Nonplanar Faults: Mechanics of Slip and Off-fault Damage

Dieterich, James H.; Smith, D. E.

doi:10.1007/978-3-0346-0138-2_12

Cited by 61 publications

(90 citation statements)

References 31 publications

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“…Helmstetter and Shaw [2006] showed similar results from numerical simulations of the aftershock occurrence by using the rate-and statedependent friction law [e.g., Dieterich, 1994, Dieterich et al, 2000. Several studies also considered the aftershock occurrence associated with heterogeneous stress change due to the complex slip [e.g., Marsan, 2006;Hainzl and Marsan, 2008] or with nonplanar faults [Dieterich and Smith, 2009]. These results are generally consistent with our observations on the relationship between aftershock distribution and the main shock slip in Figure 8.…”

Section: Aftershock Seismicity and Slip Distribution Of The Main Shocksupporting

confidence: 87%

Kīholo Bay, Hawai‘i, earthquake sequence of 2006: Relationship of the main shock slip with locations and source parameters of aftershocks

2010

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[1] We study the source process of the Kīholo Bay earthquake (M W 6.7), which occurred beneath the northwest part of the Island of Hawai'i on 15 October 2006, and static stress drops of small earthquakes that occurred in 2006 and 2007 around the main shock including aftershocks. We relocate the aftershocks to determine the fault plane from the two nodal planes. The relocated aftershocks define an E-W trending plane that dips to the south, in good agreement with one of the nodal planes given by the Global Centroid Moment Tensor solution. Waveform inversion is performed with multiple time windows to investigate the rupture speed and the slip distribution of the main shock. Waveforms of an aftershock with M W 5.2 are used to calculate empirical Green's functions. Our results indicate that the rupture propagated unilaterally to the west with a rupture speed greater than 3.0 km/s (63% of the shear wave velocity). This westward rupture is consistent with the fact that aftershocks are distributed predominantly to the west of the main shock epicenter. Most aftershocks are located on the edge of patches with a large slip, or asperities and some also occur inside the patches. We also estimate static stress drops of 39 earthquakes (2.5 < M L < 3.5) that occurred in 2006 and 2007 near the source region of the Kīholo Bay earthquake. Static stress drops range from 0.12 to 8.6 MPa and aftershocks around large slip patches of the main shock likely to have larger stress drops.

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Section: Aftershock Seismicity and Slip Distribution Of The Main Shocksupporting

confidence: 87%

Kīholo Bay, Hawai‘i, earthquake sequence of 2006: Relationship of the main shock slip with locations and source parameters of aftershocks

2010

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“…More than one slip surface is involved, different elements of the moment tensor have different time functions, and a volume change is generally present. However, in recent years there have been a number of studies of off-fault seismicity, which consists of the small earthquakes that are invariably found in a zone extending away from tectonic faults (see for instance POLIAKOV et al 2002;RICE et al 2005;VIESCA et al 2008;SAMMIS et al 2009;DIETERICH and SMITH 2009;POWERS and JORDAN 2010). Thus, while the induced earthquakes and extended crack model of this study may not be appropriate analogs for ordinary tectonic earthquakes, they may be more appropriate analogs for the off-fault seismicity that accompanies tectonic earthquakes.…”

Section: Figure 10mentioning

confidence: 86%

A Source Model for Induced Earthquakes at the Geysers Geothermal Reservoir

Johnson

2014

Pure Appl. Geophys.

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Abstract-The results of a previous study on source mechanisms of small earthquakes at the Geysers geothermal reservoir in northern California are used to investigate an extended crack model for seismic events. The seismic events are characterized by their first-degree moment tensors and interpreted in terms of a model that is a combination of a shear crack and wing cracks. Solutions to both forward and inverse problems are obtained that can be used with either dynamic or static moment tensors. The model contains failure criteria, explains isotropic parts that are commonly observed in induced earthquakes, and produces estimates of crack dimensions and maximum amount of slip. Effects of fluid pressure are easily incorporated into the model as an effective stress. The model is applied to static moment tensors of 20 earthquakes that occurred during a controlled injection project in the northwest Geysers. For earthquakes in the moment magnitude range of 0.9-2.8, the model predicts shear crack radii in the range of 10-150 m, wing crack lengths in the range of 2-25 m, and maximum slips in the range of 0.3-1.1 cm. Only limited results are obtained for the time-dependence of the earthquake process, but the model is consistent with corner frequencies of the isotropic part of the moment tensor being greater than the deviatoric part and waveforms of direct p waves that become more emergent for larger events.

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“…The model does not account for numerous factors in the faulting process, including opening normal to the fault, nonuniform friction, displacement gradients, influence of fault tips, host rock anisotropy, selfaffine fault geometries, 3-D fault geometries, or pore fluid pressure variability [e.g., Dieterich and Smith, 2009;Griffith et al, 2010;Ritz and Pollard, 2012;Ritz et al, 2015]. As a result, it does not account for changes in elastic moduli in the damage zone resulting from accumulated inelastic deformation [e.g., Faulkner et al, 2006;Cappa et al, 2014;Xu et al, 2014].…”

Section: Journal Of Geophysical Research: Solid Earthmentioning

confidence: 99%

The damage is done: Low fault friction recorded in the damage zone of the shallow Japan Trench décollement

Keren

Kirkpatrick

2016

JGR Solid Earth

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Fault damage zones record the integrated deformation caused by repeated slip on faults and reflect the conditions that control slip behavior. To investigate the Japan Trench décollement, we characterized the damage zone close to the fault from drill core recovered during Integrated Ocean Drilling Program Expedition 343 (Japan Trench Fast Drilling Project (JFAST)). Core‐scale and microscale structures include phyllosilicate bands, shear fractures, and joints. They are most abundant near the décollement and decrease in density sharply above and below the fault. Power law fits describing the change in structure density with distance from the fault result in decay exponents (n) of 1.57 in the footwall and 0.73 in the hanging wall. Microstructure decay exponents are 1.09 in the footwall and 0.50 in the hanging wall. Observed damage zone thickness is on the order of a few tens of meters. Core‐scale structures dip between ~10° and ~70° and are mutually crosscutting. Compared to similar offset faults, the décollement has large decay exponents and a relatively narrow damage zone. Motivated by independent constraints demonstrating that the plate boundary is weak, we tested if the observed damage zone characteristics could be consistent with low‐friction fault. Quasi‐static models of off‐fault stresses and deformation due to slip on a wavy, frictional fault under conditions similar to the JFAST site predict that low‐friction fault produces narrow damage zones with no preferred orientations of structures. These results are consistent with long‐term frictional weakness on the décollement at the JFAST site.

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Nonplanar Faults: Mechanics of Slip and Off-fault Damage

Cited by 61 publications

References 31 publications

Kīholo Bay, Hawai‘i, earthquake sequence of 2006: Relationship of the main shock slip with locations and source parameters of aftershocks

Kīholo Bay, Hawai‘i, earthquake sequence of 2006: Relationship of the main shock slip with locations and source parameters of aftershocks

A Source Model for Induced Earthquakes at the Geysers Geothermal Reservoir

The damage is done: Low fault friction recorded in the damage zone of the shallow Japan Trench décollement

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