Modeling the shortening history of a fault tip fold using structural and geomorphic records of deformation

We present a methodology to derive the growth history of a fault tip fold above a basal detachment. Our approach is based on modeling the stratigraphic and geomorphic records of deformation, as well as the finite structure of the fold constrained from seismic profiles. We parameterize the spatial deformation pattern using a simple formulation of the displacement field derived from sandbox experiments. Assuming a stationary spatial pattern of deformation, we simulate the gradual warping and uplift of stratigraphic and geomorphic markers, which provides an estimate of the cumulative amounts of shortening they have recorded. This approach allows modeling of isolated terraces or growth strata. We apply this method to the study of two fault tip folds in the Tien Shan, the Yakeng and Anjihai anticlines, documenting their deformation history over the past 6–7 Myr. We show that the modern shortening rates can be estimated from the width of the fold topography provided that the sedimentation rate is known, yielding respective rates of 2.15 and 1.12 mm/yr across Yakeng and Anjihai, consistent with the deformation recorded by fluvial and alluvial terraces. This study demonstrates that the shortening rates across both folds accelerated significantly since the onset of folding. It also illustrates the usefulness of a simple geometric folding model and highlights the importance of considering local interactions between tectonic deformation, sedimentation, and erosion

A Comparison of the Performance of Neural Q-learning and Soar-RL on a Derivative of the Block Design (BD)/Block Design Multiple Choice (BDMC) Subtests on the WISC-IV Intelligence Test

Teaching an autonomous agent to perform tasks that are simple to humans can be complex, especially when the task requires successive steps, has a low likelihood of successful completion with a brute force approach, and when the solution space is too large or too complex to be explicitly encoded. Reinforcement learning algorithms are particularly suited to such situations, and are based on rewards that help the agent to find the optimal action to execute given a certain state. The task investigated in this thesis is a modified form of the Block Design (BD) and Block Design Multiple Choice (BDMC) subtests, used by the Fourth Edition of the Wechsler Intelligence Scale for Children (WISC-IV) to partially assess childrens\u27 learning abilities. This thesis investigates the implementation, training, and performance of two reinforcement learning architectures for this problem: Soar-RL, a production system capable of reinforcement learning, and a Q-learning neural network. The objective is to help define the advantages and disadvantages of solving problems using these architectures. This thesis will show that Soar is intuitive for implementation and is able to find an optimal policy, although it is limited by its execution of exploratory actions. The neural network is also able to find an optimal policy and outperforms Soar, but the convergence of the solution is highly dependent on the architecture of the neural network

Comment on “Magnetostratigraphic study of the Kuche Depression, Tarim Basin, and Cenozoic uplift of the Tian Shan Range, Western China” Baochun Huang, John D.A. Piper, Shoutao Peng, Tao Liu, Zhong Li, Qingchen Wang, Rixiang Zhu

International audienceThe recent publication of “Magnetostratigraphic study of the Kuche Depression, Tarim Basin, and Cenozoic uplift of the Tian Shan Range,Western China” by B.C. Huang, J.D.A. Piper, S.T. Peng, T. Liu, Z. Li, Q.C. Wang, R.X. Zhu [Earth Planet. Sci. Lett., 2006, doi:10.1016/j.epsl.2006.09.020] discusses the Cenozoic uplift history of the Tianshan Mountains by studying the magnetostratigraphy of Paleogene to Neogene continental sediments from two sections located in the Kuche basin at the northern edge of the Tarim basin. To support their conclusion they reinterpreted a magnetostratigraphic study of the Yaha section, which lies ~ 10 km south of their sections, we previously published [J. Charreau, S. Gilder, Y. Chen, S. Dominguez, J.-P. Avouac, S. Sen, M. Jolivet, Y. Li and W. Wang, Magnetostratigraphy of the Yaha section, Tarim Basin (China): 11 Ma acceleration in erosion and uplift of the Tianshan Mountains, Geology 34(3), 2006, 181­184.]. Here, (1) we argue that the interpretations of the sedimentation rate changes they proposed for the Kuche sections are partially invalid, (2) we disagree with their reinterpretation of the age of the Yaha section, and (3) we think that the way they interpret their AMS data is incorrect