Improving Resolution of Near Surface Structure Imaging Based on Elastic Full Waveform Inversion

Abstract

Estimating structure of pyroclastic deposits plays an important role in the interpretation of volcanic geology and evaluation of potential hazard. We aim to invert near surface seismic data to produce high-resolution images of pyroclastic density current deposits resulting from the 18 May 1980 volcanic eruption at Mount St. Helens, Washington, USA. Elastic full waveform inversion is a popular data fitting method used to estimate seismic properties of the earth. Due to the great challenges in the convergence of elastic full waveform inversion when inverting high-frequency and complex near-surface land seismic data, we develop a specific workflow to improve the resolution of velocity models that progress from traveltime inversion and surface wave inversion to full elastic full waveform inversion. The final inverted models include fine-scale feature structures that compare favourably to an adjacent outcrop. The final data fitting shows significant improvement with normalized waveform misfit decreasing from 1 to 0.4.