Low Coseismic Shear Stress on the Tohoku-Oki Megathrust Determined from Laboratory Experiments

<jats:title>Deep Drilling for Earthquake Clues</jats:title> <jats:p> The 2011 <jats:italic>M</jats:italic> <jats:sub>w</jats:sub> 9.0 Tohoku-Oki earthquake and tsunami were remarkable in many regards, including the rupturing of shallow trench sediments with huge associated slip (see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6163" page="1178" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1246518"> <jats:bold>Wang and Kinoshita</jats:bold> </jats:related-article> ). The Japan Trench Fast Drilling Project rapid response drilling expedition sought to sample and monitor the fault zone directly through a series of boreholes. <jats:bold> Chester <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6163" page="1208" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1243719">1208</jats:related-article> ) describe the structure and composition of the thin fault zone, which is predominately comprised of weak clay-rich sediments. Using these same fault-zone materials, <jats:bold> Ujiie <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6163" page="1211" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1243485">1211</jats:related-article> ) performed high-velocity frictional experiments to determine the physical controls on the large slip that occurred during the earthquake. Finally, <jats:bold> Fulton <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6163" page="1214" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1243641">1214</jats:related-article> ) measured in situ temperature anomalies across the fault zone for 9 months, establishing a baseline for frictional resistance and stress during and following the earthquake. </jats:p>