Research & Projects

During my PhD, I first investigated how thermally activated friction processes shape the spectrum of slip behaviors in nature. Using a physical framework grounded in laboratory experiments, I showed that a single type of fault material can produce very different behaviors such as pulse-like ruptures, seismic swarms, and slow-slip events depending on grain-scale mechanisms (Wang & Barbot, 2023, EPSL). Incorporating multiple competing deformation and healing mechanisms further revealed how evolving fault rheology due to evolving strain rate and temperature can naturally explain puzzling features seen in nature, including why the seismogenic zone deepens after large earthquakes and why shallow slow earthquakes occur (Wang, Liu & Barbot, in prep; Liu, Wang et al., under review).

To constrain these models, I conducted rock friction experiments on samples from New Zealand’s Alpine Fault under hydrothermal conditions. These experiments revealed a counterintuitive “negative healing” phenomenon—faults weaken with time. We explained this using a second state variable describing degradation of contact in fault zones (Wang, Barbot & Kitajima, in prep). This mechanism helps explain why natural faults are weak and why recurrence intervals may be shorter than predicted.

Scaling up to natural fault zones, I used dynamic earthquake cycle simulations to show that along-strike variations in long-term slip rate, rather than geometric complexity alone, govern rupture segmentation and maximum earthquake size on the East Anatolian and Sagaing faults which hosted devastating M7.8 earthquakes recently (Wang & Barbot, 2024, Geology; Liu, Wang et al., under review). Complementary global analyses of repeating earthquakes (Wang, Wu & Zhou, submitted), and rupture energetics (Wang & Houston, in prep) revealed new scaling relations consistent with classic models and systematic energy decay for global earthquakes, offering new constraints on fault heterogeneity and rupture dynamics.

The East Anatolian fault in Turkey exhibits along-strike rupture segmentation, typically resulting in earthquakes with moment magnitude (Mw) up to 7.5 that are confined to indi- vidual segments. However, on 6 February 2023, a catastrophic Mw 7.8 earthquake struck near Kahramanmaraş (southeastern Turkey), defying previous expectations by rupturing multiple segments spanning over 300 km and overcoming multiple geometric complexities. 

Scientific Question

What controls the rupture segmentation? Why a devastating multi-segment rupture can occasionally occur?

Results

We explore the mechanics of successive single- and multi-segment ruptures using numerical models of the seismic cycle calibrated to historical earthquake records and geodetic observations of the 2023 doublet. Our model successfully reproduces the observed historical rupture segmentation and the rare occurrence of multi-segment earthquakes. The segmentation pattern is influenced by variations in long-term slip rate along strike across the kinematically complex fault network between the Arabian and Anatolian plates. Our physics-based seismic cycle simulations shed light on the long-term variability of earthquake size that shapes seismic hazards.

Publications

Wang, B., & Barbot, S. (2024). Rupture segmentation on the East Anatolian fault (Turkey) controlled by along-strike variations in long-term slip rates in a structurally complex fault system. Geology.

Earthquake cycles are controlled by dynamically evolving friction on a geologic fault. With accumulating laboratory experiments under hydrothermal conditions, a three-regime frictional behavior controlled by the competition of multiple mechanisms appears to emerge for various rocks. Numerical simulations help explore the implications of the experimentally constrained friction law for natural earthquakes. However, the widely used rate- and state-dependent friction law fails to capture the observed full range of frictional behavior with constant parameters that are independent of environmental variables such as temperature. The empirical nature also impedes extrapolation of lab results to large-scale natural faults.

Objectives

We propose to develop a new earthquake cycle simulator based on a physical friction model that incorporates the state-of-art knowledge from lab and field. This new physics-based earthquake simulator provides a foundation for extrapolating the knowledge from the lab and field observations to large-scale natural faults operating at millennia time scale. It may shed light on understanding the rheology of rocks and the dynamics of earthquake cycles in nature.

Publications & Presentations

Wang, B., & Barbot, S. (2023). Pulse-like ruptures, seismic swarms, and tremorgenic slow-slip events with thermally activated friction. Earth and Planetary Science Letters, 603, 117983.

Wang  B., Liu, M. & Barbot, S. D. (2024, 08). Effects of Competing Deformation and Healing Mechanisms in Earthquake Cycles. Poster Prensentation at 2024 GRC Rock Deformation.

Wang  B., Liu, M. & Barbot, S. D. (2024, 12). Simulating Earthquake Cycles Using Lab-derived, Physics-based Friction with Multiple Deformation and Healing Mechanisms. Oral Presentation at 2024 AGU