PyLith 1.0: A Finite-Element Code for Modeling Quasi-Static and Dynamic Crustal Defor-

We have developed open-source finite-element software for 2-D and 3-D dynamic and quasi-static modeling of crustal deformation. This software, PyLith 1.0, combines the quasi-static modeling functionality of PyLith 0.8 and its predecessors (LithoMop and Tecton) and the dynamic modeling functionality of EqSim. The target applications contain spatial scales ranging from tens of meters to hundreds of kilometers with temporal scales for dynamic modeling ranging from milliseconds to minutes and temporal scales for quasistatic modeling ranging from minutes to hundreds of years. This software, PyLith 1.0, is part of the NSF funded Computational Infrastructure for Geodynamics and runs on a wide variety of platforms, from laptops to Beowulf clusters (executables are available for OSX, Linux, and Windows). PyLith uses a general, parallel, graph data structure called Sieve for storing the finite-element mesh. This permits use of a variety of 2-D and 3-D cell types including triangles, quadrilaterals, hexahedra, and tetrahedra. Current features include kinematic fault interface conditions, Dirichlet (displacement) boundary conditions, linear elastic and Maxwell linear viscoelastic materials, and quasi-static and dynamic time-stepping. Future releases will add traction and absorbing boundary conditions, dynamic fault interface conditions (employing fault constitutive models), generalized Maxwell viscoelastic materials, and automated calculation of suites of Green's functions. We also plan to extend PyLith to allow coupling multiple simultaneous simulations. For example, this could include (1) coupling an interseismic deformation simulation to a spontaneous earthquake rupture simulation (each using subsets of the software), (2) coupling a spontaneous earthquake rupture simulation to a global wave propagation simulation, or (3) coupling a short-term crustal deformation simulation to a mantle convection simulation and an orogenesis and basin formation simulation.