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Western US intermountain seismicity caused by changes in upper mantle flow.
Thorsten W Becker1, Anthony R Lowry2, Claudio Faccenna3
1Department of Earth Sciences, University of Southern California, Los Angeles, California 90089-0740, USA.
Nature
|August 28, 2015
Summary
Mantle flow, not gravitational energy, is a primary driver of intraplate earthquakes. Improved models link seismicity to changing mantle flow, enhancing our understanding of seismic hazard in continental interiors.
Area of Science:
- Solid Earth geophysics
- Tectonophysics
- Seismology
Background:
- Intraplate earthquakes, occurring away from plate boundaries, pose a challenge to plate tectonic theory.
- Seismicity in the western US is concentrated in an 'intermountain' belt, coinciding with lithospheric structural gradients.
- The precise cause of seismicity localization in these zones remains poorly understood.
Purpose of the Study:
- To investigate the relationship between mantle flow dynamics and intraplate seismicity.
- To identify the primary drivers of continental deformation and seismicity in intraplate settings.
- To improve predictive models for seismic hazard assessment in tectonically active continental regions.
Main Methods:
- Utilized improved mantle flow models to simulate geodynamic processes.
- Analyzed the correlation between seismicity rates and the rate of change in dynamic topography (vertical normal stress from mantle flow).
- Compared the predictive skill of mantle flow dynamics against other potential forcings.
Main Results:
- A significant relationship was identified between seismicity and the rate of change in dynamic topography.
- Mantle flow dynamics demonstrated higher predictive skill for seismicity than other examined forcings.
- Gravitational potential energy variations were found to play a minor role in seismicity.
Conclusions:
- Active mantle flow is a major contributor to seismogenic intraplate deformation.
- Seismicity localization is governed by convective changes in vertical normal stress modulated by lithospheric strength heterogeneities.
- Mantle flow significantly influences topography, tectonics, and seismic hazard in intraplate regions.
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