Proposed Components for CA for Feb. 2007 Version of National Maps

1. Proposed Components for CA for Feb. 2007 Version of National Maps Because of issues with inversion for A faults: Use WG02 for northern CA A-faults Use Biasi and Weldon for southern San Andreas (slip rates OK?); a key issue here Use WG06 a priori geologic insight model for multisegment ruptures on San Jacinto, Elsinore, and Garlock faults (adjusted to get observed slip rates) Use B faults from WG06; link up some B faults as suggested No new C zones (some of them seem to be problematic: some very narrow zones with a lot of slip; how many M6.5’s?)

2. Possible Components for CA for Feb. 2007 Version of National Maps, continued Remove about 10% moment from A and B faults to account for afterslip, aftershocks, coupling, etc. Use new Felzer catalog (aftershocks/foreshocks removed) to make background seismicity grid; use corrections for mag. uncert. and rounding; use b-value of 0.8 Adjust rate of M ≥ 6.5 events from background to fit rate of observed events not on A or B faults (or could determine new b-value above M≥5.0) Remove Mendocino fault; treat with anisotropic smoothed seismicity

3. Keep transpressional/transtensional boundary used in 1996 and 2002 maps (e.g., GR-char weighting) • Keep treatment of Mchar uncertainty on faults used in 2002 maps • Adhere to non-overlapping magnitudes between background and faults, as in 2002 • We estimate that this model will overpredict rate of M≥6.5 earthquakes by about a factor of 1.5, for the non-extensional portion of CA

4. Battle of the M≥6.5 bulge • All rates are for non-extensional part of CA: • Predicted rate of M≥6.5 from 2002 model: 0.414 (including 0.076 from gridded seismicity) • Make Parkfield less than M6.5, rate becomes: 0.373 • Remove Mendocino fault (0.0284), rate becomes: 0.345 • Remove 10% of fault rate (0.027) for aftershocks, etc.: 0.318 • Adjust gridded rate by -0.05, assuming rate of M≥ 6.5 events not on a and b faults is 0.026 • Now total rate is: 0.268 • Observed rate without events west of -125: about 0.17-0.19 (Mueller’s rate for all CA is 0.21; take 10% off for more limited area; 0.17 if you adjust Felzer’s total rate of 0.19) • So overprediction is about factor of 1.4-1.6 (depending on which observed rate is used). • Predicted rate will be reduced further by using multi-segment rupture model for San Jacinto, Elsinore, and Garlock faults, and connecting some B faults • There’s also the issue of completeness of M6.5’s back to 1850.

5. Treatment of Uncertainty in Mchar in 2002 maps • Aleatory sigma of 0.12 m.u. (truncated at about 2.5 sigma) • Epistemic uncertainty: Ellsworth B and Hanks and Bakun; equal weight • Additional epistemic uncertainty: -0.2, 0., +0.2 m.u., with weights of 0.2, 0.6 ,0.2 (reduced to ± 0.1 for longest ruptures) • Gives additional epistemic sigma of 0.12 m.u., since 0.2, 0.6, .2 wt corresponds to 90% confidence limit, (1.65 sigma). • Wells and Coppersmith (1994): sigma of 0.25

6. NSHMP Schedule for 2007 • Feb. 15: deliver draft maps to BSSC • March 15: finish written report on draft maps • April 15: Review meeting of external advisory panel; get comments to revise maps • June 1: Put first set of trial maps on Web for public review • Aug. 1: end of public comment period • Aug 15: Second meeting of external advisory panel • Sept. 30: Release final maps to BSSC

7. Proposed Cascadia model • Using advice from Alan Nelson and Brian Atwater; based on paleoseismic data summarized in Nelson et al. (2006) • M8.8-M9.2: rupture whole CSZ, average recurrence time of 500 yr • M8.0-8.6: floating ruptures, average recurrence time of 600 yr; uniform distribution in magnitude • Use same logic tree for rupture geometry as in 2002 maps • Produces similar hazard values as 2002 maps