Why large earthquakes do not nucleate at shallow depths

Das, S.; Scholz, C. H.

doi:10.1038/305621a0

Cited by 182 publications

(79 citation statements)

References 11 publications

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“…12), supporting our idea of a two-layer model of the lithospheric mantle deformation. Numerical modelling studies suggest that the large earthquakes initiate in a large stress-drop regime at greater depth whereas small earthquakes initiate at shallow depth 52 , confirmed by the 2012 earthquakes, supporting our observation.…”

Section: Discussionsupporting

confidence: 87%

“…Sediments and the crust follow the Byerlee law rheology 43 . Just below the Moho, the presence of only B10-15% of lizardite serpentinization can reduce the strength of the lithosphere significantly 52 , and particularly that of serpentinite-bearing faults, owing to its low coefficient of friction relative to the Byerlee law (mB0.3-0.4 versus mB0.85). At a depth of 25-30 km, at the stability limit of lizardite serpentinite, the strength of the lithosphere should increase due to the change in friction according to the Byerlee law (mB0.85).…”

Section: Discussionmentioning

confidence: 99%

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Seismic evidence of a two-layer lithospheric deformation in the Indian Ocean

Qin

Singh

2015

Nat Commun

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Intra-plate deformation and associated earthquakes are enigmatic features on the Earth. The Wharton Basin in the Indian Ocean is one of the most active intra-plate deformation zones, confirmed by the occurrence of the 2012 great earthquakes (MwZ8.2). These earthquakes seem to have ruptured the whole lithosphere, but how this deformation is distributed at depth remains unknown. Here we present seismic reflection images that show faults down to 45 km depth. The amplitude of these reflections in the mantle first decreases with depth down to 25 km and then remains constant down to 45 km. The number of faults imaged along the profile and the number of earthquakes as a function of depth show a similar pattern, suggesting that the lithospheric mantle deformation can be divided into two layers: a highly fractured fluid-filled serpentinized upper layer and a pristine brittle lithospheric mantle where great earthquakes initiate and large stress drops occur.

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Section: Discussionsupporting

confidence: 87%

Section: Discussionmentioning

confidence: 99%

Seismic evidence of a two-layer lithospheric deformation in the Indian Ocean

Qin

Singh

2015

Nat Commun

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“…The magnitude-depth relationship shows that moderate to larger earthquakes are more likely to nucleate near the base of the seismogenic zone in the ELA basin area, which is consistent with previous studies (Sibson, 1982;Das and Scholz, 1983). One of the statistical parameters that depicts the properties of regional seismicity is the b value in the (Gutenberg and Richter, 1944).…”

Section: Discussionsupporting

confidence: 77%

Evidence for Vertical Partitioning of Strike-Slip and Compressional Tectonics from Seismicity, Focal Mechanisms, and Stress Drops in the East Los Angeles Basin Area, California

Yang¹,

Hauksson²

2011

Bulletin of the Seismological Society of America

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We have synthesized the characteristics of the seismogenic zone in the east Los Angeles basin by analyzing earthquake data recorded during the past 30 years . The seismicity is distributed along the Whittier fault, with the majority of earthquakes located adjacent to the south side, in the depth range from 0 to 9 km, with b value of 1:1 0:05 and mostly normal and strike-slip faulting. Within the depth range of 9-12 km, the seismicity is scattered uniformly across the region, the b value is 1:0 0:05, and all three faulting styles are present. At the deepest depths (12-18 km), seismicity is sparse and primarily limited to a few clusters striking north; these deeper earthquakes primarily have reverse fault motion, and the b value is 0:78 0:04. Inversion of high-quality focal-mechanism data for the orientation of the regional stress field showed that the direction of maximum compressional stress rotates from N12°W at shallow depth to due north at the bottom of the seismogenic zone. Similarly, a depth dependence is observed in stress drops calculated from P-wave source spectra, which indicate stress drop generally increases from ∼7 MPa at shallow depth (3 km) to ∼53 MPa at the base of the seismogenic zone (17 km). Overall, our results provide new evidence for the vertical partitioning of styles of deformation and state of stress within this complex fault system in the east Los Angeles basin.Online Material: Stress drop fits to source spectra.

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“…A rough fault at shallow depths, unable to produce significant seismicity because of low lithospheric pressure (see Figure 5) [Das and Scholz, 1983], with a seismologically conditionally stable roughness profile ( Figure 6b);…”

Section: Implications For Subduction Zone Seismogenesismentioning

confidence: 99%

Seismic variability of subduction thrust faults: Insights from laboratory models

Corbi¹,

Funiciello²,

Faccenna³

et al. 2011

J. Geophys. Res.

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[1] Laboratory models are realized to investigate the role of interface roughness, driving rate, and pressure on friction dynamics. The setup consists of a gelatin block driven at constant velocity over sand paper. The interface roughness is quantified in terms of amplitude and wavelength of protrusions, jointly expressed by a reference roughness parameter obtained by their product. Frictional behavior shows a systematic dependence on system parameters. Both stick slip and stable sliding occur, depending on driving rate and interface roughness. Stress drop and frequency of slip episodes vary directly and inversely, respectively, with the reference roughness parameter, reflecting the fundamental role for the amplitude of protrusions. An increase in pressure tends to favor stick slip. Static friction is a steeply decreasing function of the reference roughness parameter. The velocity strengthening/weakening parameter in the state-and rate-dependent dynamic friction law becomes negative for specific values of the reference roughness parameter which are intermediate with respect to the explored range. Despite the simplifications of the adopted setup, which does not address the problem of off-fault fracturing, a comparison of the experimental results with the depth distribution of seismic energy release along subduction thrust faults leads to the hypothesis that their behavior is primarily controlled by the depth-and time-dependent distribution of protrusions. A rough subduction fault at shallow depths, unable to produce significant seismicity because of low lithostatic pressure, evolves into a moderately rough, velocity-weakening fault at intermediate depths. The magnitude of events in this range is calibrated by the interplay between surface roughness and subduction rate. At larger depths, the roughness further decreases and stable sliding becomes gradually more predominant. Thus, although interplate seismicity is ultimately controlled by tectonic parameters (velocity of the plates/trench and the thermal regime), the direct control is exercised by the resulting frictional properties of the plate interface.

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Why large earthquakes do not nucleate at shallow depths

Cited by 182 publications

References 11 publications

Seismic evidence of a two-layer lithospheric deformation in the Indian Ocean

Seismic evidence of a two-layer lithospheric deformation in the Indian Ocean

Evidence for Vertical Partitioning of Strike-Slip and Compressional Tectonics from Seismicity, Focal Mechanisms, and Stress Drops in the East Los Angeles Basin Area, California

Seismic variability of subduction thrust faults: Insights from laboratory models

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