Seismo Lab Brown Bag Seminar

Tectonic stress fields induce both brittle and ductile deformation, driving changes in surface morphology. However, the relationship between stress sources and surface processes remains incompletely understood. This study investigates how tectonic stress, arising from lithospheric heterogeneity and mantle flow, shapes geomorphic features and erosion patterns. We first model global tectonic stress fields driven by lithospheric heterogeneity, using gravitational potential energy variations and finite element methods. The results show strong sensitivity to structural assumptions, including mantle density, integration depth, and isostatic conditions. Uncertainty in lithospheric structure remains a key factor in evaluating the relative contributions of different stress sources. To connect stress fields to surface features, we analyze global alignments among stress orientations, fault traces, and river networks. Faults generally align with the maximum horizontal compressive stress, while major rivers follow fault traces. Normal faulting is more closely associated with stress from lithospheric heterogeneity, whereas reverse faults align with mantle-driven stress, indicating regime-dependent stress control. We propose a metric to quantify the relative influence of mantle flow versus lithospheric structure, offering insights into lithospheric strength. Finally, we examine how active faulting influences erosion. Using global 10Be-derived erosion rates, we show that erosional efficiency increases near faults and decays with distance, consistent with long-range damage effects likely caused by seismic shaking. Machine learning identifies fault proximity as the dominant control on erosional efficiency, surpassing the influence of climate and lithology. These findings highlight the importance of tectonic stress in shaping surface processes and constraining lithospheric mechanical behavior.