Pole-Tide Modulation of Slow Slip Events at Circum-Pacific Subduction Zones

Shen, Zheng‐Kang; Wang, Qingliang; Bürgmann, Roland; Wan, Yizhao; Ning, Jieyuan

doi:10.1785/0120050020

Cited by 35 publications

(38 citation statements)

References 45 publications

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“…For example, the 14-month periodicity of ETS in Northern Cascadia has the same periodicity as the Chandler Wobble (also called the pole-tides). Based on this connection, some have argued that the small gravitation changes associated with the Chandler Wobble are responsible for the periodicity of ETS in Cascadia (Miller et al, 2002;Shen et al, 2005). Similar claims have been made for ETS in Mexico and Japan, where climatic loading has been argued as the source of the~12 and~6 month periodicities of ETS in those locations respectively (Lowry, 2006).…”

Section: Case Study Ii: Stress Interactions Of Tremor With Other Eartmentioning

confidence: 73%

Non-volcanic Tremor: A Window into the Roots of Fault Zones

Rubinstein

Shelly

Ellsworth

2009

New Frontiers in Integrated Solid Earth Sciences

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The recent discovery of non-volcanic tremor in Japan and the coincidence of tremor with slow-slip in Cascadia have made earth scientists reevaluate our models for the physical processes in subduction zones and on faults in general. Subduction zones have been studied very closely since the discovery of slow-slip and tremor. This has led to the discovery of a number of related phenomena including low frequency earthquakes and very low frequency earthquakes. All of these events fall into what some have called a new class of events that are governed under a different frictional regime than simple brittle failure. While this model is appealing to many, consensus as to exactly what process generates tremor has yet to be reached. Tremor and related events also provide a window into the deep roots of subduction zones, a poorly understood region that is largely devoid of seismicity. Given that such fundamental questions remain about non-volcanic tremor, slow-slip, and the region in which they occur, we expect that this will be a fruitful field for a long time to come.

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Section: Case Study Ii: Stress Interactions Of Tremor With Other Eartmentioning

confidence: 73%

Non-volcanic Tremor: A Window into the Roots of Fault Zones

Rubinstein

Shelly

Ellsworth

2009

New Frontiers in Integrated Solid Earth Sciences

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“…Early attempts at explaining the periodicity of ETS appealed to modulation by periodic external forces including seasonal hydrologic loads (Lowry, 2006) and the Earth's 14-month pole tides (Shen et al, 2005). In the first case periodic slow fault slip may be a resonant response to small cyclical stress perturbations driven by climatic redistribution of the atmosphere, hydrosphere and cryosphere.…”

Section: Structural Controls On Deep Slow Earthquake Recurrencementioning

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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“…Factors controlling ETS periodicity are poorly constrained. One possibility involves modulation by periodic external forces including seasonal hydrologic loads and the Earth's 14-month pole tides [16][17][18] , but these cannot explain the wide range of observed periods. Segmentation of ETS behaviour in Cascadia correlates qualitatively with the overriding forearc structure and geology 3 ; however, the exact nature of this relation is elusive.…”

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confidence: 99%

Possible control of subduction zone slow-earthquake periodicity by silica enrichment

Audet

Bürgmann

2014

Nature

174

211

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Seismic and geodetic observations in subduction zone forearcs indicate that slow earthquakes, including episodic tremor and slip, recur at intervals of less than six months to more than two years. In Cascadia, slow slip is segmented along strike and tremor data show a gradation from large, infrequent slip episodes to small, frequent slip events with increasing depth of the plate interface. Observations and models of slow slip and tremor require the presence of near-lithostatic pore-fluid pressures in slow-earthquake source regions; however, direct evidence of factors controlling the variability in recurrence times is elusive. Here we compile seismic data from subduction zone forearcs exhibiting recurring slow earthquakes and show that the average ratio of compressional (P)-wave velocity to shear (S)-wave velocity (vP/vS) of the overlying forearc crust ranges between 1.6 and 2.0 and is linearly related to the average recurrence time of slow earthquakes. In northern Cascadia, forearc vP/vS values decrease with increasing depth of the plate interface and with decreasing tremor-episode recurrence intervals. Low vP/vS values require a large addition of quartz in a mostly mafic forearc environment. We propose that silica enrichment varying from 5 per cent to 15 per cent by volume from slab-derived fluids and upward mineralization in quartz veins can explain the range of observed vP/vS values as well as the downdip decrease in vP/vS. The solubility of silica depends on temperature, and deposition prevails near the base of the forearc crust. We further propose that the strong temperature dependence of healing and permeability reduction in silica-rich fault gouge via dissolution-precipitation creep can explain the reduction in tremor recurrence time with progressive silica enrichment. Lower gouge permeability at higher temperatures leads to faster fluid overpressure development and low effective fault-normal stress, and therefore shorter recurrence times. Our results also agree with numerical models of slip stabilization under fault zone dilatancy strengthening caused by decreasing fluid pressure as pore space increases. This implies that temperature-dependent silica deposition, permeability reduction and fluid overpressure development control dilatancy and slow-earthquake behaviour.

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Pole-Tide Modulation of Slow Slip Events at Circum-Pacific Subduction Zones

Cited by 35 publications

References 45 publications

Non-volcanic Tremor: A Window into the Roots of Fault Zones

Non-volcanic Tremor: A Window into the Roots of Fault Zones

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

Possible control of subduction zone slow-earthquake periodicity by silica enrichment

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