallow depth, a high Vp/Vs anomaly located at 1 km suggests the presence of rocks containing fluids in the liquid phase. Finally, maps of the Vp*Vs product show a high Vp*Vs horseshoe-shaped anomaly located at 2 km depth. It is consistent with gravity data and well data and might constitute the on-land remainder of the caldera rim, detected below sea level by tomography using active source seismic data.

Characterization of a photometric anomaly in lunar Mare Nubium

NASA Astrophysics Data System (ADS)

Korokhin, Viktor; Shkuratov, Yuriy; Kaydash, Vadym; Basilevsky, Alexander; Rohachova, Larysa; Velikodsky, Yuri; Opanasenko, Nickolay; Videen, Gorden; Stankevich, Dmitry; Kaluhina, Olena

2016-03-01

A novel approach of constructing photometrically seamless mosaics of reflectance, color-ratios, and phase-curve slopes using LROC WAC images has been developed, which can be used to map the photometric parameters of the lunar surface. The approach takes into account both geometric corrections with data on local topography and photometric conjunctions using our simple photometric model. New mosaics obtained with the technique allow more reliable studies of structural and chemical characteristics of the lunar surface. This approach has been applied to analyze the photometric anomaly (21.6 S, 17.7 W, ~40 km in size) in Mare Nubium detected earlier with our Earth-based observations. For each point of the scene the parameters were calculated using the least-square method for several tens of source WAC images. Clementine mosaics also were used in the analysis, e.g., in order to estimate the parameter of maturity degree Is/FeO. The anomaly has low FeO and TiO2 abundance and reveals a higher slope of the phase function than surroundings. Thermal data from LRO Diviner measurements do not show anomalies in this region. We consider this area as a shallow flooding of an elevated formation of highland composition, the material of which could have been excavated and mixed up with upper layers of the lunar surface through meteoroid impacts. The anomalous behavior of the phase function can be explained by the difference of surface structure in the anomaly and surrounding regions on the scale of less than several centimeters. This may be due to larger quantities of small fragments of rocks and clumps on the surface and/or the presence of agglomerates having open structure.

Geophysical interpretation of U, Th, and rare earth element mineralization of the Bokan Mountain peralkaline granite complex, Prince of Wales Island, southeast Alaska

USGS Publications Warehouse

McCafferty, Anne E.; Stoeser, Douglas B.; Van Gosen, Bradley S.

2014-01-01

A prospectivity map for rare earth element (REE) mineralization at the Bokan Mountain peralkaline granite complex, Prince of Wales Island, southeastern Alaska, was calculated from high-resolution airborne gamma-ray data. The map displays areas with similar radioelement concentrations as those over the Dotson REE-vein-dike system, which is characterized by moderately high %K, eU, and eTh (%K, percent potassium; eU, equivalent parts per million uranium; and eTh, equivalent parts per million thorium). Gamma-ray concentrations of rocks that share a similar range as those over the Dotson zone are inferred to locate high concentrations of REE-bearing minerals. An approximately 1300-m-long prospective tract corresponds to shallowly exposed locations of the Dotson zone. Prospective areas of REE mineralization also occur in continuous swaths along the outer edge of the pluton, over known but undeveloped REE occurrences, and within discrete regions in the older Paleozoic country rocks. Detailed mineralogical examinations of samples from the Dotson zone provide a means to understand the possible causes of the airborne Th and U anomalies and their relation to REE minerals. Thorium is sited primarily in thorite. Uranium also occurs in thorite and in a complex suite of ±Ti±Nb±Y oxide minerals, which include fergusonite, polycrase, and aeschynite. These oxides, along with Y-silicates, are the chief heavy REE (HREE)-bearing minerals. Hence, the eU anomalies, in particular, may indicate other occurrences of similar HREE-enrichment. Uranium and Th chemistry along the Dotson zone showed elevated U and total REEs east of the Camp Creek fault, which suggested the potential for increased HREEs based on their association with U-oxide minerals. A uranium prospectivity map, based on signatures present over the Ross-Adams mine area, was characterized by extremely high radioelement values. Known uranium deposits were identified in the U-prospectivity map, but the largest tract occurs over a radioelement-rich granite phase within the pluton that is likely not related to mineralization. Neither mineralization type displays a well-defined airborne magnetic signature.

Near Space Tracking of the EM Phenomena Associated with the Main Earthquakes

NASA Technical Reports Server (NTRS)

Ouzounov, Dimitar; Taylor, Patrick; Bryant, Nevin; Pulinets, Sergey; Liu, Jann-Yenq; Yang, Kwang-Su

2004-01-01

Searching for electromagnetic (EM) phenomena originating in the Earth's crust prior to major earthquakes (M>5) are the object of this exploratory study. We present the idea of a possible relationship between: (1) electro-chemical and thermodynamic processes in the Earth's crust and (2) ionic enhancement of the atmosphere/ionosphere with tectonic stress and earthquake activity. The major source of these signals are proposed to originate from electromagnetic phenomenon which are responsible for these observed pre-seismic processes, such as, enhanced IR emission, also born as thermal anomalies, generation of long wave radiation, light emission caused by ground-to-air electric discharges, Total Electron Content (TEC) ionospheric anomalies and ionospheric plasma variations. The source of these data will include: (i) ionospheric plasma perturbations data from the recently launched DEMETER mission and currently available TEC/GPS network data; (ii) geomagnetic data from ORSTED and CHAMP; (iii) Thermal infra-red (TIR) transients mapped by the polar orbiting (NOAA/AVHRR, MODIS) and (iv) geosynchronous weather satellites measurements of GOES, METEOSAT. This approach requires continues observations and data collecting, in addition to both ground and space based monitoring over selected regions in order to investigate the various techniques for recording possible anomalies. During the space campaign emphasis will be on IR emission, obtained from TIR (thermal infrared) satellites, that records land/sea surface temperature anomalies and changes in the plasma and total electron content (TEC) of the ionosphere that occur over areas of potential earthquake activity.

InfoDROUGHT: Technical reliability assessment using crop yield data at the Spanish-national level

NASA Astrophysics Data System (ADS)

Contreras, Sergio; Garcia-León, David; Hunink, Johannes E.

2017-04-01

Drought monitoring (DM) is a key component of risk-centered drought preparedness plans and drought policies. InfoDROUGHT (www.infosequia.es) is a a site- and user-tailored and fully-integrated DM system which combines functionalities for: a) the operational satellite-based weekly-1km tracking of severity and spatial extent of drought impacts, b) the interactive and faster query and delivery of drought information through a web-mapping service. InfoDROUGHT has a flexible and modular structure. The calibration (threshold definitions) and validation of the system is performed by combining expert knowledge and auxiliary impact assessments and datasets. Different technical solutions (basic or advanced versions) or deployment options (open-standard or restricted-authenticated) can be purchased by end-users and customers according to their needs. In this analysis, the technical reliability of InfoDROUGHT and its performance for detecting drought impacts on agriculture has been evaluated in the 2003-2014 period by exploring and quantifying the relationships among the drought severity indices reported by InfoDROUGHT and the annual yield anomalies observed for different rainfed crops (maize, wheat, barley) at Spain. We hypothesize a positive relationship between the crop anomalies and the drought severity level detected by InfoDROUGHT. Annual yield anomalies were computed at the province administrative level as the difference between the annual yield reported by the Spanish Annual Survey of Crop Acreages and Yields (ESYRCE database) and the mean annual yield estimated during the study period. Yield anomalies were finally compared against drought greenness-based and thermal-based drought indices (VCI and TCI, respectively) to check the coherence of the outputs and the hypothesis stated. InfoDROUGHT has been partly funded by the Spanish Ministry of Economy and Competiveness through a Torres-Quevedo grant, and by the H2020-EU project "Bridging the Gap for Innovations in Disaster Resilience" (www.brigaid.eu).

Impact of Land Use Land Cover Change on East Asian monsoon

NASA Astrophysics Data System (ADS)

Chilukoti, N.; Xue, Y.; Liu, Y.; Lee, J.

2017-12-01

Humans modify the Earth's terrestrial surface on a continental scale by removing natural vegetation for crops/grazing. The current rates, extents and intensities of Land Use and Land Cover Change (LULCC) are greater than ever in history. The earlier studies of Land-atmosphere interactions used specified land surface conditions without interannual variations. In this study using NCEP CFSv2 coupled with Simplified Simple Biosphere (SSiB) model, biogeophysical impacts of LULCC on climate variability, anomaly, and changes are investigated by using the LULCC map from the Hurtt et al. (2006, 2011), which covered 66 years from 1950-2015 with annual variability. We combined the changes in crop and pasture fractions and consider as LULCC. A methodology had been developed to convert the Hurtt LULCC change map with 1° resolution to the GCM grid points. Since the GCM has only one dominant type, when the crop and pasture frction value at one point was larger than the critical value, that grid was assigned as degraded. Comprehensive evaluation was conducted to ensure the consistence of the trend of land degradation in the Hurtt's map and in the GCM LULCC map. In the degraded point, trees were changed to low vegetation or grasses, and low vegetation to bare soil. A set of surface parameters such as leaf area index, vegetation height, roughness length, and soil parameters, associated with vegetation are changed to show the degradation effects. We integrated the model with the potential vegetation map and the map with LULCC from 1950 to 2015, and the results indicate the LULCC causes precipitation reduction globally, with the strongest signals over monsoon regions. For instance, the degradation in Mexico, West Africa, south and East Asia and South America produced significant precipitation anomalies, some of which are consistent with observed regional precipitation anomalies. Meanwhile, it has also found that the LULCC enhances the surface warming during the summer in monsoon regions. The LULCC caused reduction in water released into the atmosphere from the surface through a reduction in transpiration and canopy evaporation, and changes in magnitude and pattern of moisture flux convergence, resulting in precipitation changes, and reduced evaporation lead to warm surface temperature during the summer season.

GIS prospectivity mapping and 3D modeling validation for potential uranium deposit targets in Shangnan district, China

NASA Astrophysics Data System (ADS)

Xie, Jiayu; Wang, Gongwen; Sha, Yazhou; Liu, Jiajun; Wen, Botao; Nie, Ming; Zhang, Shuai

2017-04-01

Integrating multi-source geoscience information (such as geology, geophysics, geochemistry, and remote sensing) using GIS mapping is one of the key topics and frontiers in quantitative geosciences for mineral exploration. GIS prospective mapping and three-dimensional (3D) modeling can be used not only to extract exploration criteria and delineate metallogenetic targets but also to provide important information for the quantitative assessment of mineral resources. This paper uses the Shangnan district of Shaanxi province (China) as a case study area. GIS mapping and potential granite-hydrothermal uranium targeting were conducted in the study area combining weights of evidence (WofE) and concentration-area (C-A) fractal methods with multi-source geoscience information. 3D deposit-scale modeling using GOCAD software was performed to validate the shapes and features of the potential targets at the subsurface. The research results show that: (1) the known deposits have potential zones at depth, and the 3D geological models can delineate surface or subsurface ore-forming features, which can be used to analyze the uncertainty of the shape and feature of prospectivity mapping at the subsurface; (2) single geochemistry anomalies or remote sensing anomalies at the surface require combining the depth exploration criteria of geophysics to identify potential targets; and (3) the single or sparse exploration criteria zone with few mineralization spots at the surface has high uncertainty in terms of the exploration target.

Use of ERTS-1 data: Summary report of work on ten tasks. [solving natural resources and environmental quality problems using ERTS-1 MSS data

NASA Technical Reports Server (NTRS)

Thomson, F. J.; Polcyn, F. C.; Bryan, M. L.; Sattinger, I. J.; Malila, W. A.; Nalepka, R. F.; Wezernak, C. T.; Horvath, R.; Vincent, R. K. (Principal Investigator)

1974-01-01

The author has identified the following significant results. Depth mapping's for a portion of Lake Michigan and at the Little Bahama Bank test site have been verified by use of navigation charts and on-site visits. A thirteen category recognition map of Yellowstone Park has been prepared. Model calculation of atmospheric effects for various altitudes have been prepared. Radar, SLAR, and ERTS-1 data for flooded areas of Monroe County, Michigan are being studied. Water bodies can be reliably recognized and mapped using maximum likelihood processing of ERTS-1 digital data. Wetland mapping has been accomplished by slicing of single band and/or ratio processing of two bands for a single observation date. Both analog and digital processing have been used to map the Lake Ontario basin using ERTS-1 data. Operating characteristic curves were developed for the proportion estimation algorithm to determine its performance in the measurement of surface water area. The signal in band MSS-5 was related to sediment content of waters by modelling approach and by relating surface measurements of water to processed ERTS data. Radiance anomalies in ERTS-1 data could be associated with the presence of oil on water in San Francisco Bay, but the anomalies were of the same order as those caused by variations in sediment concentration and tidal flushing.

Evaluation of HCMM satellite data for estuarine tidal circulation patterns and thermal inertia soil moisture measurements. [Delaware Bay, Cooper River, and the Potomac River estuaries; Luverne, Minnesota, soil moisture, and water temperature of Lake Anna, Virginia

NASA Technical Reports Server (NTRS)

Wiesnet, D. R.; Mcginnis, D. F., Jr. (Principal Investigator); Matson, M.; Pritchard, J. A.

1981-01-01

Digital thermal maps of the Cooper River (SC) and the Potomac River estuaries were prepared from heat capacity mapping radiometer (HCMR) tapes. Tidal phases were correctly interpreted and verified. Synoptic surface circulation patterns were charted by location thermal fronts and water mass boundaries within the estuaries. Thermal anomalies were detected adjacent of a conventional power plant on the Potomac. Under optimum conditions, estuaries as small as the Cooper River can be monitored for generalized thermal/tidal circulation patterns by the HCMM-type IR sensors. The HCMM thermal inertia approach to estimating soil moisture at the Luverne (MN) test site was found to be unsatisfactory as a NESS operational satellite technique because of cloud cover interference. Thermal-IR data show similar structure of the Baltimore and Washington heat islands when compared to NOAA AVHRR thermal-IR data. Thermal anomalies from the warm water discharge water of a nuclear power plant were mapped in Lake Anna, Virginia.

Surface wave tomography of North America and the Caribbean using global and regional broad-band networks: Phase velocity maps and limitations of ray theory

USGS Publications Warehouse

Godey, S.; Snieder, R.; Villasenor, A.; Benz, H.M.

2003-01-01

We present phase velocity maps of fundamental mode Rayleigh waves across the North American and Caribbean plates. Our data set consists of 1846 waveforms from 172 events recorded at 91 broad-band stations operating in North America. We compute phase velocity maps in four narrow period bands between 50 and 150 s using a non-linear waveform inversion method that solves for phase velocity perturbations relative to a reference Earth model (PREM). Our results show a strong velocity contrast between high velocities beneath the stable North American craton, and lower velocities in the tectonically active western margin, in agreement with other regional and global surface wave tomography studies. We perform detailed comparisons with global model results, which display good agreement between phase velocity maps in the location and amplitude of the anomalies. However, forward modelling shows that regional maps are more accurate for predicting waveforms. In addition, at long periods, the amplitude of the velocity anomalies imaged in our regional phase velocity maps is three time larger than in global phase velocity models. This amplitude factor is necessary to explain the data accurately, showing that regional models provide a better image of velocity structures. Synthetic tests show that the raypath coverage used in this study enables one to resolve velocity features of the order of 800-1000 km. However, only larger length-scale features are observed in the phase velocity maps. The limitation in resolution of our maps can be attributed to the wave propagation theory used in the inversion. Ray theory does not account for off-great-circle ray propagation effects, such as ray bending or scattering. For wavelengths less than 1000 km, scattering effects are significant and may need to be considered.

The major tectonic boundaries of the Northern Red Sea rift, Egypt derived from geophysical data analysis

NASA Astrophysics Data System (ADS)

Saleh, Salah; Pamukçu, Oya; Brimich, Ladislav

2017-09-01

In the present study, we have attempted to map the plate boundary between Arabia and Africa at the Northern Red Sea rift region including the Suez rift, Gulf of Aqaba-Dead Sea transform and southeastern Mediterranean region by using gravity data analysis. In the boundary analysis method which was used; low-pass filtered gravity anomalies of the Northern Red Sea rift region were computed. Different crustal types and thicknesses, sediment thicknesses and different heat flow anomalies were evaluated. According to the results, there are six subzones (crustal blocks) separated from each other by tectonic plate boundaries and/or lineaments. It seems that these tectonic boundaries reveal complex structural lineaments, which are mostly influenced by a predominant set of NNW-SSE to NW-SE trending lineaments bordering the Red Sea and Suez rift regions. On the other side, the E-W and N-S to NNE-SSW trended lineaments bordering the South-eastern Mediterranean, Northern Sinai and Aqaba-Dead Sea transform regions, respectively. The analysis of the low pass filtered Bouguer anomaly maps reveals that the positive regional anomaly over both the Red Sea rift and South-eastern Mediterranean basin subzones are considered to be caused by the high density of the oceanic crust and/or the anomalous upper mantle structures beneath these regions whereas, the broad medium anomalies along the western half of Central Sinai with the Suez rift and the Eastern Desert subzones are attributed to low-density sediments of the Suez rift and/or the thick upper continental crustal thickness below these zones. There are observable negative anomalies over the Northern Arabia subzone, particularly in the areas covered by Cenozoic volcanics. These negative anomalies may be attributed to both the low densities of the surface volcanics and/or to a very thick upper continental crust. On the contrary, the negative anomaly which belongs to the Gulf of Aqaba-Dead Sea transform zone is due to crustal thickening (with limited heat flow values) below this region. Additionally in this study, the crustal thinning was investigated with heat flow, magnetic and free air gravity anomalies in the Northern Red Sea rift region. In fact, the crustal thinning of the study area was also proportional to the regions of observable high heat flow values. Finally, our results were found to be well correlated with the topography, free air, aeromagnetic and heat flow dataset profiles crossing most of the study area.

The Hatu gold anomaly, Xinjiang-Uygur Autonomous Region, China - testing the hypothesis of aeolian transport of gold

USGS Publications Warehouse

Smith, D.B.; Theobald, P.K.; Shiquan, S.; Tianxiang, R.; Zhihui, H.

1993-01-01

In 1987, a cooperative project between the U.S. Geological Survey and the Institute of Geophysical and Geochemical Exploration was initiated to evaluate the origin of the Hatu gold anomaly. The anomaly is located in the Hatu mining district in the northwest corner of Xinjiang-Uygur Autonomous Region in northwest China. The climate is semiarid to arid and wind erosion predominates. A regional soil survey of the Hatu district, based on samples collected on a 200 by 500 m grid and composited prior to chemical analysis to a density of one sample per square km, delineated a series of south-southeast-trending Au anomalies. Anomalous Au values range from 5 ppb to more than 700 ppb. The Hatu anomaly, the most prominent of these anomalies, is more than 30 km long and about 5 km wide. The mining town of Hatu and the economic gold deposits of Qiqu 1 and Qiqu 2 are at the northern end of this anomaly. The axis of the Hatu anomaly cuts across mapped structure and stratigraphy in the district, but is parallel to the prevailing wind direction. This observation led to the hypothesis that the Hatu anomaly is the result of acolian dispersion of gold from the vicinity of Qiqu 1 and Qiqu 2. The alternative interpretation, that the anomalies reflected additional primary gold occurrences, was not consistent with existing information on the known occurrences and the geology. The investigation led to the identification of three types of gold in heavy-mineral concentrates derived from stream sediments that were collected along the axis of the Hatu anomaly: (1) free gold, (2) gold in pyrite, and (3) gold included in quartz. Gold in quartz was only observed within 2 km of Qiqu 1. The size of the gold particles and the number of gold particles in these samples did not decrease with distance from Qiqu 1 as would be expected from aeolian or fluvial dispersion from a point source. Instead, both the size and amount of gold increased significantly at a distance of 3.5 km from Qiqu 1 and this increase continued to approximately 5.5 km from Qiqu 1. The mean intermediate diameter of gold particles increased from 0.1 mm to approximately 0.25 mm and the gold particle content increased from approximately 0.3 particles per kg of sample to almost 8 particles per kg of sample. The morphology of the gold changed from a delicate filigree texture near Qiqu 1 to coarse, blocky particles in the southern part of the anomaly. The Hatu anomaly is caused primarily by alluvial dispersion of free gold from local point sources along the anomaly. Aeolian dispersion is restricted to very fine-grained (??2 ??m) gold included in sulfide minerals or quartz grains and is significant only within 1-2 km of the known deposits. ?? 1993.

The Gabbs Valley, Nevada, geothermal prospect: Exploring for a potential blind geothermal resource

NASA Astrophysics Data System (ADS)

Payne, J.; Bell, J. W.; Calvin, W. M.

2012-12-01

The Gabbs Valley prospect in west-central Nevada is a potential blind geothermal resource system. Possible structural controls on this system were investigated using high-resolution LiDAR, low sun-angle aerial (LSA) photography, exploratory fault trenching and a shallow temperature survey. Active Holocene faults have previously been identified at 37 geothermal systems with indication of temperatures greater than 100° C in the western Nevada region. Active fault controls in Gabbs Valley include both Holocene and historical structures. Two historical earthquakes occurring in 1932 and 1954 have overlapping surface rupture patterns in Gabbs Valley. Three active fault systems identified through LSA and LiDAR mapping have characteristics of Basin and Range normal faulting and Walker Lane oblique dextral faulting. The East Monte Cristo Mountains fault zone is an 8.5 km long continuous NNE striking, discrete fault with roughly 0.5 m right-normal historic motion and 3 m vertical Quaternary separation. The Phillips Wash fault zone is an 8.2 km long distributed fault system striking NE to N, with Quaternary fault scarps of 1-3 m vertical separation and a 500 m wide graben adjacent to the Cobble Cuesta anticline. This fault displays ponded drainages, an offset terrace riser and right stepping en echelon fault patterns suggestive of left lateral offset, and fault trenching exposed non-matching stratigraphy typical of a significant component of lateral offset. The unnamed faults of Gabbs Valley are a 10.6 km long system of normal faults striking NNE and Quaternary scarps are up to 4 m high. These normal faults largely do not have historic surface rupture, but a small segment of 1932 rupture has been identified. A shallow (2 m deep) temperature survey of 80 points covering roughly 65 square kilometers was completed. Data were collected over approximately 2 months, and continual base station temperature measurements were used to seasonally correct temperature measurements. A 2.5 km long temperature anomaly greater than 3° C above background temperatures forms west-northwest trending zone between terminations of the Phillips Wash fault zone and unnamed faults of Gabbs Valley to the south. Rupture segments of two young active faults bracket the temperature anomaly. The temperature anomaly may be due to several possible causes. 1. Increases in stress near the rupture segments or tip-lines of these faults, or where multiple fault splays exist, can increase fault permeability. The un-ruptured segments of these faults may be controlling the location of the Gabbs Valley thermal anomaly between ruptured segments of the 1932 Cedar Mountain and 1954 Fairview Peak earthquakes. 2. Numerous unnamed normal faults may interact and the hanging wall of these faults is hosting the thermal anomaly. The size and extent of the anomaly may be due to its proximity to a flat playa and not the direct location of the shallow heat anomaly. 3. The linear northwest nature of the thermal anomaly may reflect a hydrologic barrier in the subsurface controlling where heated fluids rise. A concealed NW- striking fault is possible, but has not been identified in previous studies or in the LiDAR or LSA fault mapping.

Oil and gas exploration system and method for detecting trace amounts of hydrocarbon gases in the atmosphere

DOEpatents

Wamsley, Paula R.; Weimer, Carl S.; Nelson, Loren D.; O'Brien, Martin J.

2003-01-01

An oil and gas exploration system and method for land and airborne operations, the system and method used for locating subsurface hydrocarbon deposits based upon a remote detection of trace amounts of gases in the atmosphere. The detection of one or more target gases in the atmosphere is used to indicate a possible subsurface oil and gas deposit. By mapping a plurality of gas targets over a selected survey area, the survey area can be analyzed for measurable concentration anomalies. The anomalies are interpreted along with other exploration data to evaluate the value of an underground deposit. The system includes a differential absorption lidar (DIAL) system with a spectroscopic grade laser light and a light detector. The laser light is continuously tunable in a mid-infrared range, 2 to 5 micrometers, for choosing appropriate wavelengths to measure different gases and avoid absorption bands of interference gases. The laser light has sufficient optical energy to measure atmospheric concentrations of a gas over a path as long as a mile and greater. The detection of the gas is based on optical absorption measurements at specific wavelengths in the open atmosphere. Light that is detected using the light detector contains an absorption signature acquired as the light travels through the atmosphere from the laser source and back to the light detector. The absorption signature of each gas is processed and then analyzed to determine if a potential anomaly exists.

Location Accuracy of INS/Gravity-Integrated Navigation System on the Basis of Ocean Experiment and Simulation

PubMed Central

Wang, Hubiao; Chai, Hua; Bao, Lifeng; Wang, Yong

2017-01-01

An experiment comparing the location accuracy of gravity matching-aided navigation in the ocean and simulation is very important to evaluate the feasibility and the performance of an INS/gravity-integrated navigation system (IGNS) in underwater navigation. Based on a 1′ × 1′ marine gravity anomaly reference map and multi-model adaptive Kalman filtering algorithm, a matching location experiment of IGNS was conducted using data obtained using marine gravimeter. The location accuracy under actual ocean conditions was 2.83 nautical miles (n miles). Several groups of simulated data of marine gravity anomalies were obtained by establishing normally distributed random error N(u,σ2) with varying mean u and noise variance σ2. Thereafter, the matching location of IGNS was simulated. The results show that the changes in u had little effect on the location accuracy. However, an increase in σ2 resulted in a significant decrease in the location accuracy. A comparison between the actual ocean experiment and the simulation along the same route demonstrated the effectiveness of the proposed simulation method and quantitative analysis results. In addition, given the gravimeter (1–2 mGal accuracy) and the reference map (resolution 1′ × 1′; accuracy 3–8 mGal), location accuracy of IGNS was up to reach ~1.0–3.0 n miles in the South China Sea. PMID:29261136

Location Accuracy of INS/Gravity-Integrated Navigation System on the Basis of Ocean Experiment and Simulation.

PubMed

Wang, Hubiao; Wu, Lin; Chai, Hua; Bao, Lifeng; Wang, Yong

2017-12-20

An experiment comparing the location accuracy of gravity matching-aided navigation in the ocean and simulation is very important to evaluate the feasibility and the performance of an INS/gravity-integrated navigation system (IGNS) in underwater navigation. Based on a 1' × 1' marine gravity anomaly reference map and multi-model adaptive Kalman filtering algorithm, a matching location experiment of IGNS was conducted using data obtained using marine gravimeter. The location accuracy under actual ocean conditions was 2.83 nautical miles (n miles). Several groups of simulated data of marine gravity anomalies were obtained by establishing normally distributed random error N ( u , σ 2 ) with varying mean u and noise variance σ 2 . Thereafter, the matching location of IGNS was simulated. The results show that the changes in u had little effect on the location accuracy. However, an increase in σ 2 resulted in a significant decrease in the location accuracy. A comparison between the actual ocean experiment and the simulation along the same route demonstrated the effectiveness of the proposed simulation method and quantitative analysis results. In addition, given the gravimeter (1-2 mGal accuracy) and the reference map (resolution 1' × 1'; accuracy 3-8 mGal), location accuracy of IGNS was up to reach ~1.0-3.0 n miles in the South China Sea.

Dilution correction equation revisited: The impact of stream slope, relief ratio and area size of basin on geochemical anomalies

NASA Astrophysics Data System (ADS)

Shahrestani, Shahed; Mokhtari, Ahmad Reza

2017-04-01

Stream sediment sampling is a well-known technique used to discover the geochemical anomalies in regional exploration activities. In an upstream catchment basin of stream sediment sample, the geochemical signals originating from probable mineralization could be diluted due to mixing with the weathering material coming from the non-anomalous sources. Hawkes's equation (1976) was an attempt to overcome the problem in which the area size of catchment basin was used to remove dilution from geochemical anomalies. However, the metal content of a stream sediment sample could be linked to several geomorphological, sedimentological, climatic and geological factors. The area size is not itself a comprehensive representative of dilution taking place in a catchment basin. The aim of the present study was to consider a number of geomorphological factors affecting the sediment supply, transportation processes, storage and in general, the geochemistry of stream sediments and their incorporation in the dilution correction procedure. This was organized through employing the concept of sediment yield and sediment delivery ratio and linking such characteristics to the dilution phenomenon in a catchment basin. Main stream slope (MSS), relief ratio (RR) and area size (Aa) of catchment basin were selected as the important proxies (PSDRa) for sediment delivery ratio and then entered to the Hawkes's equation. Then, Hawkes's and new equations were applied on the stream sediment dataset collected from Takhte-Soleyman district, west of Iran for Au, As and Sb values. A number of large and small gold, antimony and arsenic mineral occurrences were used to evaluate the results. Anomaly maps based on the new equations displayed improvement in anomaly delineation taking the spatial distribution of mineral deposits into account and could present new catchment basins containing known mineralization as the anomaly class, especially in the case of Au and As. Four catchment basins having Au and As mineralization were added to anomaly class and also one catchment basin with known As occurrence was highlighted as anomalous using new approach. The results demonstrated the usefulness of considering geomorphological parameters in dealing with dilution phenomenon in a catchment basin.

Identification of best particle radiation shielded region through Energetic Neutral Atoms mapping

NASA Astrophysics Data System (ADS)

Milillo, A.; De Angelis, E.; Mura, A.; Orsini, S.; Mangano, V.; Massetti, S.; Rispoli, R.; Lazzarotto, F.; Vertolli, N.; Lavagna, M.; Ferrari, F.; Lunghi, P.; Attinà, P.; Parissenti, G.

2017-09-01

The lunar surface is directly exposed either to direct solar wind, or to Earth's magnetospheric plasma due to the Moon's lack of a magnetosphere or a dense atmosphere. This exposure could create inhospitable conditions for a possible human presence on the Moon, so it is crucial to investigate the close-to-surface environment for establishing the best reliable locations for future human bases. Although it lacks a global magnetic field, the Moon possesses magnetic anomalies that create mini-magnetospheres, where the solar wind is partly deflected. The local protection of the surface from the solar wind radiation inside the mini-magnetospheres could make these sites preferred for future lunar colonization. It is crucial a detailed characterization of these sites. In this paper, an investigation based on the detection of Energetic Neutral Atoms (ENA) from the surface for identifying the best particle radiation shielded region is proposed. A high spatial resolution mapping via ENA is a feasible and it is powerful way for reaching this goal.

Areas with Surface Thermal Anomalies as Detected by ASTER and LANDSAT Data around South Canyon Hot Springs, Garfield County, Colorado

DOE Data Explorer

Khalid Hussein

2012-02-01

This map shows areas of anomalous surface temperature around South Canyon Hot Springs as identified from ASTER and LANDSAT thermal data and spatial based insolation model. The temperature for the ASTER data was calculated using the Emissivity Normalization Algorithm that separate temperature from emissivity. The incoming solar radiation was calculated using spatial based insolation model developed by Fu and Rich (1999). Then the temperature due to solar radiation was calculated using emissivity derived from ASTER data. The residual temperature, i.e. temperature due to solar radiation subtracted from ASTER temperature was used to identify thermally anomalous areas. Areas having anomalous temperature in the ASTER data are shown in blue diagonal hatch, while areas having anomalous temperature in the LANDSAT data are shown in magenta on the map. Thermal springs and areas with favorable geochemistry are also shown. Springs or wells having non-favorable geochemistry are shown as blue dots.

Accuracy of the determination of mean anomalies and mean geoid undulations from a satellite gravity field mapping mission

NASA Technical Reports Server (NTRS)

Jekeli, C.; Rapp, R. H.

1980-01-01

Improved knowledge of the Earth's gravity field was obtained from new and improved satellite measurements such as satellite to satellite tracking and gradiometry. This improvement was examined by estimating the accuracy of the determination of mean anomalies and mean undulations in various size blocks based on an assumed mission. In this report the accuracy is considered through a commission error due to measurement noise propagation and a truncation error due to unobservable higher degree terms in the geopotential. To do this the spectrum of the measurement was related to the spectrum of the disturbing potential of the Earth's gravity field. Equations were derived for a low-low (radial or horizontal separation) mission and a gradiometer mission. For a low-low mission of six month's duration, at an altitude of 160 km, with a data noise of plus or minus 1 micrometers sec for a four second integration time, we would expect to determine 1 deg x 1 deg mean anomalies to an accuracy of plus or minus 2.3 mgals and 1 deg x 1 deg mean geoid undulations to plus or minus 4.3 cm. A very fast Fortran program is available to study various mission configurations and block sizes.

Study of ionospheric precursors using GPS and GIM-TEC data related to earthquakes occurred on 16 April and 24 September, 2013 in Pakistan region

NASA Astrophysics Data System (ADS)

Pundhir, Devbrat; Singh, Birbal; Singh, O. P.; Gupta, Saral Kumar; Karia, S. P.; Pathak, K. N.

2017-11-01

In this paper, we have examined the diurnal variations of GPS-TEC observed at two Indian stations of Agra (27.2°N, 78°E) and Surat (21.16°N, 72.78°E) and global ionospheric maps data (GIM-TEC) for the months of April and September 2013 in search of ionospheric precursors of three major earthquakes (M > 6.5) that occurred in these months. The well-established quartile based statistical technique is adopted for the analysis of TEC data. The results show two kinds of anomalies, one in which simultaneous enhancements in TEC occurred in the three sets of data, 1-9 days and 3 days before the main shock in the two months respectively, and another in which anomalies occurred 15 days before in April, and 21 days before in September at Surat respectively. The depletions have also been found in three data sets but they are not significant. These anomalies are unlikely be influenced by geomagnetic parameters due to quiet magnetic conditions. The effect of also solar activity have also been considered and examined very precisely. The results are interpreted in terms of Lithosphere-Atmosphere-Ionosphere coupling (LAIC) mechanisms available in the literature.

Pre-earthquake Anomalies of the Ion Velocity in the Ionosphere

NASA Astrophysics Data System (ADS)

Liu, J. Y. G.; Chao, C. K.

2016-12-01

In the paper, pre-earthquake ionospheric anomalies (PEIAs) of the ion velocity, which are further employed to estimate the seismo-ionospheric electric fields, are for the first time reported. To see whether ionospheric ion velocity can be used to detect PEIAs or not, we examine concurrent measurements of the ion density, ion temperature, and the ion velocity probed by ROCSAT/IPEI (ionospheric Plasma and Electrodynamics Instrument), as well as the global ionospheric map (GIM) of the total electron content (TEC) derived by ground-based GPS receivers during the 31 March 2002 M6.8 Earthquake in Taiwan. It is found around the epicenter area 1-5 days before the earthquake that the GIM TEC significantly decreases, while the ROCSAT/IPEI ion density significantly decreases and ion velocity in the downward direction anomalously increases. The increase in the downward velocity implies that a westward electric field of about 0.91mV/m generated during the earthquake period is essential.

Interferometric imaging of the 2011-2013 Campi Flegrei unrest

NASA Astrophysics Data System (ADS)

De Siena, Luca; Nakahara, Hisashi; Zaccarelli, Lucia; Sammarco, Carmelo; La Rocca, Mario; Bianco, Francesca

2017-04-01

After its 1983-84 seismic and deformation crisis, seismologists have recorded very low and clustered seismicity at Campi Flegrei caldera (Italy). Hence, noise interferometry imaging has become the only option to image the present volcano logical state of the volcano. Three-component noise data recorded before, during, and after Campi Flegrei last deformation and geochemical unrest (2011-2013) have thus been processed with up-to-date interferometric imaging workflow based on MSNoise. Noise anisotropy, which strongly affects measurements throughout the caldera at all frequencies, has been accounted for by self-correlation measurements and smoothed by phase weighted stacking and phase-match filtering. The final group-velocity maps show strong low-velocity anomalies at the location of the last Campi Flegrei eruption (1538 A.D.). The main low-velocity anomalies contour Solfatara volcano and follow geomorphological cross-faulting. The comparison with geophysical imaging results obtained during the last seismic unrest at the caldera suggest strong changes in the physical properties of the volcano, particularly in the area of major hydrogeological hazard.

Altered Orientation and Flight Paths of Pigeons Reared on Gravity Anomalies: A GPS Tracking Study

PubMed Central

Blaser, Nicole; Guskov, Sergei I.; Meskenaite, Virginia; Kanevskyi, Valerii A.; Lipp, Hans-Peter

2013-01-01

The mechanisms of pigeon homing are still not understood, in particular how they determine their position at unfamiliar locations. The “gravity vector” theory holds that pigeons memorize the gravity vector at their home loft and deduct home direction and distance from the angular difference between memorized and actual gravity vector. However, the gravity vector is tilted by different densities in the earth crust leading to gravity anomalies. We predicted that pigeons reared on different gravity anomalies would show different initial orientation and also show changes in their flight path when crossing a gravity anomaly. We reared one group of pigeons in a strong gravity anomaly with a north-to-south gravity gradient, and the other group of pigeons in a normal area but on a spot with a strong local anomaly with a west-to-east gravity gradient. After training over shorter distances, pigeons were released from a gravitationally and geomagnetically normal site 50 km north in the same direction for both home lofts. As expected by the theory, the two groups of pigeons showed divergent initial orientation. In addition, some of the GPS-tracked pigeons also showed changes in their flight paths when crossing gravity anomalies. We conclude that even small local gravity anomalies at the birth place of pigeons may have the potential to bias the map sense of pigeons, while reactivity to gravity gradients during flight was variable and appeared to depend on individual navigational strategies and frequency of position updates. PMID:24194860

Altered orientation and flight paths of pigeons reared on gravity anomalies: a GPS tracking study.

PubMed

Blaser, Nicole; Guskov, Sergei I; Meskenaite, Virginia; Kanevskyi, Valerii A; Lipp, Hans-Peter

2013-01-01

The mechanisms of pigeon homing are still not understood, in particular how they determine their position at unfamiliar locations. The "gravity vector" theory holds that pigeons memorize the gravity vector at their home loft and deduct home direction and distance from the angular difference between memorized and actual gravity vector. However, the gravity vector is tilted by different densities in the earth crust leading to gravity anomalies. We predicted that pigeons reared on different gravity anomalies would show different initial orientation and also show changes in their flight path when crossing a gravity anomaly. We reared one group of pigeons in a strong gravity anomaly with a north-to-south gravity gradient, and the other group of pigeons in a normal area but on a spot with a strong local anomaly with a west-to-east gravity gradient. After training over shorter distances, pigeons were released from a gravitationally and geomagnetically normal site 50 km north in the same direction for both home lofts. As expected by the theory, the two groups of pigeons showed divergent initial orientation. In addition, some of the GPS-tracked pigeons also showed changes in their flight paths when crossing gravity anomalies. We conclude that even small local gravity anomalies at the birth place of pigeons may have the potential to bias the map sense of pigeons, while reactivity to gravity gradients during flight was variable and appeared to depend on individual navigational strategies and frequency of position updates.

Evaluation of ERTS imagery for spectral geological mapping in diverse terranes of New York State

NASA Technical Reports Server (NTRS)

Isachsen, Y. W.; Fakundiny, R. H.; Forster, S. W.

1974-01-01

Linear anomalies dominate the new geological information derived from ERTS-1 imagery, total lengths now exceeding 6000 km. Experimentation with a variety of viewing techniques suggests that conventional photogeologic analyses of band 7 results in the location of more than 97 percent of all linears found. The maxima on rose diagrams for ERTS-1 anomalies correspond well with those for mapped faults and topographic lineaments, despite a difference in relative magnitudes of maxima thought due to solar illumination direction. A multiscale analysis of linears showed that single topographic linears at 1:2,500,000 became segmented at 1:1,000,000, aligned zones of shorter parallel, en echelon, or conjugate linears at 1:500,000, and still shorter linears lacking obvious alignment at 1:250,000. Visible glacial features include individual drumlins, best seen in winter imagery, drumlinoids, eskers, ice-marginal drainage channels, glacial lake shorelines and sand plains, and end moraines.

Method for identifying anomalous terrestrial heat flows

DOEpatents

Del Grande, Nancy Kerr

1977-01-25

A method for locating and mapping the magnitude and extent of terrestrial heat-flow anomalies from 5 to 50 times average with a tenfold improved sensitivity over orthodox applications of aerial temperature-sensing surveys as used for geothermal reconnaissance. The method remotely senses surface temperature anomalies such as occur from geothermal resources or oxidizing ore bodies by: measuring the spectral, spatial, statistical, thermal, and temporal features characterizing infrared radiation emitted by natural terrestrial surfaces; deriving from these measurements the true surface temperature with uncertainties as small as 0.05 to 0.5 K; removing effects related to natural temperature variations of topographic, hydrologic, or meteoric origin, the surface composition, detector noise, and atmospheric conditions; factoring out the ambient normal-surface temperature for non-thermally enhanced areas surveyed under otherwise identical environmental conditions; distinguishing significant residual temperature enhancements characteristic of anomalous heat flows and mapping the extent and magnitude of anomalous heat flows where they occur.

Estimating Antarctic Near-Surface Magnetic Anomalies from Oersted and CHAMP Satellite Magnetometer Observations

NASA Technical Reports Server (NTRS)

vonFrese, Ralph R. B.; Kim, Hyung Rae; Gaya-Pique, Luis R.; Taylor, Patrick T.; Golynsky, Alexander V.; Kim, Jeong Woo

2004-01-01

Significant improvement in predicting near-surface magnetic anomalies can result from the highly accurate magnetic observations of the CHAMP satellite that is orbiting at about 400 km altitude. In general, regional magnetic signals of the crust are strongly masked by the core field and its secular variations due to wavelength coupling in the spherical harmonic representation and thus are difficult to isolate in the satellite measurements. However, efforts to isolate the regional lithospheric from core field components can exploit the correlations between the CHAMP magnetic anomalies and the pseudo magnetic effects inferred from gravity-derived crustal thickness variations. In addition, we can use spectral correlation theory to filter the static lithospheric field components from the dynamic external field effects. Employing these procedures, we processed the CHAMP magnetic conservations for an improved magnetic anomaly map of the Antarctic crust. Relative to the much higher altitude Oersted and noisier Magsat observations, CHAMP magnetic anomalies at 400 km altitude reveal new details on the effects of intra-crustal magnetic features and crustal thickness variations of the Antarctic. Moreover, these results greatly facilitate predicting magnetic anomalies in the regional coverage gaps of the ADMAP compilation of Antarctic magnetic anomalies from shipborne, airborne and ground surveys. Our analysis suggests that considerable new insights on the magnetic properties of the lithosphere may be revealed by a further order-of-magnitude improvement in the accuracy of the magnetometer.

Atmospheric response to anomalous autumn surface forcing in the Arctic Basin

NASA Astrophysics Data System (ADS)

Cassano, Elizabeth N.; Cassano, John J.

2017-09-01

Data from four reanalyses are analyzed to evaluate the downstream atmospheric response both spatially and temporally to anomalous autumn surface forcing in the Arctic Basin. Running weekly mean skin temperature anomalies were classified using the self-organizing map algorithm. The resulting classes were used to both composite the initial atmospheric state and determine how the atmosphere evolves from this state. The strongest response was to anomalous forcing—positive skin temperature and total surface energy flux anomalies and reduced sea ice concentration—in the Barents and Kara Seas. Analysis of the evolution of the atmospheric state for 12 weeks after the initial forcing showed a persistence in the anomalies in this area which led to a buildup of heat in the atmosphere. This resulted in positive 1000-500 hPa thickness and high-pressure circulation anomalies in this area which were associated with cold air advection and temperatures over much of central and northern Asia. Evaluation of days with the opposite forcing (i.e., negative skin temperature anomalies and increased sea ice concentration in the Barents and Kara Seas) showed a mirrored, opposite downstream atmospheric response. Other patterns with positive skin temperature anomalies in the Arctic Basin did not show the same response most likely because the anomalies were not as strong nor did they persist for as many weeks following the initial forcing.

Gravity field of Venus at constant altitude and comparison with earth

NASA Technical Reports Server (NTRS)

Bowin, C.; Abers, G.; Shure, L.

1985-01-01

The gravity field of Venus is characterized in gravity-anomaly and geoid-undulation maps produced by applying the harmonic-spline technique (Shure et al., 1982 and 1983; Parker and Shure, 1982) to Pioneer Venus Orbiter line-of-sight data. A positive correlation between Venusian topographic features and gravity anomalies is observed, in contrast to the noncorrelation seen on earth, and attributed to the thicker crust of Venus (70-80 vs 5-40 km for earth), crustal loading by recent volcanism, and possible regional elevation due to deep heating and thermal expansion.

Gravity anomalies, plate tectonics and the lateral growth of Precambrian North America

NASA Technical Reports Server (NTRS)

Thomas, M. D.; Grieve, R. A. F.; Sharpton, V. L.

1988-01-01

The widespread gravity coverage of North America provides a picture of the gross structural fabric of the continent via the trends of gravity anomalies. The structural picture so obtained reveals a mosaic of gravity trend domains, many of which correlate closely with structural provinces and orogenic terranes. The gravity trend map, interpreted in the light of plate-tectonic theory, thus provides a new perspective for examining the mode of assembly and growth of North America. Suture zones, palaeosubduction directions, and perhaps, contrasting tectonic histories may be identified using gravity patterns.

Seismo-electromagnetic anomalies observed by Fomosat-1 and GIM TEC during January 27 1999 to July 2004

NASA Astrophysics Data System (ADS)

Yu, C. Y.; Liu, J. Y. G.

2014-12-01

In this study, we examine the pre-earthquake ionospheric anomalies (PEIAs) by the electron density (Ne) and ion temperature (Ti) observed by FORMOSAT-1 (ROCSAT-1) satellite during magnitude greater than 7.0 worldwide earthquakes during 1999-2004. Meanwhile, PEIAs is also currently investigated to have a better understanding of the spatial distribution of the ROCSAT-1 SIPs. Total electron density (TEC) of the global ionosphere map (GIM) confirm that the anomalous feature appear near the epicenters before the earthquakes.

Statistical Techniques For Real-time Anomaly Detection Using Spark Over Multi-source VMware Performance Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solaimani, Mohiuddin; Iftekhar, Mohammed; Khan, Latifur

Anomaly detection refers to the identi cation of an irregular or unusual pat- tern which deviates from what is standard, normal, or expected. Such deviated patterns typically correspond to samples of interest and are assigned different labels in different domains, such as outliers, anomalies, exceptions, or malware. Detecting anomalies in fast, voluminous streams of data is a formidable chal- lenge. This paper presents a novel, generic, real-time distributed anomaly detection framework for heterogeneous streaming data where anomalies appear as a group. We have developed a distributed statistical approach to build a model and later use it to detect anomaly. Asmore » a case study, we investigate group anomaly de- tection for a VMware-based cloud data center, which maintains a large number of virtual machines (VMs). We have built our framework using Apache Spark to get higher throughput and lower data processing time on streaming data. We have developed a window-based statistical anomaly detection technique to detect anomalies that appear sporadically. We then relaxed this constraint with higher accuracy by implementing a cluster-based technique to detect sporadic and continuous anomalies. We conclude that our cluster-based technique out- performs other statistical techniques with higher accuracy and lower processing time.« less

Observations of the Weddell Sea Anomaly in the ground-based and space-borne TEC measurements

NASA Astrophysics Data System (ADS)

Zakharenkova, Irina; Cherniak, Iurii; Shagimuratov, Irk

2017-08-01

The Weddell Sea Anomaly (WSA) is a summer ionospheric anomaly, which is characterized by a greater nighttime ionospheric density than that in daytime in the region near the Weddell Sea. We investigate the WSA signatures in the ground-based TEC (vertical total electron content) by using GPS and GLONASS measurements of the dense regional GNSS networks in South America. We constructed the high-resolution regional TEC maps for December 2014-January 2015. The WSA effects of the TEC exceed the noontime values are registered starting from 17 LT, it reaches its maximum at 01-05 LT and starts to disappear after 09 LT. Maximal TEC enhancements were as large as a factor of 2.5-3.5 and were registered at 03-04 LT. This effect was mainly localized in the geographical region of 55°S-75°S latitude and 80°W-30°W longitude, close to the Antarctic Peninsula. Further, we examined the WSA occurrence in the topside ionosphere by using GPS measurements from a zenith-looking GPS antenna on board three Swarm satellites to determine topside TEC (above ∼500 km altitude) at the topside ionosphere-plasmasphere system. Global maps of the topside TEC indicated that the zone with significant WSA effect in the topside TEC (TEC increase ∼2-4 times the noontime level) had a large spatial extent over southern Pacific and Atlantic Ocean. It was observed around 150°W-20°W and between 40°S and 70°S during 23 LT - 06 LT. For the first time, the WSA signatures were shown in the topside TEC data derived from the GPS measurements onboard the Swarm constellation. Independently, two other instruments - FORMOSAT-3/COSMIC radio occultation electron density profiles and in situ measurements by the Langmuir Probe instrument onboard Swarm satellites - were able to confirm: (1) the same location of the WSA zone as revealed in Swarm TEC; (2) the most-pronounced WSA effect, as a maximal electron density exceed over the noontime values, corresponds to altitudes above 400-500 km.

An immunity-based anomaly detection system with sensor agents.

PubMed

Okamoto, Takeshi; Ishida, Yoshiteru

2009-01-01

This paper proposes an immunity-based anomaly detection system with sensor agents based on the specificity and diversity of the immune system. Each agent is specialized to react to the behavior of a specific user. Multiple diverse agents decide whether the behavior is normal or abnormal. Conventional systems have used only a single sensor to detect anomalies, while the immunity-based system makes use of multiple sensors, which leads to improvements in detection accuracy. In addition, we propose an evaluation framework for the anomaly detection system, which is capable of evaluating the differences in detection accuracy between internal and external anomalies. This paper focuses on anomaly detection in user's command sequences on UNIX-like systems. In experiments, the immunity-based system outperformed some of the best conventional systems.

Remanent and induced contributions of the Earth's magnetization

NASA Astrophysics Data System (ADS)

Vervelidou, Foteini; Lesur, Vincent; Thébault, Erwan; Dyment, Jérôme; Holschneider, Matthias

2016-04-01

Inverting the magnetic field of crustal origin for the magnetization distribution that generates it suffers from non-uniqueness. The reason for this is the so-called annihilators, i.e. structures that produce no visible magnetic field outside the sources. Gubbins et al., 2011 uses the complex vector Spherical Harmonics notation in order to separate the Vertical Integrated Magnetization (VIM) distribution into the parts that do and do not contribute to the magnetic field measured in source free regions. We use their formalism and convert a crustal SH model based on the WDMAM into a model for the equivalent magnetization. However, we extend their formalism and assume that the magnetization is confined within a layer of finite thickness. A different thickness is considered for the oceanic crust than for the continental one. It is well known that the large scales of the crustal field are entirely masked by the Earth's main field. Therefore, we complement the WDMAM based magnetization map (SH degrees 16 to 800) with the magnetization map for the large wavelengths (SH degrees 1-15) that was recently derived by Vervelidou and Thébault (2015) from a series of regional statistical analyses of the World Digital Magnetic Anomaly Map. Finally we propose a tentative separation of this magnetization map into induced and remanent contributions on a regional scale. We do so based on the direction of the core magnetic field. We discuss the implications of these results in terms of the tectonic history of the Earth.

Long time series analysis of ionospheric TEC disturbance over seismically region in southwest China during low solar activity

NASA Astrophysics Data System (ADS)

Yan, Xiangxiang; Yu, Tao; Shan, Xinjian; Liu, Zhan; Wang, Zhenjie

2016-04-01

Recently, there are growing interests in studying the seismo-ionospheric disturbance prior to earthquakes, mainly including the anomalies in the electric field, magnetic field and plasma parameters. However, there are still some controversies over this topic, mainly because of strong day-to-day variability of the ionosphere itself. It is hard to determine whether the different forms of ionospheric disturbances are associated with earthquakes or not. Using data of Crustal Movement Observation Network of China (CMONC) and IGS (International GNSS Service), we attempt to give a statistical investigation about the total electron content (TEC) perturbation before 30 Mw6.0+ earthquakes during January 2000 to December 2010 in China. To determine the abnormal TEC signals, a quartile-based process is performed. At each time point we calculated the median M using the TEC values at the same local time for the preceding 15 days. In addition, we calculated the maps of differential TEC from global ionosphere maps (GIM) in the above period. It is shown that TEC anomalies were detected before 20 earthquakes, nearly 67%. The anomalies represent positive before most events and occurred mostly within 2-6 days before the shocks, significantly during the afternoon period, 1200-2000LT. Part of perturbations appeared more than one time. Moreover, the affected area of TEC is not coincide with the vertical projection of the epicenter but shifts equatorward and is controlled by equatorial ionization anomaly (EIA) crest. On the other hand, we analyzed variations of TEC over southwest China during a period of low solar and geomagnetic activity in April-October 2008, based on the data of CMONC. During that time, six large earthquakes with magnitude M≧6.0 occurred around the southwest region of China. The method to detect abnormal TEC signals is same with above statistical study. Known that the decisive role in the ionosphere state is performed by space weather effects, we compared the TEC variations with time series of EUV solar radiation, Bz component of the interplanetary magnetic field (IMF), index of geomagnetic activity Dst and planetary index Kp, respectively. It is found that the observed anomalies in the regional TEC were in good correlation with the variations of above solar and geomagnetic activities. We have not detected obvious TEC disturbance before five earthquakes expect for Wenchuan earthquake. In order to additionally check the spatial occurrence of the observed anomalies, we chose a 'check-region' with the same geomagnetic latitudes as the epicentral area of the six considered earthquakes, and analyzed the TEC changes. The result shows that the time series of anomalous TEC in 'check-region' is similar to the epicentral area, which was dominated by space weather. Therefore, we are suspicious of the results of statistical investigation showed here or other similar papers, which indicates the difficulties in identifying earthquake precursors in the ionosphere TEC. The seismo-ionospheric coupling process is complex, and it is necessary to strengthen the observation of multi-parameters on the ground, in the atmosphere and ionosphere synchronously.

High-Resolution Aeromagnetic Survey To Image Shallow Faults, Poncha Springs and Vicinity, Chaffee County, Colorado

USGS Publications Warehouse

Grauch, V.J.S.; Drenth, Benjamin J.

2009-01-01

High-resolution aeromagnetic data were acquired over the town of Poncha Springs and areas to the northwest to image faults, especially where they are concealed. Because this area has known hot springs, faults or fault intersections at depth can provide pathways for upward migration of geothermal fluids or concentrate fracturing that enhances permeability. Thus, mapping concealed faults provides a focus for follow-up geothermal studies. Fault interpretation was accomplished by synthesizing interpretative maps derived from several different analytical methods, along with preliminary depth estimates. Faults were interpreted along linear aeromagnetic anomalies and breaks in anomaly patterns. Many linear features correspond to topographic features, such as drainages. A few of these are inferred to be fault-related. The interpreted faults show an overall pattern of criss-crossing fault zones, some of which appear to step over where they cross. Faults mapped by geologists suggest similar crossing patterns in exposed rocks along the mountain front. In low-lying areas, interpreted faults show zones of west-northwest-, north-, and northwest-striking faults that cross ~3 km (~2 mi) west-northwest of the town of Poncha Springs. More easterly striking faults extend east from this juncture. The associated aeromagnetic anomalies are likely caused by magnetic contrasts associated with faulted sediments that are concealed less than 200 m (656 ft) below the valley floor. The faults may involve basement rocks at greater depth as well. A relatively shallow (<300 m or <984 ft), faulted basement block is indicated under basin-fill sediments just north of the hot springs and south of the town of Poncha Springs.

The effect of dynamic topography and gravity on lithospheric effective elastic thickness estimation: a case study

NASA Astrophysics Data System (ADS)

Bai, Yongliang; Dong, Dongdong; Kirby, Jon F.; Williams, Simon E.; Wang, Zhenjie

2018-04-01

Lithospheric effective elastic thickness (Te), a proxy for plate strength, is helpful for the understanding of subduction characteristics. Affected by curvature, faulting and magma activity, lithospheric strength near trenches should be weakened but some regional inversion studies have shown much higher Te values along some trenches than in their surroundings. In order to improve Te estimation accuracy, here we discuss the long-wavelength effect of dynamic topography and gravity on Te estimation by taking the Izu-Bonin-Mariana (IBM) Trench as a case study area. We estimate the long-wavelength influence of the density and negative buoyancy of the subducting slab on observed gravity anomalies and seafloor topography. The residual topography and gravity are used to map Te using the fan-wavelet coherence method. Maps of Te, both with and without the effects of dynamic topography and slab gravity anomaly, contain a band of high-Te values along the IBM Trench, though these values and their errors are lower when slab effects are accounted for. Nevertheless, tests show that the Te map is relatively insensitive to the choice of slab-density modelling method, even though the dynamic topography and slab-induced gravity anomaly vary considerably when the slab density is modelled by different methods. The continued presence of a high-Te band along the trench after application of dynamic corrections shows that, before using 2D inversion methods to estimate Te variations in subduction zones, there are other factors that should be considered besides the slab dynamic effects on the overriding plate.

The effect of dynamic topography and gravity on lithospheric effective elastic thickness estimation: a case study

NASA Astrophysics Data System (ADS)

Bai, Yongliang; Dong, Dongdong; Kirby, Jon F.; Williams, Simon E.; Wang, Zhenjie

2018-07-01

Lithospheric effective elastic thickness (Te), a proxy for plIate strength, is helpful for the understanding of subduction characteristics. Affected by curvature, faulting and magma activity, lithospheric strength near trenches should be weakened but some regional inversion studies have shown much higher Te values along some trenches than in their surroundings. In order to improve Te-estimation accuracy, here we discuss the long-wavelength effect of dynamic topography and gravity on Te estimation by taking the Izu-Bonin-Mariana (IBM) Trench as a case study area. We estimate the long-wavelength influence of the density and negative buoyancy of the subducting slab on observed gravity anomalies and seafloor topography. The residual topography and gravity are used to map Te using the fan-wavelet coherence method. Maps of Te, both with and without the effects of dynamic topography and slab gravity anomaly, contain a band of high-Te values along the IBM Trench, though these values and their errors are lower when slab effects are accounted for. Nevertheless, tests show that the Te map is relatively insensitive to the choice of slab-density modelling method, even though the dynamic topography and slab-induced gravity anomaly vary considerably when the slab density is modelled by different methods. The continued presence of a high-Te band along the trench after application of dynamic corrections shows that, before using 2-D inversion methods to estimate Te variations in subduction zones, there are other factors that should be considered besides the slab dynamic effects on the overriding plate.

Extracting Rayleigh wave dispersion from ambient noise across the Indian Ocean

NASA Astrophysics Data System (ADS)

Ma, Z.; Dalton, C. A.

2016-12-01

Rayleigh wave dispersion extracted from ambient seismic noise has been widely used to image crustal and uppermost mantle structure. Applications of this approach in continental settings are abundant, but there have been relatively few studies within ocean basins. In this presentation, we will first demonstrate the feasibility of extracting high quality Rayleigh wave dispersion information from ambient noise across the entire Indian Ocean basin. Phase arrival times measured from ambient noise are largely consistent with the ones predicted from 2-D phase velocity maps that were determined from earthquake data alone. Secondly, we show that adding dispersion information extracted from ambient noise to existing earthquake data can indeed improve the resolution of phase velocity maps by about 20% in the western Indian Ocean region where the station distribution is the densest. High quality Rayleigh wave dispersion information can be obtained from stacking waveforms over less than two years at land stations and less than four years at island stations. After removing the age dependent average velocities, the 2-D phase velocity maps show slow anomalies associated with the Seychelles-Mascarene plateau. Forward modeling suggests that the crust is about 15-25 km thick in this area, which agrees with previous estimates obtained from gravity data. We also observe that the slow anomaly related to the Central Indian Ridge is asymmetric. The center of this slow anomaly lies to the west side of ridge, which is opposite to the ridge migration direction. This asymmetry probably reflects the interactions between the ridge and nearby hotspots.

Electrical geophysical study over the Norman Landfill, near Norman, Oklahoma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bisdorf, R.J.

In 1995 and 1996 the US Geological Survey made 40 Schlumberger dc electrical resistivity soundings at the Norman Landfill, near Norman, Oklahoma. Interpretation of the resistivity data indicates that high resistivities (>300 ohm-m) are related to dry sand, intermediate resistivities (45-300 ohm-m) are related to freshwater saturated sand, and low resistivities (<45 ohm-m) are related to fine-grained materials or materials saturated with the conductive fluids. Interpreted resistivity maps show a low resistivity anomaly that extends from under the landfill to just past a nearby slough. This anomaly corresponds to known areas of ground water contamination. A resistivity cross section, constructedmore » from interpreted Schlumberger soundings, shows that this low resistivity anomaly is about 5 m deep and up to 9 m thick.« less

Detection of geothermal anomalies in Tengchong, Yunnan Province, China from MODIS multi-temporal night LST imagery

NASA Astrophysics Data System (ADS)

Li, H.; Kusky, T. M.; Peng, S.; Zhu, M.

2012-12-01

Thermal infrared (TIR) remote sensing is an important technique in the exploration of geothermal resources. In this study, a geothermal survey is conducted in Tengchong area of Yunnan province in China using multi-temporal MODIS LST (Land Surface Temperature). The monthly night MODIS LST data from Mar. 2000 to Mar. 2011 of the study area were collected and analyzed. The 132 month average LST map was derived and three geothermal anomalies were identified. The findings of this study agree well with the results from relative geothermal gradient measurements. Finally, we conclude that TIR remote sensing is a cost-effective technique to detect geothermal anomalies. Combining TIR remote sensing with geological analysis and the understanding of geothermal mechanism is an accurate and efficient approach to geothermal area detection.

Monitoring Drought at Continental Scales Using Thermal Remote Sensing of Evapotranspiration (Invited)

NASA Astrophysics Data System (ADS)

Anderson, M. C.; Hain, C.; Mecikalski, J. R.; Kustas, W. P.

2009-12-01

Thermal infrared (TIR) remote sensing of land-surface temperature (LST) provides valuable information about the sub-surface moisture status: soil surface temperature increases with decreasing water content, while moisture depletion in the plant root zone leads to stomatal closure, reduced transpiration, and elevated canopy temperatures that can be effectively detected from space. Empirical indices measuring anomalies in LST and vegetation amount (e.g., as quantified by the Normalized Difference Vegetation Index; NDVI) have demonstrated utility in monitoring drought conditions over large areas, but may provide ambiguous results when vegetation growth is limited by energy (radiation, air temperature) rather than moisture. A more physically based interpretation of LST and NDVI and their relationship to sub-surface moisture conditions can be obtained with a surface energy balance model driven by TIR remote sensing. In this approach, moisture stress can be quantified in terms of the reduction of evapotranspiration (ET) from the potential rate (PET) expected under non-moisture limiting conditions. The Atmosphere-Land Exchange Inverse (ALEXI) model couples a two-source (soil+canopy) land-surface model with an atmospheric boundary layer model in time-differencing mode to routinely and robustly map fluxes across the U.S. continent at 5-10km resolution using thermal band imagery from the Geostationary Operational Environmental Satellites (GOES). Finer resolution flux maps can be generated through spatial disaggregation using TIR data from polar orbiting instruments such as Landsat (60-120m) and MODIS (1km). A derived Evaporative Stress Index (ESI), given by 1-ET/PET, shows good correspondence with standard drought metrics and with patterns of antecedent precipitation, but can be produced at significantly higher spatial resolution due to limited reliance on ground observations. Because the ESI does not use precipitation data as input, it provides an independent means for assessing standard meteorologically-based drought indicators, and may be more robust in regions with limited monitoring networks. In this study, monthly maps of ESI anomalies for 2000-2008 are compared to standard drought indices and to drought classifications in the U.S. Drought Monitor. The ESI shows better skill in ranking drought severity than do precipitation-based indices composited over comparable time intervals. The thermal remote sensing inputs to ALEXI detect drought conditions even under the dense forest cover along the East Coast of the United States, where microwave soil moisture retrievals typically lose sensitivity. On the other hand, microwave observations are not constrained by cloud cover and provide better temporal continuity, but typically at significantly lower spatial resolution. A merged TIR-microwave moisture anomaly product may have potential for optimizing both spatial and temporal coverage in continental-scale drought monitoring.

Geophysical survey at Tell Barri (Syria)

NASA Astrophysics Data System (ADS)

Florio, Giovanni; Cella, Federico; Pierobon, Raffaella; Castaldo, Raffaele; Castiello, Gabriella; Fedi, Maurizio

2010-05-01

A geophysical survey at the archaeological site of Tell Barri (Northeasterm Syria) was carried out. The Tell (Arab word for "hill") is 32 m high with a whole covered area of 37 hectares. The Tell, with its huge dimensions and with a great amount of pottery on the surface, is a precious area to study the regional history from IV mill. BC to Islamic and Medieval period. The geophysical study consisted in magnetic and electromagnetic measurements in the lower town area. The aim of this survey was to provide evidence of the presence of buried archaeological structures around an already excavated area. The wall structures in the Tell Barri are made by backed or crude clay bricks. The instrument used for the magnetic survey was an Overhauser-effect proton magnetometer (Gem GSM-19GF), in gradiometric configuration. The electromagnetic instrument used, Geonics Ltd. EM31, implements a Frequency Domain Electromagnetic Method (FDEM). It was used in vertical coils configuration, and this choice should grant a maximum theoretical investigation depth of about 6 m. Before starting the measurements on a larger scale, we conducted a magnetic and EM test profile on some already excavated, outcropping, baked bricks walls. Results were encouraging, because clear and strong magnetic and EM anomalies were recorded over the outcropping walls. However, in the survey area these structures are covered by 3 to 4 meters of clay material and the increased sensors-structures distance will reduce the anomalies amplitude. Moreover, the cover material is disseminated with bricks, basalt blocks and ceramics, all of which have relevant magnetic properties. After magnetic surveying some 50 m side square areas, we verified that unfortunately their effect resulted to be dominant with respect to the deeper wall structures, degrading too much the signal-to-noise ratio. The processing and analysis of magnetic data is however currently underway and will determine decisions about further use of this method in future surveys. These disturbances were much lower in the EM data, thus, these data were acquired in 7 squares having 50 m long sides, along profiles spaced 0.5 m. The acquisition rate, combined with the operator speed, resulted in an average sampling step of 0.2-0.25 m along each profile. First, the quadrature and inphase data were interpolated at a regular step of 0.5 m and visualized in false colour maps representing the spatial variation of conductivity and magnetic susceptibility, respectively. Then, corrections for zig-zag effect and heading error were applied. In both maps many elongated anomalies are visible, often crossing each other perpendicularly and arranged with a meaningful orientation with respect to the topography. This suggest a possible archaeological meaning for these anomalies. Quadrature data were processed by AGC filter to obtain an amplitude-normalized map. Data were further processed with algorithms based on spatial derivatives that can define the position of the source bodies with higher definition. Some hypothesis about the meaning of these linear anomalies include the presence of an urbanization area, with edifices and roads. The orientation of many structures in directions parallel or perpendicular to the altitude isolines may also suggest the presence of ancient defensive structures. Thus, the main result of the geophysical investigation was to highlight that the urbanized area extent is wider than known before. The fine stratification of the archaeological remains at Tell Barri site represents a major difficulty to the interpretation. During the next mission some anomalies will be the target of excavations to improve our understanding of the conductivity pattern and its interpretation.

Ionospheric total electron content seismo-perturbation after Japan's March 11, 2011, M=9.0 Tohoku earthquake under a geomagnetic storm; a nonlinear principal component analysis

NASA Astrophysics Data System (ADS)

Lin, Jyh-Woei

2012-10-01

Nonlinear principal component analysis (NLPCA) is implemented to analyze the spatial pattern of total electron content (TEC) anomalies 3 hours after Japan's Tohoku earthquake that occurred at 05:46:23 on 11 March, 2011 (UTC) ( M w =9). A geomagnetic storm was in progress at the time of the earthquake. NLPCA and TEC data processing were conducted on the global ionospheric map (GIM) for the time between 08:30 to 09:30 UTC, about 3 hours after this devastating earthquake and ensuing tsunami. Analysis results show stark earthquake-associated TEC anomalies that are widespread, and appear to have been induced by two acoustic gravity waves due to strong shaking (vertical acoustic wave) and the generation of the tsunami (horizontal Rayleigh mode gravity wave). The TEC anomalies roughly fit the initial mainshock and movement of the tsunami. Observation of the earthquake-associated TEC anomalies does not appear to be affected by a contemporaneous geomagnetic storm.

South Atlantic Anomaly

Atmospheric Science Data Center

2013-04-19

... This map was created by specially processing MISR "dark" data taken between 3 February and 16 February 2000, while the cover was still ... Individual orbit tracks are visible, and some tracks are missing due to data gaps, missing spacecraft navigation information, or other ...

Lunar magnetic anomalies detected by the Apollo substatellite magnetometers

USGS Publications Warehouse

Hood, L.L.; Coleman, P.J.; Russell, C.T.; Wilhelms, D.E.

1979-01-01

Properties of lunar crustal magnetization thus far deduced from Apollo subsatellite magnetometer data are reviewed using two of the most accurate presently available magnetic anomaly maps - one covering a portion of the lunar near side and the other a part of the far side. The largest single anomaly found within the region of coverage on the near-side map correlates exactly with a conspicuous, light-colored marking in western Oceanus Procellarum called Reiner Gamma. This feature is interpreted as an unusual deposit of ejecta from secondary craters of the large nearby primary impact crater Cavalerius. An age for Cavalerius (and, by implication, for Reiner Gamma) of 3.2 ?? 0.2 ?? 109 y is estimated. The main (30 ?? 60 km) Reiner Gamma deposit is nearly uniformly magnetized in a single direction, with a minimum mean magnetization intensity of ???7 ?? 10-2 G cm3/g (assuming a density of 3 g/cm3), or about 700 times the stable magnetization component of the most magnetic returned samples. Additional medium-amplitude anomalies exist over the Fra Mauro Formation (Imbrium basin ejecta emplaced ???3.9 ?? 109 y ago) where it has not been flooded by mare basalt flows, but are nearly absent over the maria and over the craters Copernicus, Kepler, and Reiner and their encircling ejecta mantles. The mean altitude of the far-side anomaly gap is much higher than that of the near-side map and the surface geology is more complex, so individual anomaly sources have not yet been identified. However, it is clear that a concentration of especially strong sources exists in the vicinity of the craters Van de Graaff and Aitken. Numerical modeling of the associated fields reveals that the source locations do not correspond with the larger primary impact craters of the region and, by analogy with Reiner Gamma, may be less conspicuous secondary crater ejecta deposits. The reason for a special concentration of strong sources in the Van de Graaff-Aitken region is unknown, but may be indirectly related to the existence of strongly modified crustal terrain which also occurs in the same region. The inferred directions of magnetization for the several sources of the largest anomalies are highly inclined with respect to one another, but are generally depleted in the north-south direction. The north-south depletion of magnetization intensity appears to continue across the far-side within the region of coverage. The mechanism of magnetization and the origin of the magnetizing field remain unresolved, but the uniformity with which the Reiner Gamma deposit is apparently magnetized, and the north-south depletion of magnetization intensity across a substantial portion of the far side, seem to require the existence of an ambient field, perhaps of global or larger extent. The very different inferred directions of magnetization possessed by nearly adjacent sources of the Van de Graaff-Aitken anomalies, and the depletion in their north-south component of magnetization, do not favor an internally generated dipolar field oriented parallel to the present spin axis. A variably oriented interplanetary magnetizing field that was intrinsically strong or locally amplified by unknown surface processes is least inconsistent with the data. ?? 1979.

Field Line Mapping of the Polar Cap Neutral Density Anomaly

NASA Astrophysics Data System (ADS)

Sutton, E. K.; Lin, C. S.; Huang, C. Y.; Cooke, D. L.

2016-12-01

Polar cap neutral density anomaly (PCNDA) events of localized density enhancement with a half size around 700-1000 km had been frequently detected by CHAMP satellite at around 400 km during major magnetic storms with Dst < -100 nT. Density enhancement is probably produced via Joule heating of the thermosphere when a significant amount of energy is deposited in the polar cap. We have identified 12 PCNDA events measured by CHAMP during two major magnetic storms including one initiated by a large solar wind pressure pulse. Their density anomaly locations are found to scatter randomly within the polar circle of 80o magnetic latitude in the geomagnetic coordinate. However after transformed to the Geocentric Solar Wind (GSW) coordinates, their locations become aligned in the direction of solar wind velocity. To better understand the polar cap energy deposition we trace magnetic field lines to the magnetosphere up to 30 earth radii from the ionosphere at 400 km using the data-based Tsyganenko T95 and TS05 magnetic field models. Field line tracing is performed in the GSW coordinate along the CHAMP orbit as well as for the whole polar cap. Each traced magnetic field line is classified into one of the three categories, (1) magnetosphere closed field line (MC) crossing the equatorial plane within 30 earth radii, (2) open field line connected to the magnetopause (MP), or (3) open field line connected to the magnetotail lobe (MT). For nine PCNDA events among the 10 events that we are able to conduct tracing, field lines originated from the density anomaly regions are classified as MT. Only one outlier event in association with a very large IMF BZ is classified as MP. Furthermore the separation angle between the density anomaly peak and the MP-MT field line separation point at 400 km on the X- and Z-axes meridian plane varies from -4o to 16o. Based on these results we speculate that convective electric fields and field aligned currents in the ionosphere might be enhanced near the MP-MT separation point during magnetic storms, resulting in intense localized Joule heating of the thermosphere.

High-resolution near real-time drought monitoring in South Asia

NASA Astrophysics Data System (ADS)

Aadhar, Saran; Mishra, Vimal

2017-10-01

Drought in South Asia affect food and water security and pose challenges for millions of people. For policy-making, planning, and management of water resources at sub-basin or administrative levels, high-resolution datasets of precipitation and air temperature are required in near-real time. We develop a high-resolution (0.05°) bias-corrected precipitation and temperature data that can be used to monitor near real-time drought conditions over South Asia. Moreover, the dataset can be used to monitor climatic extremes (heat and cold waves, dry and wet anomalies) in South Asia. A distribution mapping method was applied to correct bias in precipitation and air temperature, which performed well compared to the other bias correction method based on linear scaling. Bias-corrected precipitation and temperature data were used to estimate Standardized precipitation index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) to assess the historical and current drought conditions in South Asia. We evaluated drought severity and extent against the satellite-based Normalized Difference Vegetation Index (NDVI) anomalies and satellite-driven Drought Severity Index (DSI) at 0.05°. The bias-corrected high-resolution data can effectively capture observed drought conditions as shown by the satellite-based drought estimates. High resolution near real-time dataset can provide valuable information for decision-making at district and sub-basin levels.

Modeling Chinese ionospheric layer parameters based on EOF analysis

NASA Astrophysics Data System (ADS)

Yu, You; Wan, Weixing; Xiong, Bo; Ren, Zhipeng; Zhao, Biqiang; Zhang, Yun; Ning, Baiqi; Liu, Libo

2015-05-01

Using 24-ionosonde observations in and around China during the 20th solar cycle, an assimilative model is constructed to map the ionospheric layer parameters (foF2, hmF2, M(3000)F2, and foE) over China based on empirical orthogonal function (EOF) analysis. First, we decompose the background maps from the International Reference Ionosphere model 2007 (IRI-07) into different EOF modes. The obtained EOF modes consist of two factors: the EOF patterns and the corresponding EOF amplitudes. These two factors individually reflect the spatial distributions (e.g., the latitudinal dependence such as the equatorial ionization anomaly structure and the longitude structure with east-west difference) and temporal variations on different time scales (e.g., solar cycle, annual, semiannual, and diurnal variations) of the layer parameters. Then, the EOF patterns and long-term observations of ionosondes are assimilated to get the observed EOF amplitudes, which are further used to construct the Chinese Ionospheric Maps (CIMs) of the layer parameters. In contrast with the IRI-07 model, the mapped CIMs successfully capture the inherent temporal and spatial variations of the ionospheric layer parameters. Finally, comparison of the modeled (EOF and IRI-07 model) and observed values reveals that the EOF model reproduces the observation with smaller root-mean-square errors and higher linear correlation coefficients. In addition, IRI discrepancy at the low latitude especially for foF2 is effectively removed by EOF model.

Modeling Chinese ionospheric layer parameters based on EOF analysis

NASA Astrophysics Data System (ADS)

Yu, You; Wan, Weixing

2016-04-01

Using 24-ionosonde observations in and around China during the 20th solar cycle, an assimilative model is constructed to map the ionospheric layer parameters (foF2, hmF2, M(3000)F2, and foE) over China based on empirical orthogonal function (EOF) analysis. First, we decompose the background maps from the International Reference Ionosphere model 2007 (IRI-07) into different EOF modes. The obtained EOF modes consist of two factors: the EOF patterns and the corresponding EOF amplitudes. These two factors individually reflect the spatial distributions (e.g., the latitudinal dependence such as the equatorial ionization anomaly structure and the longitude structure with east-west difference) and temporal variations on different time scales (e.g., solar cycle, annual, semiannual, and diurnal variations) of the layer parameters. Then, the EOF patterns and long-term observations of ionosondes are assimilated to get the observed EOF amplitudes, which are further used to construct the Chinese Ionospheric Maps (CIMs) of the layer parameters. In contrast with the IRI-07 model, the mapped CIMs successfully capture the inherent temporal and spatial variations of the ionospheric layer parameters. Finally, comparison of the modeled (EOF and IRI-07 model) and observed values reveals that the EOF model reproduces the observation with smaller root-mean-square errors and higher linear correlation co- efficients. In addition, IRI discrepancy at the low latitude especially for foF2 is effectively removed by EOF model.

Madagascar's escape from Africa: A high-resolution plate reconstruction for the Western Somali Basin and implications for supercontinent dispersal

NASA Astrophysics Data System (ADS)

Phethean, Jordan J. J.; Kalnins, Lara M.; van Hunen, Jeroen; Biffi, Paolo G.; Davies, Richard J.; McCaffrey, Ken J. W.

2016-12-01

Accurate reconstructions of the dispersal of supercontinent blocks are essential for testing continental breakup models. Here, we provide a new plate tectonic reconstruction of the opening of the Western Somali Basin during the breakup of East and West Gondwana. The model is constrained by a new comprehensive set of spreading lineaments, detected in this heavily sedimented basin using a novel technique based on directional derivatives of free-air gravity anomalies. Vertical gravity gradient and free-air gravity anomaly maps also enable the detection of extinct mid-ocean ridge segments, which can be directly compared to several previous ocean magnetic anomaly interpretations of the Western Somali Basin. The best matching interpretations have basin symmetry around the M0 anomaly; these are then used to temporally constrain our plate tectonic reconstruction. The reconstruction supports a tight fit for Gondwana fragments prior to breakup, and predicts that the continent-ocean transform margin lies along the Rovuma Basin, not along the Davie Fracture Zone (DFZ) as commonly thought. According to our reconstruction, the DFZ represents a major ocean-ocean fracture zone formed by the coalescence of several smaller fracture zones during evolving plate motions as Madagascar drifted southwards, and offshore Tanzania is an obliquely rifted, rather than transform, margin. New seismic reflection evidence for oceanic crust inboard of the DFZ strongly supports these conclusions. Our results provide important new constraints on the still enigmatic driving mechanism of continental rifting, the nature of the lithosphere in the Western Somali Basin, and its resource potential.

The Stranding Anomaly as Population Indicator: The Case of Harbour Porpoise Phocoena phocoena in North-Western Europe

PubMed Central

Peltier, Helene; Baagøe, Hans J.; Camphuysen, Kees C. J.; Czeck, Richard; Dabin, Willy; Daniel, Pierre; Deaville, Rob; Haelters, Jan; Jauniaux, Thierry; Jensen, Lasse F.; Jepson, Paul D.; Keijl, Guido O.; Siebert, Ursula; Van Canneyt, Olivier; Ridoux, Vincent

2013-01-01

Ecological indicators for monitoring strategies are expected to combine three major characteristics: ecological significance, statistical credibility, and cost-effectiveness. Strategies based on stranding networks rank highly in cost-effectiveness, but their ecological significance and statistical credibility are disputed. Our present goal is to improve the value of stranding data as population indicator as part of monitoring strategies by constructing the spatial and temporal null hypothesis for strandings. The null hypothesis is defined as: small cetacean distribution and mortality are uniform in space and constant in time. We used a drift model to map stranding probabilities and predict stranding patterns of cetacean carcasses under H0 across the North Sea, the Channel and the Bay of Biscay, for the period 1990–2009. As the most common cetacean occurring in this area, we chose the harbour porpoise Phocoena phocoena for our modelling. The difference between these strandings expected under H0 and observed strandings is defined as the stranding anomaly. It constituted the stranding data series corrected for drift conditions. Seasonal decomposition of stranding anomaly suggested that drift conditions did not explain observed seasonal variations of porpoise strandings. Long-term stranding anomalies increased first in the southern North Sea, the Channel and Bay of Biscay coasts, and finally the eastern North Sea. The hypothesis of changes in porpoise distribution was consistent with local visual surveys, mostly SCANS surveys (1994 and 2005). This new indicator could be applied to cetacean populations across the world and more widely to marine megafauna. PMID:23614031

Potential of Pest and Host Phenological Data in the Attribution of Regional Forest Disturbance Detection Maps According to Causal Agent

NASA Technical Reports Server (NTRS)

Spruce, Joseph; Hargrove, William; Norman Steve; Christie, William

2014-01-01

Near real time forest disturbance detection maps from MODIS NDVI phenology data have been produced since 2010 for the conterminous U.S., as part of the on-line ForWarn national forest threat early warning system. The latter has been used by the forest health community to identify and track many regional forest disturbances caused by multiple biotic and abiotic damage agents. Attribution of causal agents for detected disturbances has been a goal since project initiation in 2006. Combined with detailed cover type maps, geospatial pest phenology data offer a potential means for narrowing the candidate causal agents responsible for a given biotic disturbance. U.S. Aerial Detection Surveys (ADS) employ such phenology data. Historic ADS products provide general locational data on recent insect-induced forest type specific disturbances that may help in determining candidate causal agents for MODIS-based disturbance maps, especially when combined with other historic geospatial disturbance data (e.g., wildfire burn scars and drought maps). Historic ADS disturbance detection polygons can show severe and extensive regional forest disturbances, though they also can show polygons with sparsely scattered or infrequent disturbances. Examples will be discussed that use various historic disturbance data to help determine potential causes of MODIS-detected regional forest disturbance anomalies.

The FAO/NASA/NLR Artemis system - An integrated concept for environmental monitoring by satellite in support of food/feed security and desert locust surveillance

NASA Technical Reports Server (NTRS)

Hielkema, J. U.; Howard, J. A.; Tucker, C. J.; Van Ingen Schenau, H. A.

1987-01-01

The African real time environmental monitoring using imaging satellites (Artemis) system, which should monitor precipitation and vegetation conditions on a continental scale, is presented. The hardware and software characteristics of the system are illustrated and the Artemis databases are outlined. Plans for the system include the use of hourly digital Meteosat data and daily NOAA/AVHRR data to study environmental conditions. Planned mapping activities include monthly rainfall anomaly maps, normalized difference vegetation index maps for ten day and monthly periods with a spatial resolution of 7.6 km, ten day crop/rangeland moisture availability maps, and desert locust potential breeding activity factor maps for a plague prevention program.

Building the second version of the World Digital Magnetic Anomaly Map (WDMAM)

NASA Astrophysics Data System (ADS)

Lesur, Vincent; Hamoudi, Mohamed; Choi, Yujin; Dyment, Jérôme; Thébault, Erwan

2016-02-01

The World Digital Anomaly Map (WDMAM) is a worldwide compilation of near-surface magnetic data. We present here a candidate for the second version of the WDMAM and its characteristics. This candidate has been evaluated by a group of independent reviewers and has been adopted as the official second version of the WDMAM during the 26th general assembly of the International Union of Geodesy and Geomagnetism (IUGG). The way this compilation has been built is described with some details. A global magnetic field model of the lithosphere contribution, parameterised by spherical harmonics, has been derived up to degree and order 800. The model information content has been evaluated by computing local spectra. Further, the compatibility of the anomaly field displayed by the WDMAM with a pure induced magnetisation is tested by comparison with the main field strength. These studies allowed an analysis of the compilation in terms of strength and wavelength content. They confirm the extremely smooth and weak contribution of the magnetic field generated in the lithosphere over Western Europe. This apparent weakness possibly extends to the Northern African continent. However, a global analysis remains difficult to achieve given the sparseness of good quality data over very large area of oceans and continents. The WDMAM and related information can be downloaded at http://www.wdmam.org/.

Constraints on a shallow offshore gas environment determined by a multidisciplinary geophysical approach: The Malin Sea, NW Ireland

NASA Astrophysics Data System (ADS)

Garcia, Xavier; Monteys, Xavier; Evans, Rob L.; Szpak, Michal

2014-04-01

During the Irish National Seabed Survey (INSS) in 2003, a gas related pockmark field was discovered and extensively mapped in the Malin Shelf region (NW Ireland). In summer 2006, additional complementary data involving core sample analysis, multibeam and single-beam backscatter classification, and a marine controlled-source electromagnetic survey were obtained in specific locations.This multidisciplinary approach allowed us to map the upper 20 m of the seabed in an unprecedented way and to correlate the main geophysical parameters with the geological properties of the seabed. The EM data provide us with information about sediment conductivity, which can be used as a proxy for porosity and also to identify the presence of fluid and fluid migration pathways. We conclude that, as a whole, the central part of the Malin basin is characterized by higher conductivities, which we interpret as a lithological change. Within the basin several areas are characterized by conductive anomalies associated with fluid flow processes and potentially the presence of microbial activity, as suggested by previous work. Pockmark structures show a characteristic electrical signature, with high-conductivity anomalies on the edges and less conductive, homogeneous interiors with several high-conductivity anomalies, potentially associated with gas-driven microbial activity.

Aerial radiometric and magnetic reconnaissance survey of a portion of Texas: Beaumont and Palestine quadrangles, final report. Volume 1 and Volume 2A, Beaumont quadrangle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1979-12-01

Instrumentation and methods described were used for a Department of Energy (DOE) sponsored, high-sensitivity, aerial gamma-ray spectrometer and magnetometer survey of a portion of Beaumont and all of Palestine (Texas), NTMS, 1:250,000-scale quadrangles. The objective of the work was to define areas showing surface indications of a generally higher uranium content where detailed exploration for uranium would most likely be successful. A DC-3 aircraft equipped with a high-sensitivity gamma-ray spectrometer and ancillary geophysical and electronic equipment ws employed for each quadrangle. The system was calibrated using the DOE calibration facilities at Grand Junction, Colorado, and Lake Mead, Arizona. Gamma-ray spectrometricmore » data were processed to correct for variations in atmospheric, flight, and instrument conditions and were statistically evaluated to remove the effects of surface geologic variations. The resulting first-priority uranium anomalies (showing simultaneously valid eU, eU/eTh, and eU/K anomalies) were interpreted to evaluate their origin and significance. Results of the interpretation in the form of a preferred-anomaly map, along with significance-factor profile maps, stacked profiles, histograms, and descriptions of the geology and known uranium occurrences are presented in Volume 2 of this final report.« less

Aerial radiometric and magnetic reconnaissance survey of a portion of Texas: Beaumont and Palestine quadrangles, final report. Volume 1 and Volume 2B, Palestine quadrangle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1979-12-01

Instrumentation and methods described were used for a Department of Energy (DOE) sponsored, high-sensitivity, aerial gamma-ray spectrometer and magnetometer survey of a portion of Beaumont and all of Palestine (Texas), NTMS, 1:250,000-scale quadrangles. The objective of the work was to define areas showing surface indications of a generally higher uranium content where detailed exploration for uranium would most likely be successful. A DC-3 aircraft equipped with a high-sensitivity gamma-ray spectrometer and ancillary geophysical and electronic equipment was employed for each quadrangle. The system was calibrated using the DOE calibration facilities at Grand Junction, Colorado, and Lake Mead, Arizona. Gamma-ray spectrometricmore » data were processed to correct for variations in atmospheric, flight, and instrument conditions and were statistically evaluated to remove the effects of surface geologic variations. The resulting first-priority uranium anomalies (showing simultaneously valid eU, eU/eTh, and eU/K anomalies) were interpreted to evaluate their origin and significance. Results of the interpretation in the form of a preferred-anomaly map, along with significance-factor profile maps, stacked profiles, histograms, and descriptions of the geology and known uranium occurrences are presented in Volume 2 of this final report.« less

First Discovery and Investigation of a High-Temperature Hydrothermal Vent Field on the Ultra- Slow Spreading Southwest Indian Ridge

NASA Astrophysics Data System (ADS)

Tao, C.; Lin, J.; Guo, S.; Chen, Y. J.; Wu, G.; Han, X.; German, C. R.; Yoerger, D. R.; Zhu, J.; Zhou, N.; Su, X.; Baker, E. T.; Party, S.

2007-12-01

Two recent cruises on board the Chinese research vessel Dayang Yihao have successfully investigated the first active hydrothermal vent field to be located along the ultraslow spreading Southwest Indian Ridge (SWIR) and collected hydrothermal sulfide deposit samples. The newly discovered hydrothermal vent field is located on the western end of a magmatically robust spreading segment immediately west of the Gallieni transform fault. Preliminary evidence of strong turbidity anomalies was first measured during a Nov. 2005 cruise on board Dayang Yihao (InterRidge News, vol. 15, pp. 33-34, 2006). Color video footages of the seafloor in the vent-field area were first obtained by a deep-towed video camera in February 2007 during DY115-19 Leg 1, when significant water column turbidity anomalies, noticeable temperature anomalies and methane anomalies were also measured. The vent field was then precisely located, mapped, and photographed in great detail in February- March 2007 during the DY115-19 Leg 2, using the autonomous underwater vehicle ABE of the Woods Hole Oceanographic Institution. A high-resolution bathymetric map, more than 5,000 near-bottom color photos, and several types of water column data were all obtained during three phases of ABE dives. Within the approximately 120-m-long by 100-m-wide hydrothermal field, three groups of active high-temperature vents were identified and color images of black smokers and associated biological communities were obtained from ABE, flying 5 m above the seafloor. Hydrothermal sulfide deposits were then successfully obtained using a TV-guided grab.

First Discovery and Investigation of a High-Temperature Hydrothermal Vent Field on the Ultra- Slow Spreading Southwest Indian Ridge

NASA Astrophysics Data System (ADS)

Tao, C.; Lin, J.; Guo, S.; Chen, Y. J.; Wu, G.; Han, X.; German, C. R.; Yoerger, D. R.; Zhu, J.; Zhou, N.; Su, X.; Baker, E. T.; Party, S.

2004-12-01

Two recent cruises on board the Chinese research vessel Dayang Yihao have successfully investigated the first active hydrothermal vent field to be located along the ultraslow spreading Southwest Indian Ridge (SWIR) and collected hydrothermal sulfide deposit samples. The newly discovered hydrothermal vent field is located on the western end of a magmatically robust spreading segment immediately west of the Gallieni transform fault. Preliminary evidence of strong turbidity anomalies was first measured during a Nov. 2005 cruise on board Dayang Yihao (InterRidge News, vol. 15, pp. 33-34, 2006). Color video footages of the seafloor in the vent-field area were first obtained by a deep-towed video camera in February 2007 during DY115-19 Leg 1, when significant water column turbidity anomalies, noticeable temperature anomalies and methane anomalies were also measured. The vent field was then precisely located, mapped, and photographed in great detail in February- March 2007 during the DY115-19 Leg 2, using the autonomous underwater vehicle ABE of the Woods Hole Oceanographic Institution. A high-resolution bathymetric map, more than 5,000 near-bottom color photos, and several types of water column data were all obtained during three phases of ABE dives. Within the approximately 120-m-long by 100-m-wide hydrothermal field, three groups of active high-temperature vents were identified and color images of black smokers and associated biological communities were obtained from ABE, flying 5 m above the seafloor. Hydrothermal sulfide deposits were then successfully obtained using a TV-guided grab.

Evaluation of aerial thermal infrared remote sensing to identify groundwater-discharge zones in the Meduxnekeag River, Houlton, Maine

USGS Publications Warehouse

Culbertson, Charles W.; Huntington, Thomas G.; Caldwell, James M.; O'Donnell, Cara

2014-01-01

Residents of the area near Houlton, Maine, have observed seasonal episodic blooms of algae and documented elevated concentrations of fecal-coliform bacteria and inorganic nutrients and low dissolved oxygen concentrations in the Meduxnekeag River. Although point and nonpoint sources of urban and agricultural runoff likely contribute to water-quality impairment, the role of shallow groundwater inflows in delivering such contaminants to the Meduxnekeag River has not been well understood. To provide information about possible groundwater inflows to the river, airborne thermal infrared videography was evaluated as a means to identify and classify thermal anomalies in a 25-mile reach of the mainstem and tributaries of the Meduxnekeag River near Houlton, Maine. The U.S. Geological Survey, in cooperation with the Houlton Band of Maliseet Indians, collected thermal infrared images from a single-engine, fixed-wing aircraft during flights on December 3–4, 2003, and November 26, 2004. Eleven thermal anomalies were identified on the basis of data from the December 2003 flight and 17 from the November 2004 flight, which covered the same reaches of stream. Following image analysis, characterization, and prioritization, the georeferenced infrared images of the thermal anomalies were compared to features on topographic maps of the study area. The mapped anomalies were used to direct observations on the ground to confirm discharge locations and types of inflow. The variations in grayscale patterns on the images were thus confirmed as representing shallow groundwater-discharge zones (seeps), outfalls of treated wastewater, or ditches draining runoff from impervious surfaces.

Domain Anomaly Detection in Machine Perception: A System Architecture and Taxonomy.

PubMed

Kittler, Josef; Christmas, William; de Campos, Teófilo; Windridge, David; Yan, Fei; Illingworth, John; Osman, Magda

2014-05-01

We address the problem of anomaly detection in machine perception. The concept of domain anomaly is introduced as distinct from the conventional notion of anomaly used in the literature. We propose a unified framework for anomaly detection which exposes the multifaceted nature of anomalies and suggest effective mechanisms for identifying and distinguishing each facet as instruments for domain anomaly detection. The framework draws on the Bayesian probabilistic reasoning apparatus which clearly defines concepts such as outlier, noise, distribution drift, novelty detection (object, object primitive), rare events, and unexpected events. Based on these concepts we provide a taxonomy of domain anomaly events. One of the mechanisms helping to pinpoint the nature of anomaly is based on detecting incongruence between contextual and noncontextual sensor(y) data interpretation. The proposed methodology has wide applicability. It underpins in a unified way the anomaly detection applications found in the literature. To illustrate some of its distinguishing features, in here the domain anomaly detection methodology is applied to the problem of anomaly detection for a video annotation system.

Integrating age in the detection and mapping of incongruous patches in coffee (Coffea arabica) plantations using multi-temporal Landsat 8 NDVI anomalies

NASA Astrophysics Data System (ADS)

Chemura, Abel; Mutanga, Onisimo; Dube, Timothy

2017-05-01

The development of cost-effective, reliable and easy to implement crop condition monitoring methods is urgently required for perennial tree crops such as coffee (Coffea arabica), as they are grown over large areas and represent long term and higher levels of investment. These monitoring methods are useful in identifying farm areas that experience poor crop growth, pest infestation, diseases outbreaks and/or to monitor response to management interventions. This study compares field level coffee mean NDVI and LSWI anomalies and age-adjusted coffee mean NDVI and LSWI anomalies in identifying and mapping incongruous patches across perennial coffee plantations. To achieve this objective, we first derived deviation of coffee pixels from the global coffee mean NDVI and LSWI values of nine sequential Landsat 8 OLI image scenes. We then evaluated the influence of coffee age class (young, mature and old) on Landsat-scale NDVI and LSWI values using a one-way ANOVA and since results showed significant differences, we adjusted NDVI and LSWI anomalies for age-class. We then used the cumulative inverse distribution function (α ≤ 0.05) to identify fields and within field areas with excessive deviation of NDVI and LSWI from the global and the age-expected mean for each of the Landsat 8 OLI scene dates spanning three seasons. Results from accuracy assessment indicated that it was possible to separate incongruous and healthy patches using these anomalies and that using NDVI performed better than using LSWI for both global and age-adjusted mean anomalies. Using the age-adjusted anomalies performed better in separating incongruous and healthy patches than using the global mean for both NDVI (Overall accuracy = 80.9% and 68.1% respectively) and for LSWI (Overall accuracy = 68.1% and 48.9% respectively). When applied to other Landsat 8 OLI scenes, the results showed that the proportions of coffee fields that were modelled incongruent decreased with time for the young age category and while it increased for the mature and old age classes with time. We concluded that the method could be useful for the identification of anomalous patches using Landsat scale time series data to monitor large coffee plantations and provide an indication of areas requiring particular field attention.

Equivalent magnetization over the World's Ocean

NASA Astrophysics Data System (ADS)

Dyment, J.; Choi, Y.; Hamoudi, M.; Erwan, T.; Lesur, V.

2014-12-01

As a by-product of our recent work to build a candidate model over the oceans for the World Digital Magnetic Anomaly Map (WDMAM) version 2, we derived global distributions of the equivalent magnetization in oceanic domains. In a first step, we use classic point source forward modeling on a spherical Earth to build a forward model of the marine magnetic anomalies at sea-surface. We estimate magnetization vectors using the age map of the ocean floor, the relative plate motions, the apparent polar wander path for Africa, and a geomagnetic reversal time scale. As magnetized source geometry, we assume 1 km-thick layer bearing a 10 A/m magnetization following the topography of the oceanic basement as defined by the bathymetry and sedimentary thickness. Adding a present-day geomagnetic field model allows the computation of our initial magnetic anomaly model. In a second step, we adjust this model to the existing marine magnetic anomaly data, in order to make it consistent with these data. To do so, we extract synthetic magnetic along the ship tracks for which real data are available and we compare quantitatively the measured and computed anomalies on 100, 200 or 400 km-long sliding windows (depending the spreading rate). Among the possible comparison criteria, we discard the maximal range - too dependent on local values - and the correlation and coherency - the geographical adjustment between model and data being not accurate enough - to favor the standard deviation around the mean value. The ratio between the standard deviations of data and model on each sliding window represent an estimate of the magnetization ratio causing the anomalies, which we interpolate to adjust the initial magnetic anomaly model to the data and therefore compute a final model to be included in our WDMAM candidate over the oceanic regions lacking data. The above ratio, after division by the magnetization of 10 A/m used in the model, represents an estimate of the equivalent magnetization under the considered magnetized source geometry. The resulting distributions of equivalent magnetization are discussed in terms of mid-ocean ridges, presence of hotspots and oceanic plateaus, and the age of the oceanic lithosphere. Global marine magnetic data sets and models represent a useful tool to assess first order magnetic properties of the oceanic lithosphere.

Cross-linguistic variation in the neurophysiological response to semantic processing: Evidence from anomalies at the borderline of awareness

PubMed Central

Tune, Sarah; Schlesewsky, Matthias; Small, Steven L.; Sanford, Anthony J.; Bohan, Jason; Sassenhagen, Jona; Bornkessel-Schlesewsky, Ina

2014-01-01

The N400 event-related brain potential (ERP) has played a major role in the examination of how the human brain processes meaning. For current theories of the N400, classes of semantic inconsistencies which do not elicit N400 effects have proven particularly influential. Semantic anomalies that are difficult to detect are a case in point (“borderline anomalies”, e.g. “After an air crash, where should the survivors be buried?”), engendering a late positive ERP response but no N400 effect in English (Sanford, Leuthold, Bohan, & Sanford, 2011). In three auditory ERP experiments, we demonstrate that this result is subject to cross-linguistic variation. In a German version of Sanford and colleagues' experiment (Experiment 1), detected borderline anomalies elicited both N400 and late positivity effects compared to control stimuli or to missed borderline anomalies. Classic easy-to-detect semantic (non-borderline) anomalies showed the same pattern as in English (N400 plus late positivity). The cross-linguistic difference in the response to borderline anomalies was replicated in two additional studies with a slightly modified task (Experiment 2a: German; Experiment 2b: English), with a reliable LANGUAGE × ANOMALY interaction for the borderline anomalies confirming that the N400 effect is subject to systematic cross-linguistic variation. We argue that this variation results from differences in the language-specific default weighting of top-down and bottom-up information, concluding that N400 amplitude reflects the interaction between the two information sources in the form-to-meaning mapping. PMID:24447768

Airborne gamma-ray spectrometer and magnetometer survey: Weed quadrangle, California. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1981-05-01

Twelve anamolous areas attributable to gamma radiation in the uranium spectral window, and twenty-three in the thorium channel, have been recognized and delineated on the Weed quadrangle. The majority of the uranium anomalies are located in the southwestern part of the map sheet. Most of these are correlated with the pre-Cretaceous metamorphic rock system and the Mesozoic granitic rocks intrusive into it. Of the twenty-three anomalous areas of increased gamma radiation in the thorium spectral window, most are located in the northeast and the east center in a north-south trending belt. However, this apparent alignment is probably fortuitous as themore » individual anomalies are correlated with several different rock formations. Three are correlated with upper Cretaceous marine sediments, six with Ordovician marine sediments, two with Mesozoic granitic intrusives, and two with Silurian marine sediments. In the northwestern part of the quadrangle, four thorium radiation anomalies are delineated over exposures of upper Jurassic marine rocks. Anomaly 6, in the southwest, warrants attention as it suggests strong radiation in the uranium channel with little or no thorium radiation. The uranium/thorium and uranium/potassium ratio anomalies are also strong, supporting the likelihood of uranium enrichment. The feature is located on line 540, fiducials 7700 to 7720. Anomaly 7, on line 540, fiducials 8390 to 8420, shows similar characteristics although a minor thorium excursion is present. Anomaly 10, on line 3010 fiducials 9820 to 9840, is also characterized by a strong uranium radiation spike, with minor thorium radiation. The uranium/thorium and uranium/potassium ratio anomalies are well defined and relatively intense.« less

Aeromagnetic Survey of the Amargosa Desert, Nevada and California: A Tool for Understanding Near-Surface Geology and Hydrology

USGS Publications Warehouse

Blakely, Richard J.; Langenheim, V.E.; Ponce, David A.; Dixon, Gary L.

2000-01-01

A high-resolution aeromagnetic survey of the Amargosa Desert and surrounding areas provides insights into the buried geology of this structurally complex region. The survey covers an area of approximately 7,700 km2 (2,970 mi2), extending from Beatty, Nevada, to south of Shoshone, California, and includes parts of the Nevada Test Site and Death Valley National Park. Aeromagnetic flight lines were oriented east-west, spaced 400 m (0.25 mi) apart, and flown at an altitude of 150 m (500 ft) above terrain, or as low as permitted by safety considerations. Characteristic magnetic anomalies occur over volcanic terranes, such as Yucca Mountain and the Greenwater Range, and over Proterozoic basement rocks, such as Bare Mountain and the Black Mountains. Linear magnetic anomalies caused by offsets of volcanic rocks permit detailed mapping of shallow faults in volcanic terranes. Of particular interest are subtle anomalies that overlie alluvial deposits at Devils Hole and Pahrump Valley. Alignments of springs along magnetic anomalies at these locales suggest that these anomalies are caused by faults that cut the alluvium, displace magnetic rocks at depth, and eventually influence ground-water flow. Linear magnetic anomalies over the Funeral Mountains appear to coincide with a prominent set of north-northeast-striking faults that cut the Precambrian Stirling Quartzite, rocks that are typically nonmagnetic. The position and orientation of these anomalies with respect to springs north of Furnace Creek suggest that the faults may act as conduits for the flow of water from the north into Death Valley, but the mineralogical cause of the anomalies is unknown.

High-Resolution Aeromagnetic Survey over the Yucatan Peninsula - Implications for Chicxulub Impact, Secondary Craters and Regional Crustal Structures

NASA Astrophysics Data System (ADS)

Fucugauchi, J. U.; Lopez-Loera, H.; Rebolledo-Vieyra, M.

2011-12-01

We present the initial results of a low-altitude high-resolution aeromagnetic study over the Yucatan peninsula. Area surveyed extends from 86W to 91W and 18N to 21N, covering the peninsula and adjacent continental margin of Gulf of Mexico and Caribbean Sea. Aeromagnetic surveys are integrated into a regional map, and regional and residual anomalies are separated using spectral and least-squares methods. For the study, aeromagnetic field was reduced to the pole and several data filtering techniques were used, including first and second vertical derivatives, analytical signal, and upward and downward analytical continuations. The region is characterized by large amplitude broad elongated magnetic anomalies oriented north-south in the northern sector of the continental shelf, and northwest-southeast and northeast-southwest over the western and eastern sides of the peninsula, respectively. Major regional anomalies extend from the continental shelf into the peninsula, whereas other anomaly trends in the central northern sector, at northeast limit of Chicxulub crater, are restricted to the shelf. Largest anomaly on the east extends over the Holbox fracture zone. At its southern end, south of Chetumal a parallel trend extends over the Rio Hondo fault zone between Quintana Roo and Belize. On the western peninsula the anomaly is characterized by two parallel trends offset between Yucatan and Campeche. The central zone of Chicxulub is characterized by a semi-circular anomaly pattern, surrounded by long wavelength small amplitude anomalies extending to the east on the peninsula and shelf, isolated from the regional broad anomalies. To the south of Chicxulub anomaly, there is an elongated low with a central high extending southward from the terrace zone inside the crater rim. The elongated magnetic anomaly correlates with a broad gravity low, which is apparent south of the concentric zone of anomalies. To the north of Chicxulub anomaly, a magnetic high inside the crater is followed by a low outside, which extend to the north and northwest. The regional broad anomalies crossing the peninsula and shelf are interpreted as crustal structures on the Yucatan block related to pre- and rifting deformation, which include basement uplift. The southward elongated magnetic anomaly and gravity low may correspond to a pre-impact structure. From analysis of residual anomalies, we found no clear indication of secondary craters or multiple impacts.

Computing Critical Properties with Yang-Yang Anomalies

NASA Astrophysics Data System (ADS)

Orkoulas, Gerassimos; Cerdeirina, Claudio; Fisher, Michael

2017-01-01

Computation of the thermodynamics of fluids in the critical region is a challenging task owing to divergence of the correlation length and lack of particle-hole symmetries found in Ising or lattice-gas models. In addition, analysis of experiments and simulations reveals a Yang-Yang (YY) anomaly which entails sharing of the specific heat singularity between the pressure and the chemical potential. The size of the YY anomaly is measured by the YY ratio Rμ =C μ /CV of the amplitudes of C μ = - T d2 μ /dT2 and of the total specific heat CV. A ``complete scaling'' theory, in which the pressure mixes into the scaling fields, accounts for the YY anomaly. In Phys. Rev. Lett. 116, 040601 (2016), compressible cell gas (CCG) models which exhibit YY and singular diameter anomalies, have been advanced for near-critical fluids. In such models, the individual cell volumes are allowed to fluctuate. The thermodynamics of CCGs can be computed through mapping onto the Ising model via the seldom-used great grand canonical ensemble. The computations indicate that local free volume fluctuations are the origins of the YY effects. Furthermore, local energy-volume coupling (to model water) is another crucial factor underlying the phenomena.

Geochemical surveys in the United States in relation to health.

USGS Publications Warehouse

Tourtelot, H.A.

1979-01-01

Geochemical surveys in relation to health may be classified as having one, two or three dimensions. One-dimensional surveys examine relations between concentrations of elements such as Pb in soils and other media and burdens of the same elements in humans, at a given time. The spatial distributions of element concentrations are not investigated. The primary objective of two-dimensional surveys is to map the distributions of element concentrations, commonly according to stratified random sampling designs based on either conceptual landscape units or artificial sampling strata, but systematic sampling intervals have also been used. Political units have defined sample areas that coincide with the units used to accumulate epidemiological data. Element concentrations affected by point sources have also been mapped. Background values, location of natural or technological anomalies and the geographic scale of variation for several elements often are determined. Three-dimensional surveys result when two-dimensional surveys are repeated to detect environmental changes. -Author

Small-scale features in the Earth's magnetic field observed by Magsat.

USGS Publications Warehouse

Cain, J.C.; Schmitz, D.R.; Muth, L.

1984-01-01

A spherical harmonic expansion to degree and order 29 is derived using a selected magnetically quiet sample of Magsat data. Global maps representing the contribution due to terms of the expansion above n = 13 at 400 km altitude are compared with previously published residual anomaly maps and shown to be similar, even in polar regions. An expansion with such a high degree and order displays all but the sharpest features seen by the satellite and gives a more consistent picture of the high-order field structure at a constant altitude than do component maps derived independently. -Authors

Sea Surface Salinity signatures of tropical instability waves: New evidences from SMOS

NASA Astrophysics Data System (ADS)

Yin, Xiaobin; Boutin, Jacqueline; Reverdin, Gilles; Lee, Tong; Martin, Nicolas

2014-05-01

The European Space Agency's (ESA) Soil Moisture and Ocean Salinity (SMOS) mission, launched in November 2009, has been providing global maps of sea surface salinity (SSS) since 2010. SSS measurements from the SMOS satellite during June 2010 and December 2012 provide an unprecedented space-borne observation of the salinity structure of tropical instability waves (TIWs) including strong La Niña conditions during recent years. We use SMOS level 3 SSS maps averaged over 100 x 100 km2 with a 10-day running window and sampled daily over a 0.25 x 0.25° grid generated at Laboratoire d'Océanographie et du Climat: Expérimentation et Approches Numériques (http://catds.ifremer.fr/Products/Available-products-from-CEC-OS/Locean-v2013) [Boutin et al., 2013; Yin et al., 2012]. We also analyze daily SST from the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) produced on an operational basis at the UK Met Office using optimal interpolation [Donlon et al., 2011]. From a time-longitude section in the eastern Pacific ocean, westward propagations of SSS and SST anomalies along 2° N became apparent west of 90° W during June 2010 - March 2011 and June 2011 - March 2012, coincident with negative indexes in the NINO3 and NINO3.4 regions. The 33-day SSS anomaly and SST anomaly appeared together approximately in the same time and regions. The 17-day SSS anomaly is less clear than the 17-day SST anomaly. The SSS anomaly has approximate amplitude of 0.5 practical salinity scale (pss) and the SST anomaly has approximate amplitude of 2 ° C. Then, we focus on analysis of SSS and SST anomalies during June to December 2010. During this period the tropical Pacific was characterized by a strong La Niña, providing favorable conditions for the occurrence of TIWs. The high anomalies and meridional gradients of both SSS and SST appear north of the equator west of 100° W. Near 100W, they straddle the equator where South Pacific water and eastern edge upwelling water with high salinity meets the fresher Inter-tropical Convergence Zone water. SSS anomaly and SST anomaly vary in opposite phase and the amplitude of SSS anomaly is approximately 1/5 of SST anomaly. The westward propagation speed of SSS is approximately between 0.6 m/s and 1.5 m/s depending on latitude and dominant period of TIWs. Poleward propagations of waves are also observed at around 100° W. The results demonstrate the important value of SMOS SSS in studying TIWs. Reference Boutin, J., N. Martin, G. Reverdin, X. Yin and F. Gaillard (2013), Sea surface freshening inferred from SMOS and ARGO salinity: Impact of rain, Ocean Sci., 9, 183-192, doi:10.5194/os-9-183-2013. Donlon, C. J., M. Martin, J. D. Stark, J. Roberts-Jones, E. Fiedler and W. Wimmer (2012), The Operational Sea Surface Temperature and Sea Ice analysis (OSTIA), Remote Sensing of the Environment, 116, 140-158, doi: 10.1016/j.rse.2010.10.017. Yin, X., J. Boutin, and P. Spurgeon (2012), First assessment of SMOS data over open ocean: part I Pacific Ocean, IEEE Trans. Geosci. Remote Sens. 50(5), 1648-1661.

Heat flow anomalies and their interpretation

NASA Astrophysics Data System (ADS)

Chapman, David S.; Rybach, Ladislaus

1985-12-01

More than 10,000 heat flow determinations exist for the earth and the data set is growing steadily at about 450 observations per year. If heat flow is considered as a surface expression of geothermal processes at depth, the analysis of the data set should reveal properties of those thermal processes. They do, but on a variety of scales. For this review heat flow maps are classified by 4 different horizontal scales of 10 n km (n = 1, 2, 3 and 4) and attention is focussed on the interpretation of anomalies which appear with characteristic dimensions of 10 (n - 1) km in the respective representations. The largest scale of 10 4 km encompasses heat flow on a global scale. Global heat loss is 4 × 10 13 W and the process of sea floor spreading is the principal agent in delivering much of this heat to the surface. Correspondingly, active ocean ridge systems produce the most prominent heat flow anomalies at this scale with characteristic widths of 10 3 km. Shields, with similar dimensions, exhibit negative anomalies. The scale of 10 3 km includes continent wide displays. Heat flow patterns at this scale mimic tectonic units which have dimensions of a few times 10 2 km, although the thermal boundaries between these units are sometimes sharp. Heat flow anomalies at this scale also result from plate tectonic processes, and are associated with arc volcanism, back arc basins, hot spot traces, and continental rifting. There are major controversies about the extent to which these surface thermal provinces reflect upper mantle thermal conditions, and also about the origin and evolution of the thermal state of continental lithosphere. Beginning with map dimensions of 10 2 km thermal anomalies of scale 10 1 km, which have a definite crustal origin, become apparent. The origin may be tectonic, geologic, or hydrologic. Ten kilometers is a common wavelength of topographic relief which drives many groundwater flow systems producing thermal anomalies. The largest recognized continental geothermal systems have thermal anomalies 10 1 km wide and are capable of producing hundreds of megawatts of thermal energy. The smallest scale addressed in this paper is 10 1 km. Worldwide interest in exploiting geothermal systems has been responsible for a recent accumulation of heat flow data on the smallest of scales considered here. The exploration nature of the surveys involve 10's of drillholes and reveal thermal anomalies having widths of 10 0 km. These are almost certainly connected to surface and subsurface fluid discharge systems which, in spite of their restricted size, are typically delivering 10 MW of heat to the near surface environment.

Environmental magnetic methods for detecting and mapping contaminated sediments in lakes

NASA Astrophysics Data System (ADS)

Boyce, J. I.

2009-05-01

The remediation of contaminated sediments is an urgent environmental priority in the Great Lakes and requires detailed mapping of impacted sediment layer thickness, areal distribution and pollutant levels. Magnetic property measurements of sediment cores from two heavily polluted basins in Lake Ontario (Hamilton Harbour, Frenchman's Bay) show that concentrations of hydrocarbons (PAH) and a number of heavy metals (Pb, As, Ni, Cu, Cr, Zn, Cd, Fe) are strongly correlated with magnetic susceptibility. The magnetic susceptibility contrast between the contaminated sediment and underlying 'pre-colonial' sediments is sufficient to generate a total field anomaly (ca. 2-20 nT) that can be measured with a magnetometer towed above the lake bed. Systematic magnetic surveying (550 line km) of Hamilton Harbour using a towed marine magnetometer clearly identifies a number of well-defined magnetic anomalies that coincide with known accumulations of contaminated lake sediment. When calibrated against in-situ magnetic property measurements, the modeled apparent susceptibility from magnetic survey results can be used to classify the relative contaminant impact levels. The results demonstrate the potential of magnetic property measurements for rapid reconnaissance mapping of large areas of bottom contamination prior to detailed coring and sediment remediation.

Detecting anomalies in CMB maps: a new method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neelakanta, Jayanth T., E-mail: jayanthtn@gmail.com

2015-10-01

Ever since WMAP announced its first results, different analyses have shown that there is weak evidence for several large-scale anomalies in the CMB data. While the evidence for each anomaly appears to be weak, the fact that there are multiple seemingly unrelated anomalies makes it difficult to account for them via a single statistical fluke. So, one is led to considering a combination of these anomalies. But, if we ''hand-pick'' the anomalies (test statistics) to consider, we are making an a posteriori choice. In this article, we propose two statistics that do not suffer from this problem. The statistics aremore » linear and quadratic combinations of the a{sub ℓ m}'s with random co-efficients, and they test the null hypothesis that the a{sub ℓ m}'s are independent, normally-distributed, zero-mean random variables with an m-independent variance. The motivation for considering multiple modes is this: because most physical models that lead to large-scale anomalies result in coupling multiple ℓ and m modes, the ''coherence'' of this coupling should get enhanced if a combination of different modes is considered. In this sense, the statistics are thus much more generic than those that have been hitherto considered in literature. Using fiducial data, we demonstrate that the method works and discuss how it can be used with actual CMB data to make quite general statements about the incompatibility of the data with the null hypothesis.« less

Magnetic Anomalies Associated With Fracture Zones in the Cretaceous Magnetic Quiet Zone in the North Pacific Ocean

NASA Astrophysics Data System (ADS)

Ishihara, T.

2003-12-01

The existence of magnetic anomalies along east-west trending fracture zones in the north Pacific is well known. These anomalies are particularly prominent in the Cretaceous magnetic quiet zone, where no comparable anomalies are observed other than those associated with the Hawaiian Ridge and the Musician Seamounts in a newly compiled magnetic anomaly map. Model calculation was conducted using old magnetic and bathymetric data collected in the Cretaceous magnetic quiet zone. Two-dimensional simple models along north-south lines, which cross the Mendocino, Pioneer, Murray, Molokai and Clarion Fracture Zones, were constructed in order to clarify the sources of these magnetic anomalies. In these model calculations, it was assumed that the source bodies have normal remanent magnetizations with their inclinations of about 5 (for Mendocino FZ) to -25 degrees (for Clarion FZ), corresponding to the latitudes 40 degrees south of the present locations, as was suggested to have been in the late Cretaceous by some of paleomagnetic studies. This assumption is consistent with the dominance of negative anomalies in the observation. The model calculations suggest that under assumption of 0.5 km thick magnetic source bodies, remanent magnetizations more than 10 A/m should occur below some of the ridges and troughs in these fractures zones. Alternatively, in more plausible models with a remanent magnetization of 3 A/m, the magnetic source bodies should have thicknesses of up to about 5 km there.

Electroanatomic Mapping-Guided Catheter Ablation of Supraventricular Tachycardia in Children with Ebstein's Anomaly.

PubMed

Ergul, Yakup; Koca, Serhat; Akdeniz, Celal; Tuzcu, Volkan

2018-06-07

In Ebstein's anomaly (EA), tachycardia substrates are complex, and accessory pathway (AP) ablations are often challenging. This study demonstrates the utility of the EnSite Velocity system (St. Jude Medical, St Paul, MN) in the catheter ablation of supraventricular tachycardia in children with EA. Twenty patients [Female/Male = 8/12, median age 11.5 years (2.6-18)] with EA who underwent catheter ablation guided by the EnSite Velocity system between December 2011 and December 2016 were retrospectively evaluated. Five patients had severe EA, and two of them were at Fontan palliation pathway. The most common indications for ablations were palpitations/syncope and treatment-resistant arrhythmias. Thirty-one tachycardia substrate foci (21 manifest AP, 2 concealed AP, 4 Mahaim AP, 3 focal atrial tachycardias, and 1 typical atrioventricular nodal reentrant tachycardia) were detected in 20 patients. There were multiple tachycardia substrates in 11 patients (55%). The patient-based acute procedure success rate was 19/20 (95%), and the tachycardia-based success rate was 30/31 (97%). The mean procedure time was 170 ± 43 min (90-265). Fluoroscopy was not used in 15 (75%) patients. The mean fluoroscopy time in the remaining five patients was 3.6 ± 2.9 min (0.7-7.8). During a mean follow-up of 35.1 ± 20.3 months (6-60), tachycardia recurred in four patients (4/19, 21%). No complications were seen. Catheter ablation of arrhythmias can be performed effectively and safely in pediatric EA patients by using a limited fluoroscopic approach with the help of electroanatomical mapping systems. However, the rate of tachycardia recurrence at follow-up remains high.

CMB-S4 and the hemispherical variance anomaly

NASA Astrophysics Data System (ADS)

O'Dwyer, Márcio; Copi, Craig J.; Knox, Lloyd; Starkman, Glenn D.

2017-09-01

Cosmic microwave background (CMB) full-sky temperature data show a hemispherical asymmetry in power nearly aligned with the Ecliptic. In real space, this anomaly can be quantified by the temperature variance in the Northern and Southern Ecliptic hemispheres, with the Northern hemisphere displaying an anomalously low variance while the Southern hemisphere appears unremarkable [consistent with expectations from the best-fitting theory, Lambda Cold Dark Matter (ΛCDM)]. While this is a well-established result in temperature, the low signal-to-noise ratio in current polarization data prevents a similar comparison. This will change with a proposed ground-based CMB experiment, CMB-S4. With that in mind, we generate realizations of polarization maps constrained by the temperature data and predict the distribution of the hemispherical variance in polarization considering two different sky coverage scenarios possible in CMB-S4: full Ecliptic north coverage and just the portion of the North that can be observed from a ground-based telescope at the high Chilean Atacama plateau. We find that even in the set of realizations constrained by the temperature data, the low Northern hemisphere variance observed in temperature is not expected in polarization. Therefore, observing an anomalously low variance in polarization would make the hypothesis that the temperature anomaly is simply a statistical fluke more unlikely and thus increase the motivation for physical explanations. We show, within ΛCDM, how variance measurements in both sky coverage scenarios are related. We find that the variance makes for a good statistic in cases where the sky coverage is limited, however, full northern coverage is still preferable.

United States crustal thickness

NASA Technical Reports Server (NTRS)

Allenby, R. J.; Schnetzler, C. C.

1983-01-01

The thickness of the crust, the thickness of the basal (intermediate or lower) crustal layer, and the average velocity at the top of the mantle have been mapped using all available deep-penetrating seismic-refraction profiles in the conterminous United States and surrounding border areas. These profiles are indexed to their literature data sources. The more significant long wavelength anomalies on the three maps are briefly discussed and analyzed. An attempt to use Bouguer gravity to validate mantle structure was inconclusive.

Anomaly clustering in hyperspectral images

NASA Astrophysics Data System (ADS)

Doster, Timothy J.; Ross, David S.; Messinger, David W.; Basener, William F.

2009-05-01

The topological anomaly detection algorithm (TAD) differs from other anomaly detection algorithms in that it uses a topological/graph-theoretic model for the image background instead of modeling the image with a Gaussian normal distribution. In the construction of the model, TAD produces a hard threshold separating anomalous pixels from background in the image. We build on this feature of TAD by extending the algorithm so that it gives a measure of the number of anomalous objects, rather than the number of anomalous pixels, in a hyperspectral image. This is done by identifying, and integrating, clusters of anomalous pixels via a graph theoretical method combining spatial and spectral information. The method is applied to a cluttered HyMap image and combines small groups of pixels containing like materials, such as those corresponding to rooftops and cars, into individual clusters. This improves visualization and interpretation of objects.

Mapping Antarctic Crustal Thickness using Gravity Inversion and Comparison with Seismic Estimates

NASA Astrophysics Data System (ADS)

Kusznir, Nick; Ferraccioli, Fausto; Jordan, Tom

2017-04-01

Using gravity anomaly inversion, we produce comprehensive regional maps of crustal thickness and oceanic lithosphere distribution for Antarctica and the Southern Ocean. Crustal thicknesses derived from gravity inversion are consistent with seismic estimates. We determine Moho depth, crustal basement thickness, continental lithosphere thinning (1-1/β) and ocean-continent transition location using a 3D spectral domain gravity inversion method, which incorporates a lithosphere thermal gravity anomaly correction (Chappell & Kusznir 2008). The gravity anomaly contribution from ice thickness is included in the gravity inversion, as is the contribution from sediments which assumes a compaction controlled sediment density increase with depth. Data used in the gravity inversion are elevation and bathymetry, free-air gravity anomaly, the Bedmap 2 ice thickness and bedrock topography compilation south of 60 degrees south and relatively sparse constraints on sediment thickness. Ocean isochrons are used to define the cooling age of oceanic lithosphere. Crustal thicknesses from gravity inversion are compared with independent seismic estimates, which are still relatively sparse over Antarctica. Our gravity inversion study predicts thick crust (> 45 km) under interior East Antarctica, which is penetrated by narrow continental rifts featuring relatively thinner crust. The largest crustal thicknesses predicted from gravity inversion lie in the region of the Gamburtsev Subglacial Mountains, and are consistent with seismic estimates. The East Antarctic Rift System (EARS), a major Permian to Cretaceous age rift system, is imaged by our inversion and appears to extend from the continental margin at the Lambert Rift to the South Pole region, a distance of 2500 km. Offshore an extensive region of either thick oceanic crust or highly thinned continental crust lies adjacent to Oates Land and north Victoria Land, and also off West Antarctica around the Amundsen Ridges. Thin crust is predicted under the Ross Sea and beneath the West Antarctic Ice Sheet and delineates the regional extent of the broad West Antarctic Rift System (WARS). Substantial regional uplift is required under Marie Byrd Land to reconcile gravity and seismic estimates. A mantle dynamic uplift origin of the uplift is preferred to a thermal anomaly from a very young rift. The new maps produced by this study support the hypothesis that one branch of the WARS links through to the De Gerlache sea-mounts and Peter I Island in the Bellingshausen Sea region, while another branch may link to the George V Sound Rift in the Antarctic Peninsula region. Crustal thickness and lithosphere thinning derived from gravity inversion also allows the determination of circum-Antarctic ocean-continent transition structure and the mapping of continent-ocean boundary location. Superposition of illuminated satellite gravity data onto crustal thickness maps from gravity inversion provides improved determination of Southern Ocean rift orientation, pre-breakup rifted margin conjugacy and continental breakup trajectory. The continental lithosphere thinning distribution, used to define the initial thermal model temperature perturbation, is derived from the gravity inversion and uses no a priori isochron information; as a consequence the gravity inversion method provides a prediction of ocean-continent transition location, which is independent of ocean isochron information.

ENSO impacts on flood risk at the global scale

NASA Astrophysics Data System (ADS)

Ward, Philip; Dettinger, Michael; Jongman, Brenden; Kummu, Matti; Winsemius, Hessel

2014-05-01

We present the impacts of El Niño Southern Oscillation (ENSO) on society and the economy, via relationships between ENSO and the hydrological cycle. We also discuss ways in which this knowledge can be used in disaster risk management and risk reduction. This contribution provides the most recent results of an ongoing 4-year collaborative research initiative to assess and map the impacts of large scale interannual climate variability on flood hazard and risk at the global scale. We have examined anomalies in flood risk between ENSO phases, whereby flood risk is expressed in terms of indicators such as: annual expected damage; annual expected affected population; annual expected affected Gross Domestic Product (GDP). We show that large anomalies in flood risk occur during El Niño or La Niña years in basins covering large parts of the Earth's surface. These anomalies reach statistical significance river basins covering almost two-thirds of the Earth's surface. Particularly strong anomalies exist in southern Africa, parts of western Africa, Australia, parts of Central Eurasia (especially for El Niño), the western USA (especially La Niña anomalies), and parts of South America. We relate these anomalies to possible causal relationships between ENSO and flood hazard, using both modelled and observed data on flood occurrence and extremity. The implications for flood risk management are many-fold. In those regions where disaster risk is strongly influenced by ENSO, the potential predictably of ENSO could be used to develop probabilistic flood risk projections with lead times up to several seasons. Such data could be used by the insurance industry in managing risk portfolios and by multinational companies for assessing the robustness of their supply chains to potential flood-related interruptions. Seasonal forecasts of ENSO influence of peak flows could also allow for improved flood early warning and regulation by dam operators, which could also reduce overall risks (and by extension insured losses). We carried out the research by simulating daily river discharges using a global hydrological model (PCR-GLOBWB), forced with gridded climate reanalysis time-series (EU-WATCH). From this, we derived peak annual flood volumes for large-scale river basins globally. These were used to force a global inundation model (dynRout) to map inundation extent and depth for return periods between 2 and 1000 years, under El Niño conditions, neutral conditions, and La Niña conditions. Theses flood hazard maps were combined with global datasets on socioeconomic variables such as population and income to represent the socioeconomic exposure to flooding, and depth-damage curves to represent vulnerability.

The ASTER Volcano Archive (AVA): High Spatial Resolution Global Monitoring of Volcanic Eruptions

NASA Astrophysics Data System (ADS)

Linick, J. P.; Pieri, D. C.; Davies, A. G.; Reath, K.; Mars, J. C.; Hubbard, B. E.; Sanchez, R. M.; Tan, H. L.

2017-12-01

The ASTER Volcano Archive (AVA) is a data system focused on collecting and cataloguing higher level remote sensing data products for all Holocene volcanoes over the last several decades, producing volcanogenic science products for global detection, mapping, and modeling of effusive eruptions at high spatial resolution, and providing rapid bulk dissemination of relevant data products to the science community at large. Space-based optical platforms such as ASTER, EO-1, and Landsat, are a critical component for global monitoring systems to provide the capability for volcanic hazard assessment and modeling, and are a vital addition to in-situ measurements. The AVA leverages these instruments for the automated generation of lava flow emplacement maps, sulfur dioxide monitoring, thermal anomaly detection, and modeling of integrated thermal emission across the world's volcanoes. Additionally, we provide slope classified alteration and lahar inundation maps with potential inundation zones for certain relevant volcanoes. We explore the AVA's data product retrieval API, and describe how scientists can rapidly retrieve bulk products using the AVA platform with a focus on practical applications for both general analysis and hazard response.

The prediction and mapping of geoidal undulations from GEOS-3 altimetry. [gravity anomalies

NASA Technical Reports Server (NTRS)

Kearsley, W.

1978-01-01

From the adjusted altimeter data an approximation to the geoid height in ocean areas is obtained. Methods are developed to produce geoid maps in these areas. Geoid heights are obtained for grid points in the region to be mapped, and two of the parameters critical to the production of an accurate map are investigated. These are the spacing of the grid, which must be related to the half-wavelength of the altimeter signal whose amplitude is the desired accuracy of the contour; and the method adopted to predict the grid values. Least squares collocation was used to find geoid undulations on a 1 deg grid in the mapping area. Twenty maps, with their associated precisions, were produced and are included. These maps cover the Indian Ocean, Southwestern and Northeastern portions of the Pacific Ocean, and Southwest Atlantic and the U.S. Calibration Area.

Maps showing aeromagnetic data and interpretation for the Kalmiopsis Wilderness, southwestern Oregon

USGS Publications Warehouse

Blakely, Richard J.; Page, Norman J; Gray, Floyd; Senior, Lisa; Ryan, Holly F.

1983-01-01

Most individual anomalies in this area are caused by known geologic boundaries or topographic features; those that are not are of particular interest because they may reflect areas of increased or decreased magnetization associated with zones of minerlization. 

Use of MAGSAT anomaly data for crustal structure and mineral resources in the US midcontinent

NASA Technical Reports Server (NTRS)

Carmichael, R. S. (Principal Investigator); Black, R.

1982-01-01

Activities concerning the interpretation of processed MAGSAT data and maps are briefly reported. Work involving the identification of long wavelength 'regional' effects that might be associated with varying crustal thickness or Curie temperature depths is processing.

Robustness of Global Radial Anisotropy Models of the Upper Mantle

NASA Astrophysics Data System (ADS)

Xing, Z.; Beghein, C.; Yuan, K.

2014-12-01

Radial anisotropy provides important constraints on mantle deformation. While its presence is well accepted in the uppermost mantle, large discrepancies remain among existing models, even at depths well sampled by seismic data, and its presence at greater depths is highly uncertain. Surface wave phase velocity dispersion measurements are routinely used to constrain lateral variations in mantle S-wave velocity (dlnVS) and radial anisotropy (ξ=VSH2/VSV2). Here, we employed the fundamental and higher mode surface wave phase velocity maps of Visser et al. (2008) that have unprecedented sensitivity to structure down to 800-1000km depth, and we adopted a probabilistic forward modeling approach, the Neighbourhood Algorithm, to quantify posterior model uncertainties and parameter trade-offs. We investigated the effect of prior crustal corrections on 3-D ξ and dlnVS models. To avoid mapping crustal structure onto mantle heterogeneities, it is indeed important to accurately account for 3-D crustal anomalies and variations in Moho depth. One approach is to solve the non-linear problem and simultaneously constrain Moho depth and mantle anomalies (Visser et al., 2008). Another approach, taken here, is to calculate non-linear crustal corrections with an a priori crustal model, which are then applied to the phase velocity maps before inverting the remaining signal for mantle structure. In this work, we also determined laterally varying sensitivity kernels to account for lateral changes in the crust. We compare models obtained using CRUST2.0 (Bassin et al., 2000) and the new CRUST1.0 (Laske et al., 2012) models, which mostly differ under continents. Our preliminary results show strong differences (ΔdlnVS>2%) between the two models in continental dlnVS for the upper 150-200km, and strong changes in x amplitudes in the top 200km (Δξ>2%). Some of the differences in ξ persist down to the transition zone, in particular beneath central Asia and South America. Despite these discrepancies, inferences on the depth of continental roots (~200-250km) based on either the extent of the dlnVS>0 anomalies or the depth at which ξ changes sign remain independent of the crustal model employed. We also note that VSV>VSH dominates the deep upper mantle except in central Pacific, which is characterized by VSH>VSV down to the transition zone.

Conditional anomaly detection methods for patient–management alert systems

PubMed Central

Valko, Michal; Cooper, Gregory; Seybert, Amy; Visweswaran, Shyam; Saul, Melissa; Hauskrecht, Milos

2010-01-01

Anomaly detection methods can be very useful in identifying unusual or interesting patterns in data. A recently proposed conditional anomaly detection framework extends anomaly detection to the problem of identifying anomalous patterns on a subset of attributes in the data. The anomaly always depends (is conditioned) on the value of remaining attributes. The work presented in this paper focuses on instance–based methods for detecting conditional anomalies. The methods rely on the distance metric to identify examples in the dataset that are most critical for detecting the anomaly. We investigate various metrics and metric learning methods to optimize the performance of the instance–based anomaly detection methods. We show the benefits of the instance–based methods on two real–world detection problems: detection of unusual admission decisions for patients with the community–acquired pneumonia and detection of unusual orders of an HPF4 test that is used to confirm Heparin induced thrombocytopenia — a life–threatening condition caused by the Heparin therapy. PMID:25392850