Tim Dawson (California Geological Survey) Ray Weldon (University of Oregon)

Transcription

1 UCERF3: w Fault Models and Geologic Slip Rate Tim Dawson (California Geological Survey) Ray Weldon (University of Oregon) Workshop on Use of UCERF3 in the USGS National Seismic Hazard Map October 17-18

2 Latitude-longitude coordinate pairs of fault trace" Upper and lower depth" Average dip" Rake" Fault zone width (new parameter for UCERF3)" UCERF3 Fault Model" Components of the Uniform Earthquake Rupture Forecast 3 Fault parameter database stores:"

3 UCERF2 Fault Model" UCERF2 faults" UCERF2 faults" (relative to mapped Quaternary fault

4 UCERF2 Fault Model distributed shear, where known geologic slip rates don t add up the geodetic rate across the regi " Also, areas have mapped faults unknown geologic slip rates." " Use of C-zones produced notice artifacts UCERF2 model" " "

5 Components of the Uniform Earthquake Rupture Forecast 3 " tes include:" ation of additional faults and revision of existing faults from rece s. " ation of the Statewide Community Fault Model (SCFM) into the F3 fault model. " lopment of a geologically-based block model for geodesy-based mation models." aluation of fault endpoints (for fault to fault jumps)."

6 involves the on of SCFM rectilinear ntations into UCERF ameter database" more detailed ntation of faults used F2, plus additions to entory" ditions prioritized n location of block ies used by tion modelers" nsiders potential fault ions for fault to fault Clayton Contra Costa Shear Zone Franklin Joy Woods Las Positas Nacimiento Pilarcitos Southhampton Alexander Redwood Connecto Bennett Valley Connecto Mission Connecto S. Coast Ranges/San Joaquin Valley 2003 San Simeon earthquake/oceanic flt East Huasna La Panza San Luis Range-W Huasna San Luis Range-W Huasna/Avila Beach San Luis Range-W Huasna/Oceano San Luis Range-W Huasna/Olson San Luis Range-W Huasna/Pecho San Luis Range-W Huasna/San Luis Range San Luis Range-W Huasna/Wilmar Ave San Benito Connect N. Coast Ranges/Sacramento Valley Briceland Eaton Roughs King Range Spenceville Swain Ravine Wight Way Connect Cascadia/Klamath Mountains Rocky Ledge Russ Faultzone

7 n California faults wide Community odel (SCFM)" epresentations ly accepted as dips averaged for t sections" tions include he SCFM fault is ailed than the 2 modeled fault e individual ns on a case by sis." Image courtesy of Andreas Plesch (Harvard U.)

8 UCERF3 Block Model odesy-based block ation models, a ide block model fined by the ists and cists. boundaries were lly defined by ng the major, most faults, as well as uaternary-active nd fault zones.

9 UCERF2 " UCERF3 "

10 UCERF2 " UCERF3 " Perspective view of fault sections in northern California "

11 ernative fault models retains alternative fault models developed in

12 s whether fault section le surface, or a braided f related faults" r which the tion model rate applies" which microty is applied" Text r which elastic -based probability ns are applied" ent of future ruptures to F3 modeled fault"

13 ifies whether fault section imple surface, or a braided m of related faults" over which the mation model rate applies" s to which microicity is applied" over which elastic nd-based probability tions are applied" nment of future ruptures to ERF3 modeled fault"

14 ckground:" ERF2 relied on consensus slip rates for the deformation dels." rgely based on geologic rates, but modified by rmation from geodesy and plate rate constraints." nsensus rates developed over several generations of rking Groups (NSHM 1996, WG99, WG02, WG08)." ologic rates in various compilations (e.g. Petersen and snousky (1994), WGNCEP (1996), McCrory (1996), etc tewide updated table not compiled for UCERF2."

15 F3 approach of including geodetically-based deformatio ls required an updated Statewide compilation of geologic ilation of pure geologic slip rates (no geodetic inferen rences based on assumptions of recurrence and slip pe as basis for a geologically-based deformation model." gic slip rates compiled for point constraints in the geode ls." geologic bounds developed for use in subset of the ation models (e.g. Zeng model)."

16 lation focused mainly on Quaternary slip rates used by prior Wor, plus newer published rates. " se includes UCERF3 best estimate slip rates as well as:" cation" feature data (amount, sense, uncertainties (if reported), feature ata (age of feature, uncertainties, dating method)" cy of activity for each UCERF3 fault section (CGS FAM/USGS Q atabases)" ed USGS Q-faults slip rate category for UCERF3 fault section" ents" supporting information (see Appendix B for complete description

17 3 reported geologic tes in compilation" 3 UCERF3 fault ctions with a reported ologic rate (out of 50)" ly 62 fault sections th multiple reported ologic slip rates" fault sections with slip tes over different time ervals"

18 e was used to qualitative quality for:" eature" constraints" rating for reported slip es:" constrained" rately constrained" ly constrained" liable "

19 uality rankings: own by fault section" lt sections with geologic straints" ategory A " ategory B " ategory C " ategory D " t of geologic slip rates ded to geodesy-based

20 rmation Model built from geologic data, without ideration of geodetic and plate-motion models ceptually, adding up all fault slip rates should add e plate rate, or at least tell us something about ho tributed system works over longer time intervals). ry UCERF3 fault section assigned a geologically based " reported slip rates and quality rankings were examined istency with other reported rates, USGS slip rate catego ncy of activity and UCERF2-assigned rates in order to n a UCERF3 best estimate rate for each fault section."

21 em: About 177 UCERF3 have no direct geologic s onstraints." ning slip rates to faults sections without measured " polated from adjacent contiguous (or nearuous) sections (e.g. SAF offshore)" gned USGS slip rate categories (if available)" USGS rate category available, used correlation en recency of activity and slip rate "

22 -faults age category" ary active (<1.6 M)" istocene (<130 ka) " leistocene and Holocene (<15 ka)" USGS Q-faults Rate ca <0.2 mm/yr" 0.2 to 1.0 mm/yr" mm/yr" tion: How consistent are the reported rates in our ase with the rate categories assigned by the USG r: 83% of the time the reported slip rates fall with -assigned rate category

23 gory" ry active (<1.6 M)" stocene (<130 ka) " eistocene and Holocene (<15 ka)" Rate category" <0.2 mm/yr" 0.2 to 1.0 mm/ mm/y

24 -mean frequency approach to assign best-estimate slip rate to slip rate cat Median for 1-5 mm/yr category rate for known slip rates in 1-5 mm/yr category

25 Geo-deformation features:" tapers for high slip ults with long overlaps ial - Cerro Prieto, rs Creek - Maacama)"

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