Beyond Receiver Functions: Green's Function Estimation by Transdimensional Inversion and Its Application to OBS Data.

Receiver functions, calculated by deconvolving P (or vertical) component records of teleseismic waveforms from the corresponding SV (or radial) components, have been widely used to obtain receiver‐side Green's functions in an approximate form. Conventional receiver function methods, however, often fail due to numerical instability of the deconvolution and strong multiples on the P components. These problems become severe when analyzing in high frequency and using data from ocean bottom seismometers (OBSs). We present a novel technique to estimate Green's functions of receiver‐side structure from teleseismic P waveforms. In this method, two components of Green's functions, which are assumed to form a series of pulses, are directly related in a single equation without explicit deconvolution. Based on the equation, we construct posterior probability distributions regarding the number of pulses, their timing, and amplitudes within a transdimensional Bayesian framework. A reversible‐jump Markov chain Monte Carlo method is used for this purpose, and we further utilize a parallel tempering method to achieve rapid convergence. Synthetic tests and application to an OBS installed at the Yamato Basin, the Sea of Japan, show that the proposed method can estimate radial‐component Green's functions more accurately than conventional receiver function methods. We suggest that the high‐frequency Green's functions estimated by the new method can be used to reveal fine‐scale (in order ~100 m) structure of the seafloor sediment. Plain Language Summary: The receiver function is a popular tool in geophysics. It extracts useful signals from the waves of distant earthquakes to investigate the Earth's subsurface structures. However, computing receiver functions is difficult under certain conditions; (1) when working with high‐frequency waves, the receiver function method becomes unstable; (2) when working with data from the ocean bottom or sedimentary basins, strong reverberations within the sediment or from the ocean surface are troublesome. This study provides a new technique that can clear these issues, making use of advanced statistical methods. We demonstrate its advantage over the conventional receiver function methods through both simulations and a real application to an ocean bottom seismometer. We suggest that the new method has the potential to reveal fine‐scale Earth structure even beneath the seafloor. Key Points: We propose a method that estimates Green's functions of receiver‐side structure from teleseismic waveforms by transdimensional inversionThe new method does not require deconvolution and is suited to the analysis of challenging (e.g., high frequency or offshore) data setsWe demonstrate the advantage of the new method through synthetic tests and the application to real offshore data [ABSTRACT FROM AUTHOR]