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Quantifying Climate Forcing of Volcanic and Earthquake Hazards Using Statistical Analysis and Mechanical Numerical Models: Karen Luttrell

Project Title: Quantifying Climate Forcing of Volcanic and Earthquake Hazards Using Statistical Analysis and Mechanical Numerical Models
Mendenhall Fellow: Karen Luttrell, (650)329-4986,
Duty Station: Menlo Park, CA
Start Date: January 18, 2011
Education: Ph.D. (Geophysics), University of California San Diego, 2010
Research Advisors: David Hill, (650) 329-4795,; Shaul Hurwitz, (650) 329-4441,; Jeanne Hardebeck, (650) 329-4711,; David Shelly, (650) 329-4024,
  Karen Luttrell

Project Description: To first order, earthquakes and volcanic unrest are responses to stresses built up over time by the global motion of tectonic plates. However, recent research suggests that non-tectonic forces external to that system may play a non-trivial role in the timing and magnitude of such events. In particular, earthquake and volcanic activity may be influenced by hydrological forcers associated with cyclic climate phenomena and climate change. The goal of this project is to investigate this connection further.

The climate-driven hydrologic cycle can impact earthquake and volcanic processes in three potential ways. First, the lithosphere bends in response to the weight of a load emplaced or removed at the surface. This response will vary over time, as the initial stress from loading is stored in elastic deformations of the material, but over time viscous processes in the lower crust and mantle respond to dissipate those stored stresses. Second, groundwater recharge into the subsurface can alter the state of stress directly by increasing the fluid pore pressure and thus reducing the effective normal stress. Third, the changing water content of the subsurface can induce mineral alterations, changing either the elastic moduli of the crustal materials or the coefficient of friction of fault surfaces.

The global climate system introduces loads to the tectonic system over a wide variety of spatial and temporal scales.  These include everything from individual rainstorm events to seasonal precipitation accumulation, gradual changes in lake levels, and advance and retreat of mountain glaciers, to longer term climate signals like ENSO, PDO, and even the Milankovitch cycle redistribution of mass between polar ice and global oceans. Each of these is a potential forcer of seismic or volcanic unrest when it coincides with a plate boundary or other tectonically active region, but it is not currently clear which climate processes actually affect volcanic and earthquake hazard sor to what degree. This investigation will thus be carried out in two parts.

In the first portion of the project, I will carry out a detailed statistical analysis of available hydrologic and geophysical datasets to search for statistically significant temporal correlations. If a climate forcing signal is observed in the data, then in the second portion of the project I will use numerical models to quantify the magnitude of the relevant lithosphere bending and pore pressure processes in an attempt to explain the statistical correlations.

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Last modified: 16:08:30 Thu 13 Dec 2012