Higher-degree moment tensor inversion using far-field broad-band recordings: theory and evaluation of the method with application to the 1994 Boliviadeep earthquake

We present a method to estimate parameters of the extended earthquake sourc e using higher-degree moment tensors at 27 centroid locations. We show that a Taylor series expansion of Green's functions around a single centroid is not accurate enough when working with seismic wave periods and wavelengths in the range of the rupture duration and spatial extent of the fault, resp ectively. Introducing a grid of 27 centroid locations on the fault and usin g higher-degree moment tensors we are able to model adequately body and sur face waves with periods and wavelengths smaller than the rupture duration a nd fault dimensions. Under simplifying assumptions an iterative inversion s cheme is coded to estimate parameters of planar, Haskell-type faults. Reali stic inversion examples for deep and shallow earthquakes show that uni- and bidirectional rupture models, rupture direction, fault and auxiliary plane and kinematic source dimensions and times can be constrained with teleseis mic body and/or surface waves. The application to the deep Bolivia event in dicates a subhorizontal fault plane. Unidirectional rupture to the north is slightly preferred. The rupture duration of 25 s and fault dimensions of 4 7 x 25 km agree well with the estimates for the main pulse moment release g iven in other studies.