Mega-earthquakes rupture flat megathrusts

Blétery, Quentin; Thomas, Amanda M.; Rempel, A. W.; Karlstrom, L.; Sladen, Anthony; Barros, Louis De

doi:10.1126/science.aag0482

Cited by 109 publications

(100 citation statements)

References 46 publications

(4 reference statements)

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“…In addition, we found a positive correlation between the curvature of the incoming plate prior to subduction and swarm activity. Given that plate curvature is related to both the hydration of the incoming plate before subduction and heterogeneity on the plate interface [e.g., Ranero et al , ; Shillington et al , ; Bletery et al , ], the positive correlation between plate curvature and swarm activity implies that earthquake swarms are more likely to occur in subduction zones with abundant fluids and marked heterogeneity on the plate interface. SSEs are also known to occur in regions where fluids are abundant [ Kodaira et al , ; Saffer and Tobin , ], meaning that this correlation is also consistent with the idea that SSEs trigger earthquake swarms in subduction zones.…”

Section: Resultsmentioning

confidence: 99%

Detection of earthquake swarms at subduction zones globally: Insights into tectonic controls on swarm activity

Nishikawa

Ide

2017

JGR Solid Earth

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Earthquake swarms are characterized by an increase in seismicity rate that lacks a distinguished main shock and does not obey Omori's law. At subduction zones, they are thought to be related to slow‐slip events (SSEs) on the plate interface. Earthquake swarms in subduction zones can therefore be used as potential indicators of slow‐slip events. However, the global distribution of earthquake swarms at subduction zones remains unclear. Here we present a method for detecting such earthquake sequences using the space‐time epidemic‐type aftershock‐sequence model. We applied this method to seismicity (M ≥ 4.5) recorded in the Advanced National Seismic System catalog at subduction zones during the period of 1995–2009. We detected 453 swarms, which is about 6.7 times the number observed in a previous catalog. Foreshocks of some large earthquakes are also detected as earthquake swarms. In some subduction zones, such as at Ibaraki‐Oki, Japan, swarm‐like foreshocks and ordinary swarms repeatedly occur at the same location. Given that both foreshocks and swarms are related to SSEs on the plate interface, these regions may have experienced recurring SSEs. We then compare the swarm activity and tectonic properties of subduction zones, finding that swarm activity is positively correlated with curvature of the incoming plate before subduction. This result implies that swarm activity is controlled either by hydration of the incoming plate or by heterogeneity on the plate interface due to fracturing related to slab bending.

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Section: Resultsmentioning

confidence: 99%

Detection of earthquake swarms at subduction zones globally: Insights into tectonic controls on swarm activity

Nishikawa

Ide

2017

JGR Solid Earth

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“…Recent studies have suggested that smoother megathrusts naturally lead to larger earthquakes because a more homogeneous interface allows for more uniform fault strength distributions (Bletery et al, 2016). Recent studies have suggested that smoother megathrusts naturally lead to larger earthquakes because a more homogeneous interface allows for more uniform fault strength distributions (Bletery et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

How the Transition Region Along the Cascadia Megathrust Influences Coseismic Behavior: Insights From 2‐D Dynamic Rupture Simulations

Ramos

Huang

2019

Geophysical Research Letters

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There is a strong need to model potential rupture behaviors for the next Cascadia megathrust earthquake. However, there exists significant uncertainty regarding the extent of downdip rupture and rupture speed. To address this problem, we study how the transition region (i.e., the gap), which separates the locked from slow‐slip regions, influences coseismic rupture propagation using 2‐D dynamic rupture simulations governed by a slip‐weakening friction law. We show that rupture propagation through the gap is strongly controlled by the amount of accumulated tectonic initial shear stress and gap friction level. A large amplitude negative dynamic stress drop is needed to arrest downdip rupture. We also observe downdip supershear rupture when the gradient in effective normal stress from the locked to slow‐slip regions is dramatic. Our results justify kinematic rupture models that extend below the gap and suggests the possibility of high‐frequency energy radiation during the next Cascadia megathrust earthquake.

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“…Curvature of the megathrust is strongly correlated with average dip angle of the megathrust, but it is also influenced by dip of the deeper slab, which may cause shear strength to vary across the plate boundary. More shallowly dipping, flatter boundaries are able to support larger earthquakes due to more homogeneous strength (e.g., Bletery et al, 2016). The nature of the upper plate, being either continental or oceanic, also appears to be important, as are factors such as the presence of back-arc spreading and trench roll-back (Scholz and Campos, 2012).…”

Section: Large-scale Subduction Zone Parametersmentioning

confidence: 99%

Subduction zone megathrust earthquakes

2018

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Subduction zone megathrust faults host Earth's largest earthquakes, along with multitudes of smaller events that contribute to plate convergence. An understanding of the faulting behavior of megathrusts is central to seismic and tsunami hazard assessment around subduction zone margins. Cumulative sliding displacement across each megathrust, which extends from the trench to the downdip transition to interplate ductile deformation, is accommodated by a combination of rapid stick-slip earthquakes, episodic slow-slip events, and quasi-static creep. Megathrust faults have heterogeneous frictional properties that contribute to earthquake diversity, which is considered here in terms of regional variations in maximum recorded magnitudes, Gutenberg-Richter b values, earthquake productivity, and cumulative seismic moment depth distributions for the major subduction zones. Great earthquakes on megathrusts occur in irregular cycles of interseismic strain accumulation, foreshock activity, main-shock rupture, postseismic slip, viscoelastic relaxation, and fault healing, with all stages now being captured by geophysical monitoring. Observations of depth-dependent radiation characteristics, large earthquake slip distributions, variations in rupture velocities, radiated energy and stress drop, and relationships to aftershock distributions and afterslip are discussed. Seismic sequences for very large events have some degree of regularity within subduction zone segments, but this can be complicated by supercycles of intermittent huge ruptures that traverse segment boundaries. Factors influencing variability of large megathrust ruptures, such as large-scale plate structure and kinematics, presence of sediments and fluids, lower-plate bathymetric roughness, and upper-plate structure, are discussed. The diversity of megathrust failure processes presents a suite of natural hazards, including earthquake shaking, submarine slumping, and tsunami generation. Improved monitoring of the offshore environment is needed to better quantify and mitigate the threats posed by megathrust earthquakes globally.

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Mega-earthquakes rupture flat megathrusts

Cited by 109 publications

References 46 publications

Detection of earthquake swarms at subduction zones globally: Insights into tectonic controls on swarm activity

Detection of earthquake swarms at subduction zones globally: Insights into tectonic controls on swarm activity

How the Transition Region Along the Cascadia Megathrust Influences Coseismic Behavior: Insights From 2‐D Dynamic Rupture Simulations

Subduction zone megathrust earthquakes

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