Earthquake relative location based on waveform similarity

1994 ◽  
Vol 233 (3-4) ◽  
pp. 253-263 ◽  
Author(s):  
J. Mezcua ◽  
J. Rueda
Keyword(s):  
Relative Location ◽  
Waveform Similarity

High-precision, absolute earthquake location based on waveform similarity between events and application to imaging foreshocks, fault complexity and damage zones for recent western US earthquakes.

2021 ◽  
Author(s):  
Anthony Lomax ◽  
Pierre Henry ◽  
Sophie Viseur
Keyword(s):  
High Precision ◽  
Shear Crack ◽  
Earthquake Location ◽  
Relative Location ◽  
Target Event ◽  
3D Space ◽  
Crack System ◽  
Western Us ◽  
Stress Changes ◽  
Waveform Similarity

<p>We present a high-precision, absolute earthquake location procedure (NLL-SSST-coherence) based on waveform similarity between events and using the probabilistic, global-search NonLinLoc (NLL) location algorithm. NLL defines a posterior probability density function (PDF) in 3D space for absolute hypocenter location and invokes the equal differential-time (EDT) likelihood function which is very robust in the presence of outlier data. For NLL-SSST-coherence location we take initial NLL locations and iteratively generate smooth, 3D, source-specific, station travel-time corrections (SSST) for each station and phase type and an updated set of locations. Next, we greatly reduce absolute location, aleatoric error by combining location information across events based on waveform coherency between the events. This absolute coherency relocation is based on the concept that if the waveforms at a station for two or more events are very similar (have high coherency) up to a given frequency, then the distance separating these “multiplet” events is small relative to the seismic wavelength at that frequency. The NLL coherency relocation for a target event is a stack over 3D space of the event’s SSST location PDF and the SSST PDF’s for other similar events, each weighted by the waveform coherency between the target event and the other event. Absolute coherency relocation requires waveforms from only one or a few stations, allowing precise relocation for sparse networks, and for foreshocks and early aftershocks of a mainshock sequence or swarm before temporary stations are installed.</p><p>We apply the NLL-SSST-coherence procedure to the Mw5.8 Lone Pine CA, Mw5.7 Magna UT and Mw6.4 Monte Cristo NV earthquake sequences in 2020 and compare with other absolute and relative seismicity catalogs for these events. The NLL-SSST-coherence relocations generally show increased organization, clustering and depth resolution over other absolute location catalogs. The NLL-SSST-coherence relocations reflect well smaller scale patterns and features in relative location catalogs, with evidence of improved depth precision and accuracy over relative location results when there are no stations over or near the seismicity.</p><p>For all three western US sequences in 2020 the NLL-SSST-coherence relocations show mainly sparse clusters of seismicity. We interpret these clusters as damage zones around patches of principal mainshock slip containing few events, larger scale damage zone and splay structures around main slip patches, and background seismicity reactivated by stress changes from mainshock rupture. The Monte Cristo Range seismicity (Lomax 2020) shows two, en-echelon primary slip surfaces and surrounding, characteristic shear-crack features such as edge, wall, tip, and linking damage zones, showing that this sequence ruptured a complete shear crack system. See presentation EGU21-13447 for more details.</p><p>Lomax (2020) The 2020 Mw6.5 Monte Cristo NV earthquake: relocated seismicity shows rupture of a complete shear-crack system. Preprint: https://eartharxiv.org/repository/view/1904</p><p> </p>

Using waveform similarity to constrain earthquake locations

1999 ◽  
Vol 89 (4) ◽  
pp. 1143-1146 ◽  
Author(s):  
William Menke
Keyword(s):  
Travel Time ◽  
Multiple Scattering ◽  
Cross Correlation ◽  
Relative Location ◽  
Travel Times ◽  
Scattering Process ◽  
Earthquake Relocation ◽  
Earthquake Locations ◽  
Waveform Similarity ◽  
The Cross

Abstract We demonstrate that the numerical value of the cross-correlation between P or S waveforms, commonly computed to determine differential travel times for earthquake relocation, itself contains useful information about the relative location of the events. This information can be used to supplement traditional travel-time inversions (especially when few stations are available) and to investigate the heterogeneity that underlies the multiple scattering process.

Crosstalk Minimization Method for Eye-tracking-based 3D Display

2020 ◽  
Author(s):  
Seok Lee ◽  
Juyong Park ◽  
Dongkyung Nam
Keyword(s):  
Image Processing ◽  
Eye Tracking ◽  
Three Dimensional ◽  
Processing Method ◽  
Eye Position ◽  
Relative Location ◽  
3D Display ◽  
Minimization Method ◽  
3D Crosstalk ◽  
Pixel Value

In this article, the authors present an image processing method to reduce three-dimensional (3D) crosstalk for eye-tracking-based 3D display. Specifically, they considered 3D pixel crosstalk and offset crosstalk and applied different approaches based on its characteristics. For 3D pixel crosstalk which depends on the viewer’s relative location, they proposed output pixel value weighting scheme based on viewer’s eye position, and for offset crosstalk they subtracted luminance of crosstalk components according to the measured display crosstalk level in advance. By simulations and experiments using the 3D display prototypes, the authors evaluated the effectiveness of proposed method.

Functions of Same-Tracking

2017 ◽  
Author(s):  
Ruth Garrett Millikan
Keyword(s):  
Relative Location ◽  
Perceptual Constancy ◽  
Object Constancy ◽  
The Difference

There are non-uniceptual same-tracking mechanisms, mechanisms that same-track not in order to implement storage of information about their targets, but merely as an aid to the identification of further things. Examples are the various mechanisms of perceptual constancy, self-relative location trackers, object-constancy mechanisms, and same-trackers for real categories. There are also several kinds of unicepts, hence, of unitrackers, procedural, substantive, attributive. What begins as a non-uniceptual same-tracker might or might not be redeployed to serve also as a procedural unitracker, or a procedural unitracker might be redeployed to serve also as a substance unitracker or an attribute unitracker. This is possible because the difference between affordances, substances, and attributes is not a basic ontological distinction but is relative to cognitive use.

scholarly journals Duplicate Detection of Spike Events: A Relevant Problem in Human Single-Unit Recordings

2021 ◽  
Vol 11 (6) ◽  
pp. 761
Author(s):  
Gert Dehnen ◽  
Marcel S. Kehl ◽  
Alana Darcher ◽  
Tamara T. Müller ◽  
Jakob H. Macke ◽  
...  
Keyword(s):  
Data Quality ◽  
Single Unit ◽  
Human Subjects ◽  
External Noise ◽  
Hospital Environment ◽  
Noise Sources ◽  
Recording Channels ◽  
Waveform Similarity ◽  
Therapeutic Procedures ◽  
Single Unit Recordings

Single-unit recordings in the brain of behaving human subjects provide a unique opportunity to advance our understanding of neural mechanisms of cognition. These recordings are exclusively performed in medical centers during diagnostic or therapeutic procedures. The presence of medical instruments along with other aspects of the hospital environment limit the control of electrical noise compared to animal laboratory environments. Here, we highlight the problem of an increased occurrence of simultaneous spike events on different recording channels in human single-unit recordings. Most of these simultaneous events were detected in clusters previously labeled as artifacts and showed similar waveforms. These events may result from common external noise sources or from different micro-electrodes recording activity from the same neuron. To address the problem of duplicate recorded events, we introduce an open-source algorithm to identify these artificial spike events based on their synchronicity and waveform similarity. Applying our method to a comprehensive dataset of human single-unit recordings, we demonstrate that our algorithm can substantially increase the data quality of these recordings. Given our findings, we argue that future studies of single-unit activity recorded under noisy conditions should employ algorithms of this kind to improve data quality.

scholarly journals Variation of the Three-Dimensional Femoral J-Curve in the Native Knee

2021 ◽  
Vol 11 (7) ◽  
pp. 592
Author(s):  
Sonja A. G. A. Grothues ◽  
Klaus Radermacher
Keyword(s):  
Geometric Parameter ◽  
Knee Kinematics ◽  
Size Variation ◽  
Principal Component ◽  
Parameter Analysis ◽  
Patient Specific ◽  
3D Analysis ◽  
Relative Location ◽  
Shape Variation ◽  
J Curve

The native femoral J-Curve is known to be a relevant determinant of knee biomechanics. Similarly, after total knee arthroplasty, the J-Curve of the femoral implant component is reported to have a high impact on knee kinematics. The shape of the native femoral J-Curve has previously been analyzed in 2D, however, the knee motion is not planar. In this study, we investigated the J-Curve in 3D by principal component analysis (PCA) and the resulting mean shapes and modes by geometric parameter analysis. Surface models of 90 cadaveric femora were available, 56 male, 32 female and two without respective information. After the translation to a bone-specific coordinate system, relevant contours of the femoral condyles were derived using virtual rotating cutting planes. For each derived contour, an extremum search was performed. The extremum points were used to define the 3D J-Curve of each condyle. Afterwards a PCA and a geometric parameter analysis were performed on the medial and lateral 3D J-Curves. The normalized measures of the mean shapes and the aspects of shape variation of the male and female 3D J-Curves were found to be similar. When considering both female and male J-Curves in a combined analysis, the first mode of the PCA primarily consisted of changes in size, highlighting size differences between female and male femora. Apart from changes in size, variation regarding aspect ratio, arc lengths, orientation, circularity, as well as regarding relative location of the 3D J-Curves was found. The results of this study are in agreement with those of previous 2D analyses on shape and shape variation of the femoral J-Curves. The presented 3D analysis highlights new aspects of shape variability, e.g., regarding curvature and relative location in the transversal plane. Finally, the analysis presented may support the design of (patient-specific) femoral implant components for TKA.

The 3rd ACM SIGSPATIAL International Workshop on Geospatial Simulation

2021 ◽  
Vol 12 (3) ◽  
pp. 11-14
Author(s):  
Joon-Seok Kim ◽  
Taylor Anderson ◽  
Ashwin Shashidharan ◽  
Andreas Züfle
Keyword(s):  
Spatial Data ◽  
International Workshop ◽  
Data Sources ◽  
Relative Location ◽  
Technological Changes ◽  
Research Opportunities ◽  
New Methodologies ◽  
New Research

Space has long been acknowledged by researchers as a fundamental constraint which shapes our world. As technological changes have transformed the very concept of distance, the relative location and connectivity of geospatial phenomena have remained stubbornly significant in how systems function. At the same time, however, technology has advanced the science of geospatial simulation to bear on our understanding of how such systems work. While previous generations of scientists and practitioners were unable to gather spatial data or to incorporate it into models at any meaningful scale, new methodologies and data sources are becoming increasingly available to researchers, developers, users, and practitioners. These developments present new research opportunities for geospatial simulation.

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