1. 1992 M=7.3 Landers shock increases stress at Big Bear Los Angeles Big Bear Landers First 3 hr of Landers aftershocks plotted from Stein (2003)

2. 1992 M=7.3 Landers shock promotes the M=6.5 Big Bear shock 3 hr later Los Angeles Big Bear Landers First 3 hr of Landers aftershocks plotted from Stein (2003)

3. …and promotes the M=7.1 Hector Mine shock 7 yr later Los Angeles Hector Mine First 7 yr of aftershocks plotted from Stein (2003)

4. Arguments for static stress triggering Correlation of stress change & seismicity rate change (Stein, 1999; Parsons, 2002) Tidal triggering of quakes & tremor (Cochran et al, 2004; Tanaka et al, 2004) Swarms triggered by creep (Vidale & Shearer, 2006; Lohman & McGuire, 2007) Seismicity rate drop in stress shadows (Toda & Stein, 2004; Ma et al, 2005; Marsan & Nalbant, 2005: Toda et al, 2005; Mallman & Parsons, 2008; Chan & Stein, 2009) Arguments for dynamic stress triggering Remote triggering by Love waves of large mainshocks (Hill et al, 1993; Brodsky et al, 2000; Brodsky & Prejean, 2005; Gomberg & Johnson, 2005; Velasco et al, 2008) Dynamic stress directivity may explain asymmetry in aftershock distribution of large mainshocks (Kilb, Gomberg & Bodin, 2000 & 2002; Doser et al, 2009) No seismicity rate drop in stress shadows (Marsan, 2003; Felzer & Brodsky, 2004)

5. Tectonic setting (CGS report, 2003) Chelungpu fault can be taken as combination of ramp and décollement segments Tectonic setting (CGS report, 2003) 1999 M w =7.6 Chi-Chi, Taiwan, earthquake Earthquake triggering consistent with focal mech’s Seismicity rate drops in stress shadows periphery

6. Calculated Coulomb stress change for an idealized Chi-Chi rupture Ma, Chan & Stein. JGR, 2005

7. decrease Seismicity rate change (new/old) increase Observed seismicity rate changes are consistent with calculated Coulomb stress change—including stress shadows

8. Taichung Nansan Huatung Kaoping Chan & Stein (GJI, 2009)

9. Focal mechanisms of earlier aftershocks are consistent with stress increase from mainshock Chan & Stein (GJI, 2009)

10. Focal mechanisms of later aftershocks are consistent with stress increase from afterslip and relaxation Chan & Stein (GJI, 2009)

11. Postseis. stress on the focal planes of larger events Later aftershocks preferentially occur where they are brought closer to Coulomb failure by postseismic stress Chan & Stein (GJI, 2009)

12. 1997 M=6.5 & M=6.3 Kagoshima doublet: 40 days & 4 km apart Do stress shadows inhibit earthquakes? Kagoshima Toda & Stein (JGR, 2004) Japan

17. Lin & Stein (JGR, 2004)

18. Lin & Stein (2004)

19. 2010 Mw=8.8 Maule, Chile earthquake Outer rise normal aftershocks and Mw=6.9 normal after- shock above megathrust evident, but most are thrusts Stein, Toda, & Barrientos (in prep.) Normal events

20. Sites of M=6.9, outer rise, and Santiago aftershocks brought closer to failure

22. The long stress shadow cast by the 2004 M=9.2 Sumatra earthquake Volkan Sevilgen & Ross Stein (in prep.)

23. Earthquakes on Andaman Sea-Sagaing transform system shut down after Boxing Day 2004 M w =9.2 stress changes are large enough to influence seismicity 300 km behind the trench Rate drop WAF - West Andaman Fault SEU- Seuliman Fault, SFS - Sumatra Fault System

24. Seismicity rate drops along right-lateral transform segments Increase Decrease Pesicek et al (JGR, 2010) double-diff. relocations

25. Stress drops on right-lateral transform system (top) but increases on back-arc spreading ridge segments (bottom) Back-arc transform system in green

26. Stress drops on right-lateral transform (blue mechansms) where seismicity rate also drops Stress increases on back-arc ridges (red mechanisms) where seismicity rates increase Rate drop Rate drop 1400-patch source Model (shaded): Chlieh et al (JGR 2007)

27. Karen R. Felzer & Emily E. Brodsky (Nature, 2006) Decay of aftershock density with distance indicates triggering by dynamic stress Keith Richards-Dinger, Ross S. Stein & Shinji Toda (Nature, 2010) Decay of aftershock density with distance does not indicate triggering by dynamic stress Are these M=2-3 mainshocks pointing to their M≥2 aftershocks up to 50 km away?

28. Strong evidence for widespread triggering of very small shocks by very large ones Not only is there triggering on the Love wave arrival, but there is Omori decay of these remote shocks

31. 2/3 of remote aftershocks locate in large quake rupture zones or at swarm sites

32. The 5 min before the mainshocks should not exhibit the same decay as the 5 min afterwards

33. The 5 min before the mainshocks should not exhibit the same decay as the 5 min afterwards

34. Earthquakes that occur before the waves arrive from the mainshock cannot be aftershocks, and so should not occur

36. If the distant earthquakes are aftershocks of their mainshocks, they should undergo Omori temporal decay

38. Earthquakes converse through the transfer of stress