loading page

On the non uniqueness of the source, propagation and site effects decomposition
  • +4
  • Dino Bindi,
  • Kevin Mayeda,
  • Daniele Spallarossa,
  • Matteo Picozzi,
  • Paola Morasca,
  • Adrien Oth,
  • William R Walter
Dino Bindi
Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences

Corresponding Author:bindi@gfz-potsdam.de

Author Profile
Kevin Mayeda
Air Force Techical Application Center
Author Profile
Daniele Spallarossa
University of Genoa
Author Profile
Matteo Picozzi
University of Naples Federico II
Author Profile
Paola Morasca
Istituto Nazionale di Geofisica e Vulcanologia INGV
Author Profile
Adrien Oth
European Center for Geodynamics and Seismology
Author Profile
William R Walter
Lawrence Livermore National Laboratory (DOE)
Author Profile


Although the non-uniqueness of the solution is commonly mentioned in the context of studies that perform spectral decompositions to separate source and propagation effects, its impact on the interpretation of the results is often overlooked. The purpose of this study is to raise awareness on this important subject for modelers and users of the models and to evaluate the impact of strategies commonly applied to constrain the solution. In the first part, we study the connection between the source-station geometry of an actual data set and the properties of the design matrix that defines the spectral decomposition. We exemplify the analyses by considering a geometry extracted from the data set prepared for the benchmark Community Stress Drop Validation Study (Baltay et al., 2021). In the second part, we analyze two different strategies followed to constrain the solutions. The first strategy assumes a reference site condition where the average site amplification for a set of stations is constrained to values fixed a-priori. The second strategy consists in correcting the decomposed source spectra for unresolved global propagation effects. Using numerical analysis, we evaluate the impact on source scaling relationships of constraining the corner frequency of magnitude 2 events to 30 Hz when the true scaling deviates from this assumption. We show that the assumption can not only shift the overall seismic moment versus corner frequency scaling but can also affect the source parameters of larger events and modify their spectral shape.