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Research Overview
Numerical simulation of interacting faults in a complex fault system
Currently, my research is focused on numerical simulations of fault systems. I want to understand how the elastic interactions of complex fault systems, are affecting the long-term slip-rates, maximum earthquake size, and recurrence times of individual faults within the system. For this effort, I have written a number of numerical models, utilizing realtively simple friction laws to simulate interseismic and coseismic behavior. Part of this effort is to study the effect of properties of individual faults, including its average strength, and fault geometry on the overall systems behavior. A question that arises is whether signifcantly weaker faults can suck deformation i.e. slip from other, stronger structures (i.e. localize slip on weak structures). Following this line of thought, and utilizing crustal motion models as well as paleoseismic studies would allow to inversly model properties of individual structures within the system and therefore improve our ability of long-term earthquake prediction.
Furthermore, I am working on frictionless models of complex fault systems for which I study the distribution of slip necessary to release an imposed regional/tectonic stress field. This allows me to make statements about the relative activity of individual structures and whether the fault system is capable of relaxing the imposed tectonic stresses (if not, either the existence of additional structures or non-elastic strain release is infered).
Individual processes involved in faulting and fault systems are more or less well constraint. For example, rate-and-state friction laws (RSF) can explain many effects that can be observed before, during, and after an earthquake (e.g. fore- and after shocks, postseismic slip etc.). It is also known that static and dynamic stress transfer caused by an earthquake can alter (trigger or delay) the seismic cycle of a second fault -a fact that is of great importance regarding the seismic hazard posed by individual structures and long-term earthquake prediction. To better understand how the individual processes involved affect the system as a whole, it is necessary to also study them together as parts of a system. Numerical simulations provide the means needed to approach this task. Its controlled environment allows to define the systems complexity and to generate system responses to a wide range of parameters. Therefore, numerical simulations can help us to determine how individual processes effect the systems behavior. The numerical models are generally based on the derivations by Okada (1992) to determine strain (i.e. stress) and displacement due to a rectangular fault of any orientation, embedded in a homogeneous elastic half-space.
Paleoseismic investigation of the Laikipia-Marmanet Fault, Kenya
For my Diplom thesis (University of Potsdam, Germany), I conducted a paleoseismic investigation under the supervision of my advisor Prof. Manfred Strecker along the Laikipia-Marmanet Escarpment,Subukia Valley, Central Kenya Rift in summer 2003. The investigated/excavated fault was activated in a magnitude Ms = 6.9 earthquake in January, 1928. This is the largest recorded event that occurred in the rift. It formed a ~ 40km long surface rupture, with average offsets of ~ 1m. Because of the limited number of paleoseismic studies and sparse seismometer coverage, the seismic hazard posed by this and other rift-bounding structures in the region, is not well known. Hence, the goal of this study was to find evidence for faulting, prior to the 1928 event and to collect datable material so that estimates for average recurrence times can be made. Finding uncontaminated C14 samples turned out to be not possible. However, geomorphic and stratigraphic evidence show that at least 5 surface ruptureing events, prior to 1928, activated the Laikipia fault. The publication concering this work is in preperation.
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