[1] We present an automatic shear wave splitting measurement tool for local earthquakes, with the sole manual step of choosing an S arrival time. We apply the technique to three data sets recorded on Mount Ruapehu volcano in New Zealand that have previously been determined to have fast polarizations that vary in time and with earthquake depth. The technique uses an eigenvalue minimization technique, applied over multiple measurement windows. The dominant period of each waveform sets minimum and maximum window lengths. Cluster analysis determines the best solution among all the windows, and quality grading criteria assess the results automatically. When the same filters are used for events determined to be high quality from manual studies, the automatic technique returns virtually identical results. Scatter increases when the automatic technique chooses the best filter, but the average automatic results remain consistent with the manual results. When the automatic technique is used on sets that include data previously judged as poor quality, some stations yield distributions of fast polarizations that include peaks that were not present in previously published results. The difference may stem from two factors: automatic grading lets through some measurements that independent analysts consider poor quality, but also unconscious bias in the manual selection process may downgrade measurements that do not fit expectations. Nonetheless, the new objective analysis confirms changes in the average fast polarizations between 1994 and 2002 and between shallow and deep events. Therefore, this new technique is valuable for objective assessment of anisotropy and its variation in time.
<p>This thesis presents an automatic shear wave splitting measurement tool and the results from its application to data recorded in the vicinity of Mt. Ruapehu volcano on the North Island of New Zealand. The best methodology and parameters for routine automatic monitoring are determined and approximately 10,000 events are processed. About 50% of all S-phases lead to measurements of acceptable quality. Results obtained with this technique are reproducible and objective, but more scattered than results from manual measurements. The newly developed automatic measurement tool is used to measure shear wave splitting for previously analysed data and for new data recorded in 2003-2007. In contrast to previous studies at Mt. Ruapehu, we have a larger and continuous data set from numerous three-component seismic stations. No major temporal changes are found within the new data, but results vary for di erent station locations. I</p>
Two crystal plasticity-based constitutive models that differ with respect to the flow rule (rate-dependent/rate-independent) and hardening law (phenomenological/physical-based), among other aspects, are compared with each other. To this end, both crystal plasticity-based constitutive models were deployed within a finite element framework to predict the texture-induced plastic anisotropy of an AA6014-T4 aluminium alloy considering uniaxial loading at 0°, 15°, 30°, 45°, 60°, 75° and 90° with respect to the rolling direction. The results of the stress-strain curves, the normalised yield stresses and the r-values demonstrate that both crystal plasticity-based constitutive models provide comparable results. Also, the experimental r-values were predicted with reasonable accuracy. Differences with respect to the experimental normalised yield stresses are discussed and were most likely caused by an additional direction-dependent mechanism.
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