978 research outputs found
The Earth’s Interior: A New Frontier and a New Challenge for Earth Scientists
In this era of space exploration, deep expeditions to the
ocean bottom and far viewing telescopes, the Earth's interior
has emerged as one of the most challenging frontier
areas for scientific investigation. Exploration of the
crust, by seismic and other means, is well underway but
our view of the underlying mantle and core is fuzzy.
Plate tectonic theory has revolutionized Earth Science but
we still do not understand the driving mechanism or why
global processes change with time. The origins of the
magnetic field, volcanism, earthquakes, mineral resources
and mountain building processes are related to processes
in the deep interior. Planetary exploration has opened up
the new science of comparative planetology and yet, the
most fundamental questions regarding the origin, evolution
and composition of the Earth are unresolved because of our
ignorance of the characteristics of most of our planet, the
interior.
The time is now ripe to make an integrated study of the
Earth as a Planet or, in space age jargon, to undertake a
mission to Planet Earth. There are several recent developments
which make this timely
Neutrino parameters from matter effects in at long baselines
We show that the earth matter effects in the
survival probability can be used to cleanly determine the third leptonic mixing
angle and the sign of the atmospheric neutrino mass squared
difference, , using a -beam as a source.Comment: 4 pages, 4 eps figures; comments and references added, to appear in
Phys. Rev.
Core-mantle boundary deformations and J2 variations resulting from the 2004 Sumatra earthquake
The deformation at the core-mantle boundary produced by the 2004 Sumatra
earthquake is investigated by means of a semi-analytic theoretical model of
global coseismic and postseismic deformation, predicting a millimetric
coseismic perturbation over a large portion of the core-mantle boundary.
Spectral features of such deformations are analysed and discussed. The
time-dependent postseismic evolution of the elliptical part of the gravity
field (J2) is also computed for different asthenosphere viscosity models. Our
results show that, for asthenospheric viscosities smaller than 10^18 Pa s, the
postseismic J2 variation in the next years is expected to leave a detectable
signal in geodetic observations.Comment: 14 pages, 8 figures, 1 table. It will appear in Geophysical Journal
Internationa
Neutrino oscillation probabilities: Sensitivity to parameters
We study in detail the sensitivity of neutrino oscillation probabilities to
the fundamental neutrino parameters and their possible determination through
experiments. The first part of the paper is devoted to the broad theme of
isolating regions in the neutrino (and anti-neutrino) energy and propagation
length that are sensitive to the oscillation parameters. Such a study is
relevant to neutrinos both from the Earth's atmosphere or from a neutrino
factory. For completeness we discuss the sensitivity, however small, to the
parameters involved in a three-generation framework, and to the Earth matter
density profile. We then study processes relevant to atmospheric neutrinos
which are sensitive to and allow precision measurements of the mixing angle
theta_23 and mass-squared difference delta_32 apart from the mixing angle
theta_13. Crucial to this analysis is charge identification; detectors having
this capability can isolate these matter effects. In particular, we address the
issue of using matter effects to determine whether the mixing angle theta_23 is
maximal, and, if not, to explore how well its octant can be determined. When
realistic detector resolutions are included, we find that deviations of about
15% (20%) from a maximal value of sin^2 theta_23=1/2 can be measured at 95%
(99%) CL provided theta_13 is non-zero, sin^2 theta_13 >= 0.015, and the
neutrino mass ordering is normal, with fairly large exposures of 1000
kton-years.Comment: 37 pages Latex file, 30 eps figure files; minor typos fixe
Seismic radiation by magma injection: An anomalous seismic event near Tori Shima, Japan
The earthquake with a bodywave magnitude m_b=5.5, which occurred near Tori Shima, Japan, on June 13, 1984 (origin time: 0229:25.3 UT, 31.448°N, 140.036°E, depth of 10 km, m_b =5.5, M_S=5.5) is anomalous because it generated tsunamis which are disproportionately large for the magnitude of the earthquake. At Hachijo Island, 150 km from the epicenter, tsunamis were visually observed with peak-to-peak amplitude of 130 to 150 cm. Long-period seismic radiation is also anomalous. Love waves are almost absent, and Rayleigh waves are radiated with equal amplitude and phase in all directions. A simple double-couple model cannot explain these observations. With the assumption of no net volume change at the source, these data can be best explained with a compensated linear vector dipole (CLVD) with the principal tensional dipole in the vertical direction. The scalar moment of this dipole is 4×10^(24) dyn cm. Moment tensor inversions of long-period body waves and surface waves yield an almost identical solution. This CLVD source can be interpreted as horizontal fluid injection. The location of the event is in the Smith depression which is one of the nascent back arc basins just behind the Bonin arc. These basins are filled with thick sediments, and numerous young volcanoes are found near this site. Magmatic injection is most likely to occur in this tectonic environment. However, the time scale of the seismic event seems too short for magma injection to occur. A more likely mechanism involves water-magma interaction. The injection may be viewed as hydrofracturing driven by supercritical water heated by injected magma. The estimated volume of injected water is about 0.018 km^3 and that of basaltic magma is about 10% of this. This type of deformation is more efficient for tsunami generation than faulting with the same scalar moment
Which solar neutrino data favour the LMA solution?
Assuming neutrino oscillations, global analyses of solar data find that the
LOW solution is significantly disfavoured, leaving LMA as the best solution.
But the preference for LMA rests on three weak hints: the spectrum of earth
matter effects (Super-Kamiokande sees an overall day/night asymmetry only at 1
sigma), the Cl rate (but LMA and LOW predictions are both above the measured
value), the Ga rate (newer data decrease towards the LOW predictions both in
GNO and SAGE). Only new data will tell us if LMA is the true solution.Comment: 4 pages, 2 figure
Probing neutrino oscillations jointly in long and very long baseline experiments
We examine the prospects of making a joint analysis of neutrino oscillation
at two baselines with neutrino superbeams. Assuming narrow band superbeams and
a 100 kt water Cerenkov calorimeter, we calculate the event rates and
sensitivities to the matter effect, the signs of the neutrino mass differences,
the CP phase and the mixing angle \theta_{13}. Taking into account all possible
experimental errors under general consideration, we explored the optimum cases
of narrow band beam to measure the matter effect and the CP violation effect at
all baselines up to 3000 km. We then focus on two specific baselines, a long
baseline of 300 km and a very long baseline of 2100 km, and analyze their joint
capabilities. We found that the joint analysis can offer extra leverage to
resolve some of the ambiguities that are associated with the measurement at a
single baseline.Comment: 23 pages, 11 figure
The effects of matter density uncertainties on neutrino oscillations in the Earth
We compare three different methods to evaluate uncertainties in the Earth's
matter density profile, which are relevant to long baseline experiments, such
as neutrino factories.Comment: 3 pages, 1 figure. Talk given at the NuFact'02 Workshop, London, 1-6
July, 200
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