Predictability of Elementary Models for Earthquake Dynamics
Beschreibung
This thesis approaches the question of earthquake prediction on a mechanical and tribological track. It pursues a focussed and minimalistic bottom-up approach. From this point of view, earthquakes
... weiterlesenpresent as frictional instabilities, as a result of the stick-slip cycle of the underlying mechanical system.
In this thesis, elementary systems performing stick-slip are analysed experimentally, analytically and numerically. The system investigated in most detail is a single slider with one degree of freedom. The stick-slip cycle is investigated experimentally with a high resolution displacement measurement. The contacting materials are varied, metal and rock contacts under several load rates are studied. During the apparent stick phase a slowly accelerating, regular creep process is observed in all experimental configurations. The creep process as well as the fast slip events can be reproduced by a single slider mechanical model using a rate and state dependent friction law. The model reproduces the experimental velocities over five orders of magnitude.
Furthermore, the accelerating creep is identified as useful precursor to the upcoming slip event. The prediction of the time left to the next slip event is possible. Two methods of prediction are presented and tested: The stand-alone method uses only the derivatives of measured displacement data without any parameters needed; the fitting-based method uses an approximate solution of the mechanical model, fits it to the measured data and gains a prediction from the modelling results. The fitting-based prediction can be preformed earlier in the process, but the accuracy of the stand-alone prediction is higher.
In the last part of the thesis, distributed multi degree of freedom systems are investigated. Analytical studies and simulations are carried out. The statistics of events and the dynamic interaction of neighbouring regions are highlighted.
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