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Fault Slip (fault + slip)

Distribution by Scientific Domains
Earth and Environmental Science100%

Selected Abstracts

Fault slip controlled by gouge rheology: a model for slow earthquakes

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2004
A. Amoruso
SUMMARY During 1997 several slow earthquakes have been recorded by a geodetic interferometer located beneath Gran Sasso, central Italy. The strain rise times of the events range from tens to thousands of seconds and strain amplitudes are of the order of 10,9. Amplitudes scale with the square root of the rise time and this suggests a diffusive behaviour of the slip propagation along the fault. In this work, we develop a model in which slip diffusion is the result of the presence of a gouge layer between fault faces, with a viscoplastic rheology. The fluid velocity field in the gouge layer diffuses in the directions of fault length and fault thickness, with different characteristic times. This model reproduces the relation between amplitude and rise time of measured strain signals. Synthetic straingrams, obtained for a horizontally layered, flat Earth and a source located a few kilometres from the instrument, are in agreement with observed signals. [source]

A geometric and kinematic model for double-edge propagating thrusts involving hangingwall and footwall folding.

GEOLOGICAL JOURNAL, Issue 5-6 2010
An example from the Jaca, Pamplona Basin (Southern Pyrenees)
Abstract A new geometric and kinematic model is proposed for a particular type of fault-related folding based on the study of a natural example developed in Palaeogene carbonate rocks from the Jaca,Pamplona Basin (Southern Pyrenees). The example consists of a hangingwall anticline related to a reverse fault with variable displacement and a gentle footwall syncline. A detailed structural analysis of the structure and a cross-section, perpendicular to its axis and parallel to the transport direction, reveals that none of the previous published models of fault-related folds is able to simulate its main characteristics and reproduce its geometry. The main features of the new model are: double-edge propagating fault and folding developed in both the hangingwall and the footwall. A MATLAB-based program was created to calculate structural parameters such as shortening, structural relief and fault slip; obtain graphs of different parameters such as shortening versus slip along the fault, shortening versus fault length, and produce sections across forward models showing the different stages of fold growth. The model presented here gives an acceptable geometrical fit to the studied natural structure and provides a reasonable evolutionary history. In addition, the results obtained using the model are similar to those measured on the cross-section. As a final step the subsurface portion of the natural fold was completed following the constraints imposed by the model. Copyright © 2010 John Wiley & Sons, Ltd. [source]

DETERMINATION OF FAULT SLIP COMPONENTS USING SUBSURFACE STRUCTURAL CONTOURS: METHODS AND EXAMPLES

JOURNAL OF PETROLEUM GEOLOGY, Issue 3 2004
S-S. Xu
Problems with measuring fault slip in the subsurface can sometimes be overcome by using subsurface structural contour maps constructed from well logs and seismic information. These maps are useful for estimating fault slip since fault motion commonly causes the dislocation of structural contours. The dislocation of a contour is defined here as the distance in the direction of fault strike between two contours which have the same value on both sides of a fault. This dislocation can be estimated for tilted beds and folded beds as follows: (i),If a dip-slip fault offsets a tilted bed, the dislocation (Sc) of contours can be estimated from the vertical component (Sv) of the fault slip and the dip (,) of the bedding according to the following relationship: Sc= Sv/tan ,. Since Sc and , can be measured from a contour map, the vertical component of fault slip can be obtained from this equation. If a strike-slip fault offsets a tilted bed, the dislocation (Scs) of contours is equal to the strike-slip of the fault (Sc), that is, Scs= Ss. (ii),If a fault offsets a symmetric fold, the strike component (Scs) of fault slip and the dislocation of the contours (Sc) can be calculated, respectively, from the equations Scs= (Smax+ Smin) / 2 and Sc= (Smax - Smin) / 2. Smax is the greater total dislocation (Sc+ Scs) of a contour line between the two limbs of the fold and Smin is the smaller total dislocation (Sc - Scs) for the same contour line. In this case, Sv can be also calculated using the obtained value of Sc and the equation Sv= Sc tan ,. Similarly, for an asymmetric fold, the dislocation of contours due to the vertical slip component is Scb= (Smax - Smin)/(n + 1), and the strike-slip component is Ss= Scs= (nSmin+ Smax/(n + 1), where n is the ratio between the values of interlines of the two limbs, and Scb is the dislocation of contours due to the vertical slip component for either of the two limbs (here it is for limb b). In all cases, three conditions are required for the calculation of contour dislocation: (i),the contour lines must be approximately perpendicular to the fault strike; the intersection angle between the fault strike and the strike of bedding should be greater than 65°; (ii),the bed must not be dip more than 35°; and (iii),folding or flexure of the stratigraphic horizons must have occurred before faulting. These methods for determining fault slip from the dislocation of structural contours are discussed using case studies from the Cantarell oilfield complex, Campeche Sound (southern Gulf of Mexico), the Jordan-Penwell Ellenburger oilfield in Texas, and the Wilmington oilfield in California. [source]