Updating Models of Earthquake Recurrence and Rupture Geometry of the Cascadia Subduction Zone for UCERF3 and the National Seismic Hazard Maps Art Frankel U.S. Geological Survey Seattle presentation for UCERF3 SRP meeting Nov , 2010

Cascadia Subduction Zone Interface Earthquakes Major Issues for UCERF3 and NSHM What is the magnitude-frequency distribution? (rate of M9’s that rupture entire CSZ; rates of M8’s that rupture part of CSZ) Does southern CSZ produce more M8’s than northern portion? Is the CSZ segmented along strike? Can some of the “M9” quakes be series of M8s over < 20 years or so? Where is the eastern edge of the locked zone? geometry of CSZ

PacNW Plans for UCERF 3 and next update of National Seismic Hazard Maps Focused meeting on turbidite evidence for CSZ great earthquakes, Nov in Corvallis; evaluate 230 yr recurrence for M8’s on southern CSZ from turbidite and compare dates from turbidites to onshore data; compare turbidite and onshore data in northern CSZ; discuss M8 cluster possibility; discuss possible segmentation; mag- freq distributions Pacific Northwest regional workshop Fall 2011 (eastern edge of CSZ, source models, faults, attenuation relations); possible separate workshop on eastern edge of locked portion of CSZ

From 2008 NSHM Documentation

Two Sets of Scenarios for CSZ revised for 2008 Update M rupturing entire CSZ; 500 year average recurrence time from paleoevent dates (probability of 0.67) M8.0-M8.7 floating rupture zones; rupture under any location along coast with rate of 1/500, on average (probability of 0.33) equal probabilities assigned to 8.3, 8.4, 8.5, 8.6, 8.7 scenarios; 8.0,8.1,8.2 assigned half probability of others

From 2008 NSHM Documentation

From Goldfinger et al. (in press); results from turbidites This will be evaluated in Nov meeting

From Goldfinger et al. (in press)

From Nelson et al. (2006) Compilation of on land paleoseismic data

Figure from Goldfinger et al. (in press)

Where is the eastern edge of the locked zone? Thermal models Global analogs GPS data (e.g., McCaffrey; Chapman and Melbourne) Uplift data (e.g., Burgette, Weldon et al., 2009); historic and from paleoseismic Updip limit of ETS

From Chapman and Melbourne (2009): ETS and Locked Zone

0.5 wt 0.2 wt 0.1 wt

Nonvolcanic tremor locations From Aaron Wech, UW

Figure from Liu et al (2010) For Nankai Trough Comparing locked zone derived from GPS with location of LFE’s

Develop new magnitude-frequency distribution(s) for CSZ; possibly varying along CSZ Assess possibility that some “M9” quakes are series of M8s over < 20 years or so Evaluate possibility of temporal clustering of whole rupture CSZ proposed by Goldfinger et al. (in press) Revisit time-dependent model for CSZ. Do we include southern CSZ ruptures with short return times? Update location of plate interface using compilation of McCrory and other work PacNW workshop to discuss CSZ recurrence and geometry, crustal faults, atten relations (possible separate workshop on geometry of CSZ)

Possible configurations for rupture zone of great Cascadia Earthquakes From Fluck et al. (1997)

From Goldfinger et al. (in press)

From Brian Atwater (2010)