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

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. 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 timeSpatial distanceGutenberg-Richter law [M. Baiesi and M. Paczuski, PRE, 69, 066106 (2004)] [Zaliapin et al., PRL, 101, 018501 (2008)] Distance from an earthquake j to an earlier earthquake i : Definition: Property:

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 and Ben-Zion, JGR (2013) Zaliapin et al., PRL (2008)

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

10. Artifact 1: Inflated distance-to-parent

11. Error = 100m Error > 1km

12. Artifact 2: Underestimated productivity

13. Artifact 3: Overestimated background rate

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

15. Comparative analysis of alternate catalogs

16. Two types of catalog uncertainties: 1 2 3 Four artifacts of catalog uncertainties: 1 2 3 Summary o Earthquake location errors o Short-term incompleteness o Increased distance between parent and offspring o Decreased clustering (productivity) o Increased background rate o Apparent changes of b -value 44 Results seem to be independent of earthquake location method and parent-offspring identification approach Ongoing application to the problem of discriminating between tectonic and induced seismicity 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

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