FINITE DIFFERENCE WAVEFIELD MODELING OF SEISMIC WAVE PROPAGATION ACROSS THE HAWAII-EMPEROR RIDGE

Volcanic seamount chains are widespread throughout ocean basins. Active-source refraction seismology can provide images of the interiors of these volcanoes via P wave travel time tomography, but that requires proper waveform identification of seismic phases that propagate across the volcanic structures. Unfortunately, the current limitation on the number of seismic phases that can be included in tomographic analyses leads to less detailed images and a limited geological understanding of the structures being imaged. The primary objective of this study is to compare recorded seismic wavefields for recent seismic surveys across the Hawaiian-Emperor Seamount Chain against synthetic wavefields generated via waveform modeling, for simplified but realistic models of volcanic edifices and the underlying oceanic crust and mantle, with the aim of better understanding the observed seismic phases and their origins.

In our prior studies (Xu et al., 2022, Watts et al.,2021, Dunn et al., 2019, MacGregor et al., 2021), several seismic phases were identified in recorded sections collected across the Hawaiian-Emperor Chain. However, interpreting the origins of some of these phases remains challenging, and others remain a mystery. In this study, we constructed an idealized seamount model based on the best-knows seismic structure of Jimmu (Xu et al., 2022), and then utilized finite difference wavefield modelling code(Levander, 1988; Lata and Dunn, 2020) to calculate the wavefield for various source and receiver positions. Throughout the modeling process, we hope to identify additional phases with unknown origins, such as certain P-to-S converted wave phases and surface waves. By resolving these ambiguities and identifying new seismic phases, we can improve our seismic images of the Hawaiian-Emperor Chain and deepen our understanding of the degree of flexure of the crust due to volcanic loading, and the depth of sediments that fill the flexural moat that surrounds the volcanic chain. Additionally, further understanding of the seismic wavefield will lead to improvements in our knowledge of the nature of specific volcanic structures, such as volcanic cores (a high density and wave speed interior core of the seamount), rift zones, and a hypothesized “magmatic underplating” of the oceanic crust by mantle melts rising beneath the volcanic chain.