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1
Okaya, David A., i Craig M. Jarchow. "Extraction of deep crustal reflections from shallow Vibroseis data using extended correlation". GEOPHYSICS 54, nr 5 (maj 1989): 555–62. http://dx.doi.org/10.1190/1.1442682.
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Lower crustal seismic reflections can be extracted from shallow crustal seismic profiles through the application of extended correlation to uncorrelated Vibroseis seismic data. “Fixed‐bandwidth” extended correlation shortens the correlation operator before crosscorrelation, producing reflections over an increased correlation time range, all with lowered bandwidth. “Self‐truncating” extended correlation preserves the full bandwidth in the original seismic reflection times but loses bandwidth in a predictable manner at the additional (later) arrival times. Correlation wavelet shape and extra correlation time are directly related and can be calculated for specific acquisition parameters. Pre‐correlation tapering is necessary to avoid undue wavelet distortion at extended correlation times. Seismic data collected in the Basin and Range province illustrate the application of the method; the results are verified with conventional correlations of long sweep records and with impulsive source data.
2
Moore, Eli K., Daniella L. Martinez, Naman Srivastava, Shaunna M. Morrison i Stephanie J. Spielman. "Mineral Element Insiders and Outliers Play Crucial Roles in Biological Evolution". Life 12, nr 7 (24.06.2022): 951. http://dx.doi.org/10.3390/life12070951.
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The geosphere of primitive Earth was the source of life’s essential building blocks, and the geochemical interactions among chemical elements can inform the origins of biological roles of each element. Minerals provide a record of the fundamental properties that each chemical element contributes to crustal composition, evolution, and subsequent biological utilization. In this study, we investigate correlations between the mineral species and bulk crustal composition of each chemical element. There are statistically significant correlations between the number of elements that each element forms minerals with (#-mineral-elements) and the log of the number of mineral species that each element occurs in, and between #-mineral-elements and the log of the number of mineral localities of that element. There is a lesser correlation between the log of the crustal percentage of each element and #-mineral-elements. In the crustal percentage vs. #-mineral-elements plot, positive outliers have either important biological roles (S, Cu) or toxic biological impacts (Pb, As), while negative outliers have no biological importance (Sc, Ga, Br, Yb). In particular, S is an important bridge element between organic (e.g., amino acids) and inorganic (metal cofactors) biological components. While C and N rarely form minerals together, the two elements commonly form minerals with H, which coincides with the role of H as an electron donor/carrier in biological nitrogen and carbon fixation. Both abundant crustal percentage vs. #-mineral-elements insiders (elements that follow the correlation) and less abundant outsiders (positive outliers from the correlation) have important biological functions as essential structural elements and catalytic cofactors.
3
Candia, Gabriel, Alan Poulos, Juan Carlos de la Llera, Jorge G. F. Crempien i Jorge Macedo. "Correlations of spectral accelerations in the Chilean subduction zone". Earthquake Spectra 36, nr 2 (2.02.2020): 788–805. http://dx.doi.org/10.1177/8755293019891723.
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The correlation between spectral accelerations is key in the construction of conditional mean spectra, the computation of vector-valued seismic hazard, and the assessment of seismic risk of spatially distributed systems, among other applications. Spectral correlations are highly dependent on the earthquake database used, and thus, region-specific correlation models have been developed mainly for earthquakes in western United States, Europe, Middle East, and Japan. Correlation models based on global data sets for crustal and subduction zones have also become available, but there is no consensus about their applicability on a specific region. This study proposes a new correlation model for 5% damped spectral accelerations and peak ground velocity in the Chilean subduction zone. The correlations obtained were generally higher than those observed from shallow crustal earthquakes and subduction zones such as Japan and Taiwan. The study provides two illustrative applications of the correlation model: (1) computation of conditional spectra for a firm soil site located in Santiago, Chile and (2) computation of bivariate hazard for spectral accelerations at two structural periods.
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Yan, Yuping, Paul A. Mayewski, Shichang Kang i Eric Meyerson. "An ice-core proxy for Antarctic circumpolar zonal wind intensity". Annals of Glaciology 41 (2005): 121–30. http://dx.doi.org/10.3189/172756405781813294.
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AbstractUsing US National Centers for Environmental Prediction/US National Center for Atmospheric Research re-analysis data, we investigate the relationships between crustal ion (nssCa2+) concentrations from three West Antarctic ice cores, namely, Siple Dome (SD), ITASE00-1 (IT001) and ITASE01-5 (IT015), and primary components of the climate system, namely, air pressure/geopotential height, zonal (u) and meridional (v) wind strength. Linear correlation analyses between nssCa2+ concentrations and both air-pressure and wind fields for the period of overlap between records indicate that the SD nssCa2+ variation is positively correlated with spring circumpolar zonal wind, while IT001 nssCa2+ has a positive correlation with circumpolar zonal wind throughout the year (r > 0.3, p < 0.01). Intensified Southern Westerlies circulation is conducive to transport of more crustal aerosols to both sites. Further correlation analyses between nssCa2+ concentrations from SD and IT001 and atmospheric circulation suggest that the high inland plateau (represented by core IT001) is largely influenced by transport from the upper troposphere. IT015 nssCa2+ is negatively correlated with westerly wind in October and November, suggesting that stronger westerly circulation may weaken the transport of crustal species to IT015. Correlations of nssCa2+ from the three ice cores with the Antarctic Oscillation index are consistent with results developed from the wind-field investigation. In addition, calibration between nssCa2+ concentration and the multivariate El Niño–Southern Oscillation (ENSO) index shows that crustal species transport to IT001 is enhanced during strong ENSO events.
5
Bursnall, J. T., A. D. Leclair, D. E. Moser i J. A. Percival. "Structural correlation within the Kapuskasing uplift". Canadian Journal of Earth Sciences 31, nr 7 (1.07.1994): 1081–95. http://dx.doi.org/10.1139/e94-097.
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Comparison of progressive deformation and metamorphic history within and between the tectonic domains of the Kapuskasing uplift indicates significant variation in age and style of deformation across this large segment of the central Superior Province; multiple stages of tonalite and granitoid intrusion, melt generation, polyphase diachronous deformation, and likely rapid deep burial of supracrustal rocks collectively produced the complex character of this example of Archean mid to deep crust. At least four Archean deformation phases are recognized, although not all are of regional extent. Dated structural chronology suggests that the locus of the earliest recorded deformations migrated to deeper crustal levels with time. Pre-2680 Ma deformation (local D1–D2) within high-level tonalites is correlated with deformation in the Michipicoten supracrustal belt. The apparent earliest deformational fabrics at deeper crustal levels in the granulite terrane of the Kapuskasing structural zone occurred between 2660 and 2640 Ma. Archean third and fourth phase deformation phases (~ 2667 to ~ 2629 Ma) are present at mid-crustal and deeper levels and deform post-2667 Ma metaconglomerate; these resulted in large-scale folding and subhorizontal ductile shear zones, which seem to represent an important transitional zone that separated a passive upper crust from continued ductile strain at deeper levels.Subsequent uplift of the high-grade rocks was accomplished in multiple stages, initiated prior to 2.45 Ga and likely culminated around 1.9 Ga, although continued movement occurred as late as 1.14 Ga. The Ivanhoe Lake fault zone, along which much of the uplift must have occurred, exhibits some evidence of ductile deep-thrust-related fabrics, but most of the observed structures are brittle to brittle–ductile and steeply inclined. A broad zone of pervasive cataclasis and brittle–ductile shear zones is a characteristic feature of the fault zone throughout its length, and both dextral and sinistral offset are locally present. Clear ground evidence for major transcurrent or thrust displacements, however, has not been recognized.
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Bodri, L., i B. Bodri. "On the correlation between heat flow and crustal thickness". Tectonophysics 120, nr 1-2 (listopad 1985): 69–81. http://dx.doi.org/10.1016/0040-1951(85)90087-3.
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Rindraharisaona, E. J., F. Tilmann, X. Yuan, G. Rümpker, J. Giese, G. Rambolamanana i G. Barruol. "Crustal structure of southern Madagascar from receiver functions and ambient noise correlation: Implications for crustal evolution". Journal of Geophysical Research: Solid Earth 122, nr 2 (luty 2017): 1179–97. http://dx.doi.org/10.1002/2016jb013565.
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Kim, Jeong Woo, Ralph R. B. von Frese i Hyung Rae Kim. "Crustal modeling from spectrally correlated free‐air and terrain gravity data—A case study of Ohio". GEOPHYSICS 65, nr 4 (lipiec 2000): 1057–69. http://dx.doi.org/10.1190/1.1444799.
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We investigate the use of spectral correlation theory to analyze terrain gravity effects and free‐air gravity anomalies of Ohio for possible constraints on the thickness variations and neotectonics of the crust. Terrain gravity effects are computed from the topography by Gauss‐Legendre quadrature integration and are compared against independent free‐air gravity anomaly observations for their wavenumber correlation spectrum. Spectral correlation filters are designed accordingly to extract terrain‐correlated free‐air gravity anomalies that are subtracted from the terrain gravity effects for estimates of the compensated terrain gravity effects. These effects are used to model the Moho by inversion, assuming they predominantly reflect crustal thickness variations. Our results characterize the middle third of Ohio as a broad zone of thickened Precambrian crust, which also may include rifted regions where the thickness of the prerift crust has been reduced greatly. Furthermore, we find that about 83% of the instrumentally determined earthquake epicenters are located within the inferred thinner regions of Ohio’s crust or at their margins where compressional stresses may dominate. In general, these crustal thickness variations provide new constraints on modeling the tectonic evolution and geotechnical parameters of the crust—constraints that are important for evaluating earthquake hazards, the distribution and extraction of crustal resources, and the storage of hazardous waste and other crustal engineering applications.
9
Kolstrup, M. L., i V. Maupin. "Measuring and crust-correcting finite-frequency travel time residuals – application to southwestern Scandinavia". Solid Earth Discussions 7, nr 3 (1.07.2015): 1909–39. http://dx.doi.org/10.5194/sed-7-1909-2015.
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Abstract. We present a data processing routine to compute relative finite-frequency travel time residuals using a combination of the Iterative Cross-Correlation and Stack (ICCS) algorithm and the MultiChannel Cross-Correlation method (MCCC). The routine has been tailored for robust measurement of P and S wave travel times in several frequency bands and for avoiding cycle-skipping problems at the shortest periods. We also investigate the adequacy of ray theory to calculate crustal corrections for finite-frequency regional tomography in normal continental settings with non-thinned crust. We find that ray theory is valid for both P and S waves at all relevant frequencies as long as the crust does not contain low-velocity layers associated with sediments at the surface. Reverberations in the sediments perturb the arrival times of the S waves and the long-period P waves significantly, and need to be accounted for in crustal corrections. The data processing routine and crustal corrections are illustated using data from a network in southwestern Scandinavia.
10
St-Onge, M. R., D. J. Scott i N. Wodicka. "Review of crustal architecture and evolution in the Ungava Peninsula — Baffin Island area: connection to the Lithoprobe ECSOOT transect". Canadian Journal of Earth Sciences 39, nr 5 (1.05.2002): 589–610. http://dx.doi.org/10.1139/e02-022.
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Within the Trans-Hudson Orogen in northern Quebec and southern Baffin Island, parautochthonous Archean basement and Paleoproterozoic cover, as well as allochthonous (accreted) Paleoproterozoic units, are exposed in a series of antiformal culminations and complementary synclinoria. The parautochthonous rocks of the Superior Province margin and two assemblages of accreted Paleoproterozoic units (Ungava and Meta Incognita crustal terranes) define a basic tripartite crustal architecture which is characterized by polyphase deformation and metamorphic histories. Early structures and mineral assemblages are recognized in all three crustal components and shown to be temporally distinct. The earlier structures and assemblages are overprinted by younger elements and mineral assemblages that are related to at least three regional contraction episodes and one thermal event that are common to all crustal components of the orogen. Close correlation of regional aeromagnetic data in northern Quebec and southern Baffin Island with the three crustal components offers a first-order approximation of the distribution of basement lithological units across Hudson Strait. Continuation of the aeromagnetic domains beneath Ungava Bay to northeastern Quebec and northern Labrador allows for the southward extrapolation of the tripartite Trans-Hudson Orogen crustal architecture into the Lithoprobe Eastern Canadian Shield OnshoreOffshore Transect area.
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Tang, Ming, Wei-Qiang Ji, Xu Chu, Anbin Wu i Chen Chen. "Reconstructing crustal thickness evolution from europium anomalies in detrital zircons". Geology 49, nr 1 (4.09.2020): 76–80. http://dx.doi.org/10.1130/g47745.1.
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Abstract A new data compilation shows that in intermediate to felsic rocks, zircon Eu/Eu* [chondrite normalized Eu/ ] correlates with whole rock La/Yb, which has been be used to infer crustal thickness. The resultant positive correlation between zircon Eu/Eu* and crustal thickness can be explained by two processes favored during high-pressure differentiation: (1) supression of plagioclase and (2) endogenic oxidation of Eu2+ due to garnet fractionation. Here we calibrate a crustal thickness proxy based on Eu anomalies in zircons. The Eu/Eu*-in-zircon proxy makes it possible to reconstruct crustal thickness evolution in magmatic arcs and orogens using detrital zircons. To evaluate this new proxy, we analyzed detrital zircons separated from modern river sands in the Gangdese belt, southern Tibet. Our results reveal two episodes of crustal thickening (to 60–70 km) since the Cretaceous. The first thickening event occurred at 90–70 Ma, and the second at 50–30 Ma following Eurasia-India collision. These findings are temporally consistent with contractional deformation of sedimentary strata in southern Tibet.
12
Kolstrup, M. L., i V. Maupin. "Measuring and crust-correcting finite-frequency travel time residuals – application to southwestern Scandinavia". Solid Earth 6, nr 4 (9.10.2015): 1117–30. http://dx.doi.org/10.5194/se-6-1117-2015.
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Abstract. We present a data-processing routine to compute relative finite-frequency travel time residuals using a combination of the Iterative Cross-Correlation and Stack (ICCS) algorithm and the Multi-Channel Cross-Correlation method (MCCC). The routine has been tailored for robust measurement of P- and S-wave travel times in several frequency bands and for avoiding cycle-skipping problems at the shortest periods. We also investigate the adequacy of ray theory to calculate crustal corrections for finite-frequency regional tomography in normal continental settings with non-thinned crust. We find that ray theory is valid for both P and S waves at all relevant frequencies as long as the crust does not contain low-velocity layers associated with sediments at the surface. Reverberations in the sediments perturb the arrival times of the S waves and the long-period P waves significantly, and need to be accounted for in crustal corrections. The data-processing routine and crustal corrections are illustrated using data from a~network in southwestern Scandinavia.
13
Boerner, David E., Ron D. Kurtz i James A. Craven. "A summary of electromagnetic studies on the Abitibi-Grenville transect". Canadian Journal of Earth Sciences 37, nr 2-3 (2.04.2000): 427–37. http://dx.doi.org/10.1139/e99-063.
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Electromagnetic surveys on the Abitibi-Grenville Lithoprobe transect have elucidated a number of conductivity signatures that can be genetically linked to Precambrian tectonic processes. Some major fault zones are moderately conductive, possibly signalling graphite deposition from a mantle CO2 flux along crust-penetrating fault systems. However, conductive (graphitic) metasedimentary rocks characteristic of foreland basins are apparently absent from the transect area. A weak inverse correlation between metamorphic grade and electrical conductivity was observed by following rock units across the Grenville Front into high-grade equivalents within the parautochthonous belt. A uniformly conductive mid-crustal layer extends across the Grenville Front, apparently without change in character. The existence of this ubiquitous mid-crustal conductor has been interpreted to mean that electrical conductivity is controlled by the present-day pressure, temperature, and fluid saturation of the lower crust, independent of ancient structure, mineralogy, or metamorphic grade. Lower crustal (upper mantle?) electrical anisotropy is pervasive across the transect area. An apparent spatial correlation of conductivity anisotropy with Archean tectonic deformation patterns has been interpreted to indicate that the lithosphere has remained intact since the Neoarchean.
14
Strack, K. ‐M, E. Lüschen i A. W. Kötz. "Long‐offset transient electromagnetic (LOTEM) depth soundings applied to crustal studies in the Black Forest and Swabian Alb, Federal Republic of Germany". GEOPHYSICS 55, nr 7 (lipiec 1990): 834–42. http://dx.doi.org/10.1190/1.1442897.
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The long‐offset transient electromagnetics (LOTEM) sounding method is a valuable complementary technique for deep seismic exploration as applied to earth crustal investigations. During 1986, two LOTEM surveys were conducted to augment completed seismic investigations for crustal studies in southern West Germany, east of the Rhine graben. Our studies were motivated by the geoscientific activities within the framework of the German Continental Deep Drilling (KTB) project. The survey objectives were (1) to determine the applicability of the LOTEM method to crustal geophysics, (2) to investigate the correlation of resistivity anomalies with velocity anomalies, and (3) to confirm the method and interpretation in an area of known geology with existing geophysical data. The Black Forest and the Urach geothermal area survey results exhibit conductive features in the upper 10 km of the crust which were not previously defined by other geophysical data. Importantly, the results demonstrate a very strong correlation of a low‐velocity zone with low electrical resistivity at 5 to 7 km depth within the crystalline basement at both locations.
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Mamyrov, Ernes. "Control Parameters of Magnitude—Seismic Moment Correlation for the Crustal Earthquakes". Open Journal of Earthquake Research 02, nr 03 (2013): 60–74. http://dx.doi.org/10.4236/ojer.2013.23007.
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Muhumuza, K. "A Feasibility Study on Monitoring Crustal Structure Variations by Direct Comparison of Surface Wave Dispersion Curves from Ambient Seismic Noise". International Journal of Geophysics 2020 (3.02.2020): 1–11. http://dx.doi.org/10.1155/2020/5269537.
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This work assesses the feasibility of the direct use of surface-wave dispersion curves from seismic ambient noise to gain insight into the crustal structure of Bransfield Strait and detect seasonal seismic velocity changes. We cross-correlated four years of vertical component ambient noise data recorded by a seismic array in West Antarctica. To estimate fundamental mode Rayleigh wave Green’s functions, the correlations are computed in 4-hr segments, stacked over 1-year time windows and moving windows of 3 months. Rayleigh wave group dispersion curves are then measured on two spectral bands—primary (10–30 s) and secondary (5–10 s) microseisms—using frequency-time analysis. We analyze the temporal evolution of seismic velocity by comparing dispersion curves for the successive annual and 3-month correlation stacks. Our main assumption was that the Green’s functions from the cross-correlations, and thus the dispersion curves, remain invariant if the crustal structure remains unchanged. Maximum amplitudes of secondary microseisms were observed during local winter when the Southern Ocean experiences winter storms. The Rayleigh wave group velocity ranges between 2.1 and 3.7 km/s, considering our period range studied. Interannual velocity variations are not much evident. We observe a slight velocity decrease in summer and increase in winter, which could be attributed to the pressure melting of ice and an increase in ice mass, respectively. The velocity anomalies observed within the crust and upper mantle structure correlate with the major crustal and upper mantle features known from previous studies in the area. Our results demonstrate that the direct comparison of surface wave dispersion curves extracted from ambient noise might be a useful tool in monitoring crustal structure variations.
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Li, Xiaobo, Xiaoya Wang i Yanling Chen. "InSAR Atmospheric Delay Correction Model Integrated from Multi-Source Data Based on VCE". Remote Sensing 14, nr 17 (1.09.2022): 4329. http://dx.doi.org/10.3390/rs14174329.
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With the rapid development of interferometric synthetic aperture radar (InSAR) measurement technology, its measurement accuracy requirements are increasing. Atmospheric delay errors must be corrected, especially in the case of crustal deformation monitoring, the 20% variation of tropospheric water vapor among InSAR pairs generally produces range from 10 cm to 14 cm deformation errors. Such errors can be of the same magnitude as the annual changes in crustal deformation, or even greater, masking crustal deformation information and seriously affecting the results of crustal deformation monitoring. Therefore, in order to obtain a more accurate InSAR atmospheric delay correction model, this paper calculated and integrated atmospheric delays that were estimated by different sources, including the 37 pressure levels of the fifth generation of the European Centre for Medium-Range Weather Forecasts (ECMWF)) numerical weather prediction model, ECMWF Reanalysis v5 (ERA5), and Global Navigation Satellite System (GNSS) measurement data from the crustal movement observation network of China, based on the variance component estimation (VCE) weighting method. The results showed that the integrated model, based on the VCE method, is better than the generic atmospheric correction online service (GACOS) model for InSAR measuring of crustal deformation. The precision in monitoring crustal deformations was improved by approximately 5 mm, the correlation coefficient of atmospheric delay errors and crustal deformations improved from 0.287 to 0.347, and accuracy improved by approximately 25%. However, the improvement in accuracy was limited because of system error decoherence that was induced by atmospheric noise caused by abundant vegetation or snow cover. Therefore, in order to achieve more accurate results, we recommend the adoption of the multi-source integrated atmospheric delay correction model, based on the VCE method, for InSAR high-precision measuring of crustal deformation and seismic activities.
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Li, Q., i G. M. Xu. "Precursory pattern of tidal triggering of earthquakes in six regions of China: the possible relation to the crustal heterogeneity". Natural Hazards and Earth System Sciences 13, nr 10 (18.10.2013): 2605–18. http://dx.doi.org/10.5194/nhess-13-2605-2013.
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Abstract. We found the possible correlation between the precursory pattern of tidal triggering of earthquakes and the crustal heterogeneities, which is of particular importance to the researchers in earthquake prediction and earthquake hazard prevention. We investigated the connection between the tidal variations and earthquake occurrence in the Liyang, Wunansha, Cangshan, Wenan, Luquan and Yaoan regions of China. Most of the regions show a higher correlation with tidal triggering in several years preceding the large or destructive earthquakes compared to other times, indicating that the tidal triggering may inherently relate to the nucleation of the destructive earthquakes during this time. In addition, the analysis results indicate that the Liyang, Cangshan and Luquan regions, with stronger heterogeneity, show statistically significant effects of tidal triggering preceding the large or destructive earthquakes, while the Wunansha, Wenan and Yaoan regions, with relatively weak heterogeneity, show statistically insignificant effects of it, signifying that the precursory pattern of tidal triggering of earthquakes in these six regions is possibly related to the heterogeneities of the crustal rocks. The above results suggest that when people try to find the potential earthquake hazardous areas or make middle–long-term earthquake forecasting by means of precursory pattern of the tidal triggering, the crustal heterogeneity in these areas has to be taken into consideration for the purpose of increasing the prediction efficiency. If they do not consider the influence of crustal heterogeneity on the tidal triggering of earthquakes, the prediction efficiency might greatly decrease.
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Jaimes, Miguel A., i Gabriel Candia. "Interperiod Correlation Model for Mexican Interface Earthquakes". Earthquake Spectra 35, nr 3 (sierpień 2019): 1351–65. http://dx.doi.org/10.1193/080918eqs200m.
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This article presents a correlation model for pseudo-acceleration, peak ground acceleration, and peak ground velocity residuals using a database of Mexican subduction interface earthquakes at rock sites (NEHRP Class B). A mixed-effect regression model, a ground motion model, and 40 event recordings (418 records) with moment magnitude between five and eight were used to develop a magnitude-independent correlation model. This region-specific model yields consistently higher correlation values compared with similar studies developed for shallow crustal regions and other subduction zones worldwide, particularly for pseudo-acceleration values at distant periods. These results support the idea of using a region-specific and mechanism-specific correlation model for Mexico's subduction zone.
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Molchanov, O. "About climate-seismicity coupling from correlation analysis". Natural Hazards and Earth System Sciences 10, nr 2 (17.02.2010): 299–304. http://dx.doi.org/10.5194/nhess-10-299-2010.
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Abstract. We have analyzed together the slow climate temperature variations in the near-equatorial Pacific Ocean area (SSTOI indices) and crustal seismic activity in the same region during 1973–2008 time period using correlation analysis and found similarity in seismic and ENSO periodicities (the latter with time lag about 1.5 years). Trends of the processes are also similar showing about 2 times increase in average seismic energy release during the whole period of analysis and conventional 0.1 °C/(10 years) increase in SSTOI index anomalies. Our major conclusion is on real credibility of climate-seismicity coupling. It is rather probable that at least partially climate ENSO oscillations and temperature anomaly trends are induced by similar variation in seismicity.
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Bradley, Brendon A. "Empirical Correlations between Peak Ground Velocity and Spectrum-Based Intensity Measures". Earthquake Spectra 28, nr 1 (luty 2012): 17–35. http://dx.doi.org/10.1193/1.3675582.
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Empirical correlation equations between peak ground velocity ( PGV) and several spectrum-based ground motion intensity measures are developed. The intensity measures examined in particular were: peak ground acceleration ( PGA), 5% damped pseudo-spectral acceleration ( SA), acceleration spectrum intensity ( ASI), and spectrum intensity ( SI). The computed correlations were obtained using ground motions from active shallow crustal earthquakes and four ground motion prediction equations. Results indicate that PGV is strongly correlated (i.e., a correlation coefficient of [Formula: see text]) with SI, moderately correlated with medium to long-period SA (i.e., [Formula: see text] for vibration periods 0.5-3.0 seconds), and also moderately correlated with short period SA, PGA and ASI ([Formula: see text]). A simple example is used to illustrate one possible application of the developed correlation equations for ground motion selection.
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Koulakov, I., G. Maksotova, S. Mukhopadhyay, J. Raoof, J. R. Kayal, A. Jakovlev i A. Vasilevsky. "Variations of the crustal thickness in Nepal Himalayas based on tomographic inversion of regional earthquake data". Solid Earth Discussions 6, nr 2 (2.10.2014): 2867–83. http://dx.doi.org/10.5194/sed-6-2867-2014.
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Abstract. We estimate variations of the crustal thickness beneath the Nepal Himalayas based on tomographic inversion of regional earthquake data. We have obtained a low-velocity anomaly in the upper part of the model down to depths of 40 to 80 km and proposed that the lower limit of this anomaly represents variations of the Moho depth. This statement was supported by results of synthetic modeling. The obtained variations of crustal thickness match fairly well with the free-air gravity anomalies: thinner crust patterns correspond to lower gravity values and vice versa. There is also some correlation with magnetic field: higher magnetic values correspond to the major areas of thicker crust. We propose that elevated magnetic values can be associated with more rigid segments of the incoming Indian crust which cause more compression in the thrust zone and leads to stronger crustal thickening.
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Koulakov, I., G. Maksotova, S. Mukhopadhyay, J. Raoof, J. R. Kayal, A. Jakovlev i A. Vasilevsky. "Variations of the crustal thickness in Nepal Himalayas based on tomographic inversion of regional earthquake data". Solid Earth 6, nr 1 (16.02.2015): 207–16. http://dx.doi.org/10.5194/se-6-207-2015.
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Abstract. We estimate variations of the crustal thickness beneath the Nepal Himalayas based on tomographic inversion of regional earthquake data. We have obtained a low-velocity anomaly in the upper part of the model down to depths of 40 to 80 km and proposed that the lower limit of this anomaly represents variations of the Moho depth. This statement was supported by results of synthetic modeling. The obtained variations of crustal thickness match fairly well with the free-air gravity anomalies: thinner crust patterns correspond to lower gravity values and vice versa. There is also some correlation with magnetic field: higher magnetic values correspond to the major areas of thicker crust. We propose that elevated magnetic values can be associated with more rigid segments of the incoming Indian crust which cause more compression in the thrust zone and lead to stronger crustal thickening.
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Zheng, Ying, i Jafar Arkani-Hamed. "Joint inversion of gravity and magnetic anomalies of eastern Canada". Canadian Journal of Earth Sciences 35, nr 7 (1.07.1998): 832–53. http://dx.doi.org/10.1139/e98-035.
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The power spectra and degree correlation of the surface topography and free-air gravity anomalies of eastern Canada show that the gravity anomalies are subdivided into three parts. The short-wavelength components (30-170 km, shorter than 30 km are not well resolved) largely arise from density perturbations in the crust and to a lesser extent from the surface topography and Moho undulation, whereas the contribution of intracrustal sources to the intermediate-wavelength components (170-385 km) is comparable with that of the topography. The long-wavelength components (385-1536 km) are overcompensated at the Moho. We present a crustal model for the intermediate- and long-wavelength components which takes into account the surface topography, density perturbations in the crust, and Moho undulation with a certain degree of isostatic compensation. The general characteristics of this model resemble the crustal structure revealed from seismic measurements. The reduced-to-pole magnetic anomalies of eastern Canada show no pronounced correlation with the topography and with the vertical gradient of the gravity anomalies, suggesting that the source bodies are within the crust and Poisson's relationship does not hold over the entire area. Assuming that the magnetic anomalies arise from induced magnetization, lateral variations of magnetic susceptibility of the crust are determined while taking into account the effects of the surface topography and the Moho undulation of our crustal model. The intermediate- and long-wavelength components of the susceptibility contrasts delineate major collision zones as low-susceptibility regions. We interpret this in terms of thermal demagnetization of the high-magnetic crustal roots beneath the collision zones.
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He, Lanfang, Qinyun Di, Zhongxing Wang, Jianqing Lai, Guoqiang Xue i Wenbo Guo. "Crustal Structures of the Qimantagh Metallogenic Belt in the Northern Tibetan Plateau from Magnetotelluric Data and Their Correlation to the Distribution of Mineral Deposits". Minerals 13, nr 2 (4.02.2023): 225. http://dx.doi.org/10.3390/min13020225.
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Crustal structure and fluid or melt originating in the deep crust and mantle are critical in regional magmatic mineral systems. However, the crustal structure and the processes that entrain and focus fluids from a deep-source region to a metallogenic belt remain relatively undisclosed. We present a magnetotelluric (MT) study of the eastern Qimantagh Metallogenic Belt (QMB) in the northern Tibetan Plateau. Data from 33 MT stations in two sections and 7 dispersed stations are acquired using a surface electromagnetic prospecting (SEP) system in frequency band ranges from 320 Hz to 0.00034 Hz. Data are converted by Bostick conversion and two-dimensional (2D) nonlinear conjugate gradient inversion. Our MT results reveal the geoelectrical crustal structure of the QMB, which consists of a southern low-resistivity domain that reflects the Kumukuri rift, a high-resistivity middle domain that represents the southern QMB in the central Kunlun belt, and a northern low-resistivity domain that covers the northern QMB and southwestern Qaidam block. We present a comprehensive tectonic and geophysical model of QMB based on the MT interpretation and geological analysis. We infer the high-resistivity domain as a reflection of a rigid crust and detached lithospheric mantle, this belt separate the QMB into northern and southern QMB. Most of the mineral deposits are found in the northern low-resistivity domain of QMB. Our study and findings provide an understanding of the tectonic evolution of the northern Tibetan Plateau, the crustal structure that controls the temporal and spatial distribution of magmatic rocks, and the geological signature associated with mineral deposits.
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Sahroni, Anang, Leni Sophia Heliani, Cecep Pratama, Hidayat Panuntun i Wiwit Suryanto. "Preliminary result for crustal properties derivation related to tectonics for hazard mitigation in Eastern Indonesia using Teleseismic P Coda". E3S Web of Conferences 325 (2021): 01012. http://dx.doi.org/10.1051/e3sconf/202132501012.
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Eastern Indonesia is tectonically complex, formed by different plates and microplates interactions from different origins. This complexity gives geoscientists a challenge to solve the ’jigsaw’ of the complex interactions. The understanding of tectonic processes can lead to a breakthrough in both resource exploration and disaster risk reduction. We utilize teleseismic P wave coda for random coda from scattering and deterministic coda originated from the crust-mantle boundary (Moho) to derive the crustal properties, including thickness, Vp/Vs, and qualitative scattering characteristics. For the scattering properties, we apply Iterative Cross-Correlation and Stacking (ICCS) to align the waveform. At the same time, for the crust characteristic, we employ the Receiver Functions (RF) method alongside H-k stacking. The crustal thickness recovered from the RF and H-k stacking has a good correlation with the crustal origin, where the thickness in older and stable crust originated from Sundaland and Gondwana is thicker than a younger plate of the crust arc and subduction origin. The Vp/Vs is high in a region that is interpreted to be dominated by mafic lower crust originated from oceanic-oceanic subduction during Eocene, anisotropy, or by a magmatic anomaly. The P coda also correlated well with the subsurface magmatic anomaly by providing a unique pattern.
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Leary, Peter, Peter Malin i Rami Niemi. "Fluid Flow and Heat Transport Computation for Power-Law Scaling Poroperm Media". Geofluids 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/9687325.
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In applying Darcy’s law to fluid flow in geologic formations, it is generally assumed that flow variations average to an effectively constant formation flow property. This assumption is, however, fundamentally inaccurate for the ambient crust. Well-log, well-core, and well-flow empirics show that crustal flow spatial variations are systematically correlated from mm to km. Translating crustal flow spatial correlation empirics into numerical form for fluid flow/transport simulation requires computations to be performed on a single global mesh that supports long-range spatial correlation flow structures. Global meshes populated by spatially correlated stochastic poroperm distributions can be processed by 3D finite-element solvers. We model wellbore-logged Dm-scale temperature data due to heat advective flow into a well transecting small faults in a Hm-scale sandstone volume. Wellbore-centric thermal transport is described by Peclet number Pe ≡ a0φv0/D (a0 = wellbore radius, v0 = fluid velocity at a0, φ = mean crustal porosity, and D = rock-water thermal diffusivity). The modelling schema is (i) 3D global mesh for spatially correlated stochastic poropermeability; (ii) ambient percolation flow calibrated by well-core porosity-controlled permeability; (iii) advection via fault-like structures calibrated by well-log neutron porosity; (iv) flow Pe ~ 0.5 in ambient crust and Pe ~ 5 for fault-borne advection.
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Ravi Kumar, Sistla. "Crustal deformation of the Central Indian Ocean, south of Sri Lanka as inferred from gravity and magnetic data". Geology, Geophysics and Environment 48, nr 2 (5.07.2022): 89–110. http://dx.doi.org/10.7494/geol.2022.48.2.89.
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Bathymetry, gravity, and magnetic data across the Central Indian Ocean Basin (CIOB) along a WE track between 5°N to 1°N latitudes and 77°E to 90°E longitudes are used to identify crustal deformation due to tectonic features such as the Comorin Ridge, 85°E ridge, Ninety East Ridge, and major fracture zones. The tectonic features were interpreted along the North Central Indian Ocean using 2D gravity modelling to understand the origin and tectonic activity of the subsurface features. The Comorin Ridge is coupled with gravity anomalies with small amplitude varying 25–30 mGal in comparison with the ridge relief which suggests that the ridge is compensated at deeper depths. The focus of the present study is to prepare a reasonable crustal model of the Central Indian Ocean using gravity and magnetic data. The crustal depths of the Central Indian Ocean Basin (CIOB) determined from gravity data using the spectral method are compared with the 2D gravity modelling results. It has been observed that the crustal depths obtained from the Spectral method are in good correlation with results obtained from 2D gravity modelling. The average basement depths for the profiles were obtained as ~5 km and perhaps deviated approximately 1–2 km from the mean. In the case of curie isotherm, the crustal depths vary 9–12 km for all magnetic profiles which may indicate deformation.
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Nitescu, B., A. R. Cruden i R. C. Bailey. "Topography of the crustmantle interface under the Western Superior craton from gravity data". Canadian Journal of Earth Sciences 40, nr 10 (1.10.2003): 1307–20. http://dx.doi.org/10.1139/e03-042.
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The Moho undulations beneath the western part of the Archean Superior Province have been investigated with a three-dimensional gravity inversion algorithm for a single interface of constant density contrast. Inversion of the complete gravity data set produces unreal effects in the solution due to the ambiguity in the possible sources of some crustal gravity anomalies. To avoid these effects a censored gravity data set was used instead. The inversion results are consistent with reflection and refraction seismic data from the region and, therefore, provide a basis for the lateral correlation of the Moho topography between parallel seismic lines. The results indicate the existence of a major linear eastwest-trending rise of the Moho below the metasedimentary English River subprovince, which is paralleled by crustal roots below the granitegreenstone Uchi and Wabigoon subprovinces. This correlation between the subprovincial structure at the surface and deep Moho undulations suggests that the topography of the crustmantle boundary is related to the tectonic evolution of the Western Superior belts. Although certain features of the crustmantle boundary are likely inherited from the accretionary and collisional stages of the Western Superior craton, gravity-driven processes triggered by subsequent magmatism and crustal softening may have played a role in both the preservation of those features, as well as in the development of new ones.
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Chiodini, G., C. Cardellini, F. Di Luccio, J. Selva, F. Frondini, S. Caliro, A. Rosiello, G. Beddini i G. Ventura. "Correlation between tectonic CO2 Earth degassing and seismicity is revealed by a 10-year record in the Apennines, Italy". Science Advances 6, nr 35 (sierpień 2020): eabc2938. http://dx.doi.org/10.1126/sciadv.abc2938.
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Deep CO2 emissions characterize many nonvolcanic, seismically active regions worldwide, and the involvement of deep CO2 in the earthquake cycle is now generally recognized. However, no long-time records of such emissions have been published, and the temporal relations between earthquake occurrence and tectonic CO2 release remain enigmatic. Here, we report a 10-year record (2009–2018) of tectonic CO2 flux in the Apennines (Italy) during intense seismicity. The gas emission correlates with the evolution of the seismic sequences: Peaks in the deep CO2 flux are observed in periods of high seismicity and decays as the energy and number of earthquakes decrease. We propose that the evolution of seismicity is modulated by the ascent of CO2 accumulated in crustal reservoirs and originating from the melting of subducted carbonates. This large-scale, continuous process of CO2 production favors the formation of overpressurized CO2-rich reservoirs potentially able to trigger earthquakes at crustal depth.
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Samson, Scott D., P. Jonathan Patchett, William C. McClelland i George E. Gehrels. "Nd and Sr isotopic constraints on the petrogenesis of the west side of the northern Coast Mountains batholith, Alaskan and Canadian Cordillera". Canadian Journal of Earth Sciences 28, nr 6 (1.06.1991): 939–46. http://dx.doi.org/10.1139/e91-085.
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Nd and Sr isotopic ratios are reported from 15 samples of plutons of the northern Coast Mountains batholith (CMB), between. the Alexander–Wrangellia terrane and the Stikine terrane of southeastern Alaska. Samples of plutons that are part of the Late Cretaceous – Eocene CMB suite have a range in initial εNd of −3.0 to −0.2 and 87Sr/86Sr of 0.70494–0.70607. There is no correlation of isotopic ratio with age, lithology, or geographic location of these plutons. Two plutons that are probably older than the bulk of the CMB plutons have present-day εNd values of −6.8 and −2.6.The Late Cretaceous – Eocene plutons have Nd depleted-mantle model ages (tDM) of 620–1070 Ma. These data indicate that the northern CMB must contain a significant component of old, evolved continental crust. The presence of an old crustal component is further demonstrated by inherited zircons of average Early Proterozoic age contained in some plutons. The mid to Late Proterozoic tDM ages of the CMB plutons are therefore a result of a mixture of Early Proterozoic crustal material with. younger, juvenile crust. The most likely source of this old crustal component is the Yukon–Tanana terrane, a fragment composed of ancient crustal material that occurs within and directly to the west of the northern CMB. The juvenile component is probably a combination of material derived from the mantle and from anatexis of the surrounding juvenile terranes. Crustal anatexis may have occurred as a result of the intrusion of mafic melts related to subduction along the outboard margin of the Alexander–Wrangellia terrane, by crustal thickening due to the underthrusting of the Alexander–Wrangellia terrane beneath the Yukon–Tanana and Stikine terranes, or by a combination of both processes.
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Scholer, Marie, James Irving i Klaus Holliger. "Estimation of the correlation structure of crustal velocity heterogeneity from seismic reflection data". Geophysical Journal International 183, nr 3 (12.10.2010): 1408–28. http://dx.doi.org/10.1111/j.1365-246x.2010.04793.x.
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Carpentier, S. F. A., K. Roy-Chowdhury i C. A. Hurich. "Mapping correlation lengths of lower crustal heterogeneities together with their maximum-likelihood uncertainties". Tectonophysics 508, nr 1-4 (lipiec 2011): 117–30. http://dx.doi.org/10.1016/j.tecto.2010.07.008.
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WHITEHOUSE, MARTIN J., BRIAN F. WINDLEY, MAHFOOD A. O. BA-BTTAT, C. MARK FANNING i DAVID C. REX. "Crustal evolution and terrane correlation in the eastern Arabian Shield, Yemen: geochronological constraints". Journal of the Geological Society 155, nr 2 (marzec 1998): 281–95. http://dx.doi.org/10.1144/gsjgs.155.2.0281.
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Płonka, Agnieszka, Nienke Blom i Andreas Fichtner. "The imprint of crustal density heterogeneities on regional seismic wave propagation". Solid Earth 7, nr 6 (29.11.2016): 1591–608. http://dx.doi.org/10.5194/se-7-1591-2016.
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Abstract. Density heterogeneities are the source of mass transport in the Earth. However, the 3-D density structure remains poorly constrained because travel times of seismic waves are only weakly sensitive to density. Inspired by recent developments in seismic waveform tomography, we investigate whether the visibility of 3-D density heterogeneities may be improved by inverting not only travel times of specific seismic phases but complete seismograms.As a first step in this direction, we perform numerical experiments to estimate the effect of 3-D crustal density heterogeneities on regional seismic wave propagation. While a finite number of numerical experiments may not capture the full range of possible scenarios, our results still indicate that realistic crustal density variations may lead to travel-time shifts of up to ∼ 1 s and amplitude variations of several tens of percent over propagation distances of ∼ 1000 km. Both amplitude and travel-time variations increase with increasing epicentral distance and increasing medium complexity, i.e. decreasing correlation length of the heterogeneities. They are practically negligible when the correlation length of the heterogeneities is much larger than the wavelength. However, when the correlation length approaches the wavelength, density-induced waveform perturbations become prominent. Recent regional-scale full-waveform inversions that resolve structure at the scale of a wavelength already reach this regime.Our numerical experiments suggest that waveform perturbations induced by realistic crustal density variations can be observed in high-quality regional seismic data. While density-induced travel-time differences will often be small, amplitude variations exceeding ±10 % are comparable to those induced by 3-D velocity structure and attenuation. While these results certainly encourage more research on the development of 3-D density tomography, they also suggest that current full-waveform inversions that use amplitude information may be biased due to the neglect of 3-D variations in density.
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Macdonald, Katrina M., Sangeeta Sharma, Desiree Toom, Alina Chivulescu, Andrew Platt, Mike Elsasser, Lin Huang i in. "Temporally delineated sources of major chemical species in high Arctic snow". Atmospheric Chemistry and Physics 18, nr 5 (9.03.2018): 3485–503. http://dx.doi.org/10.5194/acp-18-3485-2018.
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Abstract. Long-range transport of aerosol from lower latitudes to the high Arctic may be a significant contributor to climate forcing in the Arctic. To identify the sources of key contaminants entering the Canadian High Arctic an intensive campaign of snow sampling was completed at Alert, Nunavut, from September 2014 to June 2015. Fresh snow samples collected every few days were analyzed for black carbon, major ions, and metals, and this rich data set provided an opportunity for a temporally refined source apportionment of snow composition via positive matrix factorization (PMF) in conjunction with FLEXPART (FLEXible PARTicle dispersion model) potential emission sensitivity analysis. Seven source factors were identified: sea salt, crustal metals, black carbon, carboxylic acids, nitrate, non-crustal metals, and sulfate. The sea salt and crustal factors showed good agreement with expected composition and primarily northern sources. High loadings of V and Se onto Factor 2, crustal metals, was consistent with expected elemental ratios, implying these metals were not primarily anthropogenic in origin. Factor 3, black carbon, was an acidic factor dominated by black carbon but with some sulfate contribution over the winter-haze season. The lack of K+ associated with this factor, a Eurasian source, and limited known forest fire events coincident with this factor's peak suggested a predominantly anthropogenic combustion source. Factor 4, carboxylic acids, was dominated by formate and acetate with a moderate correlation to available sunlight and an oceanic and North American source. A robust identification of this factor was not possible; however, atmospheric photochemical reactions, ocean microlayer reaction, and biomass burning were explored as potential contributors. Factor 5, nitrate, was an acidic factor dominated by NO3−, with a likely Eurasian source and mid-winter peak. The isolation of NO3− on a separate factor may reflect its complex atmospheric processing, though the associated source region suggests possibly anthropogenic precursors. Factor 6, non-crustal metals, showed heightened loadings of Sb, Pb, and As, and correlation with other metals traditionally associated with industrial activities. Similar to Factor 3 and 5, this factor appeared to be largely Eurasian in origin. Factor 7, sulfate, was dominated by SO42− and MS with a fall peak and high acidity. Coincident volcanic activity and northern source regions may suggest a processed SO2 source of this factor.
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Ariyanto, P., M. D. Atthonthowi, B. Pranata i B. S. Prayitno. "Identification of Crustal Thickness in Central Part of Sumatra Using Teleseismic Receiver Function Method". Journal of Physics: Conference Series 2110, nr 1 (1.11.2021): 012001. http://dx.doi.org/10.1088/1742-6596/2110/1/012001.
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Abstract The Central part of Sumatra is a region that has a high potential for earthquakes. This research intended to determine the crustal thickness of the earth, P and S wave velocity profiles, and vp/vs value in the Central part of Sumatra using stacking H-k and inversion techniques based on the analysis of receiver function. This study utilized teleseismic earthquake data with a distance of 30° to 90° from the station and magnitude more than 6 (M>6). The stations used in this study were 3 BMKG broadband stations located in 3 zones, the fore arc ridge zone (SISI), the volcanic zone (PLSI) and the back arc zone (TPRI). The crustal thickness varies in the fore arc ridge zone (SISI) estimated 17.8 km, volcanic zone (PLSI) reaches 29.7 km and the back arc zone (TPRI) reaches 34 km. The crustal thickness is quite thick under the PLSI and thicker beneath TPRI station. These possibly due to the effect of topography and isostatic compensation in the station. However, whether there is a correlation between crustal thickness and topography needs further research using more stations. The highest vp/vs value was found in the volcanic zone of 1.9, that might be associated with the presence partial melting beneath the station. Meanwhile, the vp/vs value in the back arc zone is 1.72, indicating a relatively more homogeneous structure.
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Burianyk, M. J. A., E. R. Kanasewich i N. Udey. "Broadside wide-angle seismic studies and three-dimensional structure of the crust in the southeast Canadian Cordillera". Canadian Journal of Earth Sciences 34, nr 8 (1.08.1997): 1156–66. http://dx.doi.org/10.1139/e17-093.
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Broadside, or fan, recordings of a Lithoprobe seismic refraction – wide-angle reflection experiment in the southeastern Canadian Cordillera show several features further illuminating the crustal structure beyond that previously derived from SCoRE '90 (Southern Cordillera Refraction Experiment of 1990) in-line data. Analysis of a nearly in-line profile centred on Castlegar, British Columbia, shows lower velocities in the upper crust associated with the Purcell Anticlinorium as well as velocity variations that may have some association with the Purcell fault zone. The depth to Moho is almost 38 km, somewhat deeper and on trend with the structure that has been established farther north. The broadside records show high signal-to-noise ratio PmP arrivals (i.e., reflections from the bottom of the crust). These PmP fan picks were analysed in regions away from in-line profiles, providing further measurements of the depth to Moho in the southeastern Cordillera. The analysis of the broadside records combined with the earlier in-line interpretations as well as older crustal seismic measurements make up a relatively high resolution database, compared with most other regions in Canada, from which we have generated maps of depth to Moho and average crustal velocity in the southeastern Cordillera of Canada. The maps show thin, low-velocity crust over much of the region and indicate a high degree of correlation between current crustal seismic properties and regional isotherms.
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Mężyk, Miłosz, Michał Malinowski i Stanisław Mazur. "Imaging the East European Craton margin in northern Poland using extended correlation processing of regional seismic reflection profiles". Solid Earth 10, nr 3 (21.05.2019): 683–96. http://dx.doi.org/10.5194/se-10-683-2019.
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Abstract. In NE Poland, Eastern European Craton (EEC) crust of Fennoscandian affinity is concealed under a Phanerozoic platform cover and penetrated by sparse, deep research wells. Most of the inferences regarding its structure rely on geophysical data. Until recently, this area was covered only by the wide-angle reflection and refraction (WARR) profiles, which show a relatively simple crustal structure with a typical three-layer cratonic crust. ION Geophysical PolandSPAN™ regional seismic programme data, acquired over the marginal part of the EEC in Poland, offered a unique opportunity to derive a detailed image of the deeper crust. Here, we apply extended correlation processing to a subset (∼950 km) of the PolandSPAN™ dataset located in NE Poland, which enabled us to extend the nominal record length of the acquired data from 12 to 22 s (∼60 km of depth). Our new processing revealed reflectivity patterns, which we primarily associate with the Paleoproterozoic crust formed during the Svekofennian (Svekobaltic) orogeny, that are similar to those observed along the BABEL and FIRE profiles in the Baltic Sea and Finland, respectively. We propose a mid- to lower-crustal, orogeny-normal lateral flow model to explain the occurrence of two sets of structures that can be collectively interpreted as kilometre-scale S–C′ shear zones. The structures define a penetrative deformation fabric invoking ductile extension of hot orogenic crust in a convergent setting. Localized reactivation of these structures provided conduits for subsequent emplacement of gabbroic magma that produced a Mesoproterozoic anorthosite–mangerite–charnockite–granite (AMCG) suite in NE Poland. Delamination of thickened orogenic lithosphere may have accounted for magmatic underplating and fractionation into the AMCG plutons. We also found sub-Moho dipping mantle reflectivity, which we tentatively explain as a signature of the crustal accretion during the Svekofennian orogeny. Later tectonic phases (e.g. Ediacaran rifting, Caledonian orogeny) did not leave a clear signature in the deeper crust; however, some of the subhorizontal reflectors below the basement, observed in the vicinity of the AMCG Mazury complex, can be alternatively linked with lower Carboniferous magmatism.
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Gladkikh, Vladislav, Robert Tenzer i Paul Denys. "Crustal Deformation due to Atmospheric Pressure Loading in New Zealand". Journal of Geodetic Science 1, nr 3 (1.09.2011): 271–79. http://dx.doi.org/10.2478/v10156-011-0005-z.
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Crustal Deformation due to Atmospheric Pressure Loading in New ZealandWe investigate atmospheric pressure loading displacements in New Zealand using global and regional air-pressure data collected over a period of 50 years (1960-2009). The elastic response of the Earth to atmospheric loading is calculated by adopting mass loading Love numbers based on the parameters of the Preliminary Reference Earth Model (PREM). The ocean response to atmospheric loading is computed utilising a modified inverted barometer theory. The results reveal that the atmospheric loading vertical displacements are typically smallest along coastal regions, while gradually increasing inland with the maximum peak-to-peak displacement of 13.1 mm for this study period. In contrast, the largest horizontal displacements are found along coastal regions, where the maximum peak-to-peak displacement reaches 2.7 mm. The vertical displacements have a high spatial correlation, whereas the spatial correlation of the horizontal displacement components is much smaller. A spectral decomposition of the atmospheric loading time series shows that the signal is a broad band with most energy between 1 week and annual periods, and with a couple of peaks corresponding to approximately annual forcing and its overtones. The largest amplitudes in the atmospheric loading time series have an annual and semi-annual period.
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Sandıkkaya, M., i L. Dinsever. "A Site Amplification Model for Crustal Earthquakes". Geosciences 8, nr 7 (17.07.2018): 264. http://dx.doi.org/10.3390/geosciences8070264.
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A global dataset which is composed of more than 20,000 records is used to develop an empirical nonlinear soil amplification model for crustal earthquakes. The model also includes the deep soil effect. The soil nonlinearity is formulated in terms of input rock motion and soil stiffness. The input rock motion is defined by the pseudo-spectral acceleration at rock site condition (PSArock) which is also modified with between-event residual. Application of PSArock simplifies the usage of the site model by diminishing the need of using the period-dependent correlation coefficients in hazard studies. The soil stiffness is expressed by a Gompertz sigmoid function which restricts the nonlinear effects at both of the very soft soil sites and very stiff soil sites. In order to surpass the effect of low magnitude and long-distant recordings on soil nonlinearity, the nonlinear site coefficients are constrained by using a limited dataset. The coefficients of linear site scaling and deep soil effect are obtained with the full database. The period average of site-variability is found to be 0.43. The sigma decreases with decreasing the soil stiffness or increasing input rock motion. After employing residual analysis, the region-dependent correction coefficients for linear site scaling are also obtained.
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Will, T. M., H. E. Frimmel, A. Zeh, P. Le Roux i E. Schmädicke. "Geochemical and isotopic constraints on the tectonic and crustal evolution of the Shackleton Range, East Antarctica, and correlation with other Gondwana crustal segments". Precambrian Research 180, nr 1-2 (czerwiec 2010): 85–112. http://dx.doi.org/10.1016/j.precamres.2010.03.005.
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Moser, D. E. "The geology and structure of the mid-crustal Wawa gneiss domain: a key to understanding tectonic variation with depth and time in the late Archean Abitibi–Wawa orogen". Canadian Journal of Earth Sciences 31, nr 7 (1.07.1994): 1064–80. http://dx.doi.org/10.1139/e94-096.
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The amphibolite-facies central Wawa gneiss domain (CWGD) preserves structures that developed at the mid-crustal level of the ca. 2.7 Ga Abitibi–Wawa orogen in the southern Superior Province. The relative ages of these domainal structures are documented and brackets on their absolute ages established using existing U–Pb age data. Correlation of tectonic events within the CWGD, and comparison of these events with the evolution of other structural levels of the orogen, has led to subdivision of orogenesis into five stages. During stage 1 (2700–2680 Ma), 2.9 and 2.7 Ga rocks were tightly folded and (or) thrusted at all crustal levels in at least one thick-skinned compression event. During stage 2 (2680–2670 Ma), folding and thrusting of Timiskaming-age sediments at high levels of the orogen was thin-skinned and had no effect on CWGD gneisses. During stage 3 (2670–2660 Ma), while the upper crust was relatively stable, a 1 km thick package of volcanics and sediments, the Borden Lake belt, was underthrust northwards to depths of 30 km and in-folded with orthogneiss of the CWGD. During stage 4 (2660–2637 Ma), coeval east–west extension and granulite metamorphism of the middle crust produced gently dipping shear zones that overprinted earlier fold structures in the CWGD and lower structural levels of the orogen. This took place with minimal effect on the upper crust. Stage 5 (2630–2580 Ma) marks a period of east–west shortening and (or) fault reactivation in the Kapuskasing uplift and upper-crustal greenstone belts that allowed penetration of deep-crustal metamorphic fluids into the latter. In general, analysis of the structural evolution of the CWGD indicates that deformation and metamorphism in the middle crust of the Abitibi–Wawa orogen outlasted that at upper-crustal levels, resulting in the generally shallower dips of planar fabrics in the deeper structural levels of the Kapuskasing uplift crustal cross section.
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Katrivanos, E., A. Kilias i D. Mountrakis. "DEFORMATION HISTORY AND CORRELATION OF PAIKON AND TZENA TERRANES (AXIOS ZONE, CENTRAL MACEDONIA, GREECE)". Bulletin of the Geological Society of Greece 50, nr 1 (27.07.2017): 34. http://dx.doi.org/10.12681/bgsg.11699.
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Paikon and Tzena terranes are situated in the centre part of Axios zone, between Almopia and Paionia ophiolitic belts. Tectonostratigraphic data reveal that both have been affected by the same polyphase deformation and metamorphism, as well that they have the same lithostratigraphic column. The first deformation phase took place during the Middle to Late Jurassic and is associated with ophiolite obduction, nappe- stacking, terrane accretion and crustal thickening (D1). Metamorphism does not exceed greenschist facies (M1). Relict HP-LT metamorphic assemblages predating M1 metamorphism are possibly developed during subduction processes and overloading of the obducted ophiolites on the continental margin, characterized the initial stages of deformation. Compressional tectonics and intense thrusting with the same kinematics continued in Lower Cretaceous time, affected all pre-Upper Cretaceous units and the obducted ophiolites (D2). This phase is associated with low-greenschist metamorphism (M2). The first main extensional event occurs in the Late Cretaceous, related to basin formation and sedimentation (D3). During Paleocene to Eocene, D4 intense imbrication of all tectonic units towards mainly SW takes place again. Nappes collapse and finally crustal exhumation taken place during Oligocene to Miocene, associated with low - angle normal faults, with a main top to the SW sense of movement (D5). In Miocene to recent times, high - angle normal and strike-slip faults are formed in an extensional to transtensional strain regime (D6), associated with Neogene to Quaternary basin formation and terrane dispersion. The basement rocks of both terranes are of Pelagonian origin, exhumed as a multiple tectonic window.
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Gregori, G. P., G. Paparo, M. Poscolieri i A. Zanini. "Acoustic emission and released seismic energy". Natural Hazards and Earth System Sciences 5, nr 6 (13.10.2005): 777–82. http://dx.doi.org/10.5194/nhess-5-777-2005.
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Abstract. Intense crises of crustal stress appear to cross large regions, and to precede by several months the eventual occurrence of some strong earthquake within them. The phenomenon is not linear, and the stress control reflects some wide scale-size rather than local effects. The stress propagation through the crust can be effectively monitored by means of acoustic emission (AE) techniques (ultrasounds). The correlation is here investigated between crustal stress crises and the total release of seismic energy within some space domain around the AE recording site. Some clear inferences can be envisaged, although a significant diagnosis of the state of the crust within a given region ought to request arrays of simultaneously operated AE recorders. Some case histories are described dealing with the Italian peninsula and with the Cephallonia Island.
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Tenzer, Robert. "Gravimetric recovery of the Moho geometry based on a generalized compensation model". Contributions to Geophysics and Geodesy 43, nr 4 (1.12.2013): 253–69. http://dx.doi.org/10.2478/congeo-2013-0016.
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Abstract Gravity data used for a recovery of the Moho depths should (optimally) comprise only the gravitational signal of the Moho geometry. This theoretical assumption is typically not required in classical isostatic models, which are applied in gravimetric inverse methods for a recovery of the Moho interface. To overcome this theoretical deficiency, we formulate the gravimetric inverse problem for the consolidated crust-stripped gravity disturbances, which have (theoretically) a maximum correlation with the Moho geometry, while the gravitational contributions of anomalous density structures within the lithosphere and sub-lithosphere mantle (including the core-mantle boundary) should be subtracted from these gravity data. In the absence of a reliable 3-D Earth’s density model, our definitions are limited to the crustal and upper mantle density structures. The gravimetric forward modeling technique is applied to compute these gravity data using available models of major known anomalous crustal and upper mantle density structures. The gravimetric inverse problem is defined by means of the (non-linear) Fredholm integral equation of the first kind. After linearization of the integral equation, the solution to the gravimetric inverse problem is given in a frequency domain. The inverse problem is formulated for a generalized crustal compensation model. It implies that the compensation equilibrium is (theoretically) attained by both, the variable depth and density of compensation. A theoretical definition of this generalized crustal compensation model and a formulation of the gravimetric inverse problem for finding the Moho depths are given in this study.
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Qu, Wei, Hailu Chen, Shichuan Liang, Qin Zhang, Lihua Zhao, Yuan Gao i Wu Zhu. "Adaptive Least-Squares Collocation Algorithm Considering Distance Scale Factor for GPS Crustal Velocity Field Fitting and Estimation". Remote Sensing 11, nr 22 (18.11.2019): 2692. http://dx.doi.org/10.3390/rs11222692.
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High-precision, high-reliability, and high-density GPS crustal velocity are extremely important requirements for geodynamic analysis. The least-squares collocation algorithm (LSC) has unique advantages over crustal movement models to overcome observation errors in GPS data and the sparseness and poor geometric distribution in GPS observations. However, traditional LSC algorithms often encounter negative covariance statistics, and thus, calculating statistical Gaussian covariance function based on the selected distance interval leads to inaccurate estimation of the correlation between the random signals. An unreliable Gaussian statistical covariance function also leads to inconsistency in observation noise and signal variance. In this study, we present an improved LSC algorithm that takes into account the combination of distance scale factor and adaptive adjustment to overcome these problems. The rationality and practicability of the new algorithm was verified by using GPS observations. Results show that the new algorithm introduces the distance scale factor, which effectively weakens the influence of systematic errors by improving the function model. The new algorithm can better reflect the characteristics of GPS crustal movement, which can provide valuable basic data for use in the analysis of regional tectonic dynamics using GPS observations.
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Jackson, S. L., i R. H. Sutcliffe. "Central Superior Province geology: evidence for an allochthonous, ensimatic, southern Abitibi greenstone belt". Canadian Journal of Earth Sciences 27, nr 4 (1.04.1990): 582–89. http://dx.doi.org/10.1139/e90-054.
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Published U–Pb geochronological, geological, and petrochemical data suggest that there are late Archean ensialic greenstone belts (GB) (Michipicoten GB and possibly the northern Abitibi GB), ensimatic greenstone belts (southern Abitibi GB and Batchawana GB), and possibly a transitional ensimatic–ensialic greenstone belt (Swayze GB) in the central Superior Province. This lateral crustal variability may preclude simple correlation of the Michipicoten GB and its substrata, as exposed in the Kapuskasing Uplift, with that of the southern Abitibi GB. Furthermore, this lateral variability may have determined the locus of the Kapuskasing Uplift. Therefore, although the Kapuskasing Uplift provides a useful general crustal model, alternative models of crustal structure and tectonics for the southern Abitibi GB warrant examination.Thrusting of a juvenile, ensimatic southern Abitibi GB over a terrane containing evolved crust is consistent with (i) the structural style of the southern Abitibi GB; (ii) juvenile southern Abitibi GB metavolcanic rocks intruded by rocks having an isotopically evolved, older component; and (iii) Proterozoic extension that preserved low-grade metavolcanic rocks within the down-dropped Cobalt Embayment, which is bounded by higher grade terranes to the east and west.
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Kley, Jonas, i César R. Monaldi. "Tectonic shortening and crustal thickness in the Central Andes: How good is the correlation?" Geology 26, nr 8 (1998): 723. http://dx.doi.org/10.1130/0091-7613(1998)026<0723:tsacti>2.3.co;2.
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Wang, Qing-Liang, Yun-Tai Chen, Du-Xin Cui, Wen-Ping Wang i Wei-Feng Liang. "Decadal correlation between crustal deformation and variation in length of day of the Earth". Earth, Planets and Space 52, nr 11 (listopad 2000): 989–92. http://dx.doi.org/10.1186/bf03352318.
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