Prestack traveltime inversion for three‐dimensional structure

Geophysics ◽  
1989 ◽  
Vol 54 (3) ◽  
pp. 359-367 ◽  
Author(s):  
Tzeu‐Lie Lin
Keyword(s):  
Iterative Method ◽  
Input Data ◽  
Three Dimensional ◽  
Velocity Fields ◽  
Dimensional Structure ◽  
Model Parameters ◽  
Traveltime Inversion ◽  
Three Dimensional Structure ◽  
Inaccurate Data ◽  
Frechet Derivatives

An iterative method for determining three‐dimensional (3-D) velocity fields is presented. The input data are offset‐dependent traveltimes for primary reflections. 3-D traveltime derivatives (the Frêchet derivatives) for the 3-D structure are derived. The algorithm simultaneously determines all of the model parameters and is exceedingly robust compared to layer‐stripping algorithms, even for inaccurate data.

Seismic tomography to obtain velocity gradients and three-dimensional structure and its application to reflection data on Vancouver Island

1990 ◽  
Vol 27 (1) ◽  
pp. 104-116 ◽  
Author(s):  
Suhas Phadke ◽  
Ernest R. Kanasewich
Keyword(s):  
Subduction Zones ◽  
Three Dimensional ◽  
Nonlinear Function ◽  
Vancouver Island ◽  
Dimensional Structure ◽  
System Of Nonlinear Equations ◽  
Model Parameters ◽  
Three Dimensional Structure ◽  
Velocity Gradients ◽  
On Line

A seismic-reflection survey was carried out on Vancouver Island as part of Lithoprobe – Phase I to study the crustal structure and tectonics of this convergent margin. Four seismic profiles, which provided structural and velocity information using standard common-depth-point stacking, were shot. The lines were crooked; hence, this approach does not give one full confidence in the results obtained. However, because of the crookedness of the lines, the reflection points were located in three-dimensional space; therefore, it was possible to obtain the three-dimensional structure of the subsurface.Since the traveltime is a nonlinear function of model parameters, an iterative, damped least-squares technique is used to obtain three-dimensional structure and velocity with gradients. The ray tracing is performed for each shot–receiver pair by solving a system of nonlinear equations. In constant-velocity media the raypath is a straight line, whereas in media with velocity varying linearly with depth the raypath follows the arc of a circle. The interfaces are defined by polynomial surfaces where the raypaths satisfy Snell's law.The method was tested for a synthetic model: it was fast and effective. Then the method was applied to a small portion of line 1 to obtain velocity gradients and three-dimensional structures of the décollement and subduction zones. For reflector C on line 1 at an approximate depth of 15 km the velocity at the top of the horizon is found to be 6.8 km/s, with a gradient of 0.034 km/s per km. The dip and strike are 3 °and N18°E, respectively. For reflector E on line 1 at an approximate depth of 28 km the velocity at the top of the horizon is found to be 7.8 km/s. The dip and strike are 8.9 °and N65°E, respectively. To obtain more precise results, efforts should be made to record at wider angles of incidence.

scholarly journals The Ambiguity Issue in Solving Inverse Problems of Small-Angle Scattering: A Consistent Approach Using an Insulin Receptor-Related Receptor as an Example. Methods for Interpreting SAXS Data

2021 ◽  
Vol 15 (3) ◽  
pp. 270-283
Author(s):  
M. V. Petoukhov ◽  
P. V. Konarev ◽  
V. V. Volkov ◽  
A. A. Mozhaev ◽  
E. V. Shtykova
Keyword(s):  
Inverse Problems ◽  
Insulin Receptor ◽  
Small Angle ◽  
Three Dimensional ◽  
Small Angle Scattering ◽  
Dimensional Structure ◽  
Model Parameters ◽  
Three Dimensional Structure ◽  
Angle Scattering ◽  
Consistent Approach

Abstract The construction of three-dimensional models of protein macromolecules is a serious challenge due to the possible ambiguity of solving the inverse problem of reconstructing a three-dimensional structure from a one-dimensional small-angle scattering profile. The target function of this task can have several local minima, which leads to the dependence of the solution on the initial values of the model parameters and on the method of finding the global minimum. The problem of creating structural models is also complicated by averaging the scattering pattern over all orientations of particles in space and by the size and shape distribution of scattering objects in the case of polydispersity and/or polymorphism. In this study, the issue of ambiguity in solving inverse problems and restoring the three-dimensional structure of a protein is considered using the structure of the ectodomain of an insulin receptor-related receptor (ectoIRR) in solution as an example. The paper presents a consistent approach to solving this problem, starting from the determination of general structural parameters and ab initio reconstruction of shape to modeling by rigid bodies (using molecular tectonics), hybrid methods, and analysis of scattering profiles by singular vector decomposition.

The Three-dimensional structure of frozen-hydrated nudaurelia capensis β virus

1987 ◽  
Vol 45 ◽  
pp. 650-651
Author(s):  
N. H. Olson ◽  
T. S. Baker ◽  
Wu Bo Mu ◽  
J. E. Johnson ◽  
D. A. Hendry
Keyword(s):  
South African ◽  
Rna Virus ◽  
Carbon Film ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Electron Dose ◽  
Total Electron ◽  
Three Dimensional Structure ◽  
Negative Stain ◽  
Dimensional Reconstruction

Nudaurelia capensis β virus (NβV) is an RNA virus of the South African Pine Emperor moth, Nudaurelia cytherea capensis (Lepidoptera: Saturniidae). The NβV capsid is a T = 4 icosahedron that contains 60T = 240 subunits of the coat protein (Mr = 61,000). A three-dimensional reconstruction of the NβV capsid was previously computed from visions embedded in negative stain suspended over holes in a carbon film. We have re-examined the three-dimensional structure of NβV, using cryo-microscopy to examine the native, unstained structure of the virion and to provide a initial phasing model for high-resolution x-ray crystallographic studiesNβV was purified and prepared for cryo-microscopy as described. Micrographs were recorded ∼1 - 2 μm underfocus at a magnification of 49,000X with a total electron dose of about 1800 e-/nm2.

Three Dimensional structure and organization of diploid chromosomes by optical section microscopy

1987 ◽  
Vol 45 ◽  
pp. 633-635
Author(s):  
David A. Agard ◽  
Yasushi Hiraoka ◽  
John W. Sedat
Keyword(s):  
Dimensional Space ◽  
Three Dimensional ◽  
Developmental State ◽  
Mitotic Cell ◽  
Biological Properties ◽  
Dimensional Structure ◽  
Specific Gene ◽  
Three Dimensional Structure ◽  
Complementary Techniques ◽  
Dynamic Structures

In an effort to understand the complex relationship between structure and biological function within the nucleus, we have embarked on a program to examine the three-dimensional structure and organization of Drosophila melanogaster embryonic chromosomes. Our overall goal is to determine how DNA and proteins are organized into complex and highly dynamic structures (chromosomes) and how these chromosomes are arranged in three dimensional space within the cell nucleus. Futher, we hope to be able to correlate structual data with such fundamental biological properties as stage in the mitotic cell cycle, developmental state and transcription at specific gene loci.Towards this end, we have been developing methodologies for the three-dimensional analysis of non-crystalline biological specimens using optical and electron microscopy. We feel that the combination of these two complementary techniques allows an unprecedented look at the structural organization of cellular components ranging in size from 100A to 100 microns.

Three-Dimensional Structure of Cloned T3 Connector Protein at 1.6nm Resolution

1990 ◽  
Vol 48 (1) ◽  
pp. 282-283
Author(s):  
José L. Carrascosa ◽  
José M. Valpuesta ◽  
Hisao Fujisawa
Keyword(s):  
Dna Sequences ◽  
Expression Vector ◽  
Three Dimensional ◽  
Deae Cellulose ◽  
Dna Packaging ◽  
Dimensional Structure ◽  
Two Dimensional ◽  
Freezing And Thawing ◽  
Three Dimensional Structure ◽  
Dimensional Reconstruction

The head to tail connector of bacteriophages plays a fundamental role in the assembly of viral heads and DNA packaging. In spite of the absence of sequence homology, the structure of connectors from different viruses (T4, Ø29, T3, P22, etc) share common morphological features, that are most clearly revealed in their three-dimensional structure. We have studied the three-dimensional reconstruction of the connector protein from phage T3 (gp 8) from tilted view of two dimensional crystals obtained from this protein after cloning and purification.DNA sequences including gene 8 from phage T3 were cloned, into Bam Hl-Eco Rl sites down stream of lambda promotor PL, in the expression vector pNT45 under the control of cI857. E R204 (pNT89) cells were incubated at 42°C for 2h, harvested and resuspended in 20 mM Tris HC1 (pH 7.4), 7mM 2 mercaptoethanol, ImM EDTA. The cells were lysed by freezing and thawing in the presence of lysozyme (lmg/ml) and ligthly sonicated. The low speed supernatant was precipitated by ammonium sulfate (60% saturated) and dissolved in the original buffer to be subjected to gel nitration through Sepharose 6B, followed by phosphocellulose colum (Pll) and DEAE cellulose colum (DE52). Purified gp8 appeared at 0.3M NaCl and formed crystals when its concentration increased above 1.5 mg/ml.

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