Displacement-length Relationships Research Articles

Paleoseismological Investigations along Joggers Park Fault, Port Blair, South Andaman: Implications towards Delineation of Blind Thrusting and Related Crustal Deformation through Ground Penetrating Radar (GPR) and Electrical Resistivity Techniques (ERT and VES)

ABSTRACT A comprehensive paleoseismological investigations was carried out along Joggers Park Fault (striking NW-SE) reveals pervasive traces of active compressional tectonics (blind thrusting) and shallow-surface recent tectonic signatures along the fault. The geometry and trends in the tectonic deformation of the blind zone (shallow-subsurface stratigraphy) were examined with GPR and electrical resistivity tomography (ERT) and vertical electrical sounding (VES), strongly demonstrates severe tectonic deformation (persistent tectonic style) from Quaternary to Holocene times in a compressive stress regime. The surface manifestation of deformation (topographic expression) along the fault can be marked as hanging wall uplift and can be visually observed in the exposed sections at nearly half kilometer distance from the table land of Joggers Park in the form of a well-defined disconnected high angle thrust fault scarp (reverse fault). The reverse fault kinematically and intimately linked with underlying fault geometry provides adduced evidence to evaluate strike displacement profiles (displacement length relationship) along the fault. In addition, deformed stacked colluvial wedge below the scarp represents a powerful basis to calibrate recent and long term slip rates of the underlying fault.

Interactions and growth of faults in an outcrop-scale system

Abstract Fault growth could be achieved by (1) synchronous increases in displacement and length or (2) rapid fault propagation succeeded by displacement-dominated growth. The second of these growth models (here referred to as the constant length model) is rarely applied to small outcrop-scale faults, yet it can account for many of the geometric and kinematic attributes of these faults. The constant length growth model is supported here using displacement profiles, displacement–length relationships and tip geometries for a system of small strike-slip faults (lengths of 1–200 m and maximum displacements of 0.001–3 m) exposed in a coastal platform in New Zealand. Displacement profiles have variable shapes that mainly reflect varying degrees of fault interaction. Increasing average displacement gradients with increasing fault size (maximum displacement and length) may indicate that the degree of interaction increases with fault size. Horsetail and synthetic splays confined to fault-tip regions are compatible with little fault propagation during much of the growth history. Fault displacements and tip geometries are consistent with a two-stage growth process initially dominated by propagation followed by displacement accumulation on faults with near-constant lengths. Retardation of propagation may arise due to fault interactions and associated reduction of tip stresses, with the early transition from propagation- to displacement-dominated growth stages produced by fault-system saturation (i.e. the onset of interactions between all faults). The constant length growth model accounts for different fault types over a range of scales and may have wide application.

Factors influencing the fault displacement-length relationship: an example from the Cantarell oilfield, Gulf of Mexico

Asumiendo que la relación entre máxima longitud y máximo desplazamiento en las fallas es lineal, investigamos los efectos de considerar distintos componentes del desplazamiento, del nivel de observación, y la presencia de enlace de fallas. Para ello usamos datos de las fallas normales del bloque Akal, en el campo petrolero de Cantarell, localizado en el Golfo de México frente a las costas de Campeche. Los datos que se utilizaron fueron tomados de mapas de contornos de cuatro horizontes diferentes. Los resultados obtenidos pueden resumirse de la manera siguiente: (1) el desplazamiento al echado es mejor que el desplazamiento vertical para el análisis de la relación D-L; (2) utilizando fallas que muestran sus dos terminaciones se logran mejores coeficientes de correlación lineal entre D y L, que utilizando fallas con una sola o ninguna terminación; (3) los coeficientes de correlación (RL2) obtenidos para las gráficas D-L en cada horizonte son distintos, lo que indica que los valores de (RL2) son dependientes del nivel de observación.

Influence of viscous layers on the growth of normal faults: insights from experimental and numerical models

The influence in space and time of viscous layers on the deformation pattern of brittle layers is investigated using wet clay/silicone putty analogue models in extension. Brittle and brittle–viscous experiments at various extension velocities are compared. Numerical models are also performed to confirm the results and to control the boundary conditions. Our results show that: (i) the presence of a basal viscous layer localizes the deformation by creating faults with very large throw. This kind of deformation distribution constrains the location of small faults, with scattered orientations, in the vicinity of the larger, in particular in relay zones. (ii) A lower strength of the viscous layer (i.e. a low extension velocity) enhances this localization of the deformation. (iii) The displacement–length relationship and the spatial distribution of small-scale faults are strongly influenced by both the rheology of the model and the amount of extension. This study shows that they are important parameters, especially when characterizing the whole fault network evolution and the relationship between large and small faults.

Lateral propagation of the surface trace of the South Alkyonides normal fault segment, central Greece: its impact on models of fault growth and displacement–length relationships

The evolution of deformed marine terraces and drainage systems have been examined in order to investigate the growth and lateral propagation of an active normal fault. Geological mapping has revealed three distinct raised marine terraces in the immediate footwall of the western end of the active South Alkyonides Fault Segment (SAFS), Gulf of Corinth, central Greece. We correlate these terraces with sea-level highstands at 125, 240 and 330 ka. Using elevation estimates of the inner edges of the terraces we show that uplift rates decrease towards the Perachora Fault Segment Boundary at the western end of the SAFS. Analysis of terraces and drainage wind gaps in the footwall of the fault shows that the surface trace of the SAFS propagated westwards at a rate of 12.1–16.7 mm/y over at least the last 330 ka. Whilst the surface trace length has increased, analysis of the geometry and kinematics of fault-slip suggests that fault length at depth has remained fixed, implying progressive increase in the values for the displacement–length ratio. If this is correct, growth is not self-similar and fault length has been established early in the evolution of the system, i.e. before 330 ka.