Grant: Research Tools and Instruments - Category 1 (<$150,000)

Funds are sought to purchase an acoustic emission system that will allow us to study the mechanisms of deep focus earthquakes at deep mantle pressure-temperature conditions. Postulated to be caused by faulting that occurs when deep mantle minerals undergo phase transformations accompanied by changes in crystal structure, deep focus earthquakes have received relatively little experimental attention. The challenges in these micro-seismic experimental studies lie in the configuration of the high pressure-temperature sample cell which is necessarily restricted in volume. Our new 3000 ton multi-anvil press will open up new research directions in our attempts to understand deep earth processes from an experimental mineral physics perspective because of the large sample size. We will perform in-situ acoustic emission measurements on mantle minerals (olivine, serpentine and associated dense hydrous magnesium silicate minerals) using the new multi-anvil apparatus at pressures and temperatures representative of the conditions located in the Mantle Transition Zone (410-520 km depth). This will require multiple ultrasonic microphones that are distributed in different positions relative to the sample. By comparing travel times of distinct microphones in a micro-seismic array, it is possible to obtain the source location of a particular acoustic emission event. Larger samples than in any previous experiment of this kind will allow for better spatial resolution concerning the location and time evolution of acoustic source generation of minerals. The research outcomes using the requested equipment will identify the role of nano-scale processes (crystal structural transformations in minerals) in producing macro-scale events (deep focus earthquakes).