Seismology applications from IPGP (CNRS, France) on EGEE

gCSMT: Grid Centroid Seismic Moment Tensor

gCSMT application is designed to determine the main characteristics of large earthquakes occurring worldwide. These characteristics describes the seismic event in term of a centroid seismic moment tensor which is the equivalent point point source approximation of the earthquake located in space and time at the barycenter of the seismic rupture.

These characteristics are:

• The scalar moment M_0 (expressed in Newton.meters), which corresponds to the amount of seismic energy radiated by the earthquake. M_0 is also converted into M_w, the moment magnitude. M_w is directly related to the actual size of the rupture (the surface of the fault involved in the event), and the average amount of slip on the fault.
• The duration of the rupture.
• The moment tensor, which corresponds to the centroid mechanism itself, i.e. the orientation of the fault and the direction of the displacement on this fault. The main interpretation of this moment tensor is given in term of two planes, one is the fault plane, the other one being the auxiliary plane. The identification of the fault plane is not possible by the sole use of seismic waves (the two planes will radiate the same seismic pattern), the ambiguity is raised using tectonic considerations and aftershocks distribution.

Eric Clévédé, Geneviève Patau, David Weissenbach (IPGP / CNRS)

SEMUM3D: simulation code for 3D seismic wave propagation in elastic, heterogeneous media at local and regional scales

SEMUM3D is especially designed for the simulation of the seismic response of complex geological media such as sedimentary basins. Spatial discretization is based on a high-order Spectral Element approximation and time discretization is based on an energy and momentum conserving second-order Newmark scheme formulated in velocity. Perfectly Matched Layers (PML) are implemented in SEMUM3D to simulate wave propagation in unbounded domains. Seismic point source and incident plane wave field are also implemented in SEMUM3D...

SEMUM3D is written in Fortran 90. Complex geometries (surface topography, interfaces) are handled by SEMUM3D using unstructured hexahedra meshes. The mesh is generated using the Cubit software. Parallel implementation of SEMUM3D is based on domain decomposition and the mesh partitioning make use of the METIS software library. It has been written with a strategy of independence with respect to any Cartesian coordinate system and can handle unstructured meshes of arbitrary topology. Communications between elements are based on face, edge and vertex communications, and require topological information for each of these objects. These objects (elements, faces, edges and vertices) are explicitly explicitly identified as Fortran-structures which can handle and optimize the communications.

SEMUM3D runs on distributed parallel architectures, using the Message Passing Interface (MPI) library (mpich) and make use of the BLAS library. The code has already been compiled on Linux using different compilers: the Intel compiler ifort (32/64 bits), the Fujitsu (32 bits) compiler, the Pathscale and Portland (64 bits) compilers.

SEMUM3D software has been ported on the EGEE Grid and ran on the IBM cluster of the Parallel Computing Center of the Institut de Physique du Globe de Paris (distributed memory of 64 bipro Opteron nodes) and on the cluster of the FUNVISIS (Venezuela).

Elise Delavaud, Jean-Pierre Vilotte, Geneviève Moguilny (IPGP / CNRS)