Towards full waveform simulation using SPECFEM3D for earthquakes in the Lesser Antilles subduction zone

How and where volatiles are released in convergent plate margins has important implications for the seismic and volcanic hazards along a subduction arc. To map the volatile transport at the Lesser Antilles subduction zone, a network of 34 ocean bottom seismometers (OBS) together with approximately 16 seismic land stations to complement the permanent network were deployed. The array traverses the arc and will record seismic waves from local and distant earthquakes to determine the regional seismicity together with the local seismic velocity and attenuation structure. Close to the NE edge of the OBS network, a magnitude 6.0 oblique-thrust earthquake occurred on March 19, 2016 immediately after the deployment of OBS stations, offering an excellent opportunity to simulate waveforms that can be compared with observations that will be retrieved mid-next year.Four constituents are essential to implement a full waveform forward simulation, namely: a 3D mesh of the geometry, a velocity model, station locations and earthquake source(s). In this study, we have built a 3D geometrical model, incorporating the 30 arc-second bathymetry data for the Lesser Antilles subduction zone. The semi-automatic meshing tool GeoCUBIT was used to generate a mesh comprising millions of hexahedral cells. An a priori 3D velocity model based on active source refraction studies is produced and subsequently used as an input for simulation. Here, to honor the geological complexity and to investigate its influence on wave propagation, we develop a new 3D slab geometry for the Lesser Antilles subduction zone by fitting the seismicity distribution. We run full waveform simulations using SPECFEM3D Cartesian for earthquakes in different locations with various mechanisms. We will present preliminary results from full waveform simulations of the March 2016 event and other synthetic earthquakes in the Lesser Antilles subduction zone.