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The extremely large slip that occurred on the shallow portion of the Japan Trench subduction zone during the 2011 Mw 9.1 Tohoku-oki earthquake directly contributed to the devastating tsunami that inundated the Pacific coast of Japan. International Ocean Discovery Program (IODP) Expedition 405 (Tracking Tsunamigenic Slip Across the Japan Trench) aimed to investigate the conditions and processes that facilitated the extremely shallow slip on the subduction interface during the 2011 Tohoku-oki earthquake to improve understanding of the factors that allow slip to the trench on subduction zones. Expedition 405 implemented a combined logging, coring, and observatory operational plan at two sites: Site C0026, ~8 km seaward of the Japan Trench, to characterize the input sediments to the subduction zone and Site C0019, ~6 km landward of the trench, where the plate boundary fault zone is present at ~825 meters below seafloor (mbsf). At Site C0026, the input section was logged to ~430 mbsf with a logging-while-drilling (LWD) assembly that characterized the succession of sediments and rocks from the seafloor to the basaltic rocks of the oceanic crust. Cores recovered from four holes as deep as 290 mbsf contain a sequence of hemipelagic and pelagic sediments that will be input into the shallow subduction system and therefore control both the localization of the plate boundary fault zone and the slip behavior of the plate boundary. Site C0019 was previously drilled in 2012 during Integrated Ocean Drilling Program Expedition 343 (Japan Trench Fast Drilling Project [JFAST]), and revisiting this site allowed temporal variations in the frontal prism and plate boundary fault zone to be evaluated. The LWD data to ~980 mbsf characterized the frontal prism, plate boundary fault zone, and lower plate to the basaltic volcanic rocks. Cores were recovered from multiple holes that contain a variety of muds from the frontal prism and the plate boundary fault zone, as well as lower plate materials. Comparison with the sediments from Site C0026 provides a basis to interpret the tectonic and sedimentological processes operating in the dynamic environment of the frontal prism. Cores from the plate boundary fault zone provide a unique window into the structural complexity of an active plate boundary fault that is known to host large seismic slip. Two borehole observatories were installed at Site C0019 that contain temperature sensors deployed to take measurements over a period of years and reveal the hydrogeologic structure of the shallow subduction system. These hugely successful drilling operations, combined with postexpedition work to measure the mechanical, frictional, paleomagnetic, and hydrogeologic properties of the core samples and to constrain the history of past seismic slip at Site C0019, will provide an unprecedented opportunity to advance our understanding of shallow subduction systems. Outreach during the expedition leveraged and elevated the success of the operations by sharing the outcomes with a variety of domestic and international audiences, including scientists, students, educators, stakeholders, and the general public. Thanks to the efforts of a large group of onboard outreach officers and their onshore support, activities included ship-to-shore broadcast events; interviews with science party members and crew; the publication of videos, blogs, magazine articles, and social media posts; and development of formalized classroom lesson plans and materials. 

We observed and modeled the elastic, inelastic and time-dependent viscous properties of damaged Berea Sandstone samples to investigate the impact of damage on the rheological properties of rocks. Cylindrical Berea Sandstone plugs were prepared both parallel and perpendicular to bedding. We impacted the samples with Split Hopkinson Pressure Bar to pervasively fracture the specimens at different strain rates. Longitudinal mode-I fractures are dominant in specimens impacted at relatively low strain rates (about 130 /s), whereas shear fractures also form in specimens deformed at high strain rates (up to 250 /s). The damaged rocks were subjected to multiple steps of differential stress loading and hold stages under 15 MPa confining pressure. A key observation is that higher damaged specimens showed greater axial and volumetric creep strain deformation during loading and hold stages. Poisson ratio also increase with increasing damage. We modeled the volumetric strain of the sandstone specimens using a Perzyna viscoplasticity law that employs the Modified Cam Clay model as the yield criterion (Haghighat et al. 2020). We deduced that fractured rocks undergo substantial bulk time-dependent deformation due to volumetric compaction and fracture closure. Damage increase results in decrease of the effective viscosity of the material. 

Borehole breakouts are used to constrain the magnitude of maximum horizontal stress. However, when the borehole wall strength is higher than the in situ tangential stress, borehole wall failure does not develop. Additional compressive stress can be induced by heating borehole walls. To validate this concept experimentally, we conducted room-temperature and elevated temperature true-triaxial tests on Berea sandstone and Niagaran dolomite samples. We used acoustic emission sensors to capture the onset of breakout development, and we measured the temperature close to borehole wall to assess the magnitude of induced thermal hoop stress. The test results show that within a specific rock type, the breakouts develop in similar manner in room-temperature and elevated-temperature tests. Therefore, the maximum horizontal stress can be constrained from the following dataset: critical tangential stress at which breakout develops, minimum horizontal stress, elastic and thermal properties, and temperature change at the borehole wall. 

We investigate the mode 1 fracture toughness and its anisotropy of Poorman Schist rocks recovered from the Enhanced Geothermal Systems Collaboration (EGS Collab) Experiment 1 site. The EGS Collab team is conducting a series of intermediate (10-20m) scale stimulation and inter-well flow tests with comprehensive instrumentation and characterization at the Sanford Underground Research Facility to validate existing theories and description of hydraulic fractures propagation and associated fluid flow. An important parameter to constrain is how the fracture toughness varies depending on the orientation of the fracture and the direction of fracture propagation, which may have controls on hydraulic fracture propagation. Fracture toughness relative to foliation orientation was determined through the utilization of Cracked Chevron Notched Brazilian Disk (CCNBD) samples in three different orientations (Divider, Arrester, and Foliation Splitting/Short Transverse). Each sample group contains at least three 25.4 mm diameter and 12.7 mm thick CCNBD samples, one of each sample type. Arrester and Foliation Splitting samples were obtained from the same sub-core while Divider samples were obtained from a separate sub-core obtained in close proximity. We found fracture toughness to be weakest in the Foliation Splitting orientation and strongest in the Divider orientation, similar to findings from anisotropic fracture toughness measured in shale rocks. Our findings on the influence of foliation orientation on fracture toughness are presented here. 

This chapter documents the methods used for shipboard measurements and analyses during International Ocean Discovery Program (IODP) Expedition 358. We conducted riser drilling from 2887.3 to 3262.5 meters below seafloor (mbsf) at Site C0002 (see Table T1 in the Expedition 358 summary chapter [Tobin et al., 2020a]) as a continuation of riser drilling in Hole C0002F begun during Integrated Ocean Drilling Program Expedition 326 (Expedition 326 Scientists, 2011) and deepened during Integrated Ocean Drilling Program Expeditions 338 and 348 (Strasser et al., 2014b; Tobin et al., 2015b). Please note that the top of Hole C0002Q begins from the top of the window cut into the Hole C0002P casing. Previous Integrated Ocean Drilling Program work at Site C0002 included logging and coring during Integrated Ocean Drilling Program Expeditions 314 (logging while drilling [LWD]), 315 (riserless coring), 332 (LWD and long-term monitoring observatory installation), 338 (riser drilling and riserless coring), and 348 (riser drilling) (Expedition 314 Scientists, 2009; Expedition 315 Scientists, 2009b; Expedition 332 Scientists, 2011; Strasser et al., 2014b; Tobin et al., 2015b). Riserless contingency drilling was also conducted at Site C0024 (LWD and coring) near the deformation front of the Nankai accretionary prism off the Kii Peninsula and at Site C0025 (coring only) in the Kumano fore-arc basin. Riser operations began with connection of the riser to the Hole C0002F wellhead, sidetrack drilling out the cement shoes from 2798 to 2966 mbsf to establish a new hole, and then running a cement bond log to check the integrity of the Hole C0002P casing-formation bonding. A new sidetrack was established parallel to previous Hole C0002P drilling and designated as Hole C0002Q to distinguish it from the overlapping interval in Hole C0002P. Several new kick offs were established (Holes C0002R–C0002T) in attempts to overcome problems drilling to the target depth and then, in the end, to collect core samples. During riser operations, we collected drilling mud, mud gas, cuttings, downhole logs, core samples, and drilling parameters (including mud flow rate, weight on bit [WOB], torque on bit, and downhole pressure, among others). Gas from drilling mud was analyzed in near–real time in a special mud-gas monitoring laboratory (MGML) and was sampled for further postcruise research. Continuous LWD data were transmitted on board and displayed in real time for QC and for initial assessment of borehole environment and formation properties. Recorded-mode LWD data provided higher spatial sampling of downhole parameters and conditions. Cuttings were sampled for standard shipboard analyses and shore-based research. Small-diameter rotary core barrel (SD-RCB; 8½ inch) coring in Hole C0002T provided only minimal core. Riserless coring at Sites C0024 and C0025 with a 10⅝ inch rotary core barrel (RCB) and hydraulic piston coring system (HPCS)/extended punch coring system (EPCS)/extended shoe coring system (ESCS) bottom-hole assembly (BHA) provided most of the core used for standard shipboard and shore-based research.