RAPID: Short-period Seismic Study of Actively Serpentinizing Lithosphere in the Oman Ophiolite

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Interaction of fluids with magnesium-rich and silicon-poor rocks results in chemical reactions that remove carbon dioxide from the fluids. This has been proposed as a means of carbon sequestration. The world's largest body of such rocks occurs in Oman, and NSF has funded a drilling program to assess the mechanisms and chemistry of fluid-rock interaction. A hydrophone array was deployed in two of the drill holes to measure cracking related to this interaction. Preliminary data show an unanticipated high frequency of cracking, which also produces standing waves with the drill hole, an organ-pipe effect. This RAPID proposal is to now deploy a dense network of seismometers around the holes, in order to locate the cracking, measure how the cracks open, and measure the velocity structure around the holes. There is substantive collaboration with scientists from Oman.A network of short-period seismometers will be deployed around a hydrophone-instrumented ICDP hole in the Oman ophiolite. Data obtained during deployment of the hydrophones show unexpectedly high amounts of seismicity and the production of acoustic standing waves in the water column. This array will permit accurate location of the events, which occur at a rate of about 10 per hour, and focal mechanisms. Moreover, the standing waves can be used as a source to image the mantle section. The motivation behind the Oman project is to test the feasibility of carbon sequestration in ultramafic rocks. The project involves substantive international collaboration.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.