Slow Earthquakes Coincident with Episodic Tremors and Slow Slip Events

Ito, Yoshihiro; Obara, Kazushige; Shiomi, Katsuhiko; Sekine, Shutaro; Hirose, Hiroo

doi:10.1126/science.1134454

Cited by 453 publications

(524 citation statements)

References 21 publications

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“…Slow earthquakes have also been reported in other tectonic environments such as the San Andreas fault (Linde et al, 1996) and Hawaii (Segall et al, 2006;Montgomery-Brown et al, 2009). Although several hypotheses have been proposed to explain these events (e.g., Ito et al, 2007;Schwartz and Rokosky, 2007;Brodsky and Mori, 2007;Ide, 2008;Liu and Rice, 2009;Ando et al, 2010;Hawthorne and Rubin, 2010;Ide, 2010;Liu and Rubin, 2010;Peng and Gomberg, 2010;Shibazaki et al, 2010), the physical mechanisms are still not fully understood.…”

Section: Introductionmentioning

confidence: 96%

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Scaling Relationships of Source Parameters for Slow Slip Events

Gao

Schmidt

Weldon

2012

Bulletin of the Seismological Society of America

108

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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Section: Introductionmentioning

confidence: 96%

“…Faults that exhibit slow slip and tremor could consist of many small-sized stronger asperities surrounded by weaker regions. The asperity model for earthquakes was first extended to SSEs as a way to explain the variety of SSEs observed on subduction zones (Ito et al, 2007).…”

Section: Average Rupture Velocity Versus Seismic Momentmentioning

confidence: 99%

Scaling Relationships of Source Parameters for Slow Slip Events

Gao

Schmidt

Weldon

2012

Bulletin of the Seismological Society of America

108

169

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“…We suggest that ductile failure of ultramylonite zones may provide a viable mechanism inducing earthquakes in the lower crust [Maggi et al, 2000]. Likewise, ductile failure is a possible mechanism explaining the occurrence of intermediate and deep nonvolcanic tremors in subduction zones [Obara, 2002;Obara and Hirose, 2006;Ito and Obara, 2006;Ito et al, 2007;Brown et al, 2009] and fault zones [Nadeau and Dolenc, 2005], which are commonly assumed to be generated by dehydration reactions and/or fluid pressure pulses.…”

Section: Geological Applicationmentioning

confidence: 99%

Superplasticity and ductile fracture of synthetic feldspar deformed to large strain

Rybacki¹,

Wirth²,

Dresen³

2010

J. Geophys. Res.

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[1] We performed high-strain torsion experiments on fine-grained (≈4 mm) anorthite aggregates in a Paterson-type gas deformation apparatus. The dense hydrous (≈0.1 wt% H 2 O) samples contain < 3 vol% Si-enriched residual glass located at triple junctions. Specimens were twisted at constant rate to a maximum shear strain of about 5 at experimental conditions of 100-400 MPa confining pressure, temperatures of 950°C-1200°C, and shear strain rates of ≈2 × 10 −5 , 5 × 10 −5 , and 2 × 10 −4 s −1 . Resulting maximum shear stresses at the sample periphery were in the range of ≈2-80 MPa. The samples showed strain hardening at slow deformation rate and strain weakening at fast strain rate, respectively. Fitting the stress strain rate data to a power law yields linear viscous behavior. Microstructural analysis shows locally enhanced dislocation density, suggesting diffusion-assisted and/or dislocation-assisted grain boundary sliding as the dominant deformation mechanism. Deformed samples exhibit abundant cavities, nucleated mostly at grain triple junctions and at grain boundaries in response to cooperative grain boundary sliding. At shear strains ≥ 2, growth and coalescence of the cavities form an anastomozing network of regularly spaced strings oriented at about 30°to the direction of maximum compressive stress and ∼15°to the shear plane. Strain is localized along these shear bands associated with a shape-preferred orientation of high-aspect ratio feldspar grains and with segregation of initial pore fluids (residual glass) into the bands. More than one third of the samples were deformed to terminal failure that occurred suddenly at shear strains of ≈3-5. The experiments indicate that cavitation damage may facilitate fluid flow and deep seismicity in highly strained shear zones.Citation: Rybacki, E., R. Wirth, and G. Dresen (2010), Superplasticity and ductile fracture of synthetic feldspar deformed to large strain,

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“…The position and effects of earthquake rupture are therefore relatively well understood, and the structure of the margin is well imaged. More recently, very low frequency (VLF) earthquakes and slow slip events have also been recorded, in the shallowest and deeper parts of the subduction system, respectively (Obara and Ito, 2005;Ito et al, 2007). The region offshore the Kii peninsula is the focus of the NanTroSEIZE experiment drilling transect and marks the western end of the 1944 earthquake rupture zone (Fig.…”

Section: Introductionmentioning

confidence: 99%

IODP Expedition 319, NanTroSEIZE Stage 2: First IODP Riser Drilling Operations and Observatory Installation Towards Understanding Subduction Zone Seismogenesis

McNeill

Saffer

Byrne

et al. 2010

Scientific Drilling

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The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is a major drilling project designed to investigate fault mechanics and the seismogenic behavior of subduction zone plate boundaries. Expedition 319 is the first riser drilling operation within scientific ocean drilling. Operations included riser drilling at Site C0009 in the forearc basin above the plate boundary fault, non-riser drilling at Site C0010 across the shallow part of the megasplay fault system-which may slip during plate boundary earthquakes-and initial drilling at Site C0011 (incoming oceanic plate) for Expedition 322. At Site C0009, new methods were tested, including analysis of drill mud cuttings and gas, and in situ measurements of stress, pore pressure, and permeability. These results, in conjunction with earlier drilling, will provide a) the history of forearc basin development (including links to growth of the megasplay fault system and modern prism), b) the first in situ hydrological measurements of the plate boundary hanging wall, and c) integration of in situ stress measurements (orientation and magnitude) across the forearc and with depth. A vertical seismic profile (VSP) experiment provides improved constraints on the deeper structure of the subduction zone. At Site C0010, logging-while-drilling measurements indicate significant changes in fault zone and hanging wall properties over short (<5 km) along-strike distances, suggesting different burial and/or uplift history. The first borehole observatory instruments were installed at Site C0010 to monitor pressure and temperature within the megasplay fault zone, and methods of deployment of more complex observatory instruments were tested for future operations.

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Slow Earthquakes Coincident with Episodic Tremors and Slow Slip Events

Cited by 453 publications

References 21 publications

Scaling Relationships of Source Parameters for Slow Slip Events

Scaling Relationships of Source Parameters for Slow Slip Events

Superplasticity and ductile fracture of synthetic feldspar deformed to large strain

IODP Expedition 319, NanTroSEIZE Stage 2: First IODP Riser Drilling Operations and Observatory Installation Towards Understanding Subduction Zone Seismogenesis

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