Seismotectonics of the Loma Prieta, California, region determined from three‐dimensional Vp, Vp/ Vs, and seismicity

Eberhart‐Phillips, Donna; Michael, Andrew J.

doi:10.1029/98jb01984

Cited by 132 publications

(100 citation statements)

References 47 publications

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“…These are regional studies, although they can center on specific faults, with a resolution of a few km. (b) Seismic reflection/refraction and travel time tomography (e.g., [7], [8] …”

Section: Imaging Methods and Data Typementioning

confidence: 99%

Characterization of Fault Zones

Ben‐Zion

Sammis

2003

Seismic Motion, Lithospheric Structures, Earthquake and Volcanic Sources: The Keiiti Aki Volume

108

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There are currently three major competing views on the nature of earthquake fault zones. The first is that faults are (possibly segmented and heterogeneous) Euclidean zones in a continuum solid. The second focuses on granular aspects of faults and deformation fields. The third is that faults are fundamentally rough fractal objects at all relevant scales. The existing data can not distinguish unequivocally between the three different views or determine their scale of relevance. However, in each observational category, the highest resolution results associated with mature faults are compatible with the continuum-Euclidean framework. A positive feedback mechanism associated with strain weakening attracts the long-term evolution of faults toward progressive regularization and Euclidean geometry. A negative feedback mechanism associated with strain hardening during initial deformation phases and around persisting geometrical irregularities generates renewed complexity. We conclude that long term slip accommodation may be accounted for to first order within the continuumEuclidean framework.

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“…These are regional studies, although they can center on specific faults, with a resolution of a few km. (b) Seismic reflection/refraction and travel time tomography (e.g., [7], [8] …”

Section: Imaging Methods and Data Typementioning

confidence: 99%

Characterization of Fault Zones

Ben‐Zion

Sammis

2003

Seismic Motion, Lithospheric Structures, Earthquake and Volcanic Sources: The Keiiti Aki Volume

108

View full text Add to dashboard Cite

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“…They used waveform cross-correlation to obtain precise relative locations for nearly 5000 magnitude 1 -3 earthquakes distributed over 60 km of the San Andreas fault near San Juan Bautista. As at Parkfield, lower velocity rocks here lie to the NE [Eberhart-Phillips and Michael, 1998;Rubin, 2002a;McGuire and Ben-Zion, 2005], so the expected direction of preferred propagation for subshear ruptures is to the SE. Roughly 300 of the microearthquakes had aftershocks that occurred within 10 hours and roughly 2 mainshock radii of the mainshock centroid.…”

Section: Introductionmentioning

confidence: 99%

Aftershock asymmetry on a bimaterial interface

2007

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[1] To better understand the asymmetric distribution of microearthquake aftershocks along the central San Andreas fault, we study dynamic models of slip-weakening ruptures on an interface separating differing elastic half-spaces. Subshear ruptures grow as slightly asymmetric bilateral cracks, with larger propagation velocities, slip velocities, and normal stress changes at the rupture front moving in the direction of slip of the medium with the lower shear wave speed (the southeast front, in the context of the San Andreas). When the SE front encounters a stress barrier, the tensile stress perturbation behind the rupture front continues forward and for a wide range of barrier strengths nucleates a dying slip pulse. This slip pulse smooths the stress field and reduces the static stress change beyond the SE front. Furthermore, because the tensile stress that carried the slip pulse into the barrier is a purely dynamic phenomenon, the SE rupture front can be left far below the failure threshold, while the NW front remains quite close to failure. Both mechanisms could contribute to the observed aftershock asymmetry. Formation of a robust slip pulse requires a peak tensile stress perturbation that approaches the nominal strength drop of the slip-weakening law. To achieve this while minimizing off-fault damage requires either substantial velocity contrasts or small reductions in friction. The simulations also show a pronounced asymmetry in the timescales over which barriers to the SE and NW experience increasing stresses, a result that has implications for the asymmetric distribution of subevents in compound earthquakes.

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“…The model resolution matrix describes the distribution of information for each node, such that each row describes the resolution of a model parameter and how well the information has peaked at this particular node or smeared to adjacent nodes (Thurber, 1993;Eberhart-Phillips and Reyners, 1997;Eberhart-Phillips and Michael, 1998;Yao et al, 1999). It provides information necessary for interpreting the distribution of ray-paths ( Figure 6) and the degree and pattern of smoothing.…”

Section: Resolution and Robustness Of Modelsmentioning

confidence: 99%

“…Estimating model fidelity or resolution in earthquake tomography may be performed by several means, such as inspecting the diagonal elements of the resolution matrix (Roeker, 1982), or by evaluating reconstructed synthetic models (e.g., checkerboards) for specific earthquake or station geometry (Humphreys and Clayton, 1988;Eberhart-Phillips and Michael, 1998).…”

Section: Resolution and Robustness Of Modelsmentioning

confidence: 99%

“…Many tomographic studies (Thurber, 1983;Eberhart-Phillips, 1990;Eberhart-Phillips and Michael, 1998), invert local earthquake arrival times for hypocentre locations and velocity structure in two steps: 1. joint inversion for the 1D velocity model and hypocentre locations, followed by 2. joint inversion for the 3D velocity model and hypocentre locations.…”

Section: A Priori Hypocentre Location For Inversionmentioning

confidence: 99%

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