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Discriminating Earthquake Catalog Errors from Seismic Patterns

Study on distinguishing genuine seismicity from catalog errors in Southern California using seismic data analysis and error identification methods.

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Discriminating Earthquake Catalog Errors from Seismic Patterns

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  1. Distinguishing artifacts of earthquake catalog errors from genuine seismicity patterns Ilya Zaliapin Department of Mathematics and Statistics University of Nevada, Reno Yehuda Ben-Zion Department of Earth Sciences University of Southern California IUGG General Assembly * Monday, June 29, 2015

  2. Data: southern California catalog by Hauksson, Yang, Shearer(2013) 117,076 earthquakes with m ≥ 2 Alternate catalogs: Richards-Dinger & Shearer (2000) ANSS 1961-1981 ANSS 1981-2013

  3. Earthquake cluster analysis Baiesi and Paczuski, PRE, 69, 066106 (2004) Zaliapin et al., PRL, 101, 018501(2008) Zaliapin and Ben-Zion, GJI, 185, 1288–1304 (2011) Zaliapin and Ben-Zion, JGR, 118, 2847-2864 (2013)

  4. (Fractal) dimension of epicenters Intercurrence time Spatial distance Gutenberg-Richter law Distance from an earthquake j to an earlier earthquake i : Definition: Property: [M. Baiesi and M. Paczuski, PRE, 69, 066106 (2004)] [Zaliapin et al., PRL, 101, 018501(2008)]

  5. Separation of clustered and background parts in southern California Background = weak links (as in stationary, inhomogeneous Poisson process) Clustered part = strong links (events are much closer to each other than in the background part) Zaliapin et al., PRL(2008) Zaliapin and Ben-Zion, JGR (2013)

  6. Earthquake location errors

  7. Two types of earthquake location errors Median error 500 m convenient measure of relative location quality rather than actual errors

  8. Spatial variability of absolute horizontal error in southern California Los Angeles San Diego

  9. Artifacts of catalog uncertainties

  10. Artifact 1: Inflated distance-to-parent

  11. Artifact 1: Inflated distance-to-parent Error > 1km Error = 100m

  12. Artifact 2: Underestimated productivity

  13. Artifact 2: Underestimated productivity Artifact 3: Overestimated background rate

  14. Artifact 4: Short-term incompleteness Frequency-size distribution Temporal evolution of b-value Close offspring Distant offspring

  15. Comparative analysis of alternate catalogs

  16. Summary Two types of catalog uncertainties: 1 1 • Earthquake location errors • Short-term incompleteness Four artifacts of catalog uncertainties: 2 2 • Increased distance between parent and offspring • Decreased clustering (productivity) • Increased background rate • Apparent changes of b-value Results seem to be independent of earthquake location method and parent-offspring identification approach 3 3 Ongoing application to the problem of discriminating between tectonic and induced seismicity 4 4 Ref: Zaliapin & Ben-Zion (2015) Artifacts of earthquake location errors and short-term incompleteness on seismicity clusters in southern California, Geophys. J. Intl., to appear

  17. Thank you!

  18. Artifact 2: Underestimated productivity Artifact 3: Overestimated background rate

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