scholarly journals Quantitative analysis of New Zealand-Antarctica plate motions during the Paleogene and Late Cretaceous

2021 ◽  
Author(s):  
◽  
Amandine Chambord
Keyword(s):  
Magnetic Anomaly ◽  
New Method ◽  
Magnetic Data ◽  
Magnetic Reversal ◽  
Tectonic Plates ◽  
Southwest Pacific ◽  
Single Plate ◽  
The Pacific ◽  
Non Destructive ◽  
Different Sources

<p>Quantifying past motions of tectonic plates in the southwest Pacific is important because the Pacific-Antarctic ridge is the only non-destructive boundary between the Pacific plate and other major plates. However, formation of sea-ice near Antarctica impairs the collection of magnetic anomaly data that are necessary to calculate plate rotations. A detailed analysis of all ship-track magnetic data available in the southwest Pacific (61 cruises, 153 profiles, including several cruises collected after 1995) is presented here. Four different sources of uncertainty are quantified: (1) confidence of magnetic anomaly identification, (2) magnetic reversal location picking precision, (3) ship navigation precision, and (4) magnetic data quality. Finite plate rotations are calculated for the southwest Pacific (42.5 to 79 Ma) using the resulting magnetic anomaly database (1528 magnetic reversal data). Finite rotations were calculated using the Hellinger criterion, or by a new method presented here that assumes orthogonality between fracture zones and ridge segments. The new method requires less parameters and is hence able better estimate rotations in cases with an uneven distribution of sparse magnetic data. Rotations and formal uncertainties are calculated for thirty-one chrons (c20y to c33o). They confirm the existence of a three plate system (Pacific, Marie Byrd Land, Bellingshausen) in the southwest Pacific from before c31o (68.7 Ma) until c28y (62.5 Ma). After c28y, the Bellingshausen and Marie Byrd Land plates moved as a single plate.</p>

scholarly journals Quantitative analysis of New Zealand-Antarctica plate motions during the Paleogene and Late Cretaceous

2021 ◽  
Author(s):  
◽  
Amandine Chambord
Keyword(s):  
Magnetic Anomaly ◽  
New Method ◽  
Magnetic Data ◽  
Magnetic Reversal ◽  
Tectonic Plates ◽  
Southwest Pacific ◽  
Single Plate ◽  
The Pacific ◽  
Non Destructive ◽  
Different Sources

<p>Quantifying past motions of tectonic plates in the southwest Pacific is important because the Pacific-Antarctic ridge is the only non-destructive boundary between the Pacific plate and other major plates. However, formation of sea-ice near Antarctica impairs the collection of magnetic anomaly data that are necessary to calculate plate rotations. A detailed analysis of all ship-track magnetic data available in the southwest Pacific (61 cruises, 153 profiles, including several cruises collected after 1995) is presented here. Four different sources of uncertainty are quantified: (1) confidence of magnetic anomaly identification, (2) magnetic reversal location picking precision, (3) ship navigation precision, and (4) magnetic data quality. Finite plate rotations are calculated for the southwest Pacific (42.5 to 79 Ma) using the resulting magnetic anomaly database (1528 magnetic reversal data). Finite rotations were calculated using the Hellinger criterion, or by a new method presented here that assumes orthogonality between fracture zones and ridge segments. The new method requires less parameters and is hence able better estimate rotations in cases with an uneven distribution of sparse magnetic data. Rotations and formal uncertainties are calculated for thirty-one chrons (c20y to c33o). They confirm the existence of a three plate system (Pacific, Marie Byrd Land, Bellingshausen) in the southwest Pacific from before c31o (68.7 Ma) until c28y (62.5 Ma). After c28y, the Bellingshausen and Marie Byrd Land plates moved as a single plate.</p>

scholarly journals First stage of INTRAMAP: INtegrated Transantarctic Mountains and Ross Sea Area Magnetic Anomaly Project

1999 ◽  
Vol 42 (2) ◽  
Author(s):  
M. Chiappini ◽  
F. Ferraccioli ◽  
E. Bozzo ◽  
D. Damaske ◽  
J. C. Behrendt
Keyword(s):  
Magnetic Anomaly ◽  
Ross Sea ◽  
Magnetic Data ◽  
Data Sets ◽  
Continental Scale ◽  
The Pacific ◽  
Victoria Land ◽  
Transantarctic Mountains ◽  
Ground Magnetic ◽  
Sea Area

INTRAMAP (INtegrated Transantarctic Mountains and Ross Sea Area Magnetic Anomaly Project) is an international effort to merge the magnetic data acquired throughout the "Ross Sea Antarctic Sector" (south of 60°S between 135°-255°E) including the Transantarctic Mountains (TAM), the Ross Sea, Marie Byrd Land, and the Pacific coast, and also to begin the compilation efforts for new data over the Wilkes Basin. This project is a component of the continental scale Antarctic Digital Magnetic Anomaly Project (ADMAP). The first stage of INTRAMAP addresses the analysis and merging of GITARA (1991-1994) and GANOVEX (1984) aeromagnetic surveys together with ground magnetic data (1984-1989). The combined data sets cover an area of approximately 30 km2 over Victoria Land and adjacent Ross Sea. Map and profile gridding were implemented to integrate the data sets. These approaches are studied for improving existing strategies to adopt for the whole magnetic compilation effort. The final microlevelled grid that we produce is a new tool for regional interpretation of the main tectonic and geologic features of this sector of Antarctica.

scholarly journals Model-Based Probabilistic Inversion Using Magnetic Data: A Case Study on the Kevitsa Deposit

Geosciences ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 150
Author(s):  
Nilgün Güdük ◽  
Miguel de la Varga ◽  
Janne Kaukolinna ◽  
Florian Wellmann
Keyword(s):  
Structural Parameters ◽  
Rock Properties ◽  
Magnetic Data ◽  
Geological Model ◽  
Borehole Data ◽  
Likelihood Functions ◽  
Different Types ◽  
Geophysical Information ◽  
Different Sources

Structural geological models are widely used to represent relevant geological interfaces and property distributions in the subsurface. Considering the inherent uncertainty of these models, the non-uniqueness of geophysical inverse problems, and the growing availability of data, there is a need for methods that integrate different types of data consistently and consider the uncertainties quantitatively. Probabilistic inference provides a suitable tool for this purpose. Using a Bayesian framework, geological modeling can be considered as an integral part of the inversion and thereby naturally constrain geophysical inversion procedures. This integration prevents geologically unrealistic results and provides the opportunity to include geological and geophysical information in the inversion. This information can be from different sources and is added to the framework through likelihood functions. We applied this methodology to the structurally complex Kevitsa deposit in Finland. We started with an interpretation-based 3D geological model and defined the uncertainties in our geological model through probability density functions. Airborne magnetic data and geological interpretations of borehole data were used to define geophysical and geological likelihoods, respectively. The geophysical data were linked to the uncertain structural parameters through the rock properties. The result of the inverse problem was an ensemble of realized models. These structural models and their uncertainties are visualized using information entropy, which allows for quantitative analysis. Our results show that with our methodology, we can use well-defined likelihood functions to add meaningful information to our initial model without requiring a computationally-heavy full grid inversion, discrepancies between model and data are spotted more easily, and the complementary strength of different types of data can be integrated into one framework.

Geochemical and Petrological Characterization of Ash Samples from Cascade Range Volcanoes

1971 ◽  
Vol 1 (2) ◽  
pp. 261-282 ◽  
Author(s):  
Keith Randle ◽  
Gordon G. Goles ◽  
Laurence R. Kittleman
Keyword(s):  
Pacific Northwest ◽  
Volcanic Ash ◽  
Cascade Range ◽  
Crystalline Material ◽  
Refractive Indices ◽  
Crystalline Materials ◽  
The Pacific ◽  
Volcanic Ashes ◽  
Different Sources

Twenty-nine samples of volcanic ash from the Pacific Northwest were analyzed by instrumental neutron activation techniques, with the aim of distinguishing among ashes from different sources. Preliminary results of petrographic studies of 42 ash or pumice samples are also reported. Geochemical characteristics of Mazama ash are defined, and problems induced by winnowing of crystalline material during transport and by weathering are discussed. Contents of La, Th, and Co, and La/Yb ratios are shown to be good discriminants. Data on refractive indices and on proportions of crystalline materials also aid in distinguishing among the various volcanic ashes studied. Ash and pumice found in archaeological contexts at Fort Rock Cave, Paisley Cave, Wildcat Canyon, and Hobo Cave are all from Mount Mazama, presumably from the culminating cruption of 7000 years ago.

scholarly journals Identifikasi Kerusakan Pasca Gempa Menggunakan Metode Object Based Image Analysist (OBIA) (Studi Kasus: Pidie Jaya, Aceh)

2017 ◽  
Author(s):  
Prila Ayu Dwi Prastiwi ◽  
agung budi harto ◽  
Ketut Wikantika ◽  
Dasapta Erwin Irawan
Keyword(s):  
Satellite Imagery ◽  
Damage Identification ◽  
Earthquake Damage ◽  
Tectonic Plates ◽  
Sensing Technology ◽  
Australian Plate ◽  
Object Based ◽  
Richter Scale ◽  
The Pacific ◽  
High Resolution Satellite Imagery

AbstrakIndonesia merupakan salah satu negara yang dilalui oleh pertemuan tiga lempeng aktif, yai- tuLempeng Indo-Australia, Lempeng Euro-Asia, danLempengPasifik. Kondisiitumenjadis- alahsatupenyebab seringterjadinyabencanaalam, khususnyagempabumi. Padatanggal 7 Desember 2016 Kota Aceh kembali diguncang gempa bumi dengan kekuatan 6,5 skala richter. Gempa bumi tersebut mengakibat ratusan bangunan mengalami kerusakan. Saat ini teknologi penginderaan jauh sangat berperan dalam melakukan identifikasi kerusakan akibat gempa. Penelitian kali ini akan berfokus pada identifikasi kerusakan bangunan yang diakibatkan oleh gempa bumi dengan menggunakan citra satelit beresolusi tinggi, yaitu citra Pleiades yang diambil tanggal 7 Desember 2016. Metode yang digunakan untuk identifikasi kerusakan bangunan adalah metode Object Based Image Analysist (OBIA). Pada proses klasifikasi, metode OBIA memandang objek tidak hanya berdasarkan nilai piksel saja melainkan berdasarkan bentuk, luasan, dan tekstur disekitarnya. Berdasarkan penelitian ini didapatkan bahwa metode OBIA terbukti dapat mengidentifikasi kerusakan bangunan pasca gempa bumi secara cepat.Kata kunci: OBIA, Citra satelit, Klasifikasi, Kerusakan pasca gempa bumi Abstract277 Jalan Ganesha No.10, Kota Bandung, Jawa Barat 40132 Indonesia e-mail: [email protected] is located in a meeting point of three active tectonic plates, the Indo-Australian Plate, Euro-Asia Plate, and the Pacific Plate. This condition causes frequent occurrence of natural disasters, especially earthquakes. On December 7, 2016 Aceh was hit by an earth- quake with a magnitude of 6.5 richter scale. The earthquake affected damaged hundreds of buldings. Nowadays remote sensing technology can be used to identify damage caused by the earthquake. This research is focused on post-earthquake damage identification using high resolution satellite imagery, the Pleiades image taken on December 7, 2016. The method used to identify the damaged buildings is the Object Based Image Analysist (OBIA) method. In the classification process, the OBIA method distinguish objects not only based on pixel values but also on the basis of the shape, area, and texture around them. This re-search has proven that OBIA method quickly identifies the damage buildings caused by the earthquake.Keywords: OBIA, Satellite Imagery, Classification, Post-Earthquake Damage

scholarly journals EVIDENCE OF MANTLE INHERITANCE ON THE ULTRA-DISTAL WESTERN IBERIAN MARGIN FROM TRANSFORMED TOTAL MAGNETIC ANOMALY

2018 ◽  
Vol 36 (3) ◽  
pp. 1 ◽  
Author(s):  
Luizemara Soares Alves Szameitat ◽  
Francisco José Fonseca Ferreira ◽  
Gianreto Manatschal ◽  
Monica da Costa Pereira Lavalle Helbron
Keyword(s):  
Steady State ◽  
Magnetic Anomaly ◽  
Oceanic Crust ◽  
Oceanic Lithosphere ◽  
Magnetic Data ◽  
Continental Lithosphere ◽  
Flow Lines ◽  
Passive Margins ◽  
Magnetic Features ◽  
Iberian Margin

ABSTRACT. Inheritance on continental lithosphere is considered as an important aspect on passive margins, since they may control magmatic budget and strain evolution during rifting and lithospheric breakup. On the distal Western Iberian margin, the transition to a steady state oceanic crust was little sampled and less investigated, in comparison to the more proximal parts near to the continental edge. In this work, we use marine magnetic data to analyze some aspects of the transition between the zone of exhumed continental mantle (ZECM) and the unequivocal oceanic crust, using transformed magnetic data. We observe that the end of the ZECM presents some straight magnetic features, especially at the eastern limit of the J anomaly. These magnetic lineaments are consistent with Early Cretaceous flow lines of the Iberian Plate. Straight structures are not expected in a newly formed oceanic lithosphere. Instead, it seems to be controlled by mantle inheritance. These straight magnetic features may indicate basement inheritance controlling magmatic insertions at the beginning of the oceanic crust formation.Keywords: Iberia, Magnetometry, Ocean-Continent Transition, Inherited Structures, Magma-Poor Margin. RESUMO. Estruturas herdadas na litosfera continental são um aspecto importante em margens passivas, pois poderão condicionar a entrada de magma e a evolução da deformação durante o rifteamento e quebra litosférica. Na porção distal da Margem Ibérica Ocidental, a transição da crosta continental até a crosta oceânica bem estabelecida possui menos dados e é menos investigada em comparação com a porção junto do limite de crosta continental. Neste trabalho, usamos dados magnéticos marinhos para analisar alguns aspectos entre a zona de exumação mantélica e a crosta oceânica inequívoca, através de dados magnéticos transformados. Observa-se que o final da zona de exumação mantélica apresenta algumas feições retilíneas, especialmente no limite leste da Anomalia J. Estes lineamentos magnéticos estão em conformidade com linhas de fluxo mesozoicas da Placa Ibérica. Feições retilíneas não são esperadas em uma litosfera oceânica neoformada. Ao contrário, estas aparentam ser um controle dado por estruturas pretéritas do manto. Portanto, estas feições magnéticas retilíneas sugerem uma herança do embasamento continental controlando as intrusões magmáticas no início da formação da crosta oceânica.Palavras-chave: Ibéria, Magnetometria, Transição Continente-Oceano, Estruturas Herdadas, Margem Pobre em Magma. 

scholarly journals Attenuation of peak ground accelerations in New Zealand earthquakes

1997 ◽  
Vol 30 (2) ◽  
pp. 133-158 ◽  
Author(s):  
J. X. Zhao ◽  
D. J. Dowrick ◽  
G. H. McVerry
Keyword(s):  
New Zealand ◽  
Substantial Effect ◽  
Tectonic Plates ◽  
The Pacific ◽  
Source Distance ◽  
Shortest Distance ◽  
Soil Deposits ◽  
Peak Ground Accelerations ◽  
The Difference ◽  
Rock And Soil

The main result of this study is the development of attenuation expressions for peak ground accelerations (PGAs) in New Zealand earthquakes, in terms of magnitude Mw and shortest distance from the source. Other factors which are modelled are depth, focal mechanism, ground class and tectonic type of earthquake i.e. crustal, interface or dipping slab. As well as being implied in the source distance, the substantial effect of depth is modelled well with a separate linear depth term. For crustal events, focal mechanisms which are predominantly reverse are found to cause PGAs that are 28 percent stronger on average than for other mechanisms. PGAs at soil sites (ie those having soil deposits >3 m thick) are found to be 53 percent stronger on average than at other (ie rock) sites, but the difference between PGAs on rock and soil sites in large amplitude shaking remains uncertain, ie near the source o f events of Mw ≥ 7. Earthquakes occurring on the interface between the Pacific and Australian tectonic plates give rise to smaller PGAs than do crustal or slab events of the same magnitude, depth and distance. Comparisons are made between our New Zealand model and some for Europe, Japan and the Western USA.

SAMPLING SYSTEMS FOR THE BIRCH CASEBEARER (LEPIDOPTERA: COLEOPHORIDAE)

1979 ◽  
Vol 111 (8) ◽  
pp. 875-882
Author(s):  
A. G. Raske ◽  
M. Alvo
Keyword(s):  
Maximum Likelihood ◽  
Sampling Plan ◽  
New Method ◽  
Betula Papyrifera ◽  
White Birch ◽  
Destructive Sampling ◽  
Damage Level ◽  
Sampling Systems ◽  
Non Destructive ◽  
Maximum Likelihood Technique

AbstractSample sizes needed to measure population levels of the birch casebearer, Coleophora fuscedinella Zeller, and its damage to white birch, Betula papyrifera Marsh, were calculated for various degrees of confidence and assurance. Both a non-destructive and a destructive sampling plan are presented and a new method to classify the damage level of a stand. This method uses a maximum likelihood technique to estimate the proportion of trees of various damage classes.

Using airborne vector magnetic data to calculate the projection of magnetic anomaly vector onto normal geomagnetic field

Geophysics ◽  
2021 ◽  
pp. 1-47
Author(s):  
Rukuan Xie ◽  
Shengqing Xiong ◽  
Shuling Duan ◽  
Jinlong Wang ◽  
Ping Wang ◽  
...  
Keyword(s):  
Magnetic Anomaly ◽  
Geomagnetic Field ◽  
Approximation Error ◽  
Magnetic Data ◽  
Total Field ◽  
Projection Formula ◽  
Total Magnetization ◽  
Vector Formula ◽  
Relationship Of ◽  
Anomaly Formula

The total-field magnetic anomaly [Formula: see text] is an approximation of the projection [Formula: see text] of the magnetic anomaly vector [Formula: see text] onto the normal geomagnetic field [Formula: see text]. However, for highly magnetic sources, the approximation error of [Formula: see text] cannot be ignored. To reduce the error, we have developed a method for calculating [Formula: see text] by using airborne vector magnetic data based on the vector relationship of geomagnetic field [Formula: see text]. The calculation uses the magnitude of the vectors [Formula: see text], [Formula: see text], and [Formula: see text] through a simple approach. To ensure that each magnitude has the same level, we normalize the magnitude of [Formula: see text] using the total-field magnetic data measured by the scalar magnetic sensor. The method is applied to the measured airborne vector magnetic data at the Qixin area of the East Tianshan Mountains in China. The results indicate that the calculated [Formula: see text] has high precision and can distinguish the approximation error less than 3.5 nT. We also analyze the characteristics of the approximation error that are caused by the effects of different total magnetization inclinations. These error characteristics are used to predict the total magnetization inclination of a 2D magnetic source based on the measured airborne vector magnetic data.

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