Velocity imaging of the shallow subsurface using 3D inversion of VSP data to visualize a saturated portion of the vadose zone at Lawrence Livermore National Laboratory

2006 ◽  
Vol 25 (3) ◽  
pp. 362-365 ◽  
Author(s):  
Jesse Crews ◽  
James W. Rector ◽  
Bob Bainer
Keyword(s):  
Vadose Zone ◽  
Lawrence Livermore National Laboratory ◽  
National Laboratory ◽  
3D Inversion ◽  
Shallow Subsurface ◽  
Velocity Imaging ◽  
Vsp Data

Scattering versus intrinsic attenuation in the vadose zone: A VSP experiment

Geophysics ◽  
2013 ◽  
Vol 78 (2) ◽  
pp. B49-B63 ◽  
Author(s):  
Maria-Daphne Mangriotis ◽  
James W. Rector ◽  
E. Frederic Herkenhoff ◽  
John C. Neu
Keyword(s):  
Frequency Dependence ◽  
Vadose Zone ◽  
Lawrence Livermore National Laboratory ◽  
Near Field ◽  
National Laboratory ◽  
P Wave ◽  
Near Surface ◽  
Intrinsic Attenuation ◽  
Impact Attenuation ◽  
Synthetic Modeling

We studied scattering versus intrinsic attenuation estimates in the vadose zone from a shallow VSP experiment conducted in the Lawrence Livermore National Laboratory (LLNL) facility. Using permanent downhole geophones and a vertical impact source, we estimated effective attenuation of the downgoing transmitted P-wave. We compared theoretical scattering attenuation estimates and finite-difference synthetics to the measured field [Formula: see text] values ([Formula: see text] being a measure of attenuation). Using a selected range of impedance profiles of variance typical for a sedimentary basin, our estimates of [Formula: see text] are in the order of 20–85. Given the short propagation pathlengths involved ([Formula: see text]), we show that attenuation due to lateral heterogeneity is not significant. We analyzed additional distorting factors, including near-field presence, local impedance effects, and interference from reflections originating beneath receivers, and found that they may significantly impact attenuation measurement in near-surface studies, and result in biased [Formula: see text] values. From a comparison of the analyzed ranges of [Formula: see text] to the measured [Formula: see text] values, we deduced [Formula: see text], which is consistently low, but whose inferred frequency dependence depends strongly on the scattering model assumed. The ranges for the [Formula: see text] factor resulting from scattering and distorting factors, and the intrinsic [Formula: see text] value were estimated as, respectively, 4–7, and 7–4. We identified two potential mechanisms which could lead to low [Formula: see text] values in the vadose zone: patchy saturation and squirt flow. We found through viscoelastic 3D synthetic modeling using a standard linear solid (SLS), that the field [Formula: see text] frequency dependence can be reproduced, although nonuniquely, for the studied range of impedance variance.

Lattice QCD on GPU clusters, using the QUDA library and the Chroma software system

2012 ◽  
Vol 26 (4) ◽  
pp. 386-398 ◽  
Author(s):  
Bálint Joó ◽  
Mike A. Clark
Keyword(s):  
Quantum Chromodynamics ◽  
Graphics Processing Units ◽  
Lawrence Livermore National Laboratory ◽  
National Laboratory ◽  
Application Framework ◽  
Software System ◽  
Nuclear Forces ◽  
Lattice Quantum Chromodynamics ◽  
Lattice Quantum ◽  
Strong Scaling

The QUDA library for optimized lattice quantum chromodynamics using GPUs, combined with a high-level application framework such as the Chroma software system, provides a powerful tool for computing quark propagators, a key step in current calculations of hadron spectroscopy, nuclear structure, and nuclear forces. In this contribution we discuss our experiences, including performance and strong scaling of the QUDA library and Chroma on the Edge Cluster at Lawrence Livermore National Laboratory and on various clusters at Jefferson Lab. We highlight some scientific successes and consider future directions for graphics processing units in lattice quantum chromodynamics calculations.

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