907 research outputs found
Holocene Earthquakes and Late Pleistocene Slip-Rate Estimates on the Wassuk Range Fault Zone, Nevada
The Wassuk Range fault zone is an 80‐km‐long, east‐dipping, high‐angle normal fault that flanks the eastern margin of the Wassuk Range in central Nevada. Observations from two alluvial fan systems truncated by the fault yield information on the vertical slip rate and Holocene earthquake history along the range front. At the apex of the Rose Creek alluvial fan, radiocarbon dating of offset stratigraphy exposed in two fault trenches shows that multiple earthquakes resulted in 7.0 m of vertical offset along the fault since ∼9400 cal B.P. These data yield a Holocene vertical slip rate of 0.7±0.1 mm/yr. The south trench exposure records at least two faulting events since ∼9400 cal B.P., with the most recent displacement postdating ∼2810 cal B.P. The north trench exposure records an ∼1 m offset between ∼610 cal B.P. and A.D. ∼1850, a 1.3‐m minimum offset prior to ∼1460 cal B.P., and one earlier undated earthquake of a similar size. Variations in stratigraphy and limited datable material preclude a unique correlation of paleoevents between the two trenches. Approximately 25 km north, the range‐front fault has truncated and uplifted a remnant of the Penrod Canyon fan by \u3e40 m since the surface was deposited ∼113 ka, based on cosmogenic dating of two large boulders. These data allow an estimate of the minimum late Pleistocene vertical slip rate at \u3e0.3–0.4 mm/yr for the Wassuk Range fault zone
Holocene Earthquakes and Late Pleistocene Slip Rate Estimates on the Wassuk Range Fault Zone, Nevada, USA
The Wassuk Range fault zone is an 80‐km‐long, east‐dipping, high‐angle normal fault that flanks the eastern margin of the Wassuk Range in central Nevada. Observations from two alluvial fan systems truncated by the fault yield information on the vertical slip rate and Holocene earthquake history along the range front. At the apex of the Rose Creek alluvial fan, radiocarbon dating of offset stratigraphy exposed in two fault trenches shows that multiple earthquakes resulted in 7.0 m of vertical offset along the fault since ∼9400 cal B.P. These data yield a Holocene vertical slip rate of 0.7±0.1 mm/yr. The south trench exposure records at least two faulting events since ∼9400 cal B.P., with the most recent displacement postdating ∼2810 cal B.P. The north trench exposure records an ∼1 m offset between ∼610 cal B.P. and A.D. ∼1850, a 1.3‐m minimum offset prior to ∼1460 cal B.P., and one earlier undated earthquake of a similar size. Variations in stratigraphy and limited datable material preclude a unique correlation of paleoevents between the two trenches. Approximately 25 km north, the range‐front fault has truncated and uplifted a remnant of the Penrod Canyon fan by \u3e40 m since the surface was deposited ∼113 ka, based on cosmogenic dating of two large boulders. These data allow an estimate of the minimum late Pleistocene vertical slip rate at \u3e0.3–0.4 mm/yr for the Wassuk Range fault zone
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Improving the condition number of estimated covariance matrices
High dimensional error covariance matrices and their inverses are used to weight the
contribution of observation and background information in data assimilation procedures. As
observation error covariance matrices are often obtained by sampling methods, estimates are
often degenerate or ill-conditioned, making it impossible to invert an observation error
covariance matrix without the use of techniques to reduce its condition number. In this paper
we present new theory for two existing methods that can be used to ‘recondition’ any covariance
matrix: ridge regression, and the minimum eigenvalue method. We compare these methods
with multiplicative variance inflation, which cannot alter the condition number of a matrix, but
is often used to account for neglected correlation information. We investigate the impact of
reconditioning on variances and correlations of a general covariance matrix in both a theoretical
and practical setting. Improved theoretical understanding provides guidance to users regarding
method selection, and choice of target condition number. The new theory shows that, for the
same target condition number, both methods increase variances compared to the original
matrix, with larger increases for ridge regression than the minimum eigenvalue method. We
prove that the ridge regression method strictly decreases the absolute value of off-diagonal
correlations. Theoretical comparison of the impact of reconditioning and multiplicative
variance inflation on the data assimilation objective function shows that variance inflation alters
information across all scales uniformly, whereas reconditioning has a larger effect on scales
corresponding to smaller eigenvalues. We then consider two examples: a general correlation
function, and an observation error covariance matrix arising from interchannel correlations. The
minimum eigenvalue method results in smaller overall changes to the correlation matrix than
ridge regression, but can increase off-diagonal correlations. Data assimilation experiments reveal
that reconditioning corrects spurious noise in the analysis but underestimates the true signal
compared to multiplicative variance inflation
Phase Transitions Driven by Vortices in 2D Superfluids and Superconductors: From Kosterlitz-Thouless to 1st Order
The Landau-Ginzburg-Wilson hamiltonian is studied for different values of the
parameter which multiplies the quartic term (it turns out that this
is equivalent to consider different values of the coherence length in
units of the lattice spacing ). It is observed that amplitude fluctuations
can change dramatically the nature of the phase transition: for small values of
(), instead of the smooth Kosterlitz-Thouless transition
there is a {\em first order} transition with a discontinuous jump in the vortex
density and a larger non-universal drop in the helicity modulus. In
particular, for sufficiently small (), the density of
bound pairs of vortex-antivortex below is so low that, drops to zero
almost for all temperature .Comment: 8 pages, 5 .eps figure
Hadronization of massive quark matter
We present a fast hadronization model for the constituent quark plasma (CQP)
produced in relativistic heavy ion collisions at SPS. The model is based on
rate equations and on an equation of state inspired by the string
phenomenology. This equation of state has a confining character. We display the
time evolution of the relevant physical quantities during the hadronization
process and the final hadron multiplicities. The results indicate that the
hadronization of CQP is fast.Comment: 12 pages, Latex, 2 EPS figures, contribution to the Proceedings of
the 4th International Conference on Strangeness in Quark Matter (SQM'98),
Padova, Italy, 20-24 July 199
First Order Transition in the Ginzburg-Landau Model
The d-dimensional complex Ginzburg-Landau (GL) model is solved according to a
variational method by separating phase and amplitude. The GL transition becomes
first order for high superfluid density because of effects of phase
fluctuations. We discuss its origin with various arguments showing that, in
particular for d = 3, the validity of our approach lies precisely in the first
order domain.Comment: 4 pages including 2 figure
Coulomb Effect: A Possible Probe for the Evolution of Hadronic Matter
Electromagnetic field produced in high-energy heavy-ion collisions contains
much useful information, because the field can be directly related to the
motion of the matter in the whole stage of the reaction. One can divide the
total electromagnetic field into three parts, i.e., the contributions from the
incident nuclei, non-participating nucleons and charged fluid, the latter
consisting of strongly interacting hadrons or quarks. Parametrizing the
space-time evolution of the charged fluid based on hydrodynamic model, we study
the development of the electromagnetic field which accompanies the high-energy
heavy-ion collisions. We found that the incident nuclei bring a rather strong
electromagnetic field to the interaction region of hadrons or quarks over a few
fm after the collision. On the other hand, the observed charged hadrons'
spectra are mostly affected (Coulomb effect) by the field of the charged fluid.
We compare the result of our model with experimental data and found that the
model reproduces them well. The pion yield ratio pi^-/pi+ at a RHIC energy,
Au+Au 100+100 GeV/nucleon, is also predicted.Comment: 23 pages, RevTex, 19 eps figures, revised versio
Observing Quark-Gluon Plasma with Strange Hadrons
We review the methods and results obtained in an analysis of the experimental
heavy ion collision research program at nuclear beam energy of 160-200A GeV. We
study strange, and more generally, hadronic particle production experimental
data. We discuss present expectations concerning how these observables will
perform at other collision energies. We also present the dynamical theory of
strangeness production and apply it to show that it agrees with available
experimental results. We describe strange hadron production from the
baryon-poor quark-gluon phase formed at much higher reaction energies, where
the abundance of strange baryons and antibaryons exceeds that of nonstrange
baryons and antibaryons.Comment: 39 journal pages (155kb text), 8 postscript figures, 8 table
Carrier-envelope phase effects on the strong-field photoemission of electrons from metallic nanostructures
Sharp metallic nanotapers irradiated with few-cycle laser pulses are emerging
as a source of highly confined coherent electron wavepackets with attosecond
duration and strong directivity. The possibility to steer, control or switch
such electron wavepackets by light is expected to pave the way towards direct
visualization of nanoplasmonic field dynamics and real-time probing of electron
motion in solid state nanostructures. Such pulses can be generated by
strong-field induced tunneling and acceleration of electrons in the near-field
of sharp gold tapers within one half-cycle of the driving laser field. Here, we
show the effect of the carrier-envelope phase of the laser field on the
generation and motion of strong-field emitted electrons from such tips. This is
a step forward towards controlling the coherent electron motion in and around
metallic nanostructures on ultrashort length and time scales
Thermal analysis of hadron multiplicities from relativistic quantum molecular dynamics
Some questions arising in the application of the thermal model to hadron
production in heavy ion collisions are studied. We do so by applying the
thermal model of hadron production to particle yields calculated by the
microscopic transport model RQMD(v2.3). We study the bias of incomplete
information about the final hadronic state on the extraction of thermal
parameters.It is found that the subset of particles measured typically in the
experiments looks more thermal than the complete set of stable particles. The
hadrons which show the largest deviations from thermal behaviour in RQMD(v2.3)
are the multistrange baryons and antibaryons. We also looked at the influence
of rapidity cuts on the extraction of thermal parameters and found that they
lead to different thermal parameters and larger disagreement between the RQMD
yields and the thermal model.Comment: 12 pages, 2 figures, uses REVTEX, only misprint and stylistic
corrections, to appear in Physical Review
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