A new regional hypocenter location method

1996 ◽  
Vol 86 (4) ◽  
pp. 946-958
Author(s):  
Zhi Xie ◽  
Terry W. Spencer ◽  
Philip D. Rabinowitz ◽  
Davis A. Fahlquist
Keyword(s):  
Data Center ◽  
Unknown Parameter ◽  
Velocity Structure ◽  
Synthetic Data ◽  
New Method ◽  
Location Problems ◽  
Location Method ◽  
Hypocenter Location ◽  
New Locations ◽  
Velocity Information

Abstract A new regional hypocenter location method is presented in this article to address location problems associated with sparse station distributions and lack of velocity information. For an arbitrary slowness structure, an unknown parameter, slowness deviation, is introduced to construct a more precise slowness model than a homogeneous slowness model. By incorporating a genetic algorithm, the new method yields reasonable solutions for epicenters and origin times both inside and outside the seismic network. The synthetic data tests indicate that outside the network the new method gives excellent results for epicenter locations compared with Geiger's method, even when Geiger's method is used with the true velocity structure. The relocation of the Loma Prieta mainshock and 26 aftershocks occurring within the first 24 h after the mainshock by using the new hypocenter location method places the aftershocks an average of 2.29 km to the southwest of the locations published by the Northern California Earthquake Data Center. The new locations are in better agreement with the geodetic measurements.

Anisotropic Statistics of Lagrangian Structure Functions and Helmholtz Decomposition

2021 ◽  
Vol 51 (5) ◽  
pp. 1375-1393
Author(s):  
Han Wang ◽  
Oliver Bühler
Keyword(s):  
Velocity Structure ◽  
Synthetic Data ◽  
Structure Functions ◽  
Separation Distance ◽  
New Method ◽  
Helmholtz Decomposition ◽  
Spatial Homogeneity ◽  
Divergent Flow ◽  
Cross Covariance ◽  
Flow Components

AbstractWe present a new method to estimate second-order horizontal velocity structure functions, as well as their Helmholtz decomposition into rotational and divergent components, from sparse data collected along Lagrangian observations. The novelty compared to existing methods is that we allow for anisotropic statistics in the velocity field and also in the collection of the Lagrangian data. Specifically, we assume only stationarity and spatial homogeneity of the data and that the cross covariance between the rotational and divergent flow components is either zero or a function of the separation distance only. No further assumptions are made and the anisotropy of the underlying flow components can be arbitrarily strong. We demonstrate our new method by testing it against synthetic data and applying it to the Lagrangian Submesoscale Experiment (LASER) dataset. We also identify an improved statistical angle-weighting technique that generally increases the accuracy of structure function estimations in the presence of anisotropy.

Anisotropic statistics of Lagrangian structure functions and Helmholtz decomposition

2021 ◽  
Author(s):  
Han Wang ◽  
Oliver Bühler
Keyword(s):  
Velocity Structure ◽  
Synthetic Data ◽  
Structure Functions ◽  
Second Order ◽  
New Method ◽  
Helmholtz Decomposition ◽  
Data Sets ◽  
Geostrophic Balance ◽  
Surface Drifter ◽  
Rotational Components

<p>Second-order velocity structure functions are commonly estimated from Lagrangian tracer trajectories.  A Helmholtz decomposition of these structure functions, which separates their divergent and rotational components, can indicate the robustness of geostrophic balance at different scales, and serves as a building block for analysis of scale-dependent energy distributions. We present a new method to estimate second-order horizontal velocity structure functions, as well as their Helmholtz decomposition, from sparse data collected by Lagrangian observations.   The novelty compared to existing methods is that we allow for anisotropic statistics in the velocity field as well as in the distribution of the Lagrangian trackers. We conduct the analysis through the lens of azimuthal Fourier expansions, and find Helmholtz decomposition formulae targeted at individual Fourier modes. We also identify an improved statistical angle-weighting technique that generally increases the accuracy of structure function estimations in the presence of anisotropy. The new methods are tested against synthetic data and applied to surface drifter data sets such as LASER and GLAD. Importantly, the new method does not require extra measurements compared to existing methods based on isotropy.</p>

A New Location Method of ROI for Contactless Palm Vein Recognition

2013 ◽  
Vol 760-762 ◽  
pp. 1398-1401
Author(s):  
Wei Wu ◽  
Wei Qi Yuan ◽  
Hui Song
Keyword(s):  
Pattern Recognition ◽  
Recognition Rate ◽  
New Method ◽  
Vein Pattern ◽  
Location Method ◽  
Vein Recognition ◽  
Palm Vein ◽  
New Location

Palm vein pattern recognition is one of the newest biometric techniques researched today.At present, literatures selecte the center of the palm as the ROI of palm vein recognition. However the vein image in this area is not clear in some peoples palm. In this paper, we proposed a new location method of ROI which takes thenar area as the ROI. In the experiment part, it compares the recognition rate between the new and the traditional ROI in self-established contactless palm vein database. The result shows that this new method has got the recognition rate of 98.9258% and has increased recognition rate 2.0911% compared with the traditional one.

scholarly journals Using control charts for on-line video summarisation

2019 ◽  
Vol 277 ◽  
pp. 01012 ◽  
Author(s):  
Clare E. Matthews ◽  
Paria Yousefi ◽  
Ludmila I. Kuncheva
Keyword(s):  
Feature Extraction ◽  
Control Chart ◽  
Control Charts ◽  
State Of The Art ◽  
Synthetic Data ◽  
New Method ◽  
Data Sets ◽  
On Line ◽  
Memory Constraints ◽  
Video Summarisation

Many existing methods for video summarisation are not suitable for on-line applications, where computational and memory constraints mean that feature extraction and frame selection must be simple and efficient. Our proposed method uses RGB moments to represent frames, and a control-chart procedure to identify shots from which keyframes are then selected. The new method produces summaries of higher quality than two state-of-the-art on-line video summarisation methods identified as the best among nine such methods in our previous study. The summary quality is measured against an objective ideal for synthetic data sets, and compared to user-generated summaries of real videos.

THE DEVELOPMENT OF A NEW METHOD OF SEISMIC VELOCITY DETERMINATION

Geophysics ◽  
1952 ◽  
Vol 17 (3) ◽  
pp. 560-574 ◽  
Author(s):  
F. P. Kokesh
Keyword(s):  
Conventional Method ◽  
Explosive Charge ◽  
Velocity Measurement ◽  
Seismic Velocity ◽  
Seismic Energy ◽  
New Method ◽  
Seismic Velocities ◽  
The Past ◽  
Velocity Information ◽  
Made In

The conventional method of making velocity surveys in bore holes is inherently expensive, time consuming, and inconvenient, and has a tendency towards non‐uniformity of results. With increasing recognition of the importance of seismic velocity information in the evaluation of seismograph data, the attention of geophysicists is turning towards means of overcoming the obstacles standing in the way of obtaining velocity information in greater volume. Considerable interest has recently been aroused in a new method of measuring seismic velocities wherein the explosive charge is placed in the hole and the seismic energy is picked up with multiple detector groups placed on the surface. Experimentation carried on during the past year indicates that the new method is quite workable. Casing perforator guns of the conventional bullet type have given results to depths exceeding 8,000 ft. with complete safety. Some experimentation with primacord as the explosive has given encouragement as a means of increasing the depth at which the method may be used. Substantial improvements have been made in the manner of obtaining the time break. This paper attempts to outline the basic problems of velocities and their measurement and describes the preliminary development that has been done thus far on the new method of velocity measurement.

Seismic tomography studies of cover thickness and near-surface bedrock velocities

Geophysics ◽  
2006 ◽  
Vol 71 (6) ◽  
pp. U77-U84 ◽  
Author(s):  
B. Bergman ◽  
A. Tryggvason ◽  
C. Juhlin
Keyword(s):  
Nuclear Waste ◽  
Velocity Structure ◽  
Synthetic Data ◽  
General Situation ◽  
Seismic Profiles ◽  
Low Velocity ◽  
Near Surface ◽  
Reflection Seismic ◽  
Crystalline Bedrock ◽  
Cover Thickness

Reflection seismic imaging of the uppermost kilometer of crystalline bedrock is an important component in site surveys for locating potential storage sites for nuclear waste in Sweden. To obtain high-quality images, refraction statics are calculated using first-break traveltimes. These first-break picks may also be used to produce tomographic velocity images of the uppermost bedrock. In an earlier study, we presented a method applicable to data sets where the vast majority of shots are located in the bedrock below the glacial deposits, or cover, typical for northern latitudes. A by-product of this method was an estimate of the cover thickness from the receiver static that was introduced to sharpen the image. We now present a modified version of this method that is applicable for sources located in or on the cover, the general situation for nuclear waste site surveys. This modified methodalso solves for 3D velocity structure and static correctionssimultaneously in the inversion process. The static corrections can then be used to estimate the cover thickness. First, we test our tomography method on synthetic data withthe shot points in the bedrock below the cover. Next, we developa strategy for the case when the sources are within the cover. Themethod is then applied to field data from five crooked-line,high-resolution reflection seismic profiles ranging in lengthfrom 2 to [Formula: see text]. The crooked-line profiles make the study 2.5dimensional regarding bedrock velocities. The cover thicknessalong the profiles varies from 0 to [Formula: see text]. Estimated thickness ofthe cover agrees well with data from boreholes drilled near theprofiles. Low-velocity zones in the uppermost bedrock generallycorrelate with locations where reflections from the stackedsections project to the surface. Thus, the method is functional,both for imaging the uppermost bedrock velocities as well as for estimating the cover thickness.

scholarly journals A new method for the in vivo identification of degenerated material property ranges of the human eye: feasibility analysis based on synthetic data

2021 ◽  
Author(s):  
Stefan Muench ◽  
Mike Roellig ◽  
Daniel Balzani
Keyword(s):  
Real Time ◽  
Test Data ◽  
Synthetic Data ◽  
New Method ◽  
Data Sets ◽  
New Approach ◽  
Full Field ◽  
Material Parameters ◽  
Virtual Test

AbstractThis paper proposes a new method for in vivo and almost real-time identification of biomechanical properties of the human cornea based on non-contact tonometer data. Further goal is to demonstrate the method’s functionality based on synthetic data serving as reference. For this purpose, a finite element model of the human eye is constructed to synthetically generate full-field displacements from different data sets with keratoconus-like degradations. Then, a new approach based on the equilibrium gap method combined with a mechanical morphing approach is proposed and used to identify the material parameters from virtual test data sets. In a further step, random absolute noise is added to the virtual test data to investigate the sensitivity of the new approach to noise. As a result, the proposed method shows a relevant accuracy in identifying material parameters based on full-field displacements. At the same time, the method turns out to work almost in real time (order of a few minutes on a regular workstation) and is thus much faster than inverse problems solved by typical forward approaches. On the other hand, the method shows a noticeable sensitivity to rather small noise amplitudes rendering the method not accurate enough for the precise identification of individual parameter values. However, analysis show that the accuracy is sufficient for the identification of property ranges which might be related to diseased tissues. Thereby, the proposed approach turns out promising with view to diagnostic purposes.

Crosswell monitoring using virtual sources and horizontal wells

Geophysics ◽  
2010 ◽  
Vol 75 (3) ◽  
pp. SA37-SA43 ◽  
Author(s):  
Joongmoo Byun ◽  
Jeongmin Yu ◽  
Soon Jee Seol
Keyword(s):  
Heavy Oil ◽  
Synthetic Data ◽  
Horizontal Wells ◽  
Time Lapse ◽  
Potential Change ◽  
New Method ◽  
Virtual Source ◽  
Vertical Wells ◽  
Monitoring Method ◽  
First Arrival

Time-lapse crosswell seismic provides an efficient way to monitor the migration of a [Formula: see text] plume or its leakage after [Formula: see text] injection into a geologic formation. Recently, crosswell seismic has become a powerful tool for monitoring underground variations, using the concept of a virtual source, with virtual sources positioned at the receivers installed in the well and thus the positions of sources and receivers can be invariant during monitoring. However, time-lapse crosswell seismic using vertical wells and virtual sources has difficulty in describing the front of a [Formula: see text] plume, which usually is parallel to the vertical wells, and in obtaining sufficient ray coverage for the first-arrival tomography. These problems arise because of the theoretical downward-illumination-directivity limitation of the virtual source. We have developed an effective monitoring method that uses virtual sources and two horizontal wells: one above and one below the [Formula: see text]sequestration reservoir. In our method, we redatum the traces that are recorded at geophones in horizontal wells from sources on the surface. The redatumed traces then become virtual traces recorded at geophones in the lower well and sent from virtual sources at the positions of the geophones in the upper well. The geometry of our method has advantages for locating the front of the [Formula: see text] plume, which is normal to the horizontal wells, compared with either real or virtual sources. The method also is advantageous in acquiring full ray coverage between the wells, and that coverage is superior to coverage acquired using vertical crosswell seismic with virtual sources. In addition, we can avoid problems related to any potential change in the medium above the reservoir and in the source and receiver positions. The results of applying our method to synthetic data that simulate [Formula: see text]-sequestration monitoring show that the front of a [Formula: see text] plume in the reservoir is depicted accurately in a velocity tomogram. The new method also can be used to monitor a reservoir during production of heavy oil.

Seismic envelope inversion and modulation signal model

Geophysics ◽  
2014 ◽  
Vol 79 (3) ◽  
pp. WA13-WA24 ◽  
Author(s):  
Ru-Shan Wu ◽  
Jingrui Luo ◽  
Bangyu Wu
Keyword(s):  
Velocity Structure ◽  
Waveform Inversion ◽  
Synthetic Data ◽  
Low Frequency ◽  
Seismic Signal ◽  
Source Spectrum ◽  
Signal Model ◽  
Waveform Data ◽  
Long Wavelength ◽  
Modulation Signal

We recognized that the envelope fluctuation and decay of seismic records carries ultra low-frequency (ULF, i.e., the frequency below the lowest frequency in the source spectrum) signals that can be used to estimate the long-wavelength velocity structure. We then developed envelope inversion for the recovery of low-wavenumber components of media (smooth background), so that the initial model dependence of waveform inversion can be reduced. We derived the misfit function and the corresponding gradient operator for envelope inversion. To understand the long-wavelength recovery by the envelope inversion, we developed a nonlinear seismic signal model, the modulation signal model, as the basis for retrieving the ULF data and studied the nonlinear scale separation by the envelope operator. To separate the envelope data from the wavefield data (envelope extraction), a demodulation operator (envelope operator) was applied to the waveform data. Numerical tests using synthetic data for the Marmousi model proved the validity and feasibility of the proposed approach. The final results of combined [Formula: see text] (envelope-inversion for smooth background plus waveform-inversion for high-resolution velocity structure) indicated that it can deliver much improved results compared with regular full-waveform inversion (FWI) alone. Furthermore, to test the independence of the envelope to the source frequency band, we used a low-cut source wavelet (cut from 5 Hz below) to generate the synthetic data. The envelope inversion and the combined [Formula: see text] showed no appreciable difference from the full-band source results. The proposed envelope inversion is also an efficient method with very little extra work compared with conventional FWI.

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