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TitleDepth-scanning algorithm: accurate, automatic, and efficient determination of focal depths for local and regional earthquakes
 
AuthorYuan, J; Kao, HORCID logo; Yu, J
SourceJournal of Geophysical Research, Solid Earth vol. 125, issue 7, e2020JB019430, 2020 p. 1-22, https://doi.org/10.1029/2020JB019430
Image
Year2020
Alt SeriesNatural Resources Canada, Contribution Series 20200109
PublisherAmerican Geophysical Union
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf; pdf
SubjectsScience and Technology; tectonics; seismicity
Illustrationsgraphs; diagrams; tables
ProgramEnvironmental Geoscience Shale Gas - induced seismicity
Released2020 06 30
AbstractPrecise source depths are critical to the understanding and interpretation of many seismological and tectonic processes. However, conventional earthquake location methods based on the arrival times of direct P and S phases have far less constraint on focal depths than on epicenters. Therefore, developing a method that can systematically and efficiently estimate focal depths with high accuracy, especially for the vast number of small earthquakes that can only be observed at local and regional distances, would make significant contributions to the geoscience research community. In this study, we develop a new method, named "Depth-Scanning Algorithm", to efficiently identify depth phases at local and regional distances. We first construct template waveforms of possible depth phases by applying various phase shifts to the original P and S waveforms to mimic the effect of reflection(s). We then systematically scan waveforms after the P and S phases for segments that match the depth-phase templates. The arrival times of those segments are compared to the theoretical arrival times of depth phases predicted with an assumed velocity model and focal depth. We repeat the above process for a range of assumed focal depths, and the one most consistent with the theoretical prediction is deemed the final solution. Synthetic tests and applications to field data demonstrate the merits of our method compared to conventional location methods.
Summary(Plain Language Summary, not published)
Precise source depths are critical to the understanding and interpretation of many seismological and tectonic processes. However, conventional earthquake location methods based on the arrival times of direct P and S phases have far less constraint on focal depths than on epicenters. Therefore, developing a method that can systematically and efficiently estimate focal depths with high accuracy, especially for the vast number of small earthquakes that can only be observed at local and regional distances, would make significant contributions to the geoscience research community. In this study, we develop a new method, named "Depth-Scanning Algorithm" (DSA), to automatically and efficiently identify seismic phases that are reflected from the free surface and the Moho discontinuity. The timing of the reflected phases is then used to constrain the precise depth of the earthquake. Synthetic tests and applications to field data demonstrate the merits of our method compared to conventional location methods.
GEOSCAN ID326417

 
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