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Barbot, S, Fialko Y, Sandwell D.  2008.  Effect of a compliant fault zone on the inferred earthquake slip distribution. Journal of Geophysical Research-Solid Earth. 113   10.1029/2007jb005256   AbstractWebsite

We present a new semi-analytic method to evaluate the deformation due to a screw dislocation in arbitrarily heterogeneous and/or anisotropic elastic half plane. The method employs integral transformations to reduce the governing partial differential equations to the integral Fredholm equation of the second kind. Dislocation sources, as well as spatial perturbations in the elastic properties are modeled using equivalent body forces. The solution to the Fredholm equation is obtained in the Fourier domain using a method of successive over-relaxation, and is mapped into the spatial domain using the inverse Fast Fourier Transform. We apply this method to investigate the effect of a soft damage zone around an earthquake fault on the co-seismic displacement field, and on the earthquake slip distribution inferred from inversions of geodetic data. In the presence of a kilometer-wide damage zone with a reduction of the effective shear modulus of a factor of 2, inversions that assume a laterally homogeneous model tend to underestimate the amount of slip in the middle of the seismogenic layer by as much as 20%. This bias may accentuate the inferred maxima in the seismic moment release at depth between 3-6 km suggested by previous studies of large strike-slip earthquakes.

Fialko, Y.  2001.  On origin of near-axis volcanism and faulting at fast spreading mid-ocean ridges. Earth and Planetary Science Letters. 190:31-39.   10.1016/s0012-821x(01)00376-4   AbstractWebsite

At fast and superfast spreading mid-ocean ridges, such as the East Pacific Rise, a plate boundary is defined by a narrow (tens to hundreds of meters wide) neovolcanic zone within which the bulk of the upper oceanic crust is created. However, detailed near-bottom observations indicate that the volcanic construction may occasionally persist several kilometers off of the ridge axis. It has been proposed that off-axis volcanism manifests tapping of a wide melting region that supplies magma to the ridge axis, or spatial migration of magmatic sources in the crust and upper mantle. We demonstrate that off-axis eruptions may be a natural consequence of variations in magma supply rate even if the ridge axis is stationary in space, and the magma delivery is perfectly focussed at the ridge axis. Theoretical modeling and field observations indicate that off-axis volcanisin may result from magma emplacement in sills that propagate toward the surface after their characteristic horizontal size exceeds their emplacement depth. Volcanic construction and faulting due to sill intrusions may contribute to the formation of abyssal hills, arguably the most abundant relief form on Earth. (C) 2001 Elsevier Science B.V. All rights reserved.

Fialko, Y, Simons M.  2000.  Deformation and seismicity in the Coso geothermal area, Inyo County, California: Observations and modeling using satellite radar interferometry. Journal of Geophysical Research-Solid Earth. 105:21781-21793.   10.1029/2000jb900169   AbstractWebsite

Interferometric synthetic aperture radar (InSAR) data collected in the Coso geothermal area, eastern California, during 1993-1999 indicate ground subsidence over a similar to 50 km(2) region that approximately coincides with the production area of the Coso geothermal plant. The maximum subsidence rate in the peak of the anomaly is similar to 3.5 cm yr(-1), and the average volumetric rate of subsidence is of the order of 10(6) m(3) yr(-1). The radar interferograms reveal a complex deformation pattern, with at least two irregular subsidence peaks in the northern part of the anomaly and a region of relative uplift on the south. We invert the InSAR displacement data for the positions, geometry, and relative strengths of the deformation sources at depth using a nonlinear least squares minimization algorithm. We use elastic solutions for a prolate uniformly pressurized spheroidal cavity in a semi-infinite body as basis functions for our inversions. Source depths inferred from our simulations range from 1 to 3 km, which corresponds to the production depths of the Coso geothermal plant. Underpressures in the geothermal reservoir inferred from the inversion are of the order of 0.1-1 MPa (except a few abnormally high underpressures that are apparently biased toward the small source dimensions). Analysis of the InSAR data covering consecutive time intervals indicates that the depths and/or horizontal extent of the deformation sources may increase with time. This increase presumably reflects increasing volumes of the subsurface reservoir affected by the geothermal exploitation. We show that clusters of microearthquakes associated with the geothermal power operation may result from perturbations in the pore fluid pressure, as well as normal and shear stresses caused by the deflation of the geothermal reservoir.

Fialko, YA, Rubin AM.  1998.  Thermodynamics of lateral dike propagation: Implications for crustal accretion at slow spreading mid-ocean ridges. Journal of Geophysical Research-Solid Earth. 103:2501-2514.   10.1029/97jb03105   AbstractWebsite

We consider solidification of hot fluid flowing through a rigid-wall channel of infinite extent. The calculated "thermal arrest" lengths are used to investigate the role of magma freezing in limiting the propagation distance of lateral dike intrusions. Our results demonstrate that for reasonable parameters the propagation distances of meter-wide dikes do not exceed the wavelength of crustal thickness variations or transform fault spacing along slow spreading ridges. This suggests that thermal controls on the crustal melt delivery system could be an important factor in modulating these variations. Unlike published results for a finite channel, which predict unlimited meltback of the channel walls if the prefreezing fluid velocity exceeds some critical value, any flow into an infinite channel will eventually freeze, provided that shear heating in the magma is negligible. The thermal arrest distances depend strongly on the average dike thickness h (proportional to h(4) for dikes driven by an along-strike topographic slope and proportional to h(2) for dikes driven by an excess source pressure). Thermal erosion of the country rocks associated with lateral dike intrusions is likely to be confined to a very small region near the ma,oma source. Substantial correlations between the along-strike bathymetry and geochemistry of the erupted lavas along individual ridge segments may be consistent with high-level basalt fractionation in the laterally propagating dikes.