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%8 2017/09 %0 Journal Article %J Journal of Geophysical Research: Solid Earth %D 2017 %T Application of an improved spectral decomposition method to examine earthquake source scaling in southern California %A Trugman, Daniel T. %A Shearer, Peter M %K 7209 Earthquake dynamics %K 7215 Earthquake source observations %K 7223 Earthquake interaction %K 7230 Seismicity and tectonics %K 7290 Computational seismology %K and prediction %K corner frequency %K earthquake hazard %K earthquake source parameters %K earthquake source scaling %K earthquake source spectra %K forecasting %K stress drop %N 4 %P 2017JB013971 %R 10.1002/2017JB013971 %U http://onlinelibrary.wiley.com/doi/10.1002/2017JB013971/abstract %V 122 %XEarthquake source spectra contain fundamental information about the dynamics of earthquake rupture. However, the inherent tradeoffs in separating source and path effects, when combined with limitations in recorded signal bandwidth, make it challenging to obtain reliable source spectral estimates for large earthquake data sets. We present here a stable and statistically robust spectral decomposition method that iteratively partitions the observed waveform spectra into source, receiver, and path terms. Unlike previous methods of its kind, our new approach provides formal uncertainty estimates and does not assume self-similar scaling in earthquake source properties. Its computational efficiency allows us to examine large data sets (tens of thousands of earthquakes) that would be impractical to analyze using standard empirical Green's function-based approaches. We apply the spectral decomposition technique to P-wave spectra from five areas of active contemporary seismicity in southern California: the Yuha Desert, the San Jacinto Fault, and the Big Bear, Landers, and Hector Mine regions of the Mojave Desert. We show that the source spectra are generally consistent with an increase in median Brune-type stress drop with seismic moment, but that this observed deviation from self-similar scaling is both model-dependent and varies in strength from region to region. We also present evidence for significant variations in median stress drop and stress drop variability on regional and local length scales. These results both contribute to our current understanding of earthquake source physics and have practical implications for the next generation of ground-motion prediction assessments.

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%8 2017/05 %0 Journal Article %J Seismological Research Letters %D 2017 %T GrowClust: A Hierarchical Clustering Algorithm for Relative Earthquake Relocation, with Application to the Spanish Springs and Sheldon, Nevada, Earthquake Sequences %A Trugman, Daniel T. %A Shearer, Peter M %P 379–391 %R 10.1785/0220160188 %U http://srl.geoscienceworld.org/content/88/2A/379 %V 88 %XAccurate earthquake locations are essential for providing reliable hazard assessments, understanding the physical mechanisms driving extended earthquake sequences, and interpreting fault structure. Techniques based on waveform cross correlation can significantly improve the precision of the relative locations of event pairs observed at a set of common stations. Here we describe GrowClust, an open‐source, relative relocation algorithm that can provide robust relocation results for earthquake sequences over a wide range of spatial and temporal scales. The method uses input differential travel times, cross‐correlation values, and reference starting locations, and applies a hybrid, hierarchical clustering algorithm to simultaneously group and relocate events within similar event clusters. The method is computationally efficient and numerically stable in its capacity to process large data sets and naturally applies greater weight to more similar event pairs. Additionally, it outputs location error estimates that can be used to help interpret the reliability and resolution of relocation results. As an example, we apply the GrowClust method to the recent Spanish Springs and Sheldon, Nevada, earthquake swarms. These sequences highlight the future potential for applying the GrowClust relocation method on a much larger scale within the region, where existing relocation results are sparse but vital for understanding the seismotectonics and seismic hazard of Nevada and eastern California.

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%0 Journal Article %J Journal of Geophysical Research: Solid Earth %D 2016 %T A comparison of long-term changes in seismicity at The Geysers, Salton Sea, and Coso geothermal fields %A Trugman, Daniel T. %A Shearer, Peter M %A Borsa, Adrian A. %A Fialko, Yuri %P 225–247 %R 10.1002/2015JB012510 %U http://doi.wiley.com/10.1002/2015JB012510 %V 121 %Xn/a

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%0 Journal Article %J Earth and Planetary Science Letters %D 2015 %T Synchronous low frequency earthquakes and implications for deep San Andreas Fault slip %A Trugman, Daniel T. %A Wu, Chunquan %A Guyer, Robert A. %A Johnson, Paul A. %P 132–139 %R 10.1016/j.epsl.2015.05.029 %U http://linkinghub.elsevier.com/retrieve/pii/S0012821X15003271 %V 424 %Xn/a

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%8 aug %0 Journal Article %J Geophysical Journal International %D 2015 %T Spatial-temporal variation of low-frequency earthquake bursts near Parkfield, California %A Wu, C. %A Guyer, R. %A Shelly, D. %A Trugman, D. %A Frank, W. %A Gomberg, J. %A Johnson, P. %P 914–919 %R 10.1093/gji/ggv194 %U http://gji.oxfordjournals.org/cgi/doi/10.1093/gji/ggv194 %V 202 %Xn/a

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%0 Journal Article %J Journal of Geophysical Research: Solid Earth %D 2015 %T Statistical tests on clustered global earthquake synthetic data sets %A Daub, Eric G. %A Trugman, Daniel T. %A Johnson, Paul A. %P 5693–5716 %R 10.1002/2014JB011777 %U http://doi.wiley.com/10.1002/2014JB011777 %V 120 %X n/a %Z n/a %0 Journal Article %J Bulletin of the Seismological Society of America %D 2014 %T A 2D Pseudodynamic Rupture Model Generator for Earthquakes on Geometrically Complex Faults %A Trugman, D. T. %A Dunham, E. M. %P 95–112 %R 10.1785/0120130138 %U http://www.bssaonline.org/cgi/doi/10.1785/0120130138 %V 104 %Xn/a

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%0 Journal Article %J Geophysical Research Letters %D 2014 %T Did stresses from the Cerro Prieto Geothermal Field influence the El Mayor-Cucapah rupture sequence? %A Trugman, Daniel T. %A Borsa, Adrian A. %A Sandwell, David T. %P 8767–8774 %R 10.1002/2014GL061959 %U http://doi.wiley.com/10.1002/2014GL061959 %V 41 %Xn/a

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%0 Journal Article %J Geophysical Research Letters %D 2013 %T Acoustic emission and microslip precursors to stick-slip failure in sheared granular material %A Johnson, P. A. %A Ferdowsi, B. %A Kaproth, B. M. %A Scuderi, M. %A Griffa, M. %A Carmeliet, J. %A Guyer, R. A. %A Le Bas, P-Y. %A Trugman, D. T. %A Marone, C. %P 5627–5631 %R 10.1002/2013GL057848 %U http://doi.wiley.com/10.1002/2013GL057848 %V 40 %X n/a %Z n/a %0 Journal Article %J Geophysical Research Letters %D 2013 %T Modeling dynamic triggering of tectonic tremor using a brittle-ductile friction model %A Trugman, Daniel T. %A Daub, Eric G. %A Guyer, Robert A. %A Johnson, Paul A. %P 5075–5079 %R 10.1002/grl.50981 %U http://doi.wiley.com/10.1002/grl.50981 %V 40 %X n/a %Z n/a