Group B, Poster #228, Community Earth Models (CEM)

Multi-parameter thermal model of California and Nevada: Insights into crustal rheology and earthquake processes along the active transtensional plate boundary

Terry Lee, Andrew V. Zuza, Daniel T. Trugman, Dominik R. Vlaha, & Wenrong Cao
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Poster Presentation

2024 SCEC Annual Meeting, Poster #228, SCEC Contribution #13823 VIEW PDF
The thermal state of the crust exerts a substantial control on its rheological and deformational properties. Elucidating the crustal thermal architecture can provide insights into the distribution and pattern of seismicity, seismic hazards, mid-lower crustal rheology, and crustal stress state. Here, we present a novel approach to construct the 3D crustal thermal structure across California and Nevada by synthesizing multiple geophysical constraints, including surface heat flow, seismogenic thickness derived from relocated earthquakes, and Moho depth and temperature. Within adaptively sized spatial bins, we produce 1D steady-state conductive thermal profiles with varying thermal properties (...e.g., radiogenic heating, thermal conductivity) that best fit the integrated geophysical datasets. Incorporating the constraints from surface heat flow, seismogenic thickness and Moho conditions allows for a full reconstruction of the crustal thermal structure, including the mid-lower crust. Our 3D thermal model can be used to extract crustal viscosity and rheological strength profiles using various material flow laws. Our model reveals an elevated thermal gradient (>30°C km^-1) and weak rheology that are clustered in the Salton Trough, Coso, Clear Lake, north-central, and southern Nevada. Conversely, a reduced thermal gradient (<20°C km^-1) and stronger rheology appear in the Great Valley, Sierra Nevada, Mojave, and eastern Great Basin. The absence of heat anomaly along the San Andreas fault zone could provide insights into the strength and non-steady-state shear heating along the plate boundary. We also evaluate the relationship between thermo-rheological structures and earthquake sequence productivity to assess how the physical condition of the crust impacts seismicity, its spatial and temporal variations, and seismic hazards. Our results can also be broadened to refine existing crustal dynamic models and provide an updated perspective on the stress state across the western United States. The completed 3D thermal model will be released to the public community, where users can access and modify the model parameters based on their study area and input data.
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Citation: Lee, T., Zuza, A. V., Trugman, D. T., Vlaha, D. R., & Cao, W. (2024, 09). Multi-parameter thermal model of California and Nevada: Insights into crustal rheology and earthquake processes along the active transtensional plate boundary. Poster Presentation at 2024 SCEC Annual Meeting.
Keywords: Thermal model, Rheology
SCEC Award: 24026
Relevant SCEC Themes:
Developing Rheologies and Bridging Multi-Scales
Advanced Modeling Frameworks