A Database of Global Centroid Moment Tensors using 3D Green's Functions in Model GLAD-M25

Abstract:

The centroid moment tensors (CMTs) provided by the Global CMT Project (https://www.globalcmt.org) have been a staple for global tomography for more than 40 years. With the evolution of tomographic methodology and computational resources, more detail in Earth's interior structure is rapidly being revealed. Over the last few years, both seismic tomography and moment-tensor inversions have shown that in a fully three-dimensional forward-modeling regime, the classic Global-CMT solutions are on average 3 km too deep, the centroid time about 1 s late, and the seismic moment approximately 5 % too low. Therefore, to keep pace with the increased capacity and demands of global tomography, a new catalog of improved, global CMT solutions suggests itself as the next step. We present a new catalog of full-waveform inverted global CMT solutions using fully-heterogeneous, 3D Green’s functions computed in global adjoint tomography model GLAD-M25. The CMT solutions are inverted in an automated workflow that takes Global-CMT solutions and inverts for new, improved CMT solutions. The workflow includes four main steps: [1] launching of the forward, three-dimensional (3D) spectral-element-method (SEM) simulations to generate synthetics, [2] downloading of the observed seismic data, [3] processing of synthetic and observed data, and [4] inversion for the six moment-tensor parameters and the centroid latitude, longitude and depth, as well as a grid search for moment magnitude and centroid time. The new catalog will be integrated into the existing ShakeMovie framework on the corresponding website (http://global.shakemovie.princeton.edu), which provides seismologists with a simple interface to access the new CMT solutions as a complement to the original ones.