[S13-P] Poster

[S13-P-05] Source properties of large earthquakes in subduction zones using 3D heterogeneous Earth: application to the Australasian region

^○Babak Hejrani, Hrvoje Tkalcic (The Australian National University, Research School of Earth Sciences, ACT, Australia)

Revealing earthquake source complexity, rupture process and the source time function of large earthquakes is an important aspect of earthquake seismology. A significant number of researchers have investigated these properties using 1D (spherically symmetric) Earth models. Using a similar approach, we first investigated 10 selected large earthquakes with moment magnitudes exceeding 7.8 in the Australasia region, occurred in Papua New Guinea, Solomon Islands, Tonga-Fiji and New Zealand. Acknowledging that seismic records contain the complexities from both source and Earth structure, we explore a hypothesis that a simple, spherically symmetric Earth structure introduces spurious effects into the source parameters.
We use 3D heterogeneous upper-mantle velocity structure and create synthetic data for scenarios that encompass complex ruptures and source time functions (at periods 40 – 200s). We then invert for the source parameters such as moment tensor, source time function and location using these synthetic data in both 1D and 3D Earth. We confirm that the source complexity can act as a compensation for the incomplete knowledge of Earth structure. Consequently, we calculate the source time function of the selected large earthquakes from the Australasian region in 3D Earth and discuss our findings. We also consider the source directivity for large earthquakes as one of the target parameters.