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Insights From 3D DEM Models Into Along-strike Variability of Ground Surface Ruptures Observed in Thrust and Reverse Fault Earthquakes

Description: 

We explore how source characteristics and geological site parameters affect along-strike variability in ground surface deformation patterns commonly associated with thrust and reverse fault earthquakes. Building on the 2D analysis by Chiama et al. (2024), which identified relationships between geological parameters (such as sediment depth, density, and fault dip) and surface rupture patterns using a suite of 3,434 2D distinct element method (DEM) models, we extend the investigation into 3D DEM models.

Our 3D models successfully reproduce major fault scarp types – monoclinal, pressure ridge, and simple – aligning with ground rupture characteristics previously identified in 2D modeling. For 3D models with homogeneous sediment strengths and constant fault dip along-strike, scarps tend to form cylindrical styles of deformation. In contrast, variability in these parameters along-strike results in diverse scarp styles, widths, and dips, as well as variable patterns of secondary fracturing. Notably, 3D scarps often display secondary conjugate fractures that facilitate hanging wall collapse and may influence long-term denudation of these features. Furthermore, we examine the effect of oblique slip which yields transitional fault scarps from thrust and reverse fault morphologies to strike-slip patterns of deformation with narrower scarp widths. These DEM models replicate surface fault rupture patterns observed in events such as 1999 Chi-Chi, 2008 Wenchuan, and the 2024 Wushi aftershock. Finally, we show that DEM models can effectively reproduce patterns of multiple rupture cycles, including erosion and sediment deposition, captured in paleoseismic trench observations. We propose that these 3D DEM models support and further augment the quantitative relationships between fault characteristics (slip, dip) and sediment strengths and thicknesses derived from the 2D DEM results of Chiama et al. (2024). Together, these results can be used to forecast along-strike patterns of ground surface deformation from thrust or reverse fault earthquakes based on specific fault characteristics and geological site conditions.

Session: The Landscape Record of Earthquakes and Faulting - II

Type: Oral

Date: 4/16/2025

Presentation Time: 10:45 AM (local time)

Presenting Author: Kristen

Student Presenter: Yes

Invited Presentation: Yes

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