CAREER: Deciphering Cavitation in Fluid-Filled Cracks and its Induced Seismicity through Integrated Physical Modeling

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Magma often moves through the ground beneath volcanoes along cracks (called 'dikes' or 'sills'), and understanding their physics is important for understanding how volcanoes work. It has been suggested that rapid growth of sills or dikes causes gas bubbles in magmas to collapse suddenly, causing cracking of the surrounding rock and volcanic tremors. If this is proven, monitoring these tremors will allow scientists to track dikes in real time as they grow, which will help them forecast the timing and size of eruptions. In this CAREER project, Dr. Roohollah Askari will conduct laboratory experiments to make bubbles in fluid-filled cracks grow and collapse, and he will monitor shaking and crack growth that result, using high-speed photography and other techniques. He will also use mathematical techniques to show that the discoveries from his laboratory experiments apply to sills and dikes under volcanoes, which are of course much larger and made of different materials. Dr. Askari and his team (including teachers) will also produce several educational videos based on the experiments, and he will host college students from Puerto Rico in his laboratory so they can learn experimental techniques along with his own students.Cracks (sills and dikes) contribute significantly to magma transport, often serving as preferential flow paths. Thus, understanding the dynamics of magmatic crack growth and its induced seismicity is crucial for estimating magma transport, monitoring the development of new cracks, and forecasting upcoming eruptions. Crack dynamics and growth may be affected significantly by bubble-magma interaction caused by cavitation. Although cavitation and bubble nucleation in magma have been studied generally, comparatively little is known about these phenomena in fluid-filled cracks, given the complex interaction between the crack fluid and walls. Shock waves that are strong enough to damage the crack walls, create sub-cracks, and be detected seismically are another possible outcome of cavitation in magmatic cracks. Understanding this process is critical to predicting when sub-dikes or sills can develop from a preexisting dike or sill. In this CAREER project, Askari will develop two analog apparatuses and conduct suites of experiments to decipher 1) the fundamental factors influencing cavitation in fluid-filled cracks, 2) the subsequent sub-crack growth mechanism, and 3) induced seismicity. This project will promote the engagement of students from underrepresented groups by offering summer research internships for students from the University of Puerto Rico. Instructional videos featuring the experiments and targeting pre-college and college-level students will be developed, assessed, and updated, in collaboration with teachers and education specialists.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.