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Quantitatively Assessing the Importance of Three-dimensional Structure for Finite Fault Inversions

Description: 

Accurately producing earthquake inversions is fundamental to understanding source processes and hazards related to large earthquakes. Unfortunately, uncertainty and nonuniqueness is inherent in the inversion process. Traditional kinematic inversions rely on 1D structural models; however, for tectonically complex regions like subduction zones, this assumption may lend to unaccounted “path effects” that may be inappropriately mapped into output source models. This then may hinder our ability to accurately image and understand large earthquakes. The simplification is often justified by assuming crustal deformation results from lower-frequency shaking that is less sensitive to structural heterogeneities. Recent work, however, demonstrated accounting for 3D structure can impact time-dependent crustal deformation. One step further, if we apply 3D structure into the inversion framework, how does this impact our ability to resolve large earthquakes and their physics? Unlike the “traditional” approach, we compute 3D Green’s Functions (GFs) for application into the inversion process. We focus on the Japan Trench and the rupture area from the 2011 M7.9 Ibaraki earthquake to assess the impact of incorporating 3D structure into the workflow. To understand the impact of 1D vs. 3D structure, we create synthetic stochastic slip rupture models based on the 2011 Ibaraki earthquake and model the surface deformation resulting from each event at GNSS stations across Japan. We then produce source inversions assuming either a 1D or 3D layered earth model and assess the dissimilarity of kinematic inversions to synthetic ruptures to quantitatively compare models. We also run inversions varying the azimuthal range that highlights or neglects regions of structural complexity and assess the coverage impact on resultant models. We find nearly all inversions from 3D GFs have lower dissimilarity values than those produced using traditional 1D GFs. This work demonstrates the importance of considering 3D structure specifically when studying crustal deformation.

Session: Advances in Reliable Earthquake Source Parameter Estimation [Poster]

Type: Poster

Date: 4/16/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: David

Student Presenter: No

Invited Presentation: 

Poster Number: 36

Authors