scholarly journals Candidates for multiple impact craters?: Popigai and Chicxulub as seen by the global high resolution gravitational field model EGM2008

Solid Earth ◽  
2010 ◽  
Vol 1 (1) ◽  
pp. 71-83 ◽  
Author(s):  
J. Klokočník ◽  
J. Kostelecký ◽  
I. Pešek ◽  
P. Novák ◽  
C. A. Wagner ◽  
...  
Keyword(s):  
Field Model ◽  
High Spatial Resolution ◽  
Seismic Profile ◽  
Impact Craters ◽  
Stokes Parameters ◽  
Disturbing Potential ◽  
Complete Set ◽  
Gravity Signal ◽  
Multiple Impact ◽  
Main Crater

Abstract. In 2008 the new Earth Gravitational Model (EGM2008) was released. It contains a complete set of spherical harmonic coefficients of the Earth's gravitational potential (Stokes parameters) to degree 2190 and order 2159 and selected orders to degree 2190, that can be used for evaluation of various potential quantities with both the unprecedented accuracy and high spatial resolution. Two such quantities, the gravity anomaly and second-order radial derivative of the disturbing potential, were computed over selected areas with known impact craters. The displays of these derivatives for two such sites clearly show not only the strong circular-like features known to be associated with them but also other symmetrical structures which appear to make them multiple impact sites. At Popigai, Siberia, the series of circular features fall in a line from the "primary crater" in the southeast (SE) direction. At Chicxulub, Yucatán, there appears to be one more crater close to the "primary" in the northeast (NE) direction, as well as possibly others in the vicinity of the main crater (SW). Gravity information alone is not, however, proof of impact craters but it is useful in identifying candidate sites for further study, for examination by geologists and geophysicists. In the case of Chicxulub, a very recent single seismic profile suggests that a more likely explanation for the observed circular like gravity signal from EGM2008 NE of the "primary" is a pre-impact basin.

scholarly journals Candidates for multiple impact craters: popigai and chicxulub as seen by EGM08, a global 5'×5' gravitational model

2010 ◽  
Vol 2 (1) ◽  
pp. 69-103 ◽  
Author(s):  
J. Klokočník ◽  
J. Kostelecký ◽  
I. Pešek ◽  
P. Novák ◽  
C. A. Wagner ◽  
...  
Keyword(s):  
High Spatial Resolution ◽  
Impact Craters ◽  
Stokes Parameters ◽  
Disturbing Potential ◽  
Gravitational Model ◽  
Secondary Crater ◽  
Complete Set ◽  
Multiple Impact ◽  
The Impact ◽  
Main Crater

Abstract. In 2008 the new Earth Gravitational Model (EGM08) was released. It contains a complete set of spherical harmonic coefficients of the Earth's gravitational potential (Stokes parameters) to degree 2190 and order 2159 that can be used for evaluation of various potential quantities with both the unprecedented accuracy and high spatial resolution. Two such quantities, the gravity anomaly and second-order radial derivative of the disturbing potential, were computed over selected areas with known impact craters. The displays of these derivatives for two such sites clearly show not only the strong circular-like features known to be associated with them but also other symmetrical structures which appear to make them multiple impact sites. At Popigai, Siberia, the secondary circular features fall in a line from the primary in the SE direction. At Chicxulub, Yucatán, there appears to be one secondary crater close to the primary in the NE direction, as well as possibly others in the vicinity of the main crater. Gravity information alone is not proof of the impact craters but it is useful in identifying candidate sites for further study, for future examination by geologists and geophysicists.

Gravity aspects from recent Earth gravity model EIGEN 6C4 for geoscience and archaeology in Sahara, Egypt

2020 ◽  
Author(s):  
Jaroslav Klokocnik ◽  
Vaclav Cilek ◽  
Jan Kostelecky ◽  
Ales Bezdek
Keyword(s):  
Field Model ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Western Desert ◽  
Archaeological Sites ◽  
Gravity Field Model ◽  
Earth Gravity ◽  
Earth Gravity Model ◽  
Gravity Signal ◽  
Libyan Desert

<p>A new method to detect paleolakes via their gravity signal is presented (here with implications for geoscience and archaeology). The gravity aspects or descriptors (gravity anomalies/disturbances, second radial derivatives, strike angles and virtual deformations) were computed from the global static combined gravity field model EIGEN 6C4 for an application in archaeology and geoscience in Egypt and surrounding countries. The model consists of the best now available satellite and terrestrial data, including gradiometry from the GOCE mission. EIGEN 6C4 has the ground resolution ~10 km. From archaeological literarure we took the positions of archaeological sites of the Holocene occupations between 8500 and 5300 BC (8.5-5.3 ky BC) in the Eastern Sahara, Western Desert, Egypt. We correlated the features found from the gravity data with the locations; the correlation is good, assuming that the sites were mostly at paleolake boarders or at rivers. We suggest position, extent and shape of a paleolake. Then, we have estimated a possible location, extent and shape of the putative paleolake(s). We also reconsider the origin of Libyan Desert glass (LDG) in the Great Sand Sea (GSS) and support a hypothesis about an older impact structure created in GSS, repeatedly filled by water, which might be a part of some of the possible paleolake(s).</p>

scholarly journals The Dynamic Evolutionary Processes of the Magnetic Fields in the Solar Active Region Boulder 5395

1993 ◽  
Vol 141 ◽  
pp. 457-460
Author(s):  
Xin Ping Liu ◽  
Hong Qi Zhang ◽  
Jing Lin ◽  
Gui Lin Liu
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Magnetic Fields ◽  
Solar Flares ◽  
Field Model ◽  
Solar Active Region ◽  
Mhd Equations ◽  
Evolutionary Processes ◽  
Magnetic Field Model ◽  
Complete Set

AbstractIn this paper, based on observational information we proposed an opening bipolar magnetic field model and studied numerically the dynamic evolutionary processes of the magnetic fields by solving a complete set of MHD equations. The aim is to discuss one of the mechanisms of energy build up of solar flares produced in the active region Boulder 5395.

Dating impact craters: palaeogeographic versus isotopic and stratigraphic methods – a brief case study

2008 ◽  
Vol 145 (4) ◽  
pp. 586-590 ◽  
Author(s):  
MARTIN SCHMIEDER ◽  
ELMAR BUCHNER
Keyword(s):  
Middle Jurassic ◽  
Impact Craters ◽  
Late Triassic ◽  
Crater Formation ◽  
Impact Event ◽  
Multiple Impact

AbstractIsotopic and stratigraphic ages of the ~ 80 km diameter Puchezh-Katunki (Russia; 220 ± 10 to 167 ± 3 Ma) and the ~ 20 km diameter Obolon (Ukraine; 215 ± 25 to 169 ± 7 Ma) impact structures are associated with significant age uncertainties. As a case study, reconstructions of the palaeogeography at the time of crater formation (Late Triassic to Middle Jurassic) based on recent palaeogeographic maps help further to constrain impact ages. Palaeogeographic studies suggest that Puchezh-Katunki is older than 170 Ma and that Obolon is younger than 185 Ma. This also rules out that Obolon formed during a ~ 214 Ma Late Triassic multiple impact event as recently discussed.

scholarly journals Evaluation of gravity field model EIGEN-6C4 by means of various functions of gravity potential, and by GNSS/levelling

2015 ◽  
Vol 14 (1) ◽  
pp. 7-28 ◽  
Author(s):  
Jan Kostelecký ◽  
Jaroslav Klokočník ◽  
Blažej Bucha ◽  
Aleš Bezděk ◽  
Christoph Förste
Keyword(s):  
Gravity Field ◽  
Field Model ◽  
Gravity Potential ◽  
Data Sets ◽  
Satellite Gravity ◽  
Disturbing Potential ◽  
Gravity Field Model ◽  
Global Gravity ◽  
Second Derivatives ◽  
Gravity Disturbances

<p>The combined gravity field model EIGEN-6C4 (Förste et al., 2014) is the latest combined global gravity field model of GFZ Potsdam and GRGS Toulouse. EIGEN-6C4 has been generated including the satellite gravity gradiometry data of the entire GOCE mission (November 2009 till October 2013) and is of maximum spherical degree and order 2190. In this study EIGEN-6C4 has been compared with EGM2008 to its maximum degree and order via gravity disturbances and T<sub>zz</sub> part of the Marussi tensor of the second derivatives of the disturbing potential. The emphasis is put on such areas where GOCE data (complete set of gradiometry measurements after reductions) in EIGEN-6C4 obviously contributes to an improvement of the gravity field description. </p><p>GNSS/levelling geoid heights are independent data source for the evaluation of gravity field models. Therefore, we use the GNSS/levelling data sets over the territories of Europe, Czech Republic and Slovakia for the evaluation of EIGEN-6C4 w.r.t. EGM2008.</p>

Preparation of TEM samples by focused ion beams

1995 ◽  
Vol 53 ◽  
pp. 518-519
Author(s):  
John F. Walker ◽  
J C Reiner ◽  
C Solenthaler
Keyword(s):  
Integrated Circuit ◽  
Polycrystalline Silicon ◽  
Field Effect Transistor ◽  
High Spatial Resolution ◽  
Ion Beam ◽  
Ion Beams ◽  
Focused Ion Beams ◽  
Precise Location ◽  
Effect Transistor ◽  
Circuit Technology

The high spatial resolution available from TEM can be used with great advantage in the field of microelectronics to identify problems associated with the continually shrinking geometries of integrated circuit technology. In many cases the location of the problem can be the most problematic element of sample preparation. Focused ion beams (FIB) have previously been used to prepare TEM specimens, but not including using the ion beam imaging capabilities to locate a buried feature of interest. Here we describe how a defect has been located using the ability of a FIB to both mill a section and to search for a defect whose precise location is unknown. The defect is known from electrical leakage measurements to be a break in the gate oxide of a field effect transistor. The gate is a square of polycrystalline silicon, approximately 1μm×1μm, on a silicon dioxide barrier which is about 17nm thick. The break in the oxide can occur anywhere within that square and is expected to be less than 100nm in diameter.

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