Depth to the Juan de Fuca slab beneath the Cascadia subduction margin– A 3-D model for sorting earthquakes

McCrory, Patricia A.; Blair, J. Luke; Oppenheimer, David H.; Walter, Stephen R.

doi:10.3133/ds91

Cited by 128 publications

(220 citation statements)

References 25 publications

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“…The characters of surface rupture distribution and the seismic reflection profiles indicate that the Chi-Chi earthquake occurred on a thrust nappe structure with a straight fault plane [40]. However, for those great earthquakes taking place on subducting interplate boundary like the 2010 Chile earthquake and the 2011 Japan earthquake, the ruptured surface on subduction fault usually has significant curvature regarding the characteristic rupture length (≥200-300 km) of great earthquakes [41].…”

Section: Discussionmentioning

confidence: 99%

Lushan M S7.0 earthquake: A special earthquake occurs on curved fault

et al. 2013

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Relocation result shows that the aftershocks of the Lushan M S 7.0 earthquake spatially distribute in a shape like "half bowl", indicating that the rupture structure of the mainshock is a highly curved surface. Kinematic analysis reveals that a laterally varied dislocation pattern occurs on this curved fault even though a single relative horizontal movement controls slip on this fault. Reverse slip prevails on curved fault. However, significant normal slip is predicted near the edge of north flank. Moreover, the north flank features left-lateral slip while the south flank contrarily features right-lateral slip. The relative scope of aftershock distribution implies inadequate breaking of the curved fault during the mainshock, calling for the attention to potential earthquake risk on the neighboring portions of the coseismic rupture due to significant increase of the coseismic Coulomb stress. Coseismic stress modeling also reveals that it is unnecessary for the stress on ruptured part to be unloaded following the earthquakes on the curved fault. The coseismic stress loading on ruptured elements unveils the specialty of faulting for the Lushan earthquake and we conclude that this specialty is due to the highly curved fault geometry.

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Section: Discussionmentioning

confidence: 99%

Lushan M S7.0 earthquake: A special earthquake occurs on curved fault

et al. 2013

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“…1) using data on the geometry and tectonic behavior of the subduction zone (Goldfinger et al 1992(Goldfinger et al , 2007Mitchell et al 1994;Hyndman and Wang 1995;McCrory et al 2004;McCaffrey et al 2007) and evolving inferences on size and frequency of earthquakes over the last 10,000 years derived from the offshore turbidite record (modified after Goldfinger et al 2008 and summarized in Goldfinger et al 2009). We assume that fault slip must roughly equal plate convergence (coupling ratio = 1.0), and that variations in time intervals between offshore turbidites are representative of variations in coseismic slip.…”

Section: Approachmentioning

confidence: 99%

Confidence levels for tsunami-inundation limits in northern Oregon inferred from a 10,000-year history of great earthquakes at the Cascadia subduction zone

et al. 2009

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To explore the local tsunami hazard from the Cascadia subduction zone we (1) evaluate geologically reasonable variability of the earthquake rupture process, (2) specify 25 deterministic earthquake sources, and (3) use resulting vertical coseismic deformations for simulation of tsunami inundation at Cannon Beach, Oregon. Maximum runup was 9-30 m (NAVD88) from earthquakes with slip of *8-38 m and M w *8.3-9.4. Minimum subduction zone slip consistent with three tsunami deposits was 14-15 m. By assigning variable weights to the source scenarios using a logic tree, we derived percentile inundation lines that express the confidence level (percentage) that a Cascadia tsunami will not exceed the line. Ninety-nine percent of Cascadia tsunami variation is covered by runup B30 m and 90% B16 m with a ''preferred'' (highest weight) value of *10 m. A hypothetical maximum-considered distant tsunami had runup of *11 m, while the historical maximum was *6.5 m.

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“…The USGS model was adopted in the 2008 USGS National Seismic Hazard Maps, while the 2012 GSC model was adopted in the 2015 National Building Code of Canada hazard maps. The geometry of the fault plane is mainly based on 3D dislocation models by Flück et al (1997) and Wang et al (2003), which were updated by McCrory et al (2006), to incorporate information from new seismic reflection/refraction studies.…”

Section: Fault Rupture Modelmentioning

confidence: 99%

Overview of Ground-Motion Issues for Cascadia Megathrust Events: Simulation of Ground-Motions and Earthquake Site Response

Ghofrani

Atkinson

Molnar

2017

Front. Built Environ.

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Ground motions for earthquakes of M7.5 to 9.0 on the Cascadia subduction interface are simulated based on a stochastic finite-fault model and used to estimate average response spectra for reference firm soil conditions. The simulations are first validated by modeling the wealth of ground-motion data from the 2011 M9.0 Tohoku earthquake of Japan. Adjustments to the calibrated model are then made to consider average source, attenuation and site parameters for the Cascadia region. This includes an evaluation of the likely variability in stress drop for large interface earthquakes and an assessment of regional attenuation and site effects. We perform best-estimate simulations for a preferred set of input parameters. Typical results suggest mean values of 5%-damped pseudoacceleration in the range from about 100 to 200 cm/s 2 , at frequencies from 1 to 4 Hz, for firm-ground conditions in Vancouver. Uncertainty in most-likely value of the parameter representing stress drop causes variability in simulated response spectra of about ±50%. Uncertainties in the attenuation model produce even larger variability in response spectral amplitudes-a factor of about two at a closest distance to the rupture plane (Rcd) of 100 km, becoming even larger at greater distances. It is thus important to establish the regional attenuation model for ground-motion simulations and to bound the source properties controlling radiation of ground motion. We calculate theoretical onedimensional spectral amplification estimates for four selected Fraser River Delta sites to show how the presence of softer sediments in the region may alter the predicted ground motions. The amplification functions are largely consistent with observed spectral amplification at Fraser River delta sites, suggesting amplification by factors of 2.5-5 at the peak frequency of the site; we note that deep sites in the delta have a low peak frequency, ∼0.3 Hz. This work will aid in seismic hazard assessment and mitigation efforts in the active Cascadia region of southwestern BC. An important consideration is that the uncertainties are large and present a dominant unknown when assessing seismic risk. We find that variability in the expected motions exceeds a factor of two even on rock-like sites, with uncertainty in site response further increasing this factor. Such large uncertainties pose a major challenge in preparing for the potential consequences of the next megathrust event in Cascadia.

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Depth to the Juan de Fuca slab beneath the Cascadia subduction margin– A 3-D model for sorting earthquakes

Cited by 128 publications

References 25 publications

Lushan M S7.0 earthquake: A special earthquake occurs on curved fault

Lushan M S7.0 earthquake: A special earthquake occurs on curved fault

Confidence levels for tsunami-inundation limits in northern Oregon inferred from a 10,000-year history of great earthquakes at the Cascadia subduction zone

Overview of Ground-Motion Issues for Cascadia Megathrust Events: Simulation of Ground-Motions and Earthquake Site Response

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