Iterative Strategies for Aftershock Classification in Automatic Seismic Processing Pipelines

Gibbons, Steven J.; Kvaerna, Tormod; Harris, David B.; Dodge, Douglas A.

doi:10.1785/0220160047

Title: Iterative Strategies for Aftershock Classification in Automatic Seismic Processing Pipelines

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Abstract

We report aftershock sequences following very large earthquakes present enormous challenges to near-real-time generation of seismic bulletins. The increase in analyst resources needed to relocate an inflated number of events is compounded by failures of phase-association algorithms and a significant deterioration in the quality of underlying, fully automatic event bulletins. Current processing pipelines were designed a generation ago, and, due to computational limitations of the time, are usually limited to single passes over the raw data. With current processing capability, multiple passes over the data are feasible. Processing the raw data at each station currently generates parametric data streams that are then scanned by a phase-association algorithm to form event hypotheses. We consider the scenario in which a large earthquake has occurred and propose to define a region of likely aftershock activity in which events are detected and accurately located, using a separate specially targeted semiautomatic process. This effort may focus on so-called pattern detectors, but here we demonstrate a more general grid-search algorithm that may cover wider source regions without requiring waveform similarity. Given many well-located aftershocks within our source region, we may remove all associated phases from the original detection lists prior to a new iteration of themore »« less

Authors:

Gibbons, Steven J. ^[1]; Kvaerna, Tormod ^[1]; Harris, David B. ^[2]; Dodge, Douglas A. ^[3]

NORSAR, Kjeller (Norway)
Deschutes Signal Processing LLC, Maupin, OR (United States)
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Publication Date:: Wed Jun 08 00:00:00 EDT 2016

Research Org.:: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Sponsoring Org.:: USDOE

OSTI Identifier:: 1438762

Report Number(s):: LLNL-JRNL-683501
Journal ID: ISSN 0895-0695

Grant/Contract Number:: AC52-07NA27344

Resource Type:: Accepted Manuscript

Journal Name:: Seismological Research Letters

Additional Journal Information:: Journal Volume: 87; Journal Issue: 4; Journal ID: ISSN 0895-0695

Publisher:: Seismological Society of America

Country of Publication:: United States

Language:: English

Subject:: 58 GEOSCIENCES

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                    Gibbons, Steven J., Kvaerna, Tormod, Harris, David B., and Dodge, Douglas A. Iterative Strategies for Aftershock Classification in Automatic Seismic Processing Pipelines.  United States: N. p., 2016. 
Web.  doi:10.1785/0220160047.

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                    Gibbons, Steven J., Kvaerna, Tormod, Harris, David B., & Dodge, Douglas A. Iterative Strategies for Aftershock Classification in Automatic Seismic Processing Pipelines.  United States.  https://doi.org/10.1785/0220160047

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                    Gibbons, Steven J., Kvaerna, Tormod, Harris, David B., and Dodge, Douglas A. Wed .  
"Iterative Strategies for Aftershock Classification in Automatic Seismic Processing Pipelines".  United States.  https://doi.org/10.1785/0220160047.  https://www.osti.gov/servlets/purl/1438762.

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@article{osti_1438762,

  title        = {Iterative Strategies for Aftershock Classification in Automatic Seismic Processing Pipelines},

  author       = {Gibbons, Steven J. and Kvaerna, Tormod and Harris, David B. and Dodge, Douglas A.},

  abstractNote = {We report aftershock sequences following very large earthquakes present enormous challenges to near-real-time generation of seismic bulletins. The increase in analyst resources needed to relocate an inflated number of events is compounded by failures of phase-association algorithms and a significant deterioration in the quality of underlying, fully automatic event bulletins. Current processing pipelines were designed a generation ago, and, due to computational limitations of the time, are usually limited to single passes over the raw data. With current processing capability, multiple passes over the data are feasible. Processing the raw data at each station currently generates parametric data streams that are then scanned by a phase-association algorithm to form event hypotheses. We consider the scenario in which a large earthquake has occurred and propose to define a region of likely aftershock activity in which events are detected and accurately located, using a separate specially targeted semiautomatic process. This effort may focus on so-called pattern detectors, but here we demonstrate a more general grid-search algorithm that may cover wider source regions without requiring waveform similarity. Given many well-located aftershocks within our source region, we may remove all associated phases from the original detection lists prior to a new iteration of the phase-association algorithm. We provide a proof-of-concept example for the 2015 Gorkha sequence, Nepal, recorded on seismic arrays of the International Monitoring System. Even with very conservative conditions for defining event hypotheses within the aftershock source region, we can automatically remove about half of the original detections that could have been generated by Nepal earthquakes and reduce the likelihood of false associations and spurious event hypotheses. Lastly, further reductions in the number of detections in the parametric data streams are likely, using correlation and subspace detectors and/or empirical matched field processing.},

  doi          = {10.1785/0220160047},

  journal      = {Seismological Research Letters},

  number       = 4,

  volume       = 87,

  place        = {United States},

  year         = {Wed Jun 08 00:00:00 EDT 2016},

  month        = {Wed Jun 08 00:00:00 EDT 2016}

}

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