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We investigate the structure of the SU͑3͒ s-wave octet and decuplet baryons employing a constituent chiral quark model. We solve a three quark system with the many range Gaussian bases, which allow the baryon to have a ͓21͔ flavor-spin symmetry as well as the usual ͓3͔ symmetry. The method which we employ here has been shown to work quite nicely to describe the nucleon and ⌬ structure. We extend this method in order to take into account a mass difference between ud and strange quarks for both kinetic energy and potential terms. Furthermore we improve the method in order to take care of the strong short range attraction due to the pseudoscalar meson exchange potential. It is found that all octet baryons gain a very strong attraction in the chiral quark model when the semirelativistic approach, namely, the relativistic expression only for the kinetic energy term is employed. It is also found that an inclusion of the additional attraction due to the sigma meson exchange and one gluon exchange potential makes the system unstable in the semirelativistic approach.

The stress states in accretionary prisms are important for understanding the building and releasing of seismic energy. Numerous researchers have conducted sandbox experiments as a scaled physical analog model to understand the formation of accretionary prisms. However, measuring stress states in laboratory sandbox experiments is still practically infeasible. Here we performed real-scale numerical sandbox experiments using the discrete element method to understand the 3D stress state in the accretionary prism. Despite the nearly uniform initial conditions, macro-scale undulations of faults, which are similar to those observed in the trenches of an accretionary prism, appear. We reveal that these undulations are caused by the formation of stress arches. We show that the mechanism behind the arch formation is the discontinuous change in the stress orientation during the rearrangement of the stress chain. Furthermore, analyses demonstrate that the in-situ stress orientation from borehole data can be a signal of either the regional direction of plate convergence or the local stress orientation associated with the stress arch. The results may greatly enhance the outcome of long term monitoring in areas, such as the Nankai Trough.