Damage in step‐overs may enable large cascading earthquakes

Finzi, Yaron; Langer, Sebastian

doi:10.1029/2012gl052436

Cited by 30 publications

(35 citation statements)

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“…We assume that both fault segments are embedded in a homogeneous elastic half‐space. However, most fault zones will include a low‐velocity layer surrounding the fault plane (Finzi & Langer, , ; Huang & Ampero, ; Lewis & Ben‐Zion, ,). The elastic modulus of this layer adjacent to the primary fault can be smaller than host rock and also different from the elastic modulus of the layer adjacent to the secondary fault.…”

Section: Discussionmentioning

confidence: 99%

Effect of Seismogenic Depth and Background Stress on Physical Limits of Earthquake Rupture Across Fault Step Overs

Bai

Ampuero

2017

JGR Solid Earth

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Earthquakes can rupture geometrically complex fault systems by breaching fault step overs. Quantifying the likelihood of rupture jump across step overs is important to evaluate earthquake hazard and to understand the interactions between dynamic rupture and fault growth processes. Here we investigate the role of seismogenic depth and background stress on physical limits of earthquake rupture across fault step overs. Our computational and theoretical study is focused on the canonical case of two parallel strike‐slip faults with large aspect ratio, uniform prestress and friction properties. We conduct a systematic set of 3‐D dynamic rupture simulations with different seismogenic depth, step over distance, and initial stresses. We find that the maximum step over distance Hc that a rupture can jump depends on seismogenic depth W and strength excess to stress drop ratio S, commonly used to evaluate probable rupture velocity, as Hc0.3em∝W/Sn, where n = 2 when Hc/W < 0.2 (or S > 1.5) and n = 1 otherwise. The critical nucleation size, largely controlled by frictional properties, has a second‐order effect on Hc. Rupture on the secondary fault is mainly triggered by the stopping phase emanated from the rupture end on the primary fault. Asymptotic analysis of the peak amplitude of stopping phases sheds light on the mechanical origin of the relations between Hc, W, and S, and leads to the scaling regime with n = 1 in far field and n = 2 in near field. The results suggest that strike‐slip earthquakes on faults with large seismogenic depth or operating at high shear stresses can jump wider step overs than observed so far in continental interplate earthquakes.

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Section: Discussionmentioning

confidence: 99%

Effect of Seismogenic Depth and Background Stress on Physical Limits of Earthquake Rupture Across Fault Step Overs

Bai

Ampuero

2017

JGR Solid Earth

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“…However, such principal stress orientation may require other mechanisms facilitating rupture transfers, such as: i) more complex fault geometries, including additional connecting fault segments as seen in fault traces by Liu et al [2003], ii) fault weakening mechanisms, such as strong velocity-weakening friction or the effect of thermal pressurization, since there is evidence of a fluid-saturated upper crust, [Fialko, 2004b], iii) compliant fault zones with reduced rigidity promoting rupture propagation [Finzi and Langer , 2012a]. Investigating the effects of these physical mechanisms on the dynamic rupture process of the Landers earthquake will be hopefully addressed in future work, but is beyond the scope of this study.…”

Section: Early Moment Release and Earthquake Initiationmentioning

confidence: 99%

Landers 1992 "reloaded": Integrative dynamic earthquake rupture modeling

Gabriel

Wollherr

Schliwa

et al. 2018

Preprint

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Key Points:• A new integrative physics-based simulation of the 1992 Landers earthquake reproduces a broad range of independent observation • Sustained dynamic rupture interconnecting the complex fault segments constraints pre-stress and fault strength • We discuss the interplay of rupture transfers, geometric fault complexity, initial stress, viscoelastic attenuation, and off-fault plasticity AbstractThe 1992 M w 7.3 Landers earthquake is perhaps one of the best studied seismic events. However, many aspects of the dynamics of the rupture process are still puzzling, e.g. how did rupture transfer between fault segments? We present 3D spontaneous dynamic rupture simulations of a new degree of realism, incorporating the interplay of fault geometry, topography, 3D rheology, off-fault plasticity and viscoelastic attenuation. The surprisingly unique scenario reproduces a broad range of observations, including final slip distribution, seismic moment-rate function, seismic waveform characteristics and peak ground velocities, as well as shallow slip deficits and mapped off-fault deformation patterns. Sustained dynamic rupture of all fault segments in general, and rupture transfers in particular, put strong constraints on amplitude and orientation of initial fault stresses and friction. Source dynamics include dynamic triggering over large distances and direct branching; rupture terminates spontaneously on most of the principal fault segments. We achieve good agreement between synthetic and observed waveform characteristics and associated peak ground velocities. Despite very complex rupture evolution, ground motion variability is close to what is commonly assumed in Ground Motion Prediction Equations. We examine the effects of variations in modeling parameterization, e.g. purely elastic setups or models neglecting viscoelastic attenuation, in comparison to our preferred model. Our integrative dynamic modeling approach demonstrates the potential of consistent in-scale earthquake rupture simulations for augmenting earthquake source observations and improving the understanding of earthquake source physics of complex, segmented fault systems.

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“…Both of these issues were subsequently, and dramatically, exemplified following the UCERF2 publication, by events such as the 2011 M 9 Tohoku earthquake with respect to segmentation (e.g., Kagan and Jackson, 2013), the 2011 M 6.3 Christchurch earthquake in terms of spatiotemporal clustering (e.g., Kaiser et al, 2012), and both the 2010 M 7.2 El Mayor-Cucapah and 2012 M 8.6 Sumatra earthquakes in regard to multifault ruptures (e.g., Hauksson et al, 2011;Meng et al, 2012). There is also now a substantial body of literature on the viability of multifault ruptures (e.g., Segall and Pollard, 1980;Knuepfer, 1989;Harris et al, 1991;Harris and Day, 1993;Lettis et al, 2002;Duan and Oglesby, 2006;Wesnousky, 2006;Shaw and Dieterich, 2007;Black and Jackson, 2008;and Finzi and Langer, 2012).…”

Section: Introductionmentioning

confidence: 99%

Uniform California Earthquake Rupture Forecast, Version 3 (UCERF3)--The Time-Independent Model

Field

Arrowsmith

Biasi

et al. 2014

Bulletin of the Seismological Society of America

506

467

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The 2014 Working Group on California Earthquake Probabilities (WGCEP14) present the time-independent component of the Uniform California Earthquake Rupture Forecast, Version 3 (UCERF3), which provides authoritative estimates of the magnitude, location, and time-averaged frequency of potentially damaging earthquakes in California. The primary achievements have been to relax fault segmentation and include multifault ruptures, both limitations of UCERF2. The rates of all earthquakes are solved for simultaneously and from a broader range of data, using a system-level inversion that is both conceptually simple and extensible. The inverse problem is large and underdetermined, so a range of models is sampled using an efficient simulated annealing algorithm. The approach is more derivative than prescriptive (e.g., magnitude-frequency distributions are no longer assumed), so new analysis tools were developed for exploring solutions. Epistemic uncertainties were also accounted for using 1440 alternative logic-tree branches, necessitating access to supercomputers. The most influential uncertainties include alternative deformation models (fault slip rates), a new smoothed seismicity algorithm, alternative values for the total rate of M w ≥ 5 events, and different scaling relationships, virtually all of which are new. As a notable first, three deformation models are based on kinematically consistent inversions of geodetic and geologic data, also providing slip-rate constraints on faults previously excluded due to lack of geologic data. The grand inversion constitutes a system-level framework for testing hypotheses and balancing the influence of different experts. For example, we demonstrate serious challenges with the Gutenberg-Richter hypothesis for individual faults. UCERF3 is still an approximation of the system, however, and the range of models is limited (e.g., constrained to stay close to UCERF2). Nevertheless, UCERF3 removes the apparent UCERF2 overprediction of M 6.5-7 earthquake rates and also includes types of multifault ruptures seen in nature. Although UCERF3 fits the data better than UCERF2 overall, there may be areas that warrant further site-specific investigation. Supporting products may be of general interest, and we list key assumptions and avenues for future model improvements. Manuscript OrganizationBecause of manuscript length and model complexity, we begin with an outline of this report to help readers navigate the various sections:

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Damage in step‐overs may enable large cascading earthquakes

Cited by 30 publications

References 50 publications

Effect of Seismogenic Depth and Background Stress on Physical Limits of Earthquake Rupture Across Fault Step Overs

Effect of Seismogenic Depth and Background Stress on Physical Limits of Earthquake Rupture Across Fault Step Overs

Landers 1992 "reloaded": Integrative dynamic earthquake rupture modeling

Uniform California Earthquake Rupture Forecast, Version 3 (UCERF3)--The Time-Independent Model

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