Rupture Heterogeneity and Directivity Effects in Back‐Projection Analysis

The back projection method is a tremendously powerful technique for investigating the time dependent earthquake source, but its physical interpretation elusive. We investigate how rupture heterogeneity and directivity can affect back-projection results (imaged location beam power) using synthetic models. Rather than attempting to model dynamics of any specific real earthquake, we use idealized kinematic models, with constant or varying velocity, peak slip rate, fault-local strike orientation along unilateral bilateral rupturing faults, perform resultant seismograms. Our experiments show track only heterogeneous processes; homogeneous not resolved in our experiments. amplitude power does necessarily correlate parameter (e.g., rate velocity) at back-projected location. Rather, it depends on spatial around front, affected by directivity. A shorter characteristic wavelength source towards array strong higher frequency. derive an equation based Doppler theory relate seismogram This theoretical relation explain frequency- array-dependent also analyze 2019 M7.6 bilaterally New Ireland earthquake. study provides novel perspective physically interpret retrieve information about characteristics.