A slow earthquake

Kanamori, Hiroo; Stewart, Gordon S.

doi:10.1016/0031-9201(79)90112-2

Cited by 80 publications

(37 citation statements)

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“…Slow slip events (sometimes referred to as slow earthquakes) had been recognized for some time in the literature using strainmeters (Linde et al, 1996) and seismometers (e.g., Kanamori and Stewart, 1979), although their importance and locations only became apparent when networks of GPS stations started recording and documenting their widespread occurrence. Associated with slow slip, a new source of seismic energy (called non-volcanic tremor) in the forearc was discovered by Obara (2002) off southwest Japan, which appeared as coherent noise propagating across arrays of seismograph stations.…”

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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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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“…Injection-triggered earthquakes have accompanied injection projects undertaken for various purposes, including the production of geothermal energy (3), secondary recovery in oil and gas fields (4), the disposal of fluid wastes, and (very rarely) hydrofracturing (5,6).…”

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Two-year survey comparing earthquake activity and injection-well locations in the Barnett Shale, Texas

Frohlich

2012

Proc. Natl. Acad. Sci. U.S.A.

228

164

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, temporary seismographs deployed under the EarthScope USArray program were situated on a 70-km grid covering the Barnett Shale in Texas, recording data that allowed sensing and locating regional earthquakes with magnitudes 1.5 and larger. I analyzed these data and located 67 earthquakes, more than eight times as many as reported by the National Earthquake Information Center. All 24 of the most reliably located epicenters occurred in eight groups within 3.2 km of one or more injection wells. These included wells near Dallas-Fort Worth and Cleburne, Texas, where earthquakes near injection wells were reported by the media in 2008 and 2009, as well as wells in six other locations, including several where no earthquakes have been reported previously. This suggests injection-triggered earthquakes are more common than is generally recognized. All the wells nearest to the earthquake groups reported maximum monthly injection rates exceeding 150,000 barrels of water per month (24,000 m 3 ∕mo) since October 2006. However, while 9 of 27 such wells in Johnson County were near earthquakes, elsewhere no earthquakes occurred near wells with similar injection rates. A plausible hypothesis to explain these observations is that injection only triggers earthquakes if injected fluids reach and relieve friction on a suitably oriented, nearby fault that is experiencing regional tectonic stress. Testing this hypothesis would require identifying geographic regions where there is interpreted subsurface structure information available to determine whether there are faults near seismically active and seismically quiescent injection wells.induced earthquakes | triggered earthquakes | unconventional gas development | seismic hazards | domestic energy policy

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“…Although the catastrophe implicit in (3) and (1) is very strong, there is a finite probability, because of the heterogeneity of the fault, that the rupture will propagate into regions in which k < K o during the nucleation phase and stop. What results is a slow earthquake 1 Kanamori, 1972;Kanamori and Stewart, 1979; Sacks et al, 19781. We expect, of course, that this is an uncommon phenomenon but worthy of study because it yields a minimum estimate of the moment in the nucleation phase.…”

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confidence: 99%

Theory of time‐dependent rupture in the Earth

Das

Scholz²

1981

J. Geophys. Res.

331

188

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Using the concepts of fracture mechanics, we develop a theory of the = earthquake mechanism which includes the phenomenon of suberitical crack growth.^.The theory specifically predicts the following phenomena: slow earthquakes, f i multiple events, delayed multiple events (doublets), postseismic rupture growth and afterslip, foreshocks, and aftershocks. The theory also predicts that there must be a nucleation stage prior to an earthquake, and suggests a physical mechanism by o _ which one earthquake may 'trigger' another, We investigate in detail two phenomena of special interest and which are not predicted by ordinary fracture mechanics: nucleation and delayed multiple events.In the first case we find that all earthquakes must be preceded by quesistatic slip over a portion of their rupture surfaces, but it may be difficult to deteet in practice. In the second case we studied two pairs of delayed multiple events that were separated by the same 'barrier' in order to calculate n. We find that the stress corrosion index, n -24. EMost oxides and silicates, however, exhibit more complicated behavior due to environmental effects. For these materials, the crack will propagate when k > Ko, where Ko < Kc, at a velocity X which is a well defined function of k.This propagation is stable and quasistatic and is referred to as suberitical crack growth. (We shall use the terms "stable", "quasi-static" and "subaritieal" to mein propagation at velocities much less than the sonic velocities of the medium). This behavior results from stress induced corrosion at the crack tip, the principal corrodent for the present application being H2O. This behavior has been firmly established in the laboratory for Mode I (tensile) cracks in a wide variety of materials including silicates and silicate glasses (see, e.g., Scholz, 1968aScholz, , 1972aMartin, 1972; Wiederhorn and Bolz, 1970;Atkinson, 1979;Lawn and Wilshaw, 1975; Knott, 19731.The form of the relationship between k and X does not vary significantly with the material; only the parameters in the law vary. As an example we show in Since n, the stress corrosion index, is large (12.5 in Fig. 1 Later we shall determine n for an earthquake and show that it is in remarkable agreement with Atkinson's results. Although we cannot prove this assumption, it seems entirely reasonable since when one considers the physical mechanism of stress corrosion there seems to be no physico-chemical reason why the process should depend on mode. The indirect evidence in support of this is that rock exhibits dilatant creep and static fatigue, both processes that result from stress corrosion, in compression and under high confining pressure (Scholz, 1968a; Kranz and Scholz, 1977; Kranz, 19801. We shall also assume that there is a lower limit, Ko, such that when k < K o no crack growth occurs. There is only limited data to K*c is a material property that for these materials can be measured only in a corrodent-free environment, e.g., a high vacuum. K c, on the other hand, is not an independent mater...

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A slow earthquake

Cited by 80 publications

References 10 publications

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

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

Two-year survey comparing earthquake activity and injection-well locations in the Barnett Shale, Texas

Theory of time‐dependent rupture in the Earth

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