Periodic Slow Earthquakes from the Cascadia Subduction Zone

Miller, M. Meghan; Melbourne, Tim; Johnson, Daniel J.; Sumner, William Q.

doi:10.1126/science.1071193

Cited by 248 publications

(198 citation statements)

References 8 publications

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“…Subduction zone megathrusts host a wide range of fault behaviors including interseismic creep, slow earthquakes, earthquakes with normal (fast) rupture velocity, tsunamogenic earthquakes, postseismic slip, and fault healing [Satake, 1994;Draggert et al, 2001, Miller et al, 2002McGuire and Segall, 2003]. These observations indicate that the limits of the seismogenic zone must be carefully defined in both space and time.…”

Section: Fault Friction and The Upper Transition From Seismic To Aseimentioning

confidence: 99%

12. Fault Friction and the Upper Transition from Seismic to Aseismic Faulting

Marone¹,

Saffer²

2007

The Seismogenic Zone of Subduction Thrust Faults

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This paper discusses the processes and mechanical factors that define the seismogenic zone and the updip transition from seismic to aseismic faulting. We review friction laws for granular and clay-rich fault zones and discuss them in the context of the mechanics of stick-slip and the requirements for instability. Seismogenic faulting is driven by the unstable release of stored elastic energy, and thus explanations of the upper stability transition must be couched in terms of fault-zone rheology. We summarize several observations that define the seismogenic zone and its upper boundary, including microseismicity, earthquake afterslip, and the spatial distribution of seismic moment release during large earthquakes. We focus on two hypotheses for the updip limit of seismic faulting. The clay mineral hypothesis posits that a thermally driven transition from a smectite to an illite structure produces a transition from aseismic to seismic behavior. The fault gouge lithification hypothesis posits that the stability transition reflects a threshold consolidation, or lithification, state and a switch from pervasive to localized shear. Existing laboratory data, which cover a limited range of conditions, indicate that the smectite-illite transformation results in an increase in friction but not a transition from stable to unstable behavior. It appears that other depth-and temperature-dependent processes may play an important role in altering the frictional properties of subduction faults and establishing the updip seismic limit.

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Section: Fault Friction and The Upper Transition From Seismic To Aseimentioning

confidence: 99%

12. Fault Friction and the Upper Transition from Seismic to Aseismic Faulting

Marone¹,

Saffer²

2007

The Seismogenic Zone of Subduction Thrust Faults

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“…The northern Cascadia subduction zone is where aseismic slow slip was discovered by Dragert et al (2001) and Miller et al (2002) using GPS data. Rogers and Dragert (2003) characterized the recurrence of aseismic slow slip in conjunction with non-volcanic tremor beneath southern Vancouver Island that firmly established the presence of slow episodic megathrust fault rupture downdip of the seismogenic zone.…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

Teleseismic constraints on the geological environment of deep episodic slow earthquakes in subduction zone forearcs: A review

2016

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More than a decade after the discovery of deep episodic slow slip and tremor, or slow earthquakes, at subduction zones, much research has been carried out to investigate the structural and seismic properties of the environment in which they occur. Slow earthquakes generally occur on the megathrust fault some distance downdip of the great earthquake seismogenic zone in the vicinity of the mantle wedge corner, where three major structural elements are in contact: the subducting oceanic crust, the overriding forearc crust and the continental mantle. In this region, thermo-petrological models predict significant fluid production from the dehydrating oceanic crust and mantle due to prograde metamorphic reactions, and their consumption by hydrating the mantle wedge. These fluids are expected to affect the dynamic stability of the megathrust fault and enable slow slip by increasing pore-fluid pressure and/or reducing friction in fault gouges.Resolving the fine-scale structure of the deep megathrust fault and the in situ distribution of fluids where slow earthquakes occur is challenging, and most advances have been made using A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTteleseismic scattering techniques (e.g., receiver functions). In this paper we review the teleseismic structure of six well-studied subduction zones (three hot, i.e., Cascadia, southwest Japan, central Mexico, and three cool, i.e., Costa Rica, Alaska, and Hikurangi) that exhibit slow earthquake processes and discuss the evidence of structural and geological controls on the slow earthquake behavior. We conclude that changes in the mechanical properties of geological materials downdip of the seismogenic zone play a dominant role in controlling slow earthquake behavior, and that near-lithostatic pore-fluid pressures near the megathrust fault may be a necessary but insufficient condition for their occurrence.

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“…The short and regular recurrence interval of ∼14:5 months (Miller et al, 2002) for SSEs in northern Cascadia makes this area ideal to test the recurrence behavior. Among the catalog of the Cascadia SSEs (Schmidt and Gao, 2010), 11 are centered near the Olympic peninsula in Washington.…”

Section: Recurrence Statisticsmentioning

confidence: 99%

Scaling Relationships of Source Parameters for Slow Slip Events

Gao

Schmidt

Weldon

2012

Bulletin of the Seismological Society of America

111

169

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To better understand the physical mechanisms of slow slip events (SSEs) detected worldwide, we explore the scaling relationships of various source parameters and compare them with similar scaling laws for earthquakes. These scaling relationships highlight differences and similarities between slow slip events and earthquakes and hold implications for the degree of heterogeneity and fault-healing characteristics. The static stress drop remains constant for different-sized events as is observed for earthquakes. However, the static stress drop of slow slip events is within a range of 0.01-1.0 MPa, 1-2 orders of magnitude lower than that found for earthquakes, which could be related to the low stress state on the fault. The average rupture velocity, ranging from kilometers per second to kilometers per day, decreases linearly with increasing seismic moment in log-log space, unlike earthquakes that are nearly constant. This inverse relationship of rupture velocity with seismic moment could be related to the heterogeneity of fault properties. Slow slip events typically have ratios of event duration over dislocation rise time less than 3, while earthquakes have ratios greater than 3. This indicates that slow slip events are less pulselike than earthquakes in their mode of propagation and suggests that the healing behind the rupture front is delayed. The recurrence statistics of slow slip events on the northern Cascadia subduction zone are weakly time predictable and moderately antislip predictable (that is, the event size and preevent recurrence interval are anticorrelated), which may indicate that healing between events strengthens the fault with time.

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Periodic Slow Earthquakes from the Cascadia Subduction Zone

Cited by 248 publications

References 8 publications

12. Fault Friction and the Upper Transition from Seismic to Aseismic Faulting

12. Fault Friction and the Upper Transition from Seismic to Aseismic Faulting

Teleseismic constraints on the geological environment of deep episodic slow earthquakes in subduction zone forearcs: A review

Scaling Relationships of Source Parameters for Slow Slip Events

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