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In this study we present the results of an ongoing 3D full-waveform inversion for theArabian-Eurasian collision zone in eastern Turkey and Iran. This is intended to extract asmuch information as possible from available seismograms in order to constrain seismicstructure in both the crust and the upper mantle. In our method we simulate the 3D visco-elastic wavefield using the newly developedspectral-element solver Salvus. Our numerical mesh honors topography of the surface andinternal discontinuities. We compare observed and synthetic waveforms using time frequencyphase misfits. Using adjoint techniques, we then compute sensitivity kernels with respect tothe model parameters, which are VSV, VSH, VPV, and VPH. Finally, the kernels enable theiterative solution of the nonlinear inverse problem with the help of the L-BFGSalgorithm. For this study we obtained seismic waveform data of 143 earthquakes within themagnitude range of Mw 4.5 to 6.3 that occurred in the region between 2012 and 2016. Theseevents were recorded by 271 broadband seismic stations belonging to the two nationalIranian networks and freely available seismic stations of the Turkish Network, madeavailable by IRIS. For data management and workflow organisation we employ theLarge-Scale Seismic Inversion Framework (LASIF), modified to operate with theAdaptable Seismic Data Format (ASDF), which facilitates simulations on large HPCclusters. Starting from the first generation of the Collaborative Seismic Earth Model, we firstconstrain longer-wavelength structure. To this end, we consider 3-component recordingsfrom a subset of 41 events in the period range from 50 to 80 s. This period range issuccessively broadened to include shorter periods; for instance, the lower end of theperiod range was meanwhile extended to 35 s. For each period band, the number andthe length of measurements are increased to ultimately comprise almost completeseismograms, and also the number of events is increased to use complete of dataset. [ABSTRACT FROM AUTHOR]