Hiroko Kitajima is at the vanguard of international research efforts to advance our understanding of plate boundary faults via scientific drilling. She has carried out foundational research and has excelled as a team leader during technically challenging expeditions to the Cascadia, Nankai, and Hikurangi subduction zones, as well as onshore drilling into the San Andreas and Alpine plate boundary faults. The Asahiko Taira Prize sets an extraordinarily high bar for a recipient: they must be early to mid-career yet have demonstrated “outstanding, transdisciplinary research accomplishment in ocean drilling.” Hiroko’s sustained, masterful and innovative research that brings together fault mechanics, physical properties and structural geology to investigate the planet’s most active and hazardous fault zones easily measures up. Hiroko has emerged as a leader in the scientific drilling research community more broadly through her careful and creative work, her command and breadth of knowledge and her talent for organizing team efforts.

The balance between frictional locking and slip in these largest of all faults is governed by the tectonic stress conditions, material properties and pressure and flow of pore fluids. All of these are notoriously hard to measure, and there are remarkably few places where our models for fault mechanics have been rigorously evaluated. Hiroko has developed and tested groundbreaking methods — rooted in experimental rock mechanics, geotechnical engineering, sedimentary geology and borehole geophysics — to determine in situ stresses and pore fluid pressure. Her approach has changed the way the community thinks about this problem and has provided among the most exacting of precious few existing constraints on the stresses along active subduction faults, illuminating in particular the low-stress and high-pore-pressure conditions that appear to promote slow earthquakes.

In addition to her scientific achievements, Hiroko has been a team leader in the shipboard laboratories on both the JOIDES Resolution and Chikyu, including a critical role as co-chief scientist for the technically complex ultradeep International Ocean Discovery Program (IODP) drilling Expedition 358 at the Nankai Trough. She was perfectly suited to be the bridge between the scientists and the engineers in this complex effort. Her body of work demonstrates that Hiroko Kitajima is a leader in brittle fault mechanics research today, especially in work that leverages the power of samples and data obtained by drilling, both in IODP and on land. I am confident that scientific fault zone drilling will be a better and more fruitful effort through her leadership for decades to come.

— Harold Tobin
University of Washington
Seattle, Washington

I am greatly honored to receive the Asahiko Taira International Scientific Ocean Drilling Research Prize. About 15 years ago, I met Dr. Taira for the first time when I participated in a public ship tour of Chikyu. At that time, I never imagined my career in ocean drilling research or being a scientist. I would like to give a special thanks to Harold Tobin for his kind citation as well as his mentorship for many years. My endeavor to understand the mechanics of earthquakes, particularly in subduction zones, initiated when I came to Texas A&M University for my graduate study, which was encouraged by my undergraduate adviser, Toshi Shimamoto. Conducting experimental rock deformation research using ocean drilling cores was one of the reasons why I chose Texas A&M (TAMU). During my Ph.D., I had an opportunity to sail for Expedition 311: Cascadia Margin Gas Hydrates and conduct research on the samples from the Nankai Trough, thanks to the generous support from my advisers, Fred and Judi Chester, and my committee member, Giovanna Biscontin, who made my foundation about soil mechanics. During my postdoc time, I was able to expand my research by integrating laboratory deformation experiments on the core samples with geophysical observation to quantitatively estimate the stress state and pore fluid pressure along the plate fault boundary at the Nankai Trough. I enjoyed and am still enjoying discussions with my postdoc adviser, Demian Saffer, on soil and rock deformation. My career in ocean drilling research was greatly established through my participation in a decade-long IODP project, the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE), as a shore-based scientist at the beginning, as a shipboard scientist in Expeditions 338 and 348 during Stage 2, and in a leadership role for the most recent expedition, Expedition 358. I enjoyed meeting and working with many researchers and learned a lot about leadership and management of such a large and challenging drilling project. I greatly appreciate the NanTroSEIZE project coordination team members, Harold, Demian, Masa Kinoshita, Greg Moore, Gaku Kimura, and Mike Underwood, for their encouragement and generous support to early-career scientists like me. Lastly, I am grateful for the support from the ship operational offices for the JOIDES Resolution at IODP-TAMU and for Chikyu at the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). Without their support, none of the scientific ocean drilling research would have been possible. I also thank my friends, colleagues and family who have been supporting my journey. — Hiroko Kitajima, Texas A&M University