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Poster Abstracts HOW DOES DAMAGE AFFECT RUPTURE PROPAGATION ACROSS A FAULT STEPOVER? (A-074) H.M. Savage and M.L. Cooke We investigate the potential for fault damage to influence earthquake rupture at fault step-overs using a mechanical numerical model that explicitly includes the generation of cracks around faults. We compare the off-fault fracture patterns and slip profiles generated along faults with a variety of frictional slip-weakening distances and step-over geometry. Models with greater damage facilitate the transfer of slip to the second fault. Increasing separation and decreasing the overlap distance reduces the transfer of slip across the step over. This is consistent with observations of rupture stopping at step-over separation greater than 4 km (Wesnousky, 2006). In cases of slip transfer, rupture is often passed to the second fault before the damage zone cracks of the first fault reach the second fault. This implies that stresses from the damage fracture tips are transmitted elastically to the second fault to trigger the onset of slip along the second fault. Consequently, the growth of damage facilitates transfer of rupture from one fault to another across the step-over. In addition, the rupture propagates along the damage-producing fault faster than along the rougher fault that does not produce damage. While this result seems counter to our understanding that damage slows rupture propagation, which is documented in our models with pre-existing damage, these model results are suggesting an additional process. The slip along the newly created damage may unclamp portions of the fault ahead of the rupture and promote faster rupture. We simulate the M7.1 Hector Mine Earthquake and compare the generated fracture patterns to maps of surface damage. Because along with the detailed damage pattern, we also know the stress drop during the earthquake, we may begin to constrain parameters like the slip-weakening distance along portions of the faults that ruptured in the Hector Mine earthquake. PREPARING TRIAL MODELS OF SPATIAL VARIABILITY IN GEOTECHNICAL VELOCITIES FOR ASSESSING EFFECTS ON GROUND MOTIONS (B-058) W.H. Savran and J.N. Louie The Clark County Parcel Map provides us with a data set of geotechnical velocities in Las Vegas Valley, at an unprecedented level of detail. Las Vegas Valley is a basin with similar geologic properties to some areas of Southern California. We first analyze elementary spatial statistical properties of the Parcel Map. We then investigate the same spatial statistics from the peak ground velocity r226e226s226u226l226t226s226 226c226o226m226p226u226t226e226d226 226f226r226o226m226 226 o 226 n 226 e 226 226 m 226 o 226 d 226 e 226 l 226 226 ( 226 B 226 l 226 a 226 c 226 k 226 226 H 226 i 226 l 226 l 226 s 226 226F226a226u226l226t226)226 226t226h226a226t226 226i226n226c226o226r226p226o226r226a226t226e226 226t226h226e226 226P226a226r226c226e226l226 226M 226a 226p226 226a226s226 226p 226a 226r226a226m226e226t226e226r226s226.226 226 W 226 e 226 226 c 226 o 226 n 226 f 226 i 226 g 226 u 226 r 226 e 226 226 f 226 i 226 n 226 i 226 t 226 e 226 - 226 d 226 i 226 f 226 f 226 e 226 r 226 e 226 n 226 c 226 e 226 226 s 226 e 226 i 226 s 226 m 226 i 226 c 226 226 w 226 a 226 v 226 e 226 226p226r226o226p226a 226g226a226t226i226o226n 226 226m226o226d226e226l226s 226 226a226t 226 2260 226. 2265226 226 H 226 z 226 226 w 226 i 226 t 226 h 226 226 L 226 L 226 N 226 L 226 s 226 226 E 226 3 226 D 226 226 c 226 o 226 d 226 e 226 , 226 226u226t226i226l226i226z226i226n226g226 226t226h226e226 226P226a226r226c226e226l226 226M226a226p226 226a226s226 226i226n226p226u226t226 226p226a226r226a226m226e226t226e226r226s226 226t226o226 226c226o226m226p226u226t226e226 226 a 226 226 P 226 G 226 V 226 226 d 226 a 226 t 226 a 226 226 s 226 e 226 t 226 226 f 226 r 226 o 226 m 226 226 t 226 h 226 e 226 226e 226a226r226t226h226q226u 226a226k 226e 226 226s226c 226e 226n226a 226r226i226o226.226 226 226T226h226e 226 226 r 226 e 226 s 226 u 226 l 226 t 226 i 226 n 226 g 226 226 P 226 G 226 V 226 226 i 226 s 226 226 f 226 r 226 a 226 c 226 t 226 a 226 l 226 226 o 226 v 226 e 226 r 226 226 t 226 h 226 e 226 226 s 226 a 226 m 226 e 226 226 s 226 p 226 a 226 t 226 i 226 a 226 l 226 226f226r226e226q226u226e226n226c226i226e226s226 226a226s226 226t226h226e226 226V226s22632260226 226d226a226t226a226 226s226e226t226s226 226a226s226s226o226c226i226a226t226e226d226 226w226i226t226h226 226t226h226e226i226r226 226 r 226 e 226 s 226 p 226 e 226 c 226 t 226 i 226 v 226 e 226 226 m 226 o 226 d 226 e 226 l 226 s 226 . 226 226 226 T 226 h 226 e 226 226 f 226 r 226 a 226 c 226 t 226 a 226 l 226 226 d 226 i 226 m 226 e 226 n 226 s 226 i 226 o 226 n 226 226 i 226 s 226 226s226y226s226t226e226m226a226t226i226c226a226l226l226y226 226l226o226w226e226r226 226i226n226 226a226l226l226 226o226f226 226t226h226e226 226P226G226V226 226m226a226p226s226 226a226s226 226o EARTHQUAKE AGES AND DISPLACEMENTS, FRAZIER MOUNTAIN PALEOSEISMIC SITE (A-141) K.M. Scharer, R.J. Weldon, B.C. Gibson, and A.R. Streig The Frazier Mountain paleoseismic site is located on a poorly understood section of the southern San Andreas fault, mid-way between the well-known Carrizo Plain and Mojave sites of Bidart Fan and Pallett Creek. Emerging paleoseismic evidence indicates that earthquakes along this stretch repeat at a similar pace, with an average interval of ~122 years between A.D. 1000 226 | Southern California Earthquake Center
Poster Abstracts and 1857. Individual intervals vary considerably, including an interval of ~325 years between the sixth and fifth earthquakes back, followed by two intervals lasting less than 50 years each. We modeled slip required to gently fold the sediments during three of the earthquakes with a 2D, optimized trishear inverse model that uses a simulated annealing algorithm. Due to the orientation of the trenches and broad shape of the folds, the slip estimate (3 m total in 3 events) is a minimum yet indicates an average magnitude of at least M7 using standard regressions. In combination, paleoseismic evidence appears similar to the historic record: individual events can be separated by less than 50 or greater than 150 years, and slip data suggest that large ≥M7 events often bridge the Carrizo and Mojave sections of the San Andreas fault. RATE/STATE FRICTIONAL NUCLEATION AND DYNAMIC RUPTURE ON LOW-STRESS FAULTS WITH THERMAL WEAKENING EFFECTS (A-095) S.V. Schmitt, A.M. Bradley, E.M. Dunham, and P. Segall It is believed that faults sustain large shear stresses during the nucleation phase, but slip at much lower stresses during earthquakes. Nucleation is typically characterized by rate- and state-dependent friction, in which slip accelerates after shear stress τ grows to about 0.6 to 0.9 times the effective normal stress σ. During earthquakes, dynamic weakening mechanisms such as shear heating-induced thermal pressurization of pore fluid and flash heating of asperity contacts allow for slip to occur at much lower values of τ. Since 0.6σ is ~100 MPa at seismogenic depths with hydrostatic pore pressure, earthquakes likely nucleate in regions of elevated τ/σ and propagate outward into regions of low τ/σ. Noda & others [JGR, 2009] investigated this issue with numerical simulations in which they included both flash weakening and thermal pressurization. They initiated ruptures with a sudden perturbation in τ on a weakly stressed fault. Flash heating quickly dominated the fault strength, with thermal pressurization contributing a modest amount of additional weakening. Recent work has shown that thermal pressurization may, however, become the dominant weakening mechanism during quasi-static nucleation, well before the onset of seismic radiation [Schmitt & others, JGR, 2011]. We present more physically-motivated simulations of early rupture that model fault weakening mechanisms through nucleation and into the dynamic slip phase. The initial τ/σ heterogeneities remain idealized, but we now consider two types. The first type is a region of elevated τ with uniform σ, while the other type has uniform τ with a low-strength region of diminished σ. We use a quasi-static code to model fault slip from well below steady-state to the early stages of nucleation. Late in nucleation, we switch to a fully dynamic code that otherwise solves the same equations for friction and coupled thermal effects. Our results indicate that there are differences between ruptures on high-stress and low-strength heterogeneities. In rate/state frictional nucleation, slip zones capable of accelerating above steady state have a minimum length dimension L. Heterogeneities must be of greater size than a few L in order to host instability at low background stress, and since L∝1/σ, nucleation under low strength conditions requires a much larger heterogeneity. Thermal weakening effects are also affected by the heterogeneity; they are subdued in the low-strength case because of reduced heating with low τ. CSEP OVERVIEW (B-117) D. Schorlemmer, M.C. Gerstenberger, N. Hirata, D.D. Jackson, C. Jiang, T.H. Jordan, W. Marzocchi, K.Z. Nanjo, G. A. Papadopoulos, D.A. Rhoades, S. Wiemer, Z. Wu, J.D. Zechar, and CSEP Working Group The Collaboratory for the Study of Earthquake Predictability (CSEP) established 4 earthquake forecast testing centers around the world. These centers are rigorously testing more than 100 earthquake forecast models in a truly prospective manner. Centers are operating in Los Angeles (US), Wellington (NZ), Tokyo (JP), and Zurich (CH), covering many different regions and tectonic environments: California, New Zealand, Western Pacific, Japan, and Italy. Besides new upcoming regional earthquake forecast testing, CSEP has started a global testing program which is targeting the magnitude range of destructive earthquakes that are relevant for seismic hazard and risk. This program is the first link in the chain of facilities that aim to test seismic hazard and risk models and their underlying hypotheses. To complement the current activities, CSEP is developing methods for assessing the reliability of earthquake early warning algorithms, for understanding the uncertainties and limits of earthquake source inversions, and for the prospective testing of ground motion prediction models. CSEP researchers are also working on creating testable models for many seismological hypotheses, e.g. characteristic earthquakes, maximum magnitude to fault length relation. CSEP is collaborating with large modeling efforts like the Uniform California Earthquake Rupture Forecast (UCERF3) and the Global Earthquake Model (GEM). We present the ongoing activities and give perspectives for the future development of CSEP and its global collaboration. RESULTS FROM THE REGIONAL EARTHQUAKE LIKELIHOOD MODELS EXPERIMENT (B-119) 2011 SCEC Annual Meeting | 227
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Table of Contents Table of Contents
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SCEC Annual Meeting Program Sunday,
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15:15 Introduction to the Automatic
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Monday, September 12th 07:00 - 08:0
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MONDAY | Meeting Program observatio
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TUESDAY | Meeting Program evolution
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TUESDAY | Meeting Program 17:20 Dra
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WEDNESDAY | Meeting Program seismic
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SCEC DIrector | Report reviews, bot
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SCEC DIrector | Report The current
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SCEC DIrector | Report meetings to
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A Word of Thanks Figure 4. This "Br
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SCEC Advisory Council | Report Afte
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SCEC Advisory Council | Report and
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SCEC Advisory Council | Report 3. C
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Input and reaction to the SCEC4 Pro
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SCEC Advisory Council | Report meet
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Communication, Education, and Outre
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SCEC Research Accomplishments | Rep
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Lett., Seismological Society of Ame
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Funning et al. resurveyed 19 GPS si
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earthquakes. They find that plastic
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Earthquake Geology SCEC Research Ac
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SCEC researchers are also attemptin
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observed waveforms (after Olsen and
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urial depth, long-term tectonic str
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Figure 31. Image of the branching j
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Workshops SCEC Research Accomplishm
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Local-Scale Models CDM group resear
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Figure 54. CLM splitting from mantl
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Figure 59. The short-term rates aft
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esponse peaks to the incident groun
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Non-Linear Structural Simulations u
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References SCEC Research Accomplish
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Draft 2012 Science Plan SCEC Planni
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Draft 2012 Science Plan H. Award Pr
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B. Proposals may be strengthened by
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Draft 2012 Science Plan 2a. Improve
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A. Seismology Draft 2012 Science Pl
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Draft 2012 Science Plan • Quantif
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IX. Interdisciplinary Focus Areas D
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Draft 2012 Science Plan E. Developm
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Draft 2012 Science Plan objectives
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Draft 2012 Science Plan relax segme
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D. National Partnerships through Ea
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A-024 VISUALIZING STRUCTURAL RESPON
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A-137 DISCOVERING THE GEOMORPHIC RE
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A-103 IMPACTS OF STATIC AND DYNAMIC
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A-072 ANALYZING BUILDING RESPONSE T
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B-147 INCORPORATING GPS VELOCITIES
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INHIBITION OF VERY STRONG SHAKING,
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B-030 EARTHQUAKE CLUSTERING AND AFT
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B-127 SEISMOGRAM-BASED ASSESSMENT O
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Poster Abstracts New paleoseismolog
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Poster Abstracts ground motion depe
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Poster Abstracts this delay becomes
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Poster Abstracts time series analys
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Poster Abstracts of a ‘weight vec
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Perris2: .17, .16, .20, .23 Poster
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Poster Abstracts amplitude with the
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Poster Abstracts COMPARISON OF CO-L
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Poster Abstracts found at other sta
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Poster Abstracts This poster will p
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Poster Abstracts Previous models of
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Poster Abstracts of surface deforma
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ADDITIONAL SHEAR RESISTANCE FROM FA
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Poster Abstracts Seismic data were
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Poster Abstracts providing omega-sq
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Poster Abstracts understanding the
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Poster Abstracts Although substanti
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Poster Abstracts We will present th
Page 179 and 180: E.H. Hearn, F.F. Pollitz, W.R. That
Page 181 and 182: S. Hiemer, Q. Wang, D.D. Jackson, Y
Page 183 and 184: Poster Abstracts STRONG GROUND MOTI
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Page 187 and 188: Poster Abstracts velocity model in
Page 189 and 190: Poster Abstracts InSAR results base
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Page 195 and 196: Poster Abstracts CRUSTAL STRUCTURE
Page 197 and 198: Poster Abstracts volume from the RG
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Page 201 and 202: Poster Abstracts and Northridge Hil
Page 203 and 204: Poster Abstracts In an emergent vie
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Page 209 and 210: Poster Abstracts Pegasus WMS provid
Page 211 and 212: Poster Abstracts THE 2011 MW 9 TOHO
Page 213 and 214: Poster Abstracts has proved to be a
Page 215 and 216: Poster Abstracts Preliminary result
Page 217 and 218: Poster Abstracts Comparison of this
Page 219 and 220: Poster Abstracts DYNAMIC RUPTURE SI
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Page 229: Poster Abstracts SPACE GEODETIC INV
Page 233 and 234: ADVANCEMENTS IN PROBABILISTIC SEISM
Page 235 and 236: CONSTANT STRESS DROP FITS EARTHQUAK
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Page 239 and 240: Poster Abstracts mainshock, but the
Page 241 and 242: Poster Abstracts PLATE TECTONICS: A
Page 243 and 244: Poster Abstracts THE MECHANICS OF E
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Page 247 and 248: Poster Abstracts Geodetic and geolo
Page 249 and 250: COMPARISONS AMONG EARTHQUAKE SIMULA
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Page 257 and 258: Poster Abstracts safety zones for t
Page 259 and 260: Z. Xu and P. Chen Poster Abstracts
Page 261 and 262: Poster Abstracts The Whittier fault
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Page 265 and 266: Poster Abstracts ground motions whi
Page 267 and 268: FREYMUELLER Jeffrey, U Alaska Fairb
Page 269 and 270: RUIZ Ricardo, Chaffey HS RUNDLE Joh
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