Search

Your search keyword '"ELLIOTT, J. R."' showing total 421 results
Start Over Author "ELLIOTT, J. R."
421 results on '"ELLIOTT, J. R."'

4. The Seismic Structure of the Sun

Author

Gough, D. O., Kosovichev, A. G., Toomre, J., Anderson, E., Antia, H. M., Basu, S., Chaboyer, B., Chitre, S. M., Christensen-Dalsgaard, J., Dziembowski, W. A., Eff-Darwich, A., Elliott, J. R., Giles, P. M., Goode, P. R., Guzik, J. A., Harvey, J. W., Hill, F., Leibacher, J. W., Richard, O., Sekii, T., Shibahashi, H., Takata, M., Thompson, M. J., Vauclair, S., and Vorontsov, S. V.

Published
1996

25. The Seismic Structure of the Sun from Gong

Author

Anderson, E., primary, Antia, H. M., additional, Basu, S., additional, Chaboyer, B., additional, Chitre, S. M., additional, Christensen-Dalsgaard, J., additional, Eff-Darwich, A., additional, Elliott, J. R., additional, Giles, P. M., additional, Gough, D. O., additional, Guzik, J. A., additional, Harvey, J. W., additional, Hill, F., additional, Leibacher, J. W., additional, Kosovichev, A. G., additional, Monteiro, M. J. P. F. G., additional, Richard, O., additional, Sekii, T., additional, Shibahashi, H., additional, Takata, M., additional, Thompson, M. J., additional, Toomre, J., additional, Vauclair, S., additional, and Vorontsov, S. V., additional

Published
1997
Full Text
View/download PDF

26. Helioseismic Constraints on New Solar Models from the MoSEC Code

Author

Elliott, J. R

Subjects
Solar Physics
Abstract

Evolutionary solar models are computed using a new stellar evolution code, MOSEC (Modular Stellar Evolution Code). This code has been designed with carefully controlled truncation errors in order to achieve a precision which reflects the increasingly accurate determination of solar interior structure by helioseismology. A series of models is constructed to investigate the effects of the choice of equation of state (OPAL or MHD-E, the latter being a version of the MHD equation of state recalculated by the author), the inclusion of helium and heavy-element settling and diffusion, and the inclusion of a simple model of mixing associated with the solar tachocline. The neutrino flux predictions are discussed, while the sound speed of the computed models is compared to that of the sun via the latest inversion of SOI-NMI p-mode frequency data. The comparison between models calculated with the OPAL and MHD-E equations of state is particularly interesting because the MHD-E equation of state includes relativistic effects for the electrons, whereas neither MHD nor OPAL do. This has a significant effect on the sound speed of the computed model, worsening the agreement with the solar sound speed. Using the OPAL equation of state and including the settling and diffusion of helium and heavy elements produces agreement in sound speed with the helioseismic results to within about +.-0.2%; the inclusion of mixing slightly improves the agreement.

Published
1998

27. Aspects of the Solar Tachocline

Author

Elliott, J. R

Subjects
Space Radiation
Abstract

The splitting of the frequencies of p-mode multiplets enables information to be gained about the internal rotation of the sun. Such data have revealed a transition at the base of the convection zone from differential rotation similar to that observed at the surface to almost solid-body rotation in the radiative interior. This transition region, known as the tachocline, has been found to be relatively narrow and centered below the base of the convection zone. In this paper, the evolution of the transition region is investigated numerically. Without a large anisotropic viscosity, the depth to which it would spread in one solar age, under the assumption of a constant prescribed differential rotation at the base of the convection zone, is found to be greater than its extent as inferred from helioseismology. In the second part of the paper a highly anisotropic turbulent viscosity with a large horizontal component, as suggested by Spiegel & Zahn (1992), is assumed. In this case, a steady tachocline is formed in which the advection of angular momentum balances the Reynolds stresses. The horizontal component of turbulent viscosity required to match the thickness of the tachocline to that obtained by helioseismology, is estimated to be 5 x 1O sq cm/s The transport of helium is studied in this case and is found to yield a sound-speed increase similar to that required by helioseismology.

Published
1997

34. Charm Photoproduction Results from E691 : The Tagged Photon Spectrometer Collaboration

Author

Anjos, J. C., Appel, J. A., Bean, A., Bracker, S. B., Browder, T. E., Cremaldi, L. M., Elliott, J. R., Escobar, C. O., Estabrooks, P., Gibney, M. C., Hartner, G. F., Karchin, P. E., Kumar, B. R., Losty, M. J., Luste, G. J., Mantsch, P. M., Martin, J. F., Mchugh, S., Menary, S. R., Morrison, R. J., Nash, T., Ong, P., Pinfold, J., Punkar, G., Purohit, M. V., Raab, J. R., Santoro, A. F. S., Sidhu, J. S., Sliwa, K., Sokoloff, M. D., Souza, M. H. G., Spalding, W. J., Streetman, M. E., Stundžia, A. B., Witherell, M. S., Kotthaus, Rainer, editor, and Kühn, Johann H., editor

Published
1989
Full Text
View/download PDF

35. Shallow earthquake inhibits unrest near Chiles-Cerro Negro volcanoes, Ecuador-Colombian border

Author

Ebmeier, S. K., Elliott, J. R., Nocquet, Jean-Mathieu, Biggs, J., Mothes, P., Jarrin, P., Yepez, M., Aguaiza, S., Lundgren, P., and Samsonov, S. V.

Subjects
volcanic hazard, InSAR, earthquake, GPS
Abstract

Magma movement or reservoir pressurisation can drive swarms of low-magnitude volcano-tectonic earthquakes, as well as occasional larger earthquakes (>M5) on local tectonic faults. Earthquakes >M5 near volcanoes are challenging to interpret in terms of evolving volcanic hazard, but are often associated with eruptions, and in some cases enhance the ascent of magma. We present geodetic observations from the first episode of unrest known to have occurred near Chiles and Cerro Negro de Mayasquer volcanoes on the Ecuador-Colombian border. A swarm of volcano-tectonic seismicity in October 2014 culminated in a M-w 5.6 earthquake south of the volcanoes. Satellite radar data spanning this earthquake detect displacements that are consistent with dextral oblique slip on a reverse fault at depths of 1.4-3.4 km within a SSW-NNE trending fault zone that last ruptured in 1886. GPS station measurements capture 20 days of uplift before the earthquake, probably originating from a pressure source similar to 10-15 km south of Volcan Chiles, at depths exceeding 13 km. After the Mw 5.6 earthquake, uplift ceased and the rate of seismicity began to decrease. Potential mechanisms for this decline in activity include a decrease in the rate of movement of magma into the shallow crust, possibly caused by the restriction of fluid pathways. Our observations demonstrate that an earthquake triggered during volcanic unrest can inhibit magmatic processes, and have implications for the hazard interpretation of the interactions between earthquakes and volcanoes.

Published
2016

36. Reading and Writing in the Time of Jesus

Author

Elliott, J. R.

Subjects
Reading and Writing in the Time of Jesus (Book) -- Book reviews, Books -- Book reviews, Philosophy and religion
Published
2006

38. Himalayan megathrust geometry and relation to topography revealed by the Gorkha earthquake

Author

Natural Environment Research Council (UK), Elliott, J. R., Jolivet, Romain, González, Pablo J., Avouac, J-P, Hollingsworth, James, Searle, M. P., Stevens, V. L., Natural Environment Research Council (UK), Elliott, J. R., Jolivet, Romain, González, Pablo J., Avouac, J-P, Hollingsworth, James, Searle, M. P., and Stevens, V. L.

Abstract

The Himalayan mountain range has been the locus of some of the largest continental earthquakes, including the 2015 magnitude 7.8 Gorkha earthquake. Competing hypotheses suggest that Himalayan topography is sustained and plate convergence is accommodated either predominantly on the main plate boundary fault, or more broadly across multiple smaller thrust faults. Here we use geodetic measurements of surface displacement to show that the Gorkha earthquake ruptured the Main Himalayan Thrust fault. The earthquake generated about 1 m of uplift in the Kathmandu Basin, yet caused the high Himalaya farther north to subside by about 0.6 m. We use the geodetic data, combined with geologic, geomorphological and geophysical analyses, to constrain the geometry of the Main Himalayan Thrust in the Kathmandu area. Structural analyses together with interseismic and coseismic displacements are best explained by a steep, shallow thrust fault flattening at depth between 5 and 15 km and connecting to a mid-crustal, steeper thrust. We suggest that present-day convergence across the Himalaya is mostly accommodated by this fault—no significant motion on smaller thrust faults is required. Furthermore, given that the Gorkha earthquake caused the high Himalayan mountains to subside and that our fault geometry explains measured interseismic displacements, we propose that growth of Himalayan topography may largely occur during the ongoing post-seismic phase.

Published
2016

47. The Dzhungarian fault: Late Quaternary tectonics and slip rate of a major right-lateral strike-slip fault in the northern Tien Shan region

Author

Campbell, G. E., Walker, R. T., Abdrakhmatov, K., Schwenninger, JL., Jackson, J., Elliott, J. R., Copley, Alex, Jackson, James [0000-0003-2927-1771], Copley, Alexander [0000-0003-0362-0494], and Apollo - University of Cambridge Repository

Subjects
late Quaternary slip rate, earthquake hazard, continental tectonics, strike-slip faulting, active faulting, sub-02, geomorphology
Abstract

The Dzhungarian strike-slip fault of Central Asia is one of a series of long, NW-SE right-lateral strike-slip faults that are characteristic of the northern Tien Shan region and extends over 300 km from the high mountains into the Kazakh Platform. Our field-based and satellite observations reveal that the Dzhungarian fault can be characterized by three 100 km long sections based on variation in strike direction. Through morphological analysis of offset streams and alluvial fans, and through optically stimulated luminescence dating, we find that the Dzhungarian fault has a minimum average late Quaternary slip rate of 2.2 ± 0.8 mm/yr and accommodates N-S shortening related to the India-Eurasia collision. This shortening may also be partly accommodated by counterclockwise rotation about a vertical axis. Evidence for a possible paleo-earthquake rupture indicates that earthquakes up to at least Mw 7 can be associated with just the partitioned component of reverse slip on segments of the central section of the fault up to 30 km long. An event rupturing longer sections of the Dzhungarian fault has the potential to generate greater magnitude earthquakes (Mw 8); however, long time periods (e.g., thousands of years) are expected in order to accumulate enough strain to generate such earthquakes.

Published
2013

48. Blind Thrusting, Surface Folding, and the Development of Geological Structure in the M w 6.3 2015 Pishan (China) Earthquake.

Author

Ainscoe, E. A., Elliott, J. R., Copley, A., Craig, T. J., Li, T., Parsons, B. E., and Walker, R. T.

Abstract

The relationship between individual earthquakes and the longer-term growth of topography and of geological structures is not fully understood, but is key to our ability to make use of topographic and geological data sets in the contexts of seismic hazard and wider-scale tectonics. Here we investigate those relationships at an active fold-and-thrust belt in the southwest Tarim Basin, Central Asia. We use seismic waveforms and interferometric synthetic aperture radar (InSAR) to determine the fault parameters and slip distribution of the 2015 M w6.3 Pishan earthquake-a blind, reverse-faulting event dipping toward the Tibetan Plateau. Our earthquake mechanism and location correspond closely to a fault mapped independently by seismic reflection, indicating that the earthquake was on a preexisting ramp fault over a depth range of ∼9-13 km. However, the geometry of folding in the overlying fluvial terraces cannot be fully explained by repeated coseismic slip in events such as the 2015 earthquake nor by the early postseismic motion shown in our interferograms; a key role in growth of the topography must be played by other mechanisms. The earthquake occurred at the Tarim-Tibet boundary, with the unusually low dip of 21°. We use our source models from Pishan and a 2012 event to argue that the Tarim Basin crust deforms only by brittle failure on faults whose effective coefficient of friction is ≤0.05 ± 0.025. In contrast, most of the Tibetan crust undergoes ductile deformation, with a viscosity of order 1020-1022 Pa s. This contrast in rheologies provides an explanation for the low dip of the earthquake fault plane. [ABSTRACT FROM AUTHOR]

Published
2017
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results