Deep Earthquakes

Frohlich, Cliff

doi:10.1038/scientificamerican0189-48

Cited by 75 publications

(162 citation statements)

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“…All of these events are characterized by shear slip on faults, just as shallow crustal earthquakes. However, anomalous behavior is observed for these deep seismic events, including a significant non‐double‐couple mechanisms [ Richardson and Jordan , ], radiated seismic energies [ Wiens , ], b ‐values and aftershock sequences [ Frohlich , ; Houston , ; Wiens and Gilbert , ], and source durations and stress drops [ Campus and Das , ; Frohlich , ; Houston , ; Poli and Prieto , ] that often differ from those observed for shallow events. Detailed comparison between deep earthquakes shows a large diversity of rupture behavior [ Wiens , ; Poli and Prieto , ], with mainly slow rupture velocity and low‐efficiency events observed in warm subducted slabs, and faster more energetic ruptures in cold slabs [ Chen et al ., ; Kanamori et al ., ; Zhan et al ., ; Poli et al ., ].…”

Section: Introductionmentioning

confidence: 99%

Global rupture parameters for deep and intermediate‐depth earthquakes

Poli

Prieto

2016

JGR Solid Earth

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We investigate the global rupture parameters for deep and intermediate‐depth earthquakes. From measurements of rupture duration and radiated seismic energy we estimate stress drop, apparent stress, and radiation efficiency and obtain a detailed earthquake energy budget. From scaling of the source parameters we highlight differences between crustal and deep seismicity, with the latter showing larger fracture energies. The observed increase of radiation efficiency with depth suggests that rupture mechanism for deep and intermediate‐depth events differs. In agreement with previous studies we observe along‐strike variability of rupture properties for deep and intermediate‐depth earthquakes, correlating with slab morphology, plate age, or presence of volcanic structures.

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Section: Introductionmentioning

confidence: 99%

Global rupture parameters for deep and intermediate‐depth earthquakes

Poli

Prieto

2016

JGR Solid Earth

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“…At shallow depths (≤60 km) where temperatures are low, deformation of the upper layers of the subducting plate is achieved primarily by brittle faulting. As subduction continues and temperature and confining pressure increase, ductile creep should become the dominant mode of deformation [e.g., Frohlich , 2006]. Nevertheless, several subduction zones have earthquakes with hypocentral depths (z h ) as great as 650–700 km.…”

Section: Introductionmentioning

confidence: 99%

Fault plane orientations of deep earthquakes in the Izu‐Bonin‐Marianas subduction zone

Myhill

Warren

2012

J. Geophys. Res.

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[1] We make use of the effects of rupture directivity on waveform shape to analyze the rupture processes of 58 large, deep earthquakes in the Izu-Bonin-Marianas subduction zone. For more than half of the analyzed earthquakes, we determine a best-fitting unilateral rupture direction using teleseismic data. For 20 of these earthquakes, the constraints on the rupture direction allow the fault plane to be identified. Where the subducting slab dips at a moderate angle, near-horizontal fault planes dominate at all studied depths (50-600 km). Within more steeply dipping slabs, fault planes tend to dip toward the south and west. Rotated into the plane of the slab, the poles of the definitively identified faults form a single tight cluster pointing up and toward the surface of the slab. Identified ruptures have a tendency to propagate away from the top surface of the slab between 100 and 300 km depth, but appear to be randomly oriented at greater depths. The occurrence of predominantly near-horizontal faults at intermediate depths agrees with previous observations in several other subduction zones. However, at depths ≥300 km, the results from the Izu-Bonin-Marianas system differ from those previously obtained for Tonga-Kermadec, where both horizontal and vertical faults were identified. We consider various physical mechanisms to explain our observations and conclude that, while pre-existing slab structures may be reactivated if they are favorably oriented, the observed asymmetry in deep fault orientations may instead result from external forces acting on the slab, and resulting changes in slab morphology.

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“…Solid lines are field boundaries from Figure 2a. Curved vertical lines are slab temperature trajectories calculated following Turcotte and Schubert [2001] and Frohlich [2004]. Slabs are abbreviated from left to right as follows: T, Tonga; I, Indonesia; M, Marianas; I, Izu‐Bonin; K, Kurile; J, Japan; P, Philippines; S, South America.…”

Section: Global Deep Seismicity Comparisonmentioning

confidence: 99%

Seismic constraints on mechanisms of deep earthquake rupture

Estabrook

2004

J. Geophys. Res.

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[1] Observations of the depth distribution of seismicity suggest that several mechanisms cause deep earthquakes. Cold subducting slabs exhibit a broad peak in seismicity between 300 and 530 km depth that is best explained by transformational faulting of metastable olivine. Cumulative seismic moment release increases sharply at $530 km depth in both cold and warm slabs, implying that events deeper than this are controlled by an equilibrium rather than a metastable phase change, which would be temperaturedependent. This, together with the observation that deep seismicity predominates near the garnet-rich upper boundary of the subducting plate (former oceanic crust), suggests that the transformation of garnet to perovskite, which may release considerable water, is integral in the cause of earthquakes deeper than 530 km, where most deep earthquakes occur.

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Deep Earthquakes

Cited by 75 publications

References 0 publications

Global rupture parameters for deep and intermediate‐depth earthquakes

Global rupture parameters for deep and intermediate‐depth earthquakes

Fault plane orientations of deep earthquakes in the Izu‐Bonin‐Marianas subduction zone

Seismic constraints on mechanisms of deep earthquake rupture

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