scholarly journals A method to fuse multiphysics waveforms and improve predictive explosion detection: theory, experiment and performance

2020 ◽  
Vol 222 (2) ◽  
pp. 1195-1212 ◽  
Author(s):  
Joshua Carmichael ◽  
Robert Nemzek ◽  
Neill Symons ◽  
Mike Begnaud
Keyword(s):  
Constructive Method ◽  
Density Functions ◽  
Baseline Method ◽  
Waveform Data ◽  
Explosion Monitoring ◽  
Seismic Waveform ◽  
Transient Energy ◽  
Fisher's Method ◽  
And Performance ◽  
Fisher’S Method

SUMMARY Natural and human-made sources of transient energy often emit multiple geophysical signatures that include mechanical and electromagnetic waveforms. We present a constructive method to fuse and evaluate statistics that we derive from such multiphysics waveforms that improves our capability to detect small, near-ground explosions over similar methods that consume single signature waveforms. Our method advances Fisher's Combined Probability Test (Fisher's Method) to operate under both hypotheses of a binary test on noisy data and provide researchers with the density functions required to forecast the ability of Fisher's Method to screen fused explosion signatures from noise. We apply this method against 12 d, multisignature explosion and noise records to show (1) that a fused multiphysics waveform statistic that combines radio, acoustic and seismic waveform data can identify explosions roughly 0.8 magnitude units lower than an acoustic emission, STA/LTA detector for the same detection probability and (2) that we can quantitatively predict how this fused, multiphysics statistic performs with Fisher's Method. Our work thereby offers a baseline method for predictive waveform fusion that supports multiphenomenological explosion monitoring (multiPEM) and is applicable to any binary testing problem in observational geophysics.

scholarly journals Batch seismic inversion using the iterative ensemble Kalman smoother

2021 ◽  
Author(s):  
Michael Gineste ◽  
Jo Eidsvik
Keyword(s):  
Seismic Data ◽  
Time Windows ◽  
Seismic Inversion ◽  
Efficient Estimation ◽  
Solution Strategy ◽  
Adaptive Procedure ◽  
Waveform Data ◽  
Kalman Smoother ◽  
Seismic Waveform ◽  
Single Batch

AbstractAn ensemble-based method for seismic inversion to estimate elastic attributes is considered, namely the iterative ensemble Kalman smoother. The main focus of this work is the challenge associated with ensemble-based inversion of seismic waveform data. The amount of seismic data is large and, depending on ensemble size, it cannot be processed in a single batch. Instead a solution strategy of partitioning the data recordings in time windows and processing these sequentially is suggested. This work demonstrates how this partitioning can be done adaptively, with a focus on reliable and efficient estimation. The adaptivity relies on an analysis of the update direction used in the iterative procedure, and an interpretation of contributions from prior and likelihood to this update. The idea is that these must balance; if the prior dominates, the estimation process is inefficient while the estimation is likely to overfit and diverge if data dominates. Two approaches to meet this balance are formulated and evaluated. One is based on an interpretation of eigenvalue distributions and how this enters and affects weighting of prior and likelihood contributions. The other is based on balancing the norm magnitude of prior and likelihood vector components in the update. Only the latter is found to sufficiently regularize the data window. Although no guarantees for avoiding ensemble divergence are provided in the paper, the results of the adaptive procedure indicate that robust estimation performance can be achieved for ensemble-based inversion of seismic waveform data.

scholarly journals Iterative Algorithm for Parameterization of Two-Region Piecewise Uniform Quantizer for the Laplacian Source

Mathematics ◽  
2021 ◽  
Vol 9 (23) ◽  
pp. 3091
Author(s):  
Jelena Nikolić ◽  
Danijela Aleksić ◽  
Zoran Perić ◽  
Milan Dinčić
Keyword(s):  
Neural Networks ◽  
Performance Assessment ◽  
Probability Density ◽  
Probability Density Functions ◽  
Density Functions ◽  
Uniform Quantization ◽  
Memory Footprint ◽  
High Bit Rates ◽  
And Performance ◽  
Laplacian Distribution

Motivated by the fact that uniform quantization is not suitable for signals having non-uniform probability density functions (pdfs), as the Laplacian pdf is, in this paper we have divided the support region of the quantizer into two disjunctive regions and utilized the simplest uniform quantization with equal bit-rates within both regions. In particular, we assumed a narrow central granular region (CGR) covering the peak of the Laplacian pdf and a wider peripheral granular region (PGR) where the pdf is predominantly tailed. We performed optimization of the widths of CGR and PGR via distortion optimization per border–clipping threshold scaling ratio which resulted in an iterative formula enabling the parametrization of our piecewise uniform quantizer (PWUQ). For medium and high bit-rates, we demonstrated the convenience of our PWUQ over the uniform quantizer, paying special attention to the case where 99.99% of the signal amplitudes belong to the support region or clipping region. We believe that the resulting formulas for PWUQ design and performance assessment are greatly beneficial in neural networks where weights and activations are typically modelled by the Laplacian distribution, and where uniform quantization is commonly used to decrease memory footprint.

Repeating Earthquakes Along the Colombian Subduction Zone

2020 ◽  
Vol 15 (5) ◽  
pp. 645-654
Author(s):  
Juan Carlos Bermúdez-Barrios ◽  
◽  
Hiroyuki Kumagai
Keyword(s):  
Subduction Zone ◽  
Threshold Value ◽  
Waveform Data ◽  
Repeating Earthquakes ◽  
Seismic Waveform ◽  
Interplate Coupling ◽  
Short Period ◽  
Tectonically Active ◽  
Waveform Similarity ◽  
Large Earthquakes

Colombia is tectonically active, and several large earthquakes have ruptured the Colombia-Ecuador subduction zone (CESZ) during the last century. Among them, the Colombia-Ecuador earthquake in 1906 (Mw 8.4) and the Tumaco earthquake in 1979 (Mw 8.3) generated destructive tsunamis. Therefore, it is important to characterize the seismic rupture processes and their relation with interplate coupling along the CESZ. We searched for repeating earthquakes by performing waveform similarity analysis. Cross correlation (CC) values were computed between earthquake pairs with hypocenter differences of less than 50 km that were located in the northern CESZ (1°–4°N) and that occurred from June 1993 to February 2018. We used broadband and short-period seismic waveform data from the Servicio Geológico Colombiano (SGC) seismic network. A CC threshold value of 0.90 was used to identify the waveform similarity and select repeating earthquakes. We found repeating earthquakes distributed near the trench and the coast. Our estimated repeating earthquakes near the trench suggest that the interplate coupling in this region is low. This is in clear constrast to the occurrence of a large slip in the 1906 Colombia-Ecuador earthquake along the trench in the southern part of the CESZ, and suggests that rupture modes are different between the northern and southern parts of CESZ near the trench.

A target-oriented scheme for efficient inversion of time-lapse seismic waveform data

2018 ◽  
Author(s):  
Xingguo Huang ◽  
Morten Jakobsen ◽  
Kjersti Solberg Eikrem ◽  
Geir Nævdal
Keyword(s):  
Time Lapse ◽  
Waveform Data ◽  
Seismic Waveform

Source Characteristics of the 2017 Ms 6.6 (Mw 6.3) Jinghe Earthquake in the Northeastern Tien Shan

2020 ◽  
Vol 91 (2A) ◽  
pp. 745-757
Author(s):  
Xu Zhang ◽  
Li-Sheng Xu ◽  
Jun Luo ◽  
Wanpeng Feng ◽  
Hai-Lin Du ◽  
...  
Keyword(s):  
Energy Release ◽  
Joint Inversion ◽  
Near Field ◽  
Tien Shan ◽  
Rupture Velocity ◽  
The West ◽  
Waveform Data ◽  
Source Characteristics ◽  
Seismic Waveform ◽  
Finite Fault

Abstract On 8 August 2017, an Ms 6.6 earthquake occurred in the northeastern Tien Shan orogenic belt. To reveal the source characteristics of this earthquake completely, the teleseismic and near-field seismic waveform data were collected as well as the coseismic Interferometric Synthetic Aperture Radar displacement data, and the methods of the backprojection and the finite-fault joint inversion were adopted. The backprojection of the teleseismic recordings indicates a unilateral rupture propagating 15 km westward. Two stages of the rupture were recognized from the backprojection results: in the first ∼5  s, the rupture took place near the hypocenter, with an accelerating energy release but a small rupture velocity; then the rupture extended to the west, with a decelerating energy release but a relatively fast rupture velocity. The joint inversion of the multiple datasets shows a major slip asperity of about 24  km × 18  km. The asperity extended mainly to the west, with a duration of approximately 10 s. The average rupture velocity over the asperity was estimated to be approximately 2.0  km/s, which is close to that 1.9  km/s estimated by the backprojection. It is interesting that the high-frequency sources were aligned almost on the margin of the slip asperity. Moreover, the occurrence of the earthquake sequence is found to relate with the low-VP/VS zone, implying a tectonic property, which controls the nucleation and rupture of earthquakes.

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