The Mechanics of Deep Earthquakes

Green, Harry W.; Houston, Heidi

doi:10.1146/annurev.ea.23.050195.001125

Cited by 365 publications

(245 citation statements)

References 87 publications

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“…However, if we assume that the maximum earthquake size is similar at all depths, then we can estimate by calculating the seismic moment rate and comparing it to an approximate estimate of the subducting slab deformation in these depth intervals. There is no consensus (FROHLICH, 1989;STEIN, 1995;SILVER et al, 1995;GREEN and HOUSTON, 1995;LAY and WALLACE, 1995;KIRBY et al, 1996;NOTHARD et al, 1996;MCGUIRE et al, 1997) on the rupture geometry and mechanism of the deeper earthquakes. This uncertainty makes estimation of the deformation rate ambiguous and highly nonunique.…”

Section: Seismic Efficiency Coefficientmentioning

confidence: 99%

“…Global average values for the moment-frequency relation parameters are similar (Tables 1-5); therefore we conjecture that if we could observe regional seismicity for prolonged periods, we would see decreased regional random fluctuations. Might it similarly be possible that the depth distribution of deeper earthquakes which exhibits a bimodal pattern (FROHLICH, 1989;GREEN and HOUSTON, 1995;LAY and WALLACE, 1995), is also a transient feature?…”

Section: B-and I-6alue Variationsmentioning

confidence: 99%

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Universality of the Seismic Moment-frequency Relation

Kagan

1999

Seismicity Patterns, Their Statistical Significance and Physical Meaning

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149

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Abstract-We analyze the seismic moment-frequency relation in various depth ranges and for different seismic regions, using Flinn-Engdahl's regionalization of global seismicity. Three earthquake lists of centroid-moment tensor data have been used: the Harvard catalog, the USGS catalog, and the HUANG et al. (1997) catalog of deep earthquakes. The results confirm the universality of the i-values and the maximum moment for shallow earthquakes in continental regions, as well as at and near continental boundaries. Moreover, we show that although fluctuations in earthquake size distribution increase with depth, the i-values for earthquakes in the depth range of 0 -500 km exhibit no statistically significant regional variations. The regional variations are significant only for deep events near the 660 km boundary. For declustered shallow earthquake catalogs and deeper events, we show that the worldwide i-values have the same value of 0.609 0.02. This finding suggests that the i-value is a universal constant. We investigate the statistical correlations between the numbers of seismic events in different depth ranges and the correlation of the tectonic deformation rate and seismic activity (the number of earthquakes above a certain threshold level per year). The high level of these correlations suggests that seismic activity indicates tectonic deformation rate in subduction zones. Combined with the universality of the i-value, this finding implies little if any variation in maximum earthquake seismic moment among various subduction zones. If we assume that earthquakes of maximum size are similar in different depth ranges and the seismic efficiency coefficient, , is close to 100% for shallow seismicity, then we can estimate for deeper earthquakes: for intermediate earthquakes :5%, and : 1% for deep events. These results may lead to new theoretical understanding of the earthquake process and better estimates of seismic hazard.

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Section: Seismic Efficiency Coefficientmentioning

confidence: 99%

Section: B-and I-6alue Variationsmentioning

confidence: 99%

Universality of the Seismic Moment-frequency Relation

Kagan

1999

Seismicity Patterns, Their Statistical Significance and Physical Meaning

179

149

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“…Seismic wave radiation from deep-focus earthquakes is generally indistinguishable from that for shallow stick-slip frictional-sliding earthquakes, but the confining pressure and temperature are so high for deepfocus events that a distinct process is likely needed to account for their abrupt energy release (e.g., Green and Houston, 1995;Houston, 2015). The two largest recorded deep-focus earthquakes both have seismic wave radiation consistent with shear dislocation on one or more fault planes, but exhibit dramatic differences in rupture characteristics.…”

Section: Introductionmentioning

confidence: 99%

“…Currently favored ideas for nucleation and growth of deepfocus earthquakes include transformational faulting triggered by metastable olivine transforming to spinel in the cold, stressed core of the slab (e.g., Green and Burnley, 1989;Wiens et al, 1993;Green and Houston, 1995;Kirby et al, 1996;Green, 2007), thermal instability and run-away shear melting (Kanamori et al, 1998;Ogawa, 1987;Karato et al, 2001), and dehydration embrittlement (possibly involving release of H 2 O or CO 2 as hydrous or carbonate phases destabilize with increasing pressure) (e.g., Silver et al, 1995;Omori et al, 2004;Meade and Jeanloz, 1991). All of these proposed mechanisms are influenced by the thermal structure of deep slabs and the deviatoric stress conditions associated with the slabs impinging on the 660-km seismic discontinuity, which resists penetration due to the associated endothermic phase change of spinel to perovskite plus ferropericlase mineralogy (Green and Houston, 1995;Karato et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

“…All of these proposed mechanisms are influenced by the thermal structure of deep slabs and the deviatoric stress conditions associated with the slabs impinging on the 660-km seismic discontinuity, which resists penetration due to the associated endothermic phase change of spinel to perovskite plus ferropericlase mineralogy (Green and Houston, 1995;Karato et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

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The isolated ∼680 km deep 30 May 2015 MW 7.9 Ogasawara (Bonin) Islands earthquake

Lay

Zhan

et al. 2016

Earth and Planetary Science Letters

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The isolated ~680 km deep 30 May 2015 MW 7.9 Ogasawara (Bonin) Islands earthquake Deep-focus earthquakes, located in very high-pressure conditions 300 to 700 km below the Earth's surface within sinking slabs of relatively cold oceanic lithosphere, are mysterious phenomena. The largest recorded deep-focus earthquake (M W 7.9) in the Izu-Bonin slab struck on 30 May 2015 beneath the Ogasawara (Bonin) Islands, isolated from prior seismicity by over 100 km in depth, and followed by only a few small aftershocks. Globally, this is the deepest (680 km centroid depth) event with M W ≥ 7.8 in the seismological record. Seismicity indicates along-strike contortion of the Izu-Bonin slab, with horizontal flattening near a depth of 550 km in the Izu region and rapid steepening to near-vertical toward the south above the location of the 2015 event. This event was exceptionally well-recorded by seismic stations around the world, allowing detailed constraints to be placed on the source process. Analyses of a large global data set of P, SH and pP seismic phases using short-period back-projection, subevent directivity, and broadband finite-fault inversion indicate that the mainshock ruptured a shallowly-dipping fault plane with patchy slip that spread over a distance of ∼40 km with a multi-stage expansion rate (∼5+ km/s down-dip initially, ∼3 km/s up-dip later). During the 17 s total rupture duration the radiated energy was ∼3.3 × 10 16 J and the stress drop was ∼38 MPa. The radiation efficiency is moderate (0.34), intermediate to that of the 1994 Bolivia and 2013 Sea of Okhotsk M W 8.3 deep earthquakes, indicating that source processes of very large deep earthquakes sample a wide range of behavior from dissipative, more viscous failure to very brittle failure. The isolated occurrence of the event, much deeper than the apparently thermally-bounded distribution of Bonin-slab seismicity above 600 km depth, suggests that localized stress concentration associated with the pronounced deformation of the Izu-Bonin slab and proximity to the 660-km phase transition likely played a dominant role in generating this major earthquake.

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Breaking the oceanic lithosphere of a subducting slab: The 2013 Khash, Iran earthquake

Barnhart

Hayes

Samsonov

et al. 2014

Geophysical Research Letters

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[1] Large intermediate-depth, intraslab normal-faulting earthquakes are a common, dangerous, but poorly understood phenomenon in subduction zones owing to a paucity of near-field geophysical observations. Seismological and high-quality geodetic observations of the 2013 M w 7.7 Khash, Iran earthquake reveal that at least half of the oceanic lithosphere, including the mantle and entire crust, ruptured in a single earthquake, confirming with unprecedented resolution that large earthquakes can nucleate in and rupture through the oceanic mantle. A rupture width of at least 55 km is required to explain both Interferometric Synthetic Aperture Radar observations and teleseismic waveforms, with the majority of slip occurring in the oceanic mantle. Combining our well-constrained earthquake slip distributions with the causative fault orientation and geometry of the local subduction zone, we hypothesize that the Khash earthquake likely occurred as the combined result of slab-bending forces and dehydration of hydrous minerals along a preexisting fault formed prior to subduction.

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The Mechanics of Deep Earthquakes

Cited by 365 publications

References 87 publications

Universality of the Seismic Moment-frequency Relation

Universality of the Seismic Moment-frequency Relation

The isolated ∼680 km deep 30 May 2015 MW 7.9 Ogasawara (Bonin) Islands earthquake

Breaking the oceanic lithosphere of a subducting slab: The 2013 Khash, Iran earthquake

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